Home

Delphi User's Guide

1. end end end The file manager application now lets you change the attributes on any selected file Moving copying and renaming files Moving copying and renaming files are all similar operations in that they all produce a file from another file The difference is in how they treat the original file Copying leaves the original file alone Renaming changes the name of the original file Moving deletes the original file after copying it to its new location The run time library provides a function called RenameFile that handles renaming The FMXUutils unit provides similar procedures called MoveFile and CopyFile for those Chapter 13 File manager example 373 operations Each routine takes two string parameters the name of the original file and the name of the destination file In fact you can easily provide a single method in your application that handles any of the three operations The following code shows a method called ConfirmChange that displays a confirmation dialog box then performs the specified operation if confirmed procedure TFMForm ConfirmChange const ACaption FromFile ToFile string begin if MessageDlg Format s s to s ACaption FromFile ToFile mtConfirmation mbYes mbNo 0 mrYes then begin if ACaption Move then MoveFile FromFile ToFile else if ACaption Copy then CopyFile FromFile ToFile else if ACaption Rename th
2. Count Count 1 Counter Text IntToStr Count end procedure TForm1 DivideClick Sender TObject var FirstNumber SecondNumber Integer begin FirstNumber StrToInt Edit1 Text SecondNumber StrToInt Edit2 Text Edit3 Text IntToStr FirstNumber div SecondNumber Count Count 1 Counter Text IntToStr Count end initialization Co nt U end Chapter 5 Writing Object Pascal code 183 So far the application doesn t allow users to make any data entry errors For example if a user neglects to enter a value in one of the two edit boxes before clicking a button the application stops running To ensure that this doesn t happen you ll write some code to check for a value in the edit boxes and if there is none prompt the user to enter one Instead of writing this code twice once in each event handler you could write it once and call the routine from the event handler gt Write anew NoValue function in the implementation part of the unit placing it above all event handlers function NoValue AnEditBox TEdit Boolean begin if AnEditBox Text then begin AnEditBox Color clRed AnEditBox Text Enter a value Result True end else begin AnEditBox Color clWindow Result False end end The NoValue function determines if the edit box passed to the function is empty or not If it is the edit box color turns red the user is prompted to enter a v
3. 3 In the Add Module dialog box type the name of the unit you want to add or choose Browse to specify a search path Note that you can t specify a literal path in the Add Module dialog box The path you choose in the Add Module Browse dialog box adds the directory path to the search path listed in the Install Components dialog box 4 Choose OK to close the Add Module dialog box The name s of the component unit s you have specified appear at the bottom of the Installed Units list If you select the unit name the class names for units already residing in the library are displayed in the Component classes list Class names for newly added units are not shown 5 Choose OK to close the Install Components dialog box and rebuild the library Note that even if you ve made no changes to the unit list Delphi rebuilds the library If you have unsaved forms open you re prompted to save them Once the library is rebuilt the components you ve installed are reflected in the Component palette Newly installed components initially appear on the page of the Component palette that was specified by the component writer in the component source code You can move the components to a different page after they ve been installed on the palette For more information see the online Help topics Palette Options Environment or Customizing the Component Palette To remove components from the component library 1 Choose Options Install Componen
4. 308 Printing the contents of the memo 308 Exiting eracetully 2 4 2 0 0 an ae aw 309 Closing a window c s eo eA eed 309 Closing the child window 310 Determining whether the file has been modifed hes et aea suas e E a a S 310 Exiting the application 311 SIT o e aE RAE eile E A RE Bo O E 312 Chapter 11 Drawing graphics at run time 313 Drawing versus painting 314 Using the pixelarray 314 Manipulating pixels 314 Reading a pixel scolor 314 Setting a Pixels Color ss vue onto ie ne we 315 USME Pens 0 oat SOS Bee techno k 315 Usine Puses events aan oak a a ee eS 316 Drawing lines and polylines 316 Drawing straight lines 316 Drawing polylines Se sea sete eG 317 TDW NSS AICS coe Se sna ot Me ete ge Soe ee eta 317 Drawing rectangles and ellipses 317 Drawing rounded rectangles 318 Drawing polygons 318 Drawing special parts 318 DUMMY 47 aw ave Be bre Be E Sr Be Gr 319 Chapter 12 one the a Zul ieee PEPE i opying graphics to the Clipboard Graphics example 321 Cutting graphics to the Clipboard 355 Responding to the mouse 322 Pasting graphics from the Clipboard 355 What s ina mouse event es 322 UNITAS E crated ar weaes amp E 356 Responding to a mouse down action 323 oe ale to a mouse up action a
5. gt Write the OnClick event handler for the Character Left menu item as shown Then associate the same event handler with both the Right and Center menu items on the Character menu For more information see Chapter 3 You can test the application at this point if you like Run the application and experiment with opening and arranging new child windows and entering and aligning text Adding scroll bars dynamically Recall that you set the initial value of the ScrollBars property for the Memo component at design time When the application first runs the memo contains both vertical and horizontal scroll bars and word wrap is not selected If the user selects word wrap then only the vertical scroll bar remains as there is no need to scroll to the right because text wraps within the current size of the Memo component The OnClick event handler for the Character WordWrap command sets the value of the Memo component s WordWrap property as a toggle In other words whenever the user selects the WordWrap command the value of the WordWrap property changes to its inverse If WordWrap was True it becomes False if False it becomes True The event handler adds either vertical scroll bars or both vertical and horizontal scroll bars to the Memo component based on the value of the WordWrap property Finally it sets the Checked property to the value of the WordWrap property if WordWrap is True then the Checked property is also set to True
6. 141 Checking source code syntax 141 Compiling aproject 142 Obtaining compile status information 143 Building a project 2 4 vad kool ees Ss 143 Running a project 0000 4 143 Executing a project from Windows 143 Managing multiple project versions and team development 144 Enabling team development support 144 SUMMA s pis 2 8 Ge Oe eee ee eS 145 Part Ill Programming topics 147 Chapter 5 Writing Object Pascal code 149 Writing readable code 150 Coding Styles a4 ho hk eae SS OO ee 150 Commenting yourcode 150 Writing assignment statements 151 Assigning values to properties and variables 152 Declaring identifiers 153 Declaring variables 154 Naming avariable 154 Giving a variableatype 154 Data Ty PESE ace ay Bat Bk oe Goh SN ao SY 156 Type and assignment compatibility 157 Declaring constants 157 Calling procedures and functions 158 Calling procedures 158 Cut Copy Paste and Clear All An CaP a ee ee ee a ce ee 159 Calling procedures with parameters 160 Calling functions 161 Assigning a function s returned value 161 Using functions that return a Boolean value to branch code 162 Controlling the flow of code execution 163 The if statement eac owas ee wee Sea eS
7. Drawing graphics at run time There are three ways to get graphic images into your Delphi applications you can insert pre drawn pictures at design time create them using graphical controls at design time or draw them dynamically at run time This chapter describes how to draw graphics at run time either on a window or on a custom control or owner draw control Design time graphics using image controls are explained in Chapter 13 When you draw graphics in a Delphi application you draw on an object s canvas rather than directly on the object The canvas is a property of the object and is itself an object with its own properties The canvas object has four important properties a pen for drawing lines a brush for filling shapes a font for writing text and an array of pixels to represent the image The Font property is described in detail in Chapter 10 This chapter discusses how to use the pixel array the pen and the brush Canvases are available only at run time so you do all your work with canvases by writing code To use graphics effectively at run time you need to understand Drawing versus painting Using the pixel array Drawing lines and polylines Drawing shapes Drawing special parts If you re already familiar with the graphics capabilities of Windows you can probably go straight to the sample application in Chapter 12 You ll find that the canvas is easier to use than direct calls to the Windows Graphics Device I
8. Figure 3 4 Sample input box in running form Password Entry Form Enter Password 5 Type some text in the input box and choose OK The text appears in Label1 6 Choose Button1 again to display the input box 7 Type some text and this time choose Cancel or press Esc to exit the dialog box The text is not displayed in Label1 instead the A Default string is returned In this case the string is blank so the text in Labell s Caption property is cleared but no other text replaces it For more information about InputBox and InputQuery see the online Help topic for each function Masking input characters In a dialog box that you create yourself you can mask the characters that a user enters into an edit field Use the PasswordChar property of the Edit component to display any characters the user enters as special characters such as asterisks or pound signs To see an example of this try the following 1 Start a new blank project 2 Choose File Add File Chapter 3 Building forms and menus 83 3 In the DELPHI GALLERY subdirectory select the PASSWORD PAS file and choose OK 4 Choose View Forms and choose PasswordDIg The Password Dialog Template opens in its design time state Figure 3 5 Password Dialog Template at design time gt Select the Edit component in the Password Template Note that the PasswordChar property of the Edit component Password has already been set to When the user ent
9. Hardware exceptions Hardware exceptions can occur in two kinds of situations either the processor detects a fault it can t handle or the application intentionally generates an interrupt to break execution Hardware exception handling is not compiled into DLLs only into standalone applications The SysUtils unit defines a generic hardware exception called EProcessorException The RTL never raises an EProcessorException but it provides a base from which the specific hardware exceptions descend Table 7 4 shows the specific hardware exceptions Table 7 4 Hardware exceptions Exception Meaning EFault Base exception object from which all fault objects descend EGPFault General protection fault usually caused by an uninitialized pointer or object EStackFault Illegal access to the processor s stack segment EPageFault The Windows memory manager was unable to correctly use the swap file EInvalidOpCode Processor encountered an undefined instruction This usually means the processor was trying to execute data or uninitialized memory EBreakpoint The application generated a breakpoint interrupt ESingleStep The application generated a single step interrupt You should rarely encounter the fault exceptions other than the general protection fault because they represent serious failures in the operating environment The breakpoint 238 Delphi User s Guide and single step exceptions are generally handled by the integrated debugger
10. Inthis example you can draw a line to the point on the form where the user releases the mouse button Here s a simple OnMouseUp event handler that draws a line to the point of the mouse button release 324 Delphi User s Guide procedure TForml FormMouseUp Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin Canvas LineTo X Y draw line from PenPos to X Y end If you run the application you can draw lines by clicking dragging and releasing as shown in Figure 12 3 Figure 12 3 Graphics application with lines drawn Graphics example __ Unfortunately you can t see the line until you release the mouse button In the next section you ll give the user some intermediate feedback by drawing temporary lines while the mouse moves Responding to a mouse move An OnMouseMove event occurs periodically when the user moves the mouse The event goes to the object that was under the mouse pointer when the user pressed the button To respond to mouse movements you need to define the form s handler for the OnMouseMove event If you re not sure how to define an event handler see Chapter 2 In this example you ll use mouse move events to draw intermediate shapes while the user holds down the mouse button thus providing some feedback to the user Here s a simple OnMouseMove event handler that draws a line on a form to the location of the OnMouseMove event procedure TForml Form
11. It s a matter of personal preference whether you load the picture or other values into the About box at run time or design time If you want to share the About box as a standardized form you ll probably want to complete it at design time as nearly as possible before making it available to other developers or users For more information about sharing forms and projects see Chapter 3 and Chapter 4 Deleting event handlers When you delete a component Delphi removes its reference in the form s type declaration However deleting a component does not delete any associated methods from the unit file because as noted earlier those methods might be called by other components in the form You can still run your application so long as the method declaration and the method itself both remain in the unit file If you delete the method without deleting its declaration Delphi generates an Undefined forward error message indicating that you need to either replace the method itself if you intend to use it or delete its declaration as well as the method code if you do not intend to use it You can still explicitly delete an event handler if you choose or you can have Delphi do it for you Chapter 2 Using components and code 67 m To manually delete an event handler remove all event handler codeand the handler s declaration mM To have Delphi delete an event handler remove all the code including comments inside the event ha
12. Read Only List Files of Type Drives OLE files ole d coconut 7 Choose File Exit to close the application Note You can also save OLE objects to memory streams Use SaveToStream and LoadFromStream to work with objects in streams summary This chapter presented these topics e Creating the MDI framework For this example each OLE object that is linked or embedded is contained in an OLE container component in its own MDI child window To contain an OLE object add an OLEContainer component to the OLE Object window When an OLE object is activated in place menu items from the OLE server can be merged with the OLE container application s menus To control where menu items merge and which menu items are replaced specify appropriate values for the GroupIndex property of menu items OLE servers can also access the OLE container application s tool bar and menu bar Use the Locked property to prevent the OLE server from replacing the tool bar or status bar of the OLE container application e Inserting objects To enable the user to use the Insert Object dialog box to insert an OLE object into the OLEContainer component call InsertOLEObjectDlg To initialize the OLEContainer component assign a pointer modified by Insert OLEObjectDle to the PInitInfo property To deactivate the OLE object shift focus to another control click the client area of the form that owns the OLEContainer or set the Active property to False e
13. The first statement colors the form You could have written the statement like this Forml Color clFuchsia It s not necessary however to put the Form1 qualifier on the Color property because the Button1Click method is within the scope of the TForm1 object Any time you are within an object s scope you can omit the qualifier on all properties methods and fields that are part of the object The second statement refers to the Color property of a TEdit object Because you want to access the Color property of the TEdit1 type not of the TForm1 type you need to specify the scope of the Color property by including the name of the edit box so the compiler can determine which Color property you are referring to If you omit it the second statement is like the first the form ends up lime green and the edit box control remains unchanged when the handler runs 222 Delphi User s Guide Because it s necessary to specify the name of the edit box whose Color property you are changing you might wonder why it s not necessary to specify the name of the form as well This is unnecessary because the control Edit1 is within the scope of the TForm1 object it s declared to be a data field of TForm1 Accessing components on another form If Edit1 were on some other form you would need to preface the name of the edit box with the name of the form object variable For example if Edit1 were on Form2 it would be a data field in the TForm2 ob
14. at run time e fmtMedium is of type BOLEMedium This is simply a numeric constant used by Windows to determine the type of data of an object format You should use BOLE_MED_STREAM for linked OLE objects and BOLE_LMED_STORAGE for embedded OLE objects You use the BOLEMediumCalc function to calculate the BOLEMedium type required for this field Search online Help for BOLEMedium for more information about the BOLEMedium type e fmtIsLinkable determines if the object format is linkable Set fmtIsLinkable to True for linked OLE objects or False for embedded OLE objects e HelpContext is used to identify the Paste Special dialog box for online Help If your application is not programmed for online Help pass 0 zero for HelpContext Then a Help button won t appear in the Paste Special dialog box Pass an integer other than 0 to use HelpContext as the context sensitive online Help identification number for the dialog box e Format is modified by PasteSpecialDlg to specify the Clipboard format of the data on the Clipboard Since you can t be sure what type of data is on the Clipboard when the Paste Special dialog box is used use Format to determine how to process the data on the Clipboard Pass a variable of type Word in this parameter For this example PasteSpecialDlg will modify this variable to specify either the FEmbedClipFmt or FLinkClipFmt formats registered in the OnCreate event of OLEFrameForm this is discussed in the section Regist
15. later in this chapter Handling the exception Handling an exception means making a specific response to a specific kind of exception This clears the error condition and destroys the exception object which allows the application to continue execution You typically define exception handlers to allow your applications to recover from errors and continue running Types of exceptions you might handle include attempts to open files that don t exist writing to full disks or calculations that exceed legal bounds Some of these such as File not found are easy to correct and retry while others such as running out of memory might be more difficult for the application or the user to correct For detailed explanations see Handling RTL exceptions Handling component exceptions and Defining your own exceptions in this chapter Exceptions and the flow of execution Object Pascal makes it easy to incorporate error handling into your applications because exceptions don t get in the way of the normal flow of your code In fact by moving error checking and error handling out of the main flow of your algorithms exceptions can simplify the code you write When you declare a protected block you define specific responses to exceptions that might occur within that block When an exception occurs in that block execution immediately jumps to the response you defined then leaves the block 232 Delphi User s Guide Here
16. 1 Place an edit box and a button on a form Add a label above the edit box and put a second label beneath the edit box 2 Using the Object Inspector change these properties e Delete the text specified as the value of the Text property for the edit box e Change the Caption value for the Labell control to Enter a vowel Chapter 5 Writing Object Pascal code 203 e Delete the text specified as the value of the Caption property for the Label2 control e Change the Default property of the button to True 3 Create this event handler for the button s OnClick event procedure TForml ButtoniClick Sender TObject type TVowels set of Char var Vowels TVowels begin Vowels 2a 7 BO if Editl Text 1 in Vowels then Label2 Caption You are clever else Label2 Caption Please try again end 4 Run the application and enter a letter in the edit box The new type TVowels is a set of type Char Vowels is declared as a variable of type TVowels The first line of code after the begin reserved word builds the vowel set puts values into it and assigns this new set to the Vowels variable If the Vowels assignment looked like this Vowels then the Vowels set would contain no values and would be called an empty set The if statement uses the in operator to see if the value you entered into the edit box is in the Vowels set The expression Edit1 Text 1 in Vowels is a Boolean expression that evaluates to eit
17. 1 Select the components for which you want to create a shared event handler 2 Display the Events page of the Object Inspector and select an event 3 Type a name for the new event handler and press Enter or double click the Handler column if you want Delphi to generate a name Delphi creates an event handler in the Code Editor positioning the cursor in the begin end block If you choose not to name the event handler Delphi names it for you based on the order in which you selected the components For example if you create a shared event handler for several buttons Delphi names the event handler Button lt n gt Click where Button lt n gt is the first button you selected for sharing an event handler 4 Type the code you want executed when the selected event occurs for any of the components To see an example of these concepts perform the following steps 1 Add a SpeedButton component to MainForm 2 In MainForm select Button1 3 Display the Events page of the Object Inspector Note the events displayed 4 Press and hold Shift while you select the speed button Note how the events displayed dynamically change to show only events shared by the two components 9 Select the OnClick event and from the drop down list select Button1Click The speed button OnClick event now calls Button1 Click gt Run the program and click the speed button The About box appears Modifying a shared event handler Modifying an event handler tha
18. Adding an image control An image control is a kind of placeholder component It allows you to specify an area on a form that will contain a picture object such as a bitmap or a metafile You can either set the size of the image manually or allow the image control to adjust to the size of its picture at run time You can use an image control to hold a bitmap that isn t necessarily displayed all the time or which an application needs to use to generate other pictures The example in Chapter 13 uses image controls to hold bitmaps used to generate the items in an owner draw control Placing the control You can place an image control anywhere on a form If you take advantage of the image control s ability to size itself to its picture your only concern is setting the top left corner If the image control is a nonvisible holder for a bitmap you can place it anywhere just as you would a nonvisual component Add an image control to the graphics example s form making sure to drop it on the scroll box already aligned to the form s client area This assures that the scroll box will 348 Delphi User s Guide add any scroll bars necessary to access offscreen portions of the image s picture Set the image control s properties as shown in Table 12 3 Table 12 3 Image control properties for GRAPHEX Property Value Name Image AutoSize True Left 0 Top 0 Setting the initial bitmap size When you place an image control it has no
19. Before you begin printing you need to assign a text file variable to the printer by calling the AssignPrn procedure The File Print OnClick event handler Print1Click declares a local variable PrintText for a file of type Text as defined by the System unit Print1Click then passes this variable as a parameter to the AssignPrn method Chapter 10 Text editor example 307 Once you use AssignPrn to assign PrintText to the printer any Write or Writeln statements sent to the file variable are then written on the printer object s canvas using the Canvas property s font and pen position Here is the AssignPrn procedure call from the text editor application begin AssignPrn PrintText Rewrite PrintText The call to Rewrite a procedure in the System unit actually creates and opens the output file The AssignPrn method is declared in the Delphi Printers unit so you need to add Printers to MDIEdit s uses clause Add Printers to the uses clause in MDIEdit s interface part Here s what the uses clause should include at this point uses SysUtils WinTypes WinProcs Classes Messages Graphics Forms Controls Printers Dialogs Menus StdCtrls Clipbrd You ll add two additional Delphi units before you complete the text editor application Downloading the text When the printer is ready for input you use a for loop to write the text from the memo to the printer First you declare a counter variable var Line
20. Chapter 1 Introducing Delphi 29 Figure 1 12 The Forms Gallery Browse Gallery Password Dialog Create a new blank form Templates Use On New Project When this item is checked in the Environment options dialog box the Browse Gallery dialog box for projects appears whenever you choose New Project from the File menu You can then select from the available Project Templates and Experts The new project including all forms and components is then built by the selected project Expert or copied from the selected template and is ready for you to customize or use as is If this item is not checked in the Environment Options dialog box the Gallery does not appear when you create a new project A new blank project is created instead The Gallery is still accessible through the Options menu as you work on the new project however Note This option is disabled by default in a new Delphi installation Figure 1 13 The Projects Gallery Browse Gallery Blank project MEI Application SDI Application Creates a new blank project Templates 30 Delphi User s Guide Enabling the Gallery options Because the exercises in this part of the book assume that all Gallery options are enabled check now to make sure that they are To enable the Gallery for new projects and forms 1 Choose Options Environment from the Delphi menu bar 2 Inthe Gallery group check the Use On New Form and Use On New Project check boxes if they are not al
21. Close the running application by double clicking the Control menu box Chapter 1 Introducing Delphi 17 Handling events Events represent user actions or internal system occurrences that your application can recognize such as a mouse click The code that specifies how a component should respond to an event is called an event handler Every component has certain events to which it can respond The Events page of the Object Inspector displays all events associated with the selected component as shown in the following figure Figure 1 3 Events page Object Inspector On ctivate OnClick OnClose OnCloseQuery OnCreate OnDblClick Handler column OnDestroy Value column OnDragDrop OnDragO ver OnEnter OnExit OnkeyDown OnkeyPress OnKeyUp OnMouseDown Properties Events OO You can use the Object Inspector to generate an event handler for the form or any component you have on the form When you do so Delphi generates and maintains parts of the code for you For example the following code is the initial framework event handler that Delphi generates for the OnClick event of Button1 the event that occurs when the button is clicked on Form1 procedure TForml ButtoniClick Sender TObject begin end The first line of the event handler names the procedure TForm1 Button1Click and specifies the parameters it uses this procedure uses only one Sender of type TObject The code you insert between
22. Delphi for Windows Copyright Agreement Introduction Delphi represents a brand new way to develop applications for Windows It combines the speed and ease of use of a visual development environment with the power flexibility and reusability of a fully object oriented language the world s fastest compiler and leading edge database technology As a result Delphi lets you build sophisticated client server applications in record time Delphi includes support for creating stand alone executable EXE and dynamic link library DLL files and local or networked database applications as well as client server applications Installing Delphi Delphi and its installation program are both Windows applications so you must already have Windows running to install Delphi The installation program creates directories as needed and copies files from the distribution disk to your hard drive The installation program is largely self explanatory The following steps tell you all you need to know to install Delphi To install Delphi 1 Start Windows if it is not already running on your computer 2 Insert the Delphi CD into your CD ROM drive 3 Use Program Manager s File Run menu command or File Manager to run INSTALL SETUP EXE from the Delphi CD 4 Follow the instructions presented by the installation program When the installation program finishes its work it offers you the option of reading the README TXT file which contain
23. E To align components by using the Alignment dialog box 1 Select the component s 2 Choose Edit Align The Alignment dialog box appears Figure 2 8 Alignment dialog box Vertical No change Left sides Tops C Centers C Centers Right sides C Bottoms Space equal Space Equal Center in window Center in window 3 Select the alignment options you want in the dialog box 4 Choose OK to put your alignment options into effect You can continue to choose or modify alignment options as long as the components remain selected For more information about the Alignment palette and the Alignment dialog box see online Help Align the left edges of the top two Label components Do the same for the bottom two Label components so the components appear as shown in Figure 2 9 Chapter 2 Using components and code 51 Figure 2 9 Aligned Label components Label2 Panell Label4 Using the form grid as an alignment guide The evenly spaced dots that appear in the form at design time are the formgrid The grid makes it easier to align components visually Figure 2 10 Form grid pH Forma By default both the grid and its Snap To Grid option which causes the left and top sides of each component to always align with the nearest grid markings are enabled at design time You can however choose to disable the Snap To Grid option or disable the grid altogether You can also modify the granular
24. New Unit Open File Alt E Menu items in a menu list Save File Alt Save File As Alt O Accelerator key Close File Print Printer Setup Separator bar Alt X Keyboard shortcut Opening the Menu Designer To start using the Delphi Menu Designer first add either a MainMenu or PopupMenu component to your form Both menu components are located on the Standard page of the Component palette Figure 3 12 MainMenu and PopupMenu components MainMenu component PopupMenu component A MainMenu component creates a menu that s attached to the form s title bar A PopupMenu component creates a menu that appears when the user right clicks in the form Pop up menus do not have a menu bar To open the Menu Designer select a menu component on the form and then choose from one of the following methods e Double click the menu component e From the Properties page of the Object Inspector select the Items property and then either double click Menu in the Value column or click the ellipsis button The Menu Designer appears with the first blank menu item highlighted in the Designer and the Caption property highlighted in the Object Inspector Chapter 3 Building forms and menus 99 Figure 3 13 Menu Designer for a main menu Title bar shows Name property for Menu component Form1 MainMenul lt a Menu bar EE Placeholder for menu item Menu Designer displays WY
25. e You can change individual variables or elements of arrays and data structures but you cannot change the contents of an entire array or data structure e The expression in the New Value box need to evaluate to a result that is assignment compatible with the variable you want to assign it to A good rule of thumb is that if the assignment would cause a compile time or run time error it s not a legal modification value e You can t directly modify untyped parameters passed into a function but you can typecast them and then assign new values Warning Modifying values especially pointer values and array indexes can have undesirable effects because you can overwrite other variables and data structures Use caution whenever you modify program values from the debugger Viewing function calls While debugging it can be useful to know the order of function calls that brought you to your current program location Using the Call Stack window you can view the current sequence of function calls The Call Stack window is also helpful when you want to view the arguments passed to a function call each function listing in the window is followed by a listing that details the parameters with which the call was made m To display the Call Stack window choose View Call Stack Figure 8 6 Call Stack window l Canstaek eia TForm1 FormCreate Ptr 1CC7 A94 Fontlist Fontdraw The top of the Call Stack window lists the last function cal
26. gt Write the following OnClick event handler for the Character WordWrap menu item procedure TEditForm SetWordWrap Sender TObject begin with Memol do begin WordWrap not WordWrap if WordWrap then ScrollBars ssVertical else SerollBars ssBoth WordWrapl Checked WordWrap end end 290 Delphi User s Guide Using the Clipboard with text Most text handling applications provide users with a way to move selected text between documents including documents in different applications The Clipboard object in Delphi encapsulates the Windows Clipboard and includes methods that provide the basis for operations such as cutting copying and pasting text and other formats The Clipboard object is declared in the CLIPBRD PAS unit file Before you can access methods declared in the Clipboard object you need to add CLIPBRD PAS to any units that will use those methods In the text editor application only the MDIEdit unit calls methods of the Clipboard object Add Clipbrd to the uses clause in the MDIEdit unit s interface part Selecting text Before you can send any text to the Clipboard the text must be selected The function of reading and displaying selected text is native to the Memo and Edit components In other words you don t need to write code so that the Memo component can display selected text it comes with this behavior The Stdctrls unit in Delphi provides several methods to work with selected text Recal
27. 1 Select the breakpoint in the Breakpoint List window 2 Choose View Source or Edit Source from the SpeedMenu The Code Editor is updated to show the breakpoint s location If you choose View Breakpoint the Breakpoint List window remains active so you can modify the breakpoint or go on to view another If you choose Edit Breakpoint the Code Editor gains focus on the line containing the breakpoint enabling you to modify the source code at that location Disabling and enabling breakpoints Disabling a breakpoint hides the breakpoint from the current program run When you disable a breakpoint all the breakpoint settings remain defined but the breakpoint is hidden from the execution of your program your program will not stop on a disabled breakpoint Disabling a breakpoint is useful if you have defined a conditional breakpoint that you don t need to use now but might need to use at a later time m To disable a breakpoint 1 Open the Breakpoint List window and highlight the breakpoint you want to disable 2 Choose Disable Breakpoint from the Breakpoint List SpeedMenu You can also disable all current breakpoints by selecting the Disable All Breakpoints command on the Breakpoint List SpeedMenu m To reenable a breakpoint highlight the breakpoint in the Breakpoint List window then choose Enable Breakpoint from the SpeedMenu You can also choose Enable All Breakpoints from the SpeedMenu to enable breakpoints Deleting breakpoints Wh
28. 120 Form unit type declaration 120 Form unit var declaration 120 Form unit compiler directive 120 Unit files for procedures and functions 121 Unit files forcomponents 121 Unit object code DCU files 121 Graphical form DFM files 121 Beginning new projects 122 Beginning a project with a Project Template 122 Customizing project options 123 Environment options 123 Environment preferences 123 Autosave options 123 Gale feta oe BE Sy a ree og 124 Gallery OPHOUS s s a Jase meta Gh ea Sey 124 Specifying the default new project 124 Specifying a Project Template 124 Specifying a Project Expert 125 Specifying the default new form 125 Specifying the default mainform 125 iii Adding templates to the Gallery 126 PTOJCCL OP HONS e meg ni a ee Bes 127 De ta ltcehecek box orere eh Ae we eE 127 Form options aoaaa 127 Application page oona 128 WG EEEE te ean ec Bb ae gb te 128 Hep iee ga 4 ray 409 Ge i Goes an ea ge S 128 IEOR ga 2x HONG yw a Oe ae BS ec ea 128 COMPILE Pa bs ose BS ye es 128 Linker DAC i sotare etae BE ee 128 Directory and Conditional options 129 Managing project content 129 Using the Project Manager 129 Displaying the Project Manager 130 The Project Manager window 130
29. 331 OLE example 408 409 units to projects 25 27 119 209 210 Additional page Component palette 39 AddObject method 276 addresses exceptions 244 memory 154 AddStrings method 272 alBottom constant 345 alClient constant 289 Align command Edit 51 Align property memos 289 panels 331 345 346 scroll boxes 348 alignment components 50 52 with grids 52 text 289 in status bars 346 Alignment dialog box 51 Alignment palette 50 Alignment Palette command View 50 Alignment property status bars 346 allocated resources freeing 234 235 protecting 233 234 236 allocating memory 113 229 234 235 character strings 201 string lists 273 Index 431 AllowAllUp property 334 ampersand amp character 20 102 ancestor objects 221 223 226 See also inheriting from objects Answer tables databases 40 apostrophes in strings 200 application files See project files application icon 116 128 Application page Project Options 128 applications 75 96 126 224 See also projects client See DDE applications closing 350 file manager example 362 OLE example 404 text editor example 309 312 container See OLE applications developing 7 33 37 80 fundamentals 14 22 tools 9 10 121 distributing 22 executing 17 143 250 251 375 376 pausing execution 253 254 264 to breakpoints 253 254 258 to specific locations 251 254 file manager 359 379 initializing 116 Multiple Document Interface See MDI applications naming 128
30. Color palette Tool palette Icon editing wind w Bitmap editing window The Delphi Image editor is a design tool that you can use to create and edit bitmaps icons and cursors for display in your application You can use any Windows compatible bitmap icon or cursor those in the Image Library shipped with Delphi those you create in the Image editor or third party images you import for use in Delphi Note For more information about the Delphi Image Library search online Help under Image Library E To view the Image editor choose Tools Image Editor The Delphi development model This section describes the fundamental steps involved in developing your own custom projects with Delphi It s also easy to quickly build prototypes by using Delphi templates and database design tools For more information on using Delphi templates and other rapid form design tools see Chapter 3 of this book For more information on developing forms to access your local or remote SQL databases see Database Application Developer s Guide This section demonstrates the process of building two simple applications in Delphi The first application changes the color of your form when you click a button the second adds and clears text from a list box Each example illustrates the following steps which are common to every application you build with Delphi e Designing a form e Handling events e Starting a new pr
31. END You would probably find this version of the event handler easier to read however procedure TForml ButtoniClick Sender TObject begin Editl Color clRed end Choose a code indentation and capitalization style and break lines of code where you need to so that your code is easy for you and others to read Commenting your code You can also place comments in your code anywhere you like E To put comments in your code enclose all the text of your comments in braces For example you could add the following comment to the previous event handler 150 Delphi User s Guide procedure TForml ButtoniClick Sender TObject Changes the color of the edit box begin Editl Color clRed end Comments can extend over many lines The compiler considers everything after the first brace to be a comment until it finds the closing brace This comment runs on a bit and really doesn t say anthing useful but it shows you that comments can have multiple lines of text procedure TForml ButtoniClick Sender TObject Changes the color of the edit box begin Editl Color clRed end Don t forget to include the closing brace or the compiler considers the rest of your code to be a comment The compiler ignores all comments in the code treating them as if they were spaces Look up the Comments topic in Delphi Help for more information about adding comments to your code Use comments to help
32. Forward declarations 189 Passing parameters inv va ps at a we 190 Value parameters 191 Variable parameters 193 Constant parameters 194 Deciding which kind of parameter to use 194 Defining new datatypes 195 Enumerated types 0 0 195 DUDIANGE TY DES lt 6 stp ected a wud WAS eae 197 Aay DOSY tee e684 oe E ati dln does 199 Multidimensional arrays 200 String types Arrays of characters 200 Finding the length of astring 201 DEL LY PCS hint eat oH ate Aa Bd Ges 203 Record Ypes 4 3 oa 568 Bee pate a Owes 204 A few words about objects 205 Understanding Object Pascal units 206 Whatisa Unii esie e eek Rah ale ee 206 The structure ofaunit 206 TICS PACS AEE oaks oy ph ce ey a See ceed ash Gs ws 207 Implementation part 208 Initialization part 6 wR A ew eee es 208 How units areused 209 The uses clause in the implementation part 209 Writing a unit from scratch 209 Adding an existing unit toa project 210 DUNMINANY cou Ge BAe ao arb Bere rh re Soe ge 210 Chapter 6 Programming with Delphi objects 215 What is aivobject s 4 6 6 ga a o 215 Examining a Delphi object 216 Changing the name of acomponent 218 Inheriting data and code from an object 219 Objects components and controls 221 Object
33. Gallery oponse epyk a 84 oe Bee a 29 Use On New Form option 29 Use On New Project 30 Enabling the Gallery options 31 Desktop Contents option 31 Desktop ONIY secaos gph eae 31 Desktop And Symbols 31 Autosave Options 0 31 Editor Pilesicc amp a aint oa We ee 31 DOS KO Py eon hoo seg aie Bek gS 31 Form Designer options grid 31 Debugging options 32 Integrated Debugging 32 Step Program Block 32 Break On Exception 32 Minimize On Ruinie 2 uss ea we ew SS 32 Compiling option 0 32 SUNNA eaaa een a ee eee Gone es 32 Part II Fundamental skills 35 Chapter 2 Using components and code 37 Delphicomponents 37 The form component 38 Default Component palette pages 38 Installing additional components 42 Manipulating components in your forms 43 Setting form properties 43 The Name property 44 Adding components to the form 44 Sizing a component as youaddit 45 Selecting components in the form 46 Resizing components in the form 46 Adding multiple copies of a component 47 Grouping components 47 Cutting copying and pasting components 49 Deleting and restoring components 50 Aligning components 50 Using the form grid as a
34. PAS file contains the Object Pascal source code for the form and the DFM file contains binary code that stores the image of the form Together these two files make up the form For every additional form in a project there will be a PAS and DFM file The project DPR file For each application you develop in Delphi there is one project DPR file that keeps track of all the unit and form files in the application project 22 Delphi User s Guide When you begin a new project Delphi generates the project file and maintains this file throughout the development of the project Initially the DPR file consists of The default name of the project Delphi provides all new projects with a default name Project1 The project files for template applications have more descriptive names for example MDIApp You can change the name when you first save the project or at any time by choosing File Save As A uses clause that lists the units in the project and their associated forms if any A program block containing the code that executes the application and activates the main application form by default Form1 the first form created in a project Normally you view the project through the Project Manager but you can also view the project file as source code using the Code Editor For a detailed discussion of project source code see Chapter 4 Viewing the DPR file You can view the DPR file to see the units and forms in
35. You can view any of the unit source code files in your project by selecting the associated page in the Code Editor m To view the unit file source code click the Code Editor page tab with the name of the unit you want to view You can quickly zoom the Code Editor window to view as much code as possible by double clicking the Code Editor title bar gt Click the Unit1 page tab Figure 1 8 Default unit source code UNIT1 PAS junit Uniti Unit identifier interface Begins interface part of code uses Uses clause SysUtils WinTypes WinProcs Messages Classes Graphics Controls Forms Dialogs type TForml class TForm Delphi library units peitata added automatically Private declarations public Public declarations Form type declaration end var Formi TForm1 Form variable NEE declaration R DEM Begins implementation part of code end 1 1 Modified Insert el gt For a detailed discussion of unit file source code see Chapter 4 The uses clause in the PAS file As mentioned Delphi automatically adds the needed library units to the uses clauses of the default unit generated when you open a new project or unit This is the defaultuses clause uses SysUtils WinTypes WinProcs Messages Classes Graphics Controls Forms Dialogs When you modify a form discussed further in following sections by adding a component to it Delphi modifies the form unit s uses clause by adding
36. access libraries residing elsewhere you need to specify the library path location in this area of the dialog box See online Help for more information Enter any symbols referenced in conditional compiler directives in the Conditional Defines edit box Again see online Help for information Managing project content Delphi s object oriented architecture enables projects to use resources from a wide variety of physical locations Some of the units in a project might reside in the project directory while others might reside in the directory of the project that created them or in some other directory If you never reuse in other projects anything you create in one project you ll have little difficulty keeping track of what files are being used in a project and where they reside You ll also miss out on one of Delphi s biggest benefits however As you create new projects create new forms and units in projects and share files from other projects keeping track of what files a project uses and where those files are stored becomes more and more necessary The Delphi Project Manager makes this task and several others easier to do and more centrally accessible Using the Project Manager The Delphi Project Manager provides a high level view of the form and unit files listed in the uses clause of your DPR file It looks at the in directive to get the file names You can use the Project Manager to open add save and remove project files
37. control Note also that if you hide and show the pen and brush tool bars the scroll box moves the bitmap so that you can still draw on the upper part of the image Adding a menu Up to this point all the features you added to the graphics application use either direct interaction with the mouse or manipulation of tool bar controls to activate them The next few steps however deal with printing loading saving and Clipboard operations Although you can invoke these operations from tool bar buttons the standard expected interface for them uses menu commands Menu creation is not a major topic of this example however If you do not know how to use the Menu Designer or how to attach event handlers to menu item clicks see Chapter 3 Adda MainMenu component to the application You can place it anywhere on the form but off to the side on the main tool bar is probably convenient Create File and Edit menu titles and the items shown in Table 12 4 Table 12 4 Graphics example File and Edit menus amp File amp Edit amp New Cu amp t amp Open amp Copy amp Save amp Paste Save amp as amp Print lt hyphen gt E amp xit The remaining steps in this chapter assume that you created these menus with the specified captions and accepted the Name property values created by Delphi If you choose other names or if you choose to activate these features with tool bar buttons you need to make the necessary adjustments Now tha
38. default 60 63 defined 17 draw item 368 369 handling See event handlers measure item 367 mouse 322 326 dragging and dropping 376 379 395 421 handling 322 323 324 325 testing for 326 351 objects and 227 overview 18 19 owner draw controls and 367 369 responding to multiple 64 sharing 65 67 testing for 227 timing 41 Events page Object Inspector 11 18 65 except reserved word 239 else reserved word and 241 exception classes 241 exception handlers 232 239 242 default 241 defining 239 240 derived types 244 generating messages 240 242 243 local 242 nesting responses 233 234 scope 241 setting exception address 244 stepping through 32 exception instance 240 Exception object 236 244 exception objects 232 destroying 240 preserving 242 types declaring 244 exceptions 231 245 component 242 debugging sessions and 32 264 defined 231 defining new 244 245 hardware 238 264 overriding 233 raising 232 235 239 242 syntax 244 245 responding to 231 232 run time library 236 242 conversion 238 floating point math 237 hardware 238 heap 237 input output 237 integer math 237 typecast 238 silent 243 exchanging data 381 EXE files See executable files executable files 17 117 building 141 DDE applications and 382 including debug information 249 Execute method 295 ExecuteFile function 375 376 ExecuteMacro method 387 ExecuteMacroLines method 387 executing applications 17 143 250 251 375 376 pausing ex
39. discussed earlier Next you ll write the Save1Click method called by SaveAs1Click Creating a backup file The EditForm method for creating a backup file is part of the nested event handler for the File Save click event and is actually called by the outer program block This kind of procedure is often called a helper or subroutine because it performs a subtask as part of a larger task CreateBackup calls three Visual Class Library methods ChangeFileExt DeleteFile and RenameFile ChangeFileExt has two formal parameters FileName and Extension In the text editor application the Extension string parameter is replaced with a BackupExt constant gt Write the following constant declaration in the implementation part of the MDIEdit unit const BackupExt BAK The ChangeFileExt method combines the name of the file and the backup extension BAK into one string CreateBackup assigns this string to a local variable BackupFilename which is then used to delete the existing file and rename it with the parameters specified in the RenameFile method 302 Delphi User s Guide gt Write the following handler for the EditForm File Save OnClick event procedure TEditForm SavelClick Sender TObject procedure CreateBackup const Filename string var BackupFilename string begin BackupFilename ChangeFileExt Filename BackupExt DeleteFile BackupFilename RenameFile Filename BackupFilename end begin i
40. eA tc Be ae he ge tr ah 258 Examining program data values 258 Watching expressions 259 Formatting watch expressions 260 Disabling awatch 0 260 Deleting a Watch 4 224 ie oe a ee 260 Evaluating and modifying expressions 261 Evaluating expressions 261 Modifying the values of variables 262 Viewing function calls 0 263 Navigating to function calls 264 Handling hardware and language CC OIG sar 2a Sn 2 se eek ae at ot ty ae ak tah Oe 264 SUNMA 3 253 abe ord ee grb R Sere 265 Part IV Sample applications 267 Chapter 9 Working with string lists 269 Manipulating the stringsinalist 269 Counting the stringsinalist 270 Accessing a particular string 270 Finding the position of a string 270 Adding a string toalist 271 Moving a string withinalist 271 Deleting a string froma list 271 Copying a complete string list 272 Iterating the stringsinalist 272 Loading and saving string lists 272 Creating anew string list 273 Short term string lists 0 273 Long term string lists 274 Adding objects to a string list 275 Operating on objects in a string list 276 Accessing associated objects 276 Adding associated objects 276 UMMA AYE Acts Sen s Se dis Se Oe Senet helen tone
41. if Drawing then begin DrawShape Origin MovePt pmNotxXor erase the previous shape MovePt Point X Y record the current point DrawShape Origin MovePt pmNotXor draw the current shape end end Customizing pens and brushes A graphics program that lets you only draw black and white images isn t very interesting In order to use more colors you need to modify the pen and brush the canvas uses to do its drawing and painting In this section you ll add more tool bars to the application one each for the pen and brush Specifically you ll see how to perform the following tasks Adding hidden tool bars Hiding and showing tool bars Changing the pen style Changing the pen color Changing the pen width Changing the brush style Changing the brush color Adding hidden tool bars Tool bars don t have to be visible all the time In fact it s often convenient to be able to have a number of tool bars available but show them only when the user wants to use them Often you create a form that has several tool bars but hide some or all of them E To create a hidden tool bar 1 Add a tool bar to the form Be sure to set Align to alTop 2 Set the panel s Visible property to False Although the tool bar remains visible at design time so you can modify it it remains hidden at run time until the application specifically makes it visible 340 Delphi User s Guide For this example add two new hidden tool ba
42. s some code for example that includes a protected block If any exception occurs in the protected block execution jumps to the exception handling part which beeps Execution resumes outside the block try begin the protected block Font Name Courier if any exception occurs Font Size 24 1n any of these statements Color lt clBlue except execution jumps to here on Exception do MessageBeep 0 this handles any exception by beeping end execution resumes here outside the protected block Nesting exception responses Your code defines responses to exceptions that occur within blocks Because Pascal allows you to nest blocks inside other blocks you can customize responses even within blocks that already customize responses In the simplest case for example you can protect a resource allocation and within that protected block define blocks that allocate and protect other resources Conceptually that might look something like this Figure 7 1 Nested resource protections allocate first resource try 3 allocate second resource a gy a g code that uses both resources D g finally D release second resource O T O 2 end finally release first resource end You can also use nested blocks to define local handling for specific exceptions that overrides the handling in the surrounding block Conceptually that looks something like
43. styles 365 p PA files 116 pages Code Editor 12 moving through 62 63 Component palette 10 38 42 notebook 39 changing 363 text printing options 306 Pages property 275 Paint Box component 41 painting defined 314 See also repainting Palette page Environment Options 68 palettes Alignment 50 Component See Component palette Panel component 39 47 panels 39 331 332 345 408 adding buttons 39 aligning text 346 as containers 47 multiple 331 subdividing 346 three dimensional 346 parameters actual 191 193 changing values 193 194 constant 194 formal 191 193 194 functions 185 mouse event 322 323 omitting 208 passing 190 195 procedures 160 185 specifying 160 value 191 193 194 variable 193 194 Parameters command Run 250 parent child relationships components 48 49 MDI applications 97 PAS files 24 26 116 119 121 pass counts 258 passing parameters 190 195 password entry screens 82 83 password invalid exceptions 245 446 Delphi User s Guide PASSWORD PAS 84 PasswordChar property 83 84 Paste command Edit 50 Paste Special dialog box 395 415 417 PasteFromClipboard method 291 PasteSpecialDlg function 415 417 418 pasting components 49 50 DDE links 384 389 OLE objects 394 415 421 pasting graphics 355 pasting text 291 paths See directories Pause Program command Run 253 PChar data type 156 Pen property 315 PEN BMP 333 PenPos property 315 pens 315 316 colors 315 343 default settings 315
44. the finally part of the block even if an exception occurs in the protected block When any code in the try part of the block or any routine called by code in the try part raises an exception execution immediately jumps to the finally part which is called the cleanup code If no exception occurs the cleanup code is executed in the normal order after all the statements in the try part Here s an event handler for example that allocates memory and generates an error but still frees the allocated memory procedure TForml ButtoniClick Sender TComponent var APointer Pointer AnInteger ADividend Integer begin ADividend 0 GetMem APointer 1024 allocate 1K of memory try Aninteger 10 div ADividend this generates an error finally FreeMem APointer 1024 execution resumes here despite the error end end Chapter 7 Writing robust applications 235 The statements in the termination code do not depend on an exception occurring If no statement in the try part raises an exception execution continues through the termination code Note A resource protection block doesn t handle the exception In fact the termination code doesn t have information about whether an exception even occurred so it can t determine whether it needs to handle an exception If an exception occurs in a resource protection block execution first goes to the termination code then leaves the block with the exception stil
45. this file as the default for any new projects you create Delphi maintains all its original project defaults which the settings in DEFPROJ OPT simply override To restore Delphi s original default settings delete or rename the DEFPROJ OPT file Project options you set for an open project override the current Delphi defaults whether those defaults are as originally shipped or as modified by you or another user Form options The options on the Forms page of the Project Options dialog box enable you to change the form designated as the project s main form and to control the creation order of forms at run time For more information see Chapter 3 Chapter 4 Managing projects files and directories 127 Application page The Application page is where you specify a title Help file and icon for the project You can also specify these options as default project settings Title The text you enter here appears below the application icon when you minimize the running application If no title is specified the minimized application displays the file name of the EXE file Help file If you have created a Windows Help HLP file for the project you connect it to the application by specifying it in the Help File edit box Either type a file name or use the Browse button to select an existing Help file At run time the Help file name and path if it exists is passed to the Windows WINHELP EXE which attempts to load your help fil
46. viewing 23 141 specifying default 125 126 testing 112 Forms Gallery 29 77 79 80 adding templates 93 enabling disabling 78 Forms page Project Options 127 FormStyle property 85 96 281 forward declarations 189 190 forward reserved word 189 fractional numbers 156 262 frame windows See MDI applications main form Free method 229 freeing allocated resources 234 235 freeing memory 229 234 235 273 FreeMem procedure 235 fsMDIChild constant 97 fsMDIForm constant 97 281 fsNormal constant 97 fsStayOnTop constant 85 97 function reserved word 161 185 functions 121 183 195 207 as standalone program 134 135 availability 187 calling 20 21 161 163 recursively 189 190 viewing order 263 264 declaring 161 185 189 defined 161 headers 185 208 short form 208 predefined 158 Result variable and 187 return type omitting 208 return values 161 163 185 186 G Gallery 122 adding custom templates 126 127 options 29 31 124 changing 122 GALLERY directory 122 Gallery Options dialog box 124 127 Gauge component 42 gauges 42 adding 42 moving incrementally 39 general protection fault 238 geometric shapes See shapes GetDriveType function 362 GetFileSize function 365 GetMem procedure 235 getting help 2 3 data types 153 global scope 177 global symbols 13 global variables 181 183 glyphs 117 332 333 GPFs 238 GRAPHEX DPJ 321 Graphic property 349 354 graphical user interfaces 76 graphics 117 313 319 321 365 See also
47. 56 in code 151 152 157 run time 59 60 settings 116 117 Shape component 39 shapes 39 317 318 337 See also graphics filling 316 344 outlining 315 sharing data 390 396 sharing events 65 67 339 343 sharing forms 76 94 sharing project files 134 135 144 ShortCut property 102 shortcuts accesssing property values 54 adding to menus 102 103 menu commands 12 viewing Code Editor pages 62 Shortint data type 156 Show method 85 ShowHelp property 296 Show Message procedure 81 ShowModal method 61 85 silent exceptions 243 Single data type 156 Single Document Interface See SDI applications single quotation marks 200 Size command Edit 46 Size dialog box 46 sizing handles 46 Snap To Grid option 52 sorting strings 271 sound files See media players source code 116 117 118 119 See also code checking syntax 141 debugging 247 265 viewing 12 79 139 Code Editor window 141 spacing in code 150 speed buttons 39 adding to tool bars 331 334 assigning glyphs 332 333 engaging as toggles 334 event handlers 227 334 336 grouping 333 334 initial state setting 333 operational modes 332 SpeedBars 12 See also tool bars Project Manager 131 SpeedButton component 39 SpeedMenus Form 93 Menu Designer 105 106 Project Manager 130 spin boxes 42 SpinBox component 42 SpinEdit component 42 spreadsheets 280 SOL databases 40 SOL queries 40 stack 238 standalone debugger 249 Standard page Component palette 38 39 starting Delphi 8
48. BMP files 117 BMPDleg unit 354 BOLEFormat type 416 418 422 BOLEMedium type 416 BOLEMedium Calc function 419 Boolean conditions breakpoints 257 258 Boolean data type 156 162 Borderlcons property 87 borders 3 D panels 346 forms 44 86 hiding 289 BorderStyle property forms 86 87 memos 289 BorderWidth property 346 Borland Assist program 3 braces enclosing comments 150 branching statements 162 163 167 Breakpoint command View 255 Breakpoint List window 255 258 opening 255 breakpoints 254 258 changing 257 258 coloring 258 conditional 256 257 258 defined 253 deleting 256 displaying 255 258 invalid 255 258 setting 254 255 256 after execution begins 255 Browse Gallery dialog box 19 29 78 enabling 124 browsing through code 13 Brush property 316 BRUSH BMP 333 brushes 316 344 345 bsDialog constant 44 86 bsNone constant 87 289 bsSingle constant 87 bsSizeable constant 87 Build All command Compile 143 building forms 80 98 building projects 14 22 133 135 143 Button component 15 38 buttons 331 See also specific type adding 38 39 to dialog boxes 87 89 as active component 93 customizing 89 default 88 Minimize Maximize 44 86 mouse See mouse buttons bvLowered constant 346 Byte data type 156 C Calendar component 42 Call Stack command View 263 Call Stack window 263 264 opening 263 calling procedures and functions 20 21 158 163 order of calls 263 264 recursively 189 190 Cancel bu
49. Boh A tg bet 68 Adding and removing components from the DRO bo ath Brace hee eae Ss Seth See fee 69 Adding VBX controls 70 Handling an unsuccessful compilation 70 Saving library sourcecode 71 Using the Component Expert 71 Using customized libraries 72 DUMIMALY te bse OSes Bie Bees eee 73 Chapter 3 Building forms and menus WY Ve IS A ROMTINS s grae per ei Ye sap Ue ee ene Me 76 Designing usable forms 76 Sharing OPM Sie a 6s oe ges ok ee ae a 76 Making forms visible to other forms 76 Enabling forms to reference each other 77 Modifying asharedform 77 Using the Form Templates of the Browse GAEI 9 a stad hw Gath Dune G Wide ome pee y 77 Adding a template form to a project 78 Opening a Form Template for reference ORI S ae dete A P a EA E E E 79 ii Viewing forms and units 79 Boab CATV ORIN S ee een ge hen ae ek ete E sere 80 Using routines to display dialog boxes 80 Displaying message boxes 80 ShowMessage procedure 81 MessageDle function 81 Creating simple input forms 82 Masking input characters 83 Developing custom dialog boxes 85 Making a dialog box modal or modeless 85 Displaying a dialog box modelessly 85 Displaying a dialog box modally 86 Setting form properties for a dialog box 86 Specifying a caption for
50. Chapter 13 Responding toa mouse move File manager example 359 Adding a field to a form ODJECE za ig sesh es 326 tae in z oi 360 Refining DE ranne E a De es oe out the form i se mane ete eh a 360 Tracking the origin point 328 Pisa ecni 360 Tracking movement 329 Desi a i abet Ae ar aR eee 361 Adding atoolbartoaform 331 ee A Building the drive list 0 362 Adding speed buttons to a toolbar 331 Deens ea cages 362 Adding a speed button toatoolbar 332 ae ane the e su tae oie on 363 Assigning a speed button s glyph i Creating an owner draw control 365 Setting the initial condition of a speed ar R E on nc uoecce 365 PUHON s 4 ae he ee alae E EAER 333 ee oe ay eS Creating a group of speed buttons 333 Adding graphical objects to a string list 366 Allowing toggle buttons 334 Drawing owner draw IteMS 1 ee ee 367 Responding to clicks 334 EEE Ghata ee aia Responding toa button click 2 2 0 334 p p S AA o Drawing with different tools 334 hangin e ae Ce ee Deanne a enuinerated D ela a Reading file attributes 371 ois nging the or MU A sda rae Changing individual file attributes 372 aL tie Haning tools A a A Setting file attributes 0 373 Drawing the appropriate shapes 337 Moving copying and renaming files 373 Customizing pens and brushes 340 Executing an
51. Choose File New Project By default Delphi creates a new blank project If you or another user have enabled the Project Gallery see Chapter 3 the Browse Gallery dialog box appears with the user specified default project option selected 2 Choose OK This step applies only if you are using the Project Gallery Setting form properties The first part of creating the dialog box involves setting properties for Form1 You were introduced to the notion of properties in Chapter 1 You ll change several form properties including the form name Chapter 2 Using components and code 43 gt Set properties for Form1 as described in the following table Property Value Name AboutBox Caption About BorderStyle bsDialog Position poScreenCenter Changing BorderStyle to bsDialog removes the form s Minimize and Maximize buttons and makes its borders non resizable Changing Position to poScreenCenter ensures that the dialog box appears in the center of the screen Note that these changes become visible at run time not design time The Name property The most important of the properties you just changed is the Name property In fact the Name property is arguably the most important property for all components Every component in an application must have a unique name so assigning meaningful names at the outset not only makes your code more readable but prevents possible name conflicts later Component names must follow the standard
52. Compiling dialog box available so you can cancel a compilation in progress Figure 1 14 The Compiling dialog box summary This overview introduced the following concepts e Elements of the Delphi programming environment interface e Overview of the Delphi development model including e Setting a component s design time properties by using the Object Inspector 32 Delphi User s Guide e Writing event handler code to set properties and call methods during run time e Running your application e Structure of projects in Delphi e The types of files in a project e Setting environment preferences to control the behavior of Delphi when selecting New Project or New Form Chapter 1 Introducing Delphi 33 34 Delphi User s Guide Part Fundamental skills The chapters in this part present concepts and skills fundamental to creating Delphi applications These concepts and techniques are illustrated by simple but functional examples that you can create The three chapters making up this part are e Using components and code This chapter explains the nature of Delphi components where to find them on the Component palette how to place them on forms to create user interfaces and how to attach code to events associated with those components Additional topics include how to use the Component Expert to create custom components how to add VBX components to the Delphi Component palette and how to customize the Delphi Visual Cl
53. Guide The draw item event contains parameters indicating the index of the item to draw the rectangle in which to draw and usually some information about the state of the item such as whether the item has focus The application handles each event by rendering the appropriate item in the given rectangle For example to draw tabs in a tab set that has bitmaps associated with each string attach the following handler to the OnDrawltem event for the tab set procedure TFMForm DriveTabSetDrawTab Sender TObject TabCanvas TCanvas R TRect Index Integer Selected Boolean var Bitmap TBitmap begin Bitmap TBitmap DriveTabSet Tabs Objects Index with TabCanvas do begin Draw R Left R Top 4 Bitmap draw bitmap TextOut R Left 2 Bitmap Width position text R Top 2 DriveTabSet Tabs Index and draw it to the right of the bitmap end end Note Most draw item events don t pass a canvas object as a parameter you normally use the canvas of the control being drawn Because the tab set also has to render its tab separators between items it passes a special canvas for item drawing as a parameter Manipulating files There are several common file operations built into Object Pascal s run time library The procedures and functions for working with files operate at a high level you specify the name of the file you want to work on and the routine makes the necessary calls to the operating
54. Help Delphi s online Help provides a superset of the information presented in the printed manuals Use online Help to find e Specific procedural information regarding programming tasks in Delphi e The language definition of Object Pascal e Reference material for the Visual Component Library and the Run Time Library Using Interactive Tutors Delphi provides seven Interactive Tutors to help you get up and running quickly A quick tour overview of the Delphi programming environment A short lesson on how to create a simple application A lesson on how to add components to a form A lesson on setting component properties A lesson on creating and modifying event handlers 2 Delphi User s Guide e A lesson on creating a simple database application e A lesson on creating a more sophisticated database application Manual conventions The printed manuals for Delphi use the typefaces and symbols described in Table Intro 1 to indicate special text Table Intro 1 Typefaces and symbols in these manuals Typeface or symbol Monospace type Boldface Italics Keycaps gt Contacting Borland Meaning Monospaced text represents text as it appears onscreen or in Object Pascal code It also represents anything you must type Square brackets in text or syntax listings enclose optional items Text of this sort should not be typed verbatim Boldfaced words in text or code listings represent Object Pascal reserved words or
55. If it is Test 2 calls Test1 The two procedures continue to call each other until Alpha is no longer greater than 0 at which time the Writeln statements of the procedures run A more detailed discussion of mutual recursion and how it works is beyond the scope of this chapter The important point to note is that the Test2 procedure is declared as a forward procedure before the implementations of Test1 Test2 and the Button1Click event handler If Test2 is not declared as a forward procedure the project will not compile because the code would then be calling Test2 before it is declared Passing parameters When your code calls a procedure or function it often uses parameters to pass data to the called procedure or function The section Calling procedures with parameters on page 160 describes how to use a parameter in calling a procedure the section Writing a procedure or function header on page 185 describes how to create a parameter list in a procedure or function header This section describes the most common kinds of parameters your procedures and functions can use 190 Delphi User s Guide e Value parameters e Variable parameters e Constant parameters Any parameters specified by the calling procedure or function are called theactual parameters The corresponding parameters in the called procedure of function are called the formal parameters So in this procedure call the Edit1 parameter is the actual parameter Co
56. Integer Then you need to write a for loop to write the contents Lines property of Memo1 to the printer Here is the code that follows the call to Rewrite in the text editor application for Line 0 to Memol Lines Count 1 do Writeln Printerl Memol Lines Line The last line to be printed equals the number of lines in the memo minus one because the counting begins with zero as the first line The following section shows how all of these methods fit together into a single event handler for the EditForm File Print OnClick event Printing the contents of the memo All the code discussed in the preceding sections is used in the text editor application to handle the File Print click event This section shows the event handler in its entirety gt Write the following handler for the EditForm File Print OnClick event procedure TEditForm Print1lClick Sender TObject var Line Integer declare an integer variable for the number of lines of text PrintText System Text declare PrintText as text file defined in System unit begin if PrintDialogl Execute then 308 Delphi User s Guide begin AssignPrn PrintText assign the global variable PrintText to the printer Rewrite PrintText create and open the output file Printer Canvas Font Memol Font assign the current Font setting for Memol to the Printer object s canvas for Line 0 to Memol Lines Count 1 do Writeln PrintText Memol Line
57. Open File dialog box The Open method also uses a function ExtractFileName which takes a full file name including the file name extension and a path if specified and returns only the file name and extension For example if the user used the Open File dialog box to specify a file such as C WINDOWS DELPHI MYFILE TXT ExtractFileName when passed that file as a parameter returns only MYFILE TXT Once the file is loaded into the memo the Open method resets the value of the memo s SelStart property to zero The SelStart property returns the starting position of the selected text or the current cursor position if there is no text selected By default when lines are loaded into either an edit or a Memo component Se Start gets the value of the last position of the lines rather than the first By setting SelStart to zero the cursor appears where the user expects it that is at the beginning rather than the end of the file gt First declare the Open method Add the following line to the TEditForm type declaration section in the interface part of the MDIEdit unit procedure Open const AFilename string You declare the file name as a constant because its value won t be modified inside the method gt Now write the Open method in the implementation part procedure TEditForm Open const AFilename string begin Filename AFilename assigns the parameter passed from FrameForm OpenChild to the form variable Mem
58. This causes the menu to open enabling you to drag the item to its new location 2 Drag the menu item into the list releasing the mouse button to drop the menu item at the new location Viewing the menu You can view your menu in the form at design time without first running your program code Pop up menu components are visible in the form at design time but the pop up menus themselves are not Use the Menu Designer to view a pop up menu at design time E To view the menu 1 Ifthe form is visible click the form or from the View menu choose the form whose menu you want to view 2 If the form has more than one menu select the menu you want to view from the form s Menu property drop down list The menu appears in the form exactly as it will when you run the program Editing menu items without opening the Menu Designer This section has discussed how to set several properties for menu items for example the Name and Caption properties by using the Menu Designer The section has also described how to set menu item properties such as the ShortCut property directly in the Object Inspector just as you would for any component selected in the form 104 Delphi User s Guide When you edit a menu item by using the Menu Designer its properties are still displayed in the Object Inspector You can switch focus to the Object Inspector and continue editing the menu item properties there Or you can select the menu item from the C
59. WB2 6 Choose OK The DDEService and DDETopic properties now contain the appropriate values to establish a DDE link 7 Select the DDEClientItem component and choose the name of the linked DDEClientConv component for the DDEConv property from the list in the Object Inspector 8 Ifthe contents of the Clipboard haven t changed since you completed step 2 then the Clipboard contains a value for the DDE item of the conversation Choose this value for the DDEItem property from the drop down list in the Object Inspector If the contents of the Clipboard do not contain a value for the DDE item type the appropriate value for DDEltem in the Object Inspector For example if you copy cell A1 from page A in the Quattro Pro notebook select or type A A 1 6A 1 for DDEItem Remember that you also need to provide your application with an area and a means to display the data being exchanged The DDEltem component is nonvisual so it serves only as a means of access not a means of display To establish a DDE link at run time specify the service and topic of the conversation using the SetLink method of the DDEClientConv component The first parameter of SetLink is a string specifying the service and the second parameter is a string specifying the topic SetLink assigns these strings to the DDEService and DDETopic properties of the DDEClientConv component respectively For more information about this method search online Help for SetLink Simply
60. We a e A 9 Component palette o aaa 10 Object NSpector riani a BiG e 11 Object selector lt 4 aae Sra a e Soe 11 Code Edl senna a EUs Od OS Ete eS 11 SpeedBar acc 4 4 244 ope tees ele eo 12 Elements not visible upon starting Delphi 12 Project Manager 4 4 eid Deis oa es 12 Ment Dese NEE aie tice ten Seth at ene eS 13 Integrated debugger 13 OBlCCEBrOWSER z 6x i Bede Ae we as 13 ia Se Editon wy Bred eno bt 3 A noe GI este 14 The Delphi development model 14 Deslenine a formis os yw ote ade Bee GE A 15 Creating anew form 15 Adding components to the form 15 Setting component properties 16 The Name property 40 364 foo 4 96545 16 Running the program 17 Handling events 18 Starting a new project aoao 19 Calling procedures and functions from event handlers os een Sas wad e 20 Distributing your application 22 Overview of Delphi projects 22 The project DPR file 22 Viewing the DPRfile 23 The uses clause inthe DPR file 24 The unit PAS file 0 24 Viewing the PAS file 25 The uses clause in the PAS file 25 The form DFM file 26 The type declaration in the DFM file 26 Source code for units without forms 27 Setting environment preferences 28 Accessing environment options preferences 28
61. You use watches to monitor the changing values of variables or expressions during your program run After you enter a watch expression the Watch List window displays the current value of the expression As your program runs the value of the watch changes as your program updates the values of the variables contained in the watch expression If the execution point moves to a location where any of the variables in the watch expression are undefined then the entire watch expression becomes undefined If the execution point returns to a location where the watch expression can be evaluated then the Watch List window again displays the current value of the watch expression To open the Watch List window choose View Watches Figure 8 3 The Watch List window Watch List The easiest way to set a watch is from the Code Editor 1 Select the expression you want to monitor 2 Choose Set Watch from the Code Editor SpeedMenu to add the expression to the Watch List window You can also create a watch by doing the following 1 Open the Watch Properties dialog box using any of the following techniques e From the Main menu choose Run Add Watch e Choose Add Watch At Cursor from the Code Editor SpeedMenu Press Ctrl F5 default key mapping e Double click a watch in the Watch List window e Select a watch in the Watch List window then choose Edit from the SpeedMenu 2 In the Expression edit box enter the expression you want to watch or choose
62. a property called PenPos Pen position affects the drawing of lines only for shapes and text you specify all the coordinates you need To set the pen position call the MoveTo method of the canvas For example to move the pen position to the upper left corner of the canvas you use the following code Canvas MoveTo 0 0 Chapter 11 Drawing graphics at run time 315 Note Drawing a line with the LineTo method also moves the current position to the endpoint of the line Using brushes The Brush property of a canvas controls the way you fill areas including the interior of shapes Filling an area with a brush is a way of changing a large number of adjacent pixels in a specified way The brush has three properties you can manipulate Color Style and Bitmap The values of these properties determine the way the canvas fills shapes or other areas By default every brush starts out white with a solid style and no pattern bitmap You can set the color of a brush as you would any other Color property at run time Style lets you specify various ways to combine the brush s color with any colors already on the canvas Bitmap lets you specify a bitmap image for the brush to use as a pattern for filling shapes and other areas The sample program in Chapter 12 demonstrates the effects of each brush property Drawing lines and polylines 316 A canvas can draw two kinds of lines straight lines and polylines A straight line is just a
63. a single routine and a list that the application creates uses throughout run time and destroys before it shuts down The way you create and manage a string list depends on whether it s going to be a long term list or a short term list Short term string lists If you need to use a string list only for the duration of a single routine you can create it use it and destroy it all in one place This is the safest way to use string list objects Because the string list object allocates memory for itself and its strings it is important that you protect the allocation by using a try finally block to ensure that the object frees its memory even if an exception occurs m The basic outline of the use of a short term string list then is to 1 Construct the string list object 2 Inthe try part of a try finally block use the string list 3 In the finally part free the string list object The following event handler responds to a button click by constructing a string list using it and then destroying it again Chapter 9 Working with string lists 273 procedure TForml ButtoniClick Sender TObject var TempList TStrings declare the list begin TempList TStringList Create construct the list object try use the string list finally TempoList Free destroy the list object end end Long term string lists If you need a string list that s available at any time while your application runs you
64. a string Delete Deletes a specified number of characters from a string beginning at specified position within the string Insert Inserts another string within a string Length Returns the length of the string Pos Returns the position index of a substring within a string You can find information about using these string procedures and functions in online Help Finding the length of a string This is a simple example that finds the length of a string the user enters in an edit box Your finished form should look something like this Chapter 5 Writing Object Pascal code 201 Figure 5 23 A form for a string handling example Form1 gt To create this application 1 Add an edit box a button and two labels to a form Put Labell above the edit box control and put Label2 below the edit box control 2 Using the Object Inspector change these properties Change the caption of Labell to Enter a string Delete the caption of Label2 so the label becomes invisible Delete the text of the edit box Rename the button to FindLength Change the caption of the button to Find Length 3 Create this event handler procedure TForml FindLengthClick Sender TObject type TEditString string var UserString TEditString begin Lt UserString Editl Text Label2 Caption This string is IntToStr Length UserString characters in length end 4 Run the application When you click the button t
65. allocated to it Determining whether the file has been modified The Close method of TForm calls the CloseQuery method of TForm as mentioned previously CloseQuery returns a Boolean value for the variable CanClose which determines whether to close the form The text editor application uses CloseQuery in conjunction with the Modified property of the memo to provide users with a message that asks them whether they want to save their changes If the user cancels the message box CanClose returns False and the form doesn t close The MessageDlg function which is declared in the Dialogs unit produces the message dialog box For more information about MessageDlg refer to online Help MessageDlg calls the Format function which exists in the SysUtils unit automatically declared in the uses clause of EditForm s interface part The text editor application uses a global constant to present the user s file name in the message dialog box or Untitled if the file name has not already been saved Declare the following global constant in the implementation part of the MDIEdit unit const SWarningText Save Changes to s 310 Delphi User s Guide The EditForm CloseQuery method substitutes the s wildcard with the value of the Caption property for the text file Thus if the user has previously saved the file the file name is displayed gt Write the following handler for the EditForm OnCloseQuery event pr
66. and pass the name of the text file to load from LoadFromFile reads each line from the text file into a string in the list 272 Delphi User s Guide E Tostore a string list in a text file call the SaveToFile method and pass it the name of the text file to save to If the file doesn t already exist SaveToFile creates it Otherwise it overwrites the current contents of the file with the strings from the string list This example loads a copy of the AUTOEXEC BAT file from the root directory of the C drive into a memo field and makes a backup copy called AUTOEXEC BAK procedure TForml FormCreate Sender TObject var FileName string storage for file name begin FileName C AUTOEXEC BAT set the file name with Memol do begin LoadFromFile FileName load from file SaveToFile ChangeFileExt FileName BAK save into backup file end end Creating a new string list Most of the time when you use a string list you use one that is part of a component so you don t have to construct the list yourself However you can also create standalone string lists that have no associated component For instance your application might need to keep a list of strings for a lookup table The most important thing to remember when you create your own string list is to free the list when you finish with it There are two distinct cases you might need to handle a list that the application creates uses and destroys all in
67. application 375 Adding hidden toolbars 340 Dragging and dropping 376 Hiding O OOD eph as im Starting a drag operation 376 Changing a o me Ode 2 a Accepting dragged items 377 Changing thepencolor 343 Dropping items 378 Sevens e e ahaa eer ae ie Ending a drag operation 378 Changing the brush style 344 5 379 Changing the brush color 345 a E E E E E E Adding astatusbar 345 Chapter 14 Placing a status bar panel 345 Subdividingapanel 346 Exchanging data with DDE or OLE 381 Creating 3 D panels 346 Using DDE sssesesesesese seso 381 Updating the status bar 347 DDE conversations ai aka ee ce whoa 382 Drawing onabitmap 347 DDE services 0 eee ee eee 382 Adding a scrollable region 348 ae topics ee ee ee Adding an image control 348 IteMS ee Placing the a E a ee 348 Creating DDE client applications 383 Setting the initial bitmap size 349 Establishing a link with a DDE server 384 Drawing on the bitmap 349 S data si gon Tanaan enea apia Adding a menu Loo LLL LaLa 350 OKNE data s s eeta iie h ee SE D 5a ae 351 Controlling other applications 387 6 Stap Meu gae Oo Creating DDE server applications 388 Working with graphics files dS shite th Geshe hes 352 Establishing a lin
68. as UNIT1 PAS OLEFRAME PAS UNIT2 PAS OLEOBJ PAS PROJECT1 DPR OLE DPR Adding the OLE container component In this example a child window can contain an OLE object You ll add an OLEContainer component to OLEObjectForm to contain the OLE object An OLEContainer component can contain only one object at a time To contain more than one OLE object in a form you need to add a new OLEContainer for each OLE object However this sample application will contain only one OLE object per OLEObjectForm You ll program the OLEContainer component to contain an actual OLE object at run time in the section Inserting objects To create an OLE container application add an OLEContainer component to a form Chapter 15 OLE example 401 Add an OLE container component from the System page of the Component palette to OLEObjectForm and use the Object Inspector to set the following properties of the OLE container component Property Value Name OLEContainer Top 8 Left 8 Height 96 Width 192 OLE application menus The menus of an OLE container application behave like the menus of any other non OLE application until an OLE 2 0 object that supports in place activation is activated If you aren t familiar with designing menus see Chapter 3 When you activate an object created by an OLE 2 0 server application the server might try to merge its menus with the menus of your container application depending on the OLE server application Not
69. bitmaps images shapes copying 355 deleting 355 drawing surfaces See canvases drawing vs painting 314 editing 14 loading 352 pasting 355 printing 351 replacing 353 resizing 58 353 saving 353 string lists and 275 366 367 graphics files 121 122 352 354 graphs 42 318 erids 31 368 calendar 42 color 42 344 data 40 form 52 string See string grids group boxes 39 as containers 47 data aware 40 radio buttons and 38 GroupBox component 39 47 GroupIndex property menus 111 284 402 OLE applications 403 speed buttons 333 grouping components 47 48 grouping speed buttons 333 334 GUI applications 76 See also applications H handlers See event handlers exception handlers handles around components 46 hard disk drives See drives hardware exceptions 238 264 HasAttr function 376 HasFormat method 293 356 Header component 39 headers procedures and functions 185 208 short form 208 units 206 heap 237 Help 2 data types 153 error messages 142 Help buttons 89 296 Help Compiler Microsoft 118 Help files 118 128 specifying 297 HelpContext property 296 hidden images 366 hiding borders 289 hiding tool bars 340 342 hierarchies 13 HLP files 118 horizontal scroll bars 290 I O See input output I O devices 237 ICO files 117 icons 39 42 117 alignment 51 application 94 116 128 child windows and 287 Component palette 38 42 editing 14 OLE objects as 411 414 IDE 28 customizing 123 129 minimizing 32
70. box control named Edit1 and a button control named Button exist on the form the assignment statement runs and the edit box turns red when the user clicks the button Note that the component name precedes the property name with a period separating the component and property If you include the component name with the property there is no confusion as to which Color property should be changed In fact if you omit the component name the color of the form changes when the user clicks the button For more information about this topic see the section Understanding scope on page 177 Assigning values to properties and variables Whether you assign a value to a property or to a variable you follow the same rules The value on the right side of the assignment statement is assigned to the property or variable on the left side of the assignment statement When a value is assigned a copy of the value is placed into the property or variable The value being assigned can be a constant a literal value a variable or another property value For example var Name string Number Integer begin Name Editl Text Assigns a property value to a variable Number 15 Assigns a literal value to a variable Edit2 Text Welcome to Delphi Name Assigns a string made up of a string constant and a variable string to a property end The code example on page 151 shows you how to use an assignment statement to set or
71. change the color of a component 1in this case an edit box in response to a button click Suppose instead that you want the user to be able to use a color grid to change the color of an edit box on a form You want the edit box to change color when the user clicks a color rectangle in the color grid gt Create a form with a color grid and an edit box so that it looks similar to this Figure 5 1 A sample form for assigning a property value to another property Form1 gt Create an event handler for the OnClick event of the color grid 152 Delphi User s Guide procedure TForml ColorGridiClick Sender TObject begin Editl Color ColorGridl ForegroundColor end gt Run the application and click a color on the color grid The assignment statement assigns the value of the ColorGrid1 Foreground property to the Edit1 Color property In other words the color of the edit box control becomes the color the user clicks in the color grid You can assign the value of a property variable constant or literal to a variable or property if the assigned value is of the same type or is assignment compatible with the variable or property receiving the new value To read about type and assignment compatibility see page 157 The type of a property or variable defines the set of values the property or variable can have and the operations your code can perform on it In the previous example both Color a property of the edit box a
72. choose to display in an Image component won t often be the exact size and shape of the component You can resize either the graphic or the component by choosing from the following methods e Use the Delphi Image editor Tools Image Editor to resize the image before importing it into your form e Resize the graphic to conform to the size of the component by setting the Stretch property of the Image component to True Stretch has no effect on the size of icon ICO files e Resize the component to conform to the size of the graphic by setting the component s AutoSize property to True before you load the graphic m To resize a graphic in the form 1 Resize the Image component according to how large or small you want the image to appear in the form 2 With a graphic loaded into the Image component set the Image component s Stretch property to True Graphics that are larger will shrink to fit and those that are smaller will expand to fit the Image component Note ICO file types will not stretch to fill the image area gt Set the Stretch property to True for the Image component in the About box The bitmap stretches to fit the component Figure 2 15 About box with sized image Version a i Product Name Copyright Comments Saving your project Once you ve completed your form layout and property settings you ll probably want to save your work Since you started with a new project you could either
73. chooses File New This instance reads its initial state from the image in the form s DFM file For more information about the DFM file refer to Chapter 1 The following procedure sets the form property for an MDI child window and removes the MDI child form from the form Auto Create list You can set any form s FormStyle property to fsMDIChild however your program won t be compiled correctly if you do so for the application s main form To verify or change the application s main form choose Options Project and select the Forms page Chapter 10 Text editor example 281 E To create an MDI child form 1 Choose File New Form and choose the Blank form option Use the Object Inspector to set the new form s FormStyle property to fsMDIChild Choose Options Project to access the Forms Auto Create list In the Auto Create forms list select the MDI child form Click the gt key to move the MDI child form into the Available forms list and choose OK to exit the dialog box Note The text editor application uses just one type of child form but you can have any number of different types of child windows in an MDI application If your application uses multiple types of child windows you ll generally want to remove them from the Auto create forms list as just described and write code that specifically creates them at runtime If however your application will use only one instance of each type of child form it s probab
74. collection of Form and Project Templates and Experts supplied with Delphi Some versions of Delphi contain more Form Templates and Project Templates than are illustrated in the following figures You can develop your own forms and projects to serve as templates for your applications and add them to the Gallery making it easy to reuse forms or even entire projects in new applications For information on creating form and project templates see Chapter 3 and Chapter 4 The Use On New Form and Use On New Project check boxes in the Gallery group box control whether the Browse Gallery window is displayed when you create a new form or project in the current or future Delphi work sessions Use On New Form option When this item is checked in the Environment options dialog box the Browse Gallery dialog box for forms is displayed whenever you choose New Form from the File menu or Project Manager You can then select from the Form Templates and Experts currently available The new form is then built by the Expert or copied from the template and is ready for you to customize or use as is in your project If this item is not checked in the Environment Options dialog box the Gallery is not displayed when you create a new form and a new blank form is added to the project The Gallery is still accessible through the Options menu however The Forms Gallery is discussed in detail in Chapter 3 This option is enabled by default in a new Delphi installation
75. compiled choose Compile Build All from the Delphi menu bar The result of this command is similar to that of the Compile Compile command except that all units in the project are compiled regardless of whether or not they have changed since the last compile This technique is useful when you are unsure of exactly which files have or have not been changed or when you simply want to ensure that all files are current and synchronized Running a project You can test run a project from within Delphi or you can run the compiled EXE file from the Windows operating environment without having to run Delphi To compile and then run your application from within Delphi e Choose Run Run command from the Delphi menu bar e Choose the Run button on the Delphi SpeedBar These actions are identical to choosing the Compile Compile command except that Delphi runs your application immediately if the compile operation succeeds Executing a project from Windows Because the compiler always creates a fully compiled stand alone executable file EXE you can run your application from the Windows operating environment using the same techniques as you would for any other Windows application Chapter 4 Managing projects files and directories 143 If you have specified an icon for your project it will appear in the Program Manager if you create a Windows program item for your application or if you minimize the application while it is running For
76. compiler options Italicized words in text represent Object Pascal identifiers such as variable or type names Italics are also used to emphasize certain words such as new terms This typeface indicates a key on your keyboard For example Press Esc to exit a menu This symbol indicates the beginning of a procedure The text that follows describes a set of general steps for performing a specified kind of task This symbol indicates a specific action you should take such as a step in an example The Borland Assist program offers a range of technical support plans to fit the different needs of individuals consultants large corporations and developers To receive help with this product send in the registration card and select the Borland Assist plan that best suits your needs North American customers can register by phone 24 hours a day by calling 1 800 845 0147 For additional details on these and other Borland services see the Borland Assist Support and Services Guide included with this product Introduction 3 4 Delphi User s Guide Getting started with Delphi The single chapter making up this part Introducing Delphi introduces the Delphi integrated development environment IDE and discusses basic concepts and techniques for creating Delphi applications Part Getting started with Delphi 5 6 Delphi User s Guide Chapter Introducing Delphi Delphi is a component based application developmen
77. components Right scroll arrow JP EC TESTA eos ol me a eel Standard Additional Data Access Data Controls 4 Dialogs System AWBX 4 Samples Pointer Page tabs Components are the elements you use to build your Delphi applications They include all the visible parts of an application such as dialog boxes and buttons as well as those that aren t visible while the application is running such as system timers or Dynamic Data Exchange DDE servers Delphi components are grouped functionally on the different pages of the Component palette For example components that represent the Windows common dialog boxes are grouped on the Dialogs page of the palette You can create your own custom components and install them onto the Component palette making the Delphi environment fully extensible There is no difference in usability between the components you create yourself and those that ship with Delphi You can also install Visual Basic VBX controls and third party components And the Component palette itself is configurable and scrollable so you can select how you want components to be displayed in the palette The specific components provided with Delphi are discussed in Chapter 2 and in online Help under the search word Component Palette For information about how to configure the palette see Chapter 2 10 Delphi User s Guide Object Inspector Object Inspector Bl Object selector shows na
78. directory initially contains one unit source code PAS file and one associated graphical form DFM file The PAS file contains the source code for the form and its event handlers the DFM file contains binary code that stores the visual image data for the form Chapter 4 Managing projects files and directories 119 Not all unit files need be associated with forms For example if you write your own procedures functions DLLs or components their source code might reside in a separate PAS file that has no associated form The rest of this section explains how to generate a default unit PAS file for each purpose Form associated unit files The type of unit source code file you will probably work with most is the form associated unit This is the type of unit created whenever you open a new form As introduced in Chapter 1 Delphi generates the following code for Unit1 of a default blank project and for every unit with an associated blank form that you add to the project Of course the default unit identifier will be incrementally updated Unit2 Unit3 and so on as you add new forms unit Unitl interface uses SysUtils WinTypes WinProcs Messages Classes Graphics Controls Forms Dialogs type TForml class TForm private Private declarations public Public declarations end var Forml TForml implementation SR DFM end Form unit type declaration The type declaration or class declaration part
79. double clicking the Control menu box closesall open units in the project To close a single page choose Close Page from the Code Editor SpeedMenu Compiling building and running projects All Delphi projects have as a target a single distributable executable file either an EXE or a DLL file You can view or test your application at various stages of development by compiling building or running it You can also test the validity of your source code without attempting to compile the project Checking source code syntax The Compile menu on the Delphi menu bar provides you the option of running a syntax check on your project s source code The checking is identical to that for a compilation and errors in your code generate the same error messages However the process is faster because Delphi makes no attempt to generate object code and if the check succeeds no executable file is generated E Toruna syntax check on your project source code Chapter 4 Managing projects files and directories 141 1 Save the project source code recommended but not required 2 Choose Compile Syntax Check from the Delphi menu bar The hourglass cursor appears to indicate that syntax checking is in progress and returns to normal if the check finds no errors If an error is found The Code Editor window comes to the front The unit source file page containing the error comes to the top of the Code Editor The line containing the error is highli
80. dpr C fixed bmp D floppy bmp C fmxutils pas fmxwin pas C network bmp Drive TabSet DirectoryPanel FilePanel Once you have added all the components and set their properties you should save the project When prompted for names rename Unit1 to FMXWin and Project1 to FilManEx Add FMXtulttils to the uses clause at the top of the FMXWin unit Designing the menu Finally you need to add a menu bar to the form Menu creation is not a major topic of this example however If you do not know how to use the Menu Designer or how to attach event handlers to menu item clicks see Chapter 3 Add a MainMenu component to the application You can place it anywhere on the form but off to the side on the status bar is probably convenient Create a File menu with the Chapter 13 File manager example 361 menu items listed in Table 13 3 Note that this File menu differs from the standard File menu template Table 13 3 File menu items for the file manager example Caption Shortcut amp Open Enter amp Move F7 amp Copy F8 amp Delete Del amp Rename amp Properties Alt Enter lt hyphen gt E amp xit Before proceeding create an OnClick event handler for the File Exit menu item that closes the application s main form procedure TFMForm Exit1Click Sender TObject begin Close end Although you can generally terminate the application by double clicking the Control menu box on the caption bar it s a
81. drawing modes 330 position setting 315 324 styles 342 width 344 period declarations not within scope 178 identifiers and 152 method calls 159 subrange types 197 Picture editor 332 333 Picture Editor dialog box 57 Picture property 349 pictures 117 See also graphics loading 56 57 pie slices 318 pie shaped gauges 42 pixels reading 314 setting 315 Pixels property 314 plus sign concatenating strings 201 pmCopy constant 330 pmNotxXor constant 330 Pointer data type 156 pointer icon 38 pointers 156 237 debugging 262 263 PokeData method 387 PokeDataLines method 387 Polygon method 318 polygons 318 PolyLine method 317 polylines 316 317 poPageNums constant 306 poPrintToFile constant 307 pop up menus 38 See also menus displaying 104 drop down menus and 103 handling events 109 110 294 MDI applications 294 295 PopupMenu component 38 99 109 294 PopupMenu property 295 Pos function 201 poScreenCenter constant 44 poSelection constant 307 predefined procedures and functions 158 predefined types 156 predefined units 206 210 predesigned applications 10 predesigned forms 10 29 adding to galleries 93 126 127 adding to projects 78 79 opening for reference 79 specifying as default 125 predesigned menus 100 106 109 loading 106 predesigned projects 10 115 122 123 adding to galleries 126 127 saving 136 specifying as default 124 preexisting units 135 Preferences page Environment Options 28 32 123 prefere
82. embedded in the Delphi form 2 Drag the OLE object by clicking the mouse button while the mouse pointer is over the selected object in the server and move the mouse pointer over the design time form 3 Drop the OLE object by releasing the mouse button An OLE container is created in the form and it is initialized to contain the dropped OLE object Note For information about initializing OLEContainer components at run time see Chapter 15 OLE data in files If you want to save changes made to an OLE object from within your OLE container application the object data should be saved in a file If the object is linked the data is automatically stored in the original source file and the object is automatically updated every time the data changes Chapter 14 Exchanging data with DDE or OLE 395 If the object is embedded however the original data is stored in the form To save any edits to the embedded object your application must save the data in a special OLE file To update an embedded object that has been saved to a file your application must load the OLE object from the file Otherwise the OLEContainer will contain only the originally embedded OLE object The OLE data file is not in the same format used by the application that created the original OLE object though For example if your container application saves an embedded spreadsheet to a file the OLE server spreadsheet application wouldn t be able to open your file as a s
83. end end Drawing the appropriate shapes Drawing shapes is just as easy as drawing lines Each one takes a single statement and you ve already got all the coordinates you need gt Rewrite the OnMouseUp event handler to draw shapes for all the tools you ve defined procedure TForml FormMouseUp Sender TObject begin case DrawingTool of dtLine Chapter 12 Graphics example 337 begin Canvas MoveTo Origin X Origin Y Canvas LineTo X Y end tRectangle Canvas Rectangle Origin X Origin Y X Y tEllipse Canvas Ellipse Origin X Origin Y X Y dtRoundRect Canvas RoundRect Origin X Origin Y X Y Origin X X div 2 Origin Y Y div 2 Q Q end Drawing False end Of course you also need to update the OnMouseMove handler to draw shapes procedure TForm1 FormMouseMove Sender TObject Shift TShiftState X Y Integer begin if Drawing then begin Canvas Pen Mode pmNotXor case DrawingTool of dtLine begin Canvas MoveTo Origin X Origin Y Canvas LineTo MovePt X MovePt Y Canvas MoveTo Origin X Origin Y Canvas LineTo X Y end dtRectangle begin Canvas Rectangle Origin X Origin Y MovePt X MovePt Y Canvas Rectangle Origin X Origin Y X Y end dtEllipse begin Canvas Ellipse Origin X Origin Y X Y Canvas Ellipse Origin X Origin Y X Y end dtRoundRect begin Canvas RoundRect Origin X Origin Y X Y Origin X X div 2 Origin Y Y div 2 Canv
84. event handlers associated with a menu saved as a template since there is no way to test whether the code would be applicable in the new form When you generate a new event handler for the menu template item Delphi still generates the event handler name You can easily associate items in the menu template with existing OnClick event handlers in the form For more information see Associating a menu item with an existing event handler in the next section Associating menu events with code While you use the Delphi Menu Designer to visually design your application menus the underlying code is what makes the menus ultimately useful Each menu command needs to be able to respond to an OnClick event and there are many times when you want to change menus dynamically in response to program conditions The following topics describe how to associate code with menu events For specific code examples that demonstrate ways to dynamically modify menus in a running application refer to Chapter 10 Menu component events The MainMenu component is different from most other components in that it doesn t have any associated events You can verify this for yourself by adding a menu component to the form and then selecting the Events page of the Object Inspector You access the events for items in a main menu by means of the Menu Designer By contrast the PopupMenu component has one event the OnPopup event This is necessary because pop up menus ha
85. field 274 Delphi User s Guide end var Forml TForml implementation SR DFM procedure TForml FormCreate Sender TObject begin ClickList TStringList Create construct the list end a procedure TForml FormDestroy Sender TObject begin ClickList SaveToFile ChangeFileExt Application ExeName LOG save the list ClickList Free destroy the list object end procedure TForml FormMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin Clickinee Add Foran Click at 60 sdr e Kr as add a string to the list end end Adding objects to a string list Note In addition to its list of strings stored in the Strings property a string list can also have a list of objects which it stores in its Objects property Like Strings Objects is an indexed property but instead of an indexed list of strings it is an indexed list of objects If you re just using the strings in the list it doesn t matter whether you have objects the list does nothing with the objects unless you specifically access them Also it doesn t matter what kind of object you assign to the Objects property Delphi just holds the information you manipulate it as you need to Some string lists ignore added objects because it doesn t make sense to have them For example the string lists representing the lines in a memo do not store objects added to them Other
86. first form displayed in the running application To change the project main form 1 Choose Options Project from the Delphi menu bar to display the Project Options dialog box 2 Select the Forms page of the dialog box 3 In the Main Form combo box select the form you want as the project main form and choose the OK button Now if you run the application your new main form choice is displayed 112 Delphi User s Guide Note Specifying forms to auto create The form you specify as the project main form is always created loaded in memory when the application runs The main form is also the first form loaded unless you specify otherwise in code As you create additional forms for the project these are also auto created at run time This has the advantage of having all forms in the application available to display without writing any code to specifically create the form you still need to show or hide the form However there might be times when you decide you don t want all the forms in an application created in memory when the application first starts running you might prefer to control programmatically when the forms are created For example if there are several different forms that automatically connect to databases you might prefer to create those forms only as necessary You can use the Project Options dialog box to specify which of your application s forms will auto create at run time To specify whether for
87. following steps involved in allowing an OLE server to use the tool bar and status bar of your container application e Setting up tool bars and status bars e Adding the tool bar to the container application e Adding the status bar to the container application Setting up tool bars and status bars Usually you create tool bars and status bars by modifying Panel components When an OLE object is activated in place Panels and any other aligned controls are candidates for client space negotiation with the OLE server This means that the OLE server can replace controls except those that have been locked aligned to any edge of the client area of a form of the OLE container application For example if a Panel is alignedalTop alLeft alBottom or alRight and is not locked the OLE server can replace it If the Panel is aligned alClient or alNone the OLE server will not replace it E To prevent an OLE server application from replacing the tool bar or status bar of an OLE container application lock the tool bar or status bar Panel by assigning True to itsLocked property Adding the tool bar You create a tool bar for OLE in place activation the same way you create a tool bar fora non OLE application If you are unfamiliar with creating tool bars see Chapter 12 for information about this process m To allow an OLE server to replace the tool bar of an OLE container application with its own when an OLE object is activated in place assignalTop a
88. for EIntError came before the handler for ERangeError execution would never reach the specific handler for ERangeError Reraising the exception Sometimes when you handle an exception locally you actually want to augment the handling in the enclosing block rather than replacing it Of course when your local handler finishes its handling it destroys the exception instance so the enclosing block s handler never gets to act You can however prevent the handler from destroying the exception giving the enclosing handler a chance to respond When an exception occurs you might want to display some sort of message to the user then proceed with the standard handling To do that you declare a local exception handler that displays the message then calls the reserved word raise This is called reraising the exception as shown in this example try Statements try special statements except on ESomething do begin handling for only the special statements raise reraise the exception end end except on ESomething do handling you want in all cases end If code in the statements part raises an ESomething exception only the handler in the outer except part executes However if code in the special statements part raises ESomething the handling in the inner except part is executed followed by the more general handling in the outer except part By reraising exceptions you can easily provide special han
89. for pen and brush tool bars continued Component Property Value BrushColor BackgroundEnabled False GridOrdering g08x2 Height 30 Top 5 Width 144 Hiding and showing tool bars Often you want an application to have multiple tool bars but you don t want to clutter the form with all of them at once Or some users might not want tool bars at all As with all components tool bars can be shown or hidden at run time as needed mM To hide or show a tool bar at run time you set its Visible property to False or True respectively Usually you do this in response to particular user events or changes in the operating mode of the application A common practice is to put some kind of close button on each tool bar When the user clicks that button the application hides the corresponding tool bar For this example however you ve already provided a means to toggle these tool bars the pen and brush buttons on the main tool bar Since each click on one of those buttons presses or releases the button you can add a click event handler to each one and show or hide the corresponding tool bar depending on whether the button is up or down procedure TForml PenButtonClick Sender TObject begin PenBar Visible PenButton Down end procedure TForml BrushButtonClick Sender TObject begin BrushBar Visible BrushButton Down end If you run the application now you ll see that the pen and brush tool bars appear and disappear on demand
90. forms and menus 77 To enable or disable the Browse Gallery in the environment 1 Choose Options Environment The Environment Options dialog box appears 2 On the Preferences page check or uncheck the Use On New Form check box as appropriate in the Gallery group box For information on setting Environment Preferences see Chapter 1 When the Browse Gallery for Form Templates is enabled it appears whenever you choose File New Form from the Delphi menu bar or the New Form button on the SpeedBar Adding a template form to a project You can easily add any Form Template from the Delphi Browse Gallery to your application You can also save any form you ve designed as a template that gets installed into the Gallery For more information about saving forms as templates see Saving a form as a template on page 93 E To add a template form to your project 1 With a project open choose File New Form The Browse Gallery dialog box appears with the Blank Form option highlighted by default If another form has been specified as the Default New Form that option is highlighted instead Note Depending on which templates have been installed modified or deleted in your Delphi installation your Browse Gallery window for Form Templates might differ from that shown here Figure 3 1 Standard Delphi Form Templates in the Browse Gallery Browse Gallery ere Password Dialog Tabbed notebook dialog Create a new blank fo
91. from The term single stepping refers to using Trace Into to successively run though the statements in your program code m To issue the Trace Into command choose one of the following methods e Choose Run Trace Into e Press F7 default key mapping e Click the Trace Into SpeedButton Step Over The Step Over command like Trace Into enables you to execute program statements one at a time However if you issue the Step Over command when the execution point is located on a function call the debugger runs that function at full speed instead of tracing into it then positions the execution point on the statement that follows the function call E To issue the Step Over command choose from one of the following methods e Choose Run Step Over e Press F8 default key mapping e Click the Step Over SpeedButton As you debug you can choose to trace into some functions and step over others If you know a function performs as it was designed to you can step over calls to that function with confidence that the function call will not cause an error If on the other hand you aren t sure that a function is well behaved you can choose to Trace Into the function to verify that it works as designed 252 Delphi User s Guide Debugging your application startup code By default when you initiate a debugging session by choosing Trace Into or Step Over Delphi moves the execution point to the first line of code that contains debugg
92. from OLE server applications assign the value of the Msg parameter of the OnStatusLineEvent handler to the Caption property of the status bar panel Write the following event handler for the OnStatusLineEvent event of OLEContainer in OLEObjectForm procedure TOLEObjectForm OleContainerStatusLineEvent Sender TObject Msg String begin OLEFrameForm StatusBarPanel Caption Msg Display Msg in status bar end Save the project now then run it Chapter 15 OLE example 409 The application should look like Figure 15 4 gt Choose File Exit to close the application Figure 15 4 The OLE container application tool bar and status bar OLE Example Inserting objects At this point the OLE example application is ready to contain OLE objects This section describes the following steps involved in inserting OLE objects at run time e Using the Insert Object dialog box e Initializing the OLE container e Deactivating objects Using the Insert Object dialog box To insert an OLE object into an OLEContainer component use the Insert Object dialog box Recall from Chapter 14 that specifying the ObjClass or ObjDoc property of an OLEContainer component at design time displays the Insert Object dialog box At run time the InsertOLEObjectDig function displays the Insert Object dialog box Figure 15 5 shows this dialog box Figure 15 5 The Insert Object dialog box Create New Paradox Table Quattro Pro Graph Quattro P
93. good idea to provide the File Exit option and respond to it by closing down the application Now that you have the application set up the following sections lead you through connecting the controls and updating the status bar Building the drive list When you added the tab set to the form you probably noticed that it didn t have any tabs on it The tab set creates tabs for each item in its list of tabs represented by the Tabs property Initially that list is empty You can edit the list at design time through the Object Inspector but you can also build or change the list at run time In this example you need to build a list of disk drives at run time since you can t e sure at design time what drives will be present at run time Determining valid drives The Windows API provides a function GetDriveType that returns information about the type of a specified drive E To determine whether a drive is valid pass the number of the drive toGetDriveType The return value indicates the type of drive present a return value greater than zero indicates a valid drive Zero or a negative value indicates that the drive is not valid 362 Delphi User s Guide For now you can just check to see if there is a drive of any kind Later on you ll use the information to determine what kind of drive it is Attach the following code to the OnCreate event of the form to build a list of tabs for a tab set when the form is first created The t
94. handler for Edit Insert Object gt Open the Code Editor and write the following InitializeOLEObject method in the implementation part of the OLEOU unit This method is called by an event handler so you won t use the Object Inspector to generate it Note that after initialization the allocated memory is freed with ReleaseOLEInitInfo procedure TOLEObjectForm InitializeOLEObject Info Pointer begin OLEContainer PInitInfo Info Initialize the container by pointing to Info ReleaseOLEInit Info Info end You need to declare InitializeOLEObject in order to call it at run time Add the following line to the private part of the TOLEObjectForm type declaration in the interface part of the OLEObj unit interface type TOLEObjectForm class TForm private procedure InitializeOLEObject Info Pointer Add this line to declare procedure public end 412 Delphi User s Guide Note Next you will attach InitializeOLEObject to the OnClick event for the Edit Insert Object menu item Write the following event handler for the OnClick event of the Edit Insert Object menu item on the OLEObjectForm menu bar procedure TOLEObjectForm InsertObjectiClick Sender TObject var Info Pointer Declare the pointer to the OLE initialization info begin if InsertOLEObjectDlg OLEFrameForm 0 Info then Insert Object dialog box InitializeOLEObject Info Initialize the OLE object end The code to init
95. if needed Note Never destroy the temporary exception object Handling an exception automatically destroys the exception object If you destroy the object yourself the application attempts to destroy the object again generating a fatal application error 240 Delphi User s Guide Warning scope of exception handlers You don t have to provide handlers for every kind of exception in every block In fact you need to provide handlers only for those exceptions you want to handle specially within that particular block If a block doesn t handle a particular exception execution leaves that block and returns to the block that contains the block or to the code that called the block with the exception still raised This process repeats with increasingly broad scope until either execution reaches the outermost scope of the application or a block at some level handles the exception Providing default exception handlers You can provide a single default exception handler to handle any exceptions you haven t provided specific handlers for To do that you add anelse part to the except part of the exception handling block try Statements except on ESomething do specific exception handling code else default exception handling code end Adding default exception handling to a block guarantees that the block handles every exception in some way thereby overriding all handling from the containing block You should probably
96. if statement also includes the else reserved word The statement following else runs if the following tested condition is False Editl Text Saturday The statement in the else part clears the caption as is an empty string Note In the if statement just shown there is no semicolon until the end of theelse part If you put a semicolon before the else part Delphi generates an error 164 Delphi User s Guide Note Note Writing multiple statements within an if statement If you want more than one thing to happen when the tested condition in anif statement is True you can write multiple statements in a begin end block This expanded handler now displays a message and also turns the form yellow procedure TForml OKClick Sender TObject begin if Editl Text Saturday then begin Label2 Caption Why are you working today Forml Color clYellow end else Label2 Caption end Each statement in the begin end block ends in a semicolon When you use multiple statements in the if part of an if statement you still need to remember never to precede the else part with a semicolon That is why no semicolon follows the firstend reserved word in the previous code example You can use multiple statements any place that requires a statement as long as you start the statement part with begin and end it with end Such a statement part is known as a compound statement You can read more about compound statements in Delphi s
97. in a Quattro Pro notebook and store the data in a PChar variable named TheData execute the following code TheData DDEClientConvl RequestData A A 1 A 1 Note The memory for the PChar string returned by RequestData must be freed after your application is finished with it Use the StrDispose function to do this For example after your application has processed TheData you should deallocate it with the following code StrDispose TheData Poking data Poking data means sending data from your DDE client application to the DDE server application directly opposite the usual data flow direction for DDE 386 Delphi User s Guide Note To poke data use the PokeData or PokeDataLines methods of a DDEClientConv component PokeData pokes a PChar string while PokeDataLines pokes a TStrings object The first parameter of PokeData specifies the item of the DDE conversation usually specified in the DDEItem property of the associated DDEClientItem component The second parameter of PokeData is a PChar containing the text to send PokeDataLines functions similarly except its second parameter is of type T Strings Search online Help for PokeData or PokeDataLines for more information about these methods For example to send the text Hello from a DDEClientConv component named DDEClientConvl1 to a linked DDE server execute the following code assuming that TheText is of type PChar StrPCopy TheText Hello DDEClient
98. in more detail in the sections that follow Making forms visible to other forms As mentioned previously adding a form such as a Delphi Form Template discussed later in this chapter to your project adds it to the uses clause in the project DPR file 76 Delphi User s Guide Note but not to the uses clause of any other units in the project Before you can use the new form interactively with other forms in the project you need to add its unit identifier to the uses clause of those forms unit files Enabling forms to reference each other When two forms must reference each other it s possible to cause a Circular reference error when you compile your program To avoid such an error do one of the following e Place both uses clauses with the unit identifiers in the implementation parts of the respective unit files This is the usual means of allowing two forms to reference each other e Place one uses clause in an interface part and the other in an implementation part You rarely need to place another form s unit identifier in this unit s interface part Do not place both uses clauses in the interface parts of their respective unit files This will generate the Circular reference error at compile time Modifying a shared form If you have several projects that all use the same form changes to the shared form that you make in any of the projects show up inall of them This might be your intention If it
99. in the control the control s owner generally the form draws each item at run time The most common application for owner draw controls is to provide graphics instead of or in addition to text for items The Delphi tab set control also has a similar owner draw style Owner draw controls have one thing in common they all contain lists of items By default those lists are lists of strings which Windows displays as text Delphi enables you to associate an object with each item in a list and gives you the chance to use that object when drawing items String lists are explained in more detail in Chapter 9 In general creating an owner draw control in Delphi takes three steps 1 Setting the owner draw style 2 Adding graphical objects to a string list 3 Drawing owner draw items Setting the owner draw style Each control that has an owner draw variant has a property called Style Style determines whether the control uses the default drawing called the standard style or owner drawing For list boxes and combo boxes there is also a choice of owner draw styles calledfixed and variable as Table 13 4 describes Owner draw tab sets are always variable Although Chapter 13 File manager example 365 the size of each row and column in an owner draw grid might vary the size of each cell is fixed before drawing the grid Table 13 4 Fixed vs variable owner draw styles Owner draw style Meaning Examples Fixed Each item is the same
100. indicating which component type it tried to load but could not e Delphi always saves the last version of the component library so if you remove components that you later want to use you can easily revert to the previous version The previous version of the library file is stored with the same name and the extension BAK If you are creating multiple versions of the library you should give each version a distinct name e Always follow the installation instructions that accompany any third party components to ensure they are correctly installed in your system before adding them to a library file e Avoid using the same file name for a library and a project This section discusses the following topics Adding and removing components from the library Handling an unsuccessful compilation Using the Component Expert Using customized libraries 68 Delphi User s Guide Note Note Adding and removing components from the library You add and remove components from the library by adding or removing the unit file associated with the component s This adds the unit to the project or removes it from the project To add components to the component library 1 Choose Options Install Components The Install Components dialog box appears The directory in which the unit resides must be on the search path specified in this dialog box 2 Ifnecessary specify a path to the component unit or choose Add to open the Add Module dialog box
101. like fashion To locate an existing default event handler double click the component in the form Double click Button1 in MainForm The Code Editor opens with your cursor at the start of the first line of code for the Button1 OnClick event handler Modifying an existing event handler Once you know how to locate an event handler in the Code Editor it s easy to modify it For the purposes of the About box for example you might customize the About box caption before calling the ShowModal method to open the dialog box To do so you d add a line of code to the event handler you wrote for the Button1 OnClick event Modify the existing Button1 OnClick default event handler so that it looks like the following procedure TForml ButtoniClick Sender TObject begin AboutBox Caption About Application Title use the application s name About Box ShowModal then open the dialog box end Run the program again The About box caption displays the name of the project file Chapter 2 Using components and code 63 Figure 2 17 About box displaying program name in form title bar About My_proj E E Product Name a rai Version re Copyright Comments Note The Title property for an application which is displayed when the application is minimized as an icon defaults to the name of the project DPJ file However you can change this property by means of the Application page of the Project Options
102. ll generate a range error when you try to run the code containing the assignment If you don t have range checking turned on the code runs but the assigned value won t be what you expect In some cases you can assign values to a variable or property that is within a different category In general this process works only when assigning values from a type of a smaller range to a type of a larger range of possible values For example you can assign a value of type Integer to a property of type Double a type that accepts floating point values making the value now 10 0 You can t assign a Double value to a variable or property of type Integer however because integer values don t have fractional parts When you are unsure which types are compatible you can refer to a complete set of rules for type and assignment compatibility See the topics Type Compatibility and Assignment Compatibility in Delphi s online Help Declaring constants While variables contain values that can change as your application runs constants contain values that can t change Constants are given a value at the time they are declared Just as variables are declared in a variable declaration constants are declared in a constant declaration A constant declaration begins with the reserved word const This example declares three constants const Pi 41 bo Answer 342 ProductName Delphi Pi Answer and ProductName are all constant names that descr
103. local as possible This protects you from forgetting where a variable is used and getting side effects you don t want when your code changes the value of the variable Therefore the first method discussed earlier is probably the best choice You should consider variables with a broader scope only when your application needs to share data between different blocks Because the code now can access the necessary variables regardless of which method you chose the example works correctly almost If the FirstNumber value isn t evenly divisible by the SecondNumber value the fractional part of the result is discarded because the example is using only integer values 180 Delphi User s Guide Redeclaring identifiers in a different scope It s perfectly legal to declare an identifier in more than one place in your application as long as the scope of the identifier differs The compiler always accesses those variables that are the most local in scope This section has already discussed how two event handlers can declare the same variables FirstNumber and SecondNumber Because any identifiers declared within MultiplyClick and DivideClick are not within the same scope the two can have identifiers with the same name declared within them If First Number were declared globally within the scope of the unitand also declared locally within the scope of an event handler within the unit your application would compile without problems The compiler
104. location If you open the project at the backup location all the project files that reside within that structure are present and the project will compile If this project uses files that reside outside this tree the project might or might not compile at the backup location Check the Project Manager s file list to see if these outside files are accessible from the backup location If they are the project will compile If other backup processes already preserve these outside files then there is probably no need to make separate backup copies of them in the backup project directory Navigating among project components As you work on a project you will find that you frequently need to navigate back and forth among forms units and the various open windows such as the Project Manager Alignment Palette and so on This section explains the basic techniques involved Viewing forms and units You can easily toggle between viewing the currently displayed form and its unit source code by using commands from the View menu a keyboard shortcut or the Project Manager You can also view or edit any open unit or form by choosing commands from the View menu buttons on the Project Manager SpeedBar or commands from the Project Manager SpeedMenu Chapter 4 Managing projects files and directories 139 Toggling between form image and unit source code m To switch between viewing the current form and its unit source code use any of the followin
105. macro sent from the DDE client Search online Help for OnMacroExecute for more information about this event Mm To create a DDE server using a DDEServerConv component 1 Add DDEServerltem component and a DDEServerConv component to a form 2 Assign the name of the DDEServerConv component to the ServerConv property of the DDEServerltem component 388 Delphi User s Guide At design time choose this value from a list of possible conversations for ServerConv in the Object Inspector To establish this link at run time your application should execute code that assigns the value to the ServerConv property For example the following code links a DDEServerltem component named DDEServerItem1 to a DDEServerConv component named DDEServerConvi DDEServerIteml ServerConv DDEServerConvl1 Establishing a link with a DDE client application Typically it is up to the DDE client to establish the link with a DDE server application If you want to test a link from your DDE server you can use the Clipboard to paste a link To establish a DDE link 1 Use the CopyToClipboard method of the DDEServerltem component to copy the value of the Text or Lines property along with DDE link information to the Clipboard 2 Insert the linked data into the DDE client application Typically do this by choosing the appropriate command such as Edit Paste Special or Edit Paste Link of the client application Search online Help for CopyToClipboard for mo
106. make the Windows common dialog boxes available to your Delphi applications These dialog boxes provide all Windows based applications with a familiar consistent interface that enables the user to perform common file operations such as opening saving and printing files Each dialog box opens when its Execute method is called Execute returns a Boolean value if the user chooses OK to accept any changes made in the dialog box Execute returns True if the user chooses Cancel to escape from the dialog box without making or saving any changes Execute returns False This section discusses the following topics Common dialog box options in the Object Inspector Using the OpenDialog component Using the Save dialog box Saving the text file Using the Font dialog box Changing the font in the Memo component Chapter 10 Text editor example 295 Common dialog box options in the Object Inspector In Delphi s implementation of the common dialog boxes each dialog box with the exception of the Printer Setup dialog box includes an Options property The available settings are presented as nested properties under the Options property For example the following figure shows the nested Options settings for the Font dialog box Figure 10 5 Font dialog box component options Object Inspector Fonoi E Name FontDialog _ Options fd4nsiOnly False fdTrueTypeO False fdE ffects True fdFixedPitchC False fdForceFontE False fd
107. menu component s OnPopup event with the SetEditItems event handler The text editor however keeps each event handler 294 Delphi User s Guide separate for the purpose of clarity When the code is simple enough that duplicating it isn t a serious obstacle sometimes it makes more sense to give distinct procedures their own names This is one such example gt Generate anew event handler called SetPopupltems for the PopUpMenu component s OnPopup event that calls the UpdateMenus procedure procedure TEditForm SetPopUpItems Sender TObject begin UpdateMenus end Specifying the pop up menu for the form If you ran the application now and tried to access the pop up menu by right clicking in the memo nothing would happen That s because you haven t told the form which pop up menu to call in response to the right click The form has a PopupMenu property which you can use to specify which pop up menu the form should call gt From the Object selector select EditForm and set its PopupMenu property to PopupMenut1 Try running the application again choose File New and right click in the new child window The pop up menu appears and is fully functional Note that because no text is selected the Cut and Copy items appear dimmed The condition of the Paste item indicates whether any text exists on the Windows Clipboard Using common dialog boxes The dialog box components on the Dialogs page of the Component palette
108. more information see online Help Managing multiple project versions and team development When you are developing a complex programming project in a team setting or managing several development projects you might soon develop the need for a version control system VCS A version control system can archive files control access to project files and track multiple versions of your projects Delphi Client Server has a built in interface for Intersolv s PVCS Version Manager available separately It supports PVCS version 5 1 and later Because Delphi uses an Open Tools API it can also be used with any commercially available version control utility Enabling team development support Before using Delphi s built in team development support you need to have PVCS installed on your system and the following files must reside in your WINDOWS SYSTEM directory e PVCSVMW DLL e NWNETAPLDLL If running on a Novell network otherwise use the appropriate network support DLL as specified in PVCS documentation Consult your PVCS documentation for complete details on installing and setting up that product E To enable team development support in Delphi 1 Exit Delphi 2 Add the following lines to the DELPHIINI file located in your WINDOWS directory Version Control VCSManager c delphi bin stdvcs dll Note If the location of the DELPHI BIN directory on your system is different from that shown modify the VCS manager line to inclu
109. most likely use these techniques in other kinds of applications but by seeing these items in the context of complete applications you can better see how to integrate them into your own You can use the chapters in this part in several ways to learn to build complete applications to see how to use particular components or to see how to perform a specific task with a component The sample applications in this part describe the following skills e Using string lists This chapter presents various skills for using string list objects which appear in the text editor example and the file manager example e Text editor example This chapter demonstrates the creation and seamless integration of Multiple Document Interface MDI applications fundamental concepts and techniques for displaying and manipulating text e Using graphics at run time This chapter discusses concepts and techniques for creating graphics applications in Delphi Encapsulation of Windows GDI functions in the Delphi Canvas Part IV Sample applications 267 e Graphics example This chapter features an extension and practical application of the techniques presented in Chapter 11 including dynamic creation of tool bars and use of the pen and brush e File manager example This chapter demonstrates such concepts as building a drive list creating owner draw controls manipulating files using drag and drop techniques using file controls and
110. moving among windows 140 starting 8 identifiers See also naming constants 157 335 data types 186 335 declaring 153 157 189 as enumerated types 196 defined 153 duplicate 181 223 file attributes 372 global 177 181 183 invalid 101 local 177 180 objects and 222 223 period in names 152 qualifying 152 restrictions 154 scope 177 183 redeclaring 181 unknown 159 179 valid characters 154 variables 154 if reserved word 163 else reserved words and 164 if statements 163 166 case statements vs 166 else reserved word and 164 nesting 165 166 ifdef conditional directive 143 Ignore buttons 89 illegal typecasting 238 Image component 39 56 348 350 Image Editor 14 Image Library 128 images 117 314 See also graphics changing 353 data aware 40 drawing large 348 erasing 355 hidden 366 loading 56 57 redrawing 316 regenerating 317 resizing 58 saving 353 implementation reserved word 187 207 208 form references and 77 uses reserved word and 209 in operator 204 incorrect output 248 incremental values 42 example 171 indenting code 150 165 Index 441 indexes 199 See also arrays defined 199 range errors 243 string lists 270 275 276 string values 201 IndexOf method 270 Information command Compile 143 Information dialog box 143 inheriting from objects 219 222 initialization reserved word 208 210 initializing applications 116 array elements 200 data 208 210 objects 336 OLE containers 412 413 415 422 in
111. need to construct the list when the application is first executed then destroy it before the application is terminated E To create a string list that s available throughout run time 1 Add a field of type TStrings to the application s main form object giving it the name you want to use 2 Create a handler for the main form s OnCreate event The create event handler executes before the form appears onscreen at run time 3 In the create event handler construct the string list object 4 Create a handler for the main form s OnDestroy event The destroy event handler executes just after the main form disappears from the screen before the application stops running Any other event handlers can then access the string list by the name you declared in the first step This example features an added string list named ClickList The click event handler for the main form adds a string to the list every time the user clicks a mouse button and the application writes the list out to a file before destroying the list unit Uniti interface uses SysUtils WinTypes WinProcs Messages Classes Graphics Controls Forms Dialogs type TForml class TForm procedure FormCreate Sender TObject procedure FormDestroy Sender TObject procedure FormMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer private Private declarations public Public declarations Clickhists TStrings declare the
112. never use this all encompassing default exception handler The else clause handles all exceptions including those you know nothing about In general your code should handle only exceptions you actually know how to handle In other cases it s better to execute cleanup code and leave the handling to code that has more information about the exception and how to handle it Handling classes of exceptions Because exception objects are part of a hierarchy you can specify handlers for entire parts of the hierarchy by providing a handler for the exception class from which that part of the hierarchy descends The following block outlines an example that handles all integer math exceptions specially try statements that perform integer math operations except on EIntError do special handling for integer math errors end You can still specify specific handlers for more specific exceptions but you need to place those handlers above the generic handler because the application searches the handlers in the order they appear in and executes the first applicable handler it finds For example this block provides special handling for range errors and other handling for all other integer math errors Chapter 7 Writing robust applications 241 try statements performing integer math except on ERangeError do out of range handling on EIntError do handling for other integer math errors end Note that if the handler
113. of a memo control named Memo1 Memol CutToClipboard 158 Delphi User s Guide Note that the name of the control Memo1 is part of the method call By including the name of the control you are specifying which CutToClipboard method you want to call Separate the name of the control from the method call with a period If you omit the name of the control component or object in a method call Delphi usually displays this syntax error Unknown identifier When your application calls Memo1 CutToClipboard the code within the CutToClipboard method runs and the user s selected text is cut to the Clipboard object Cut Copy Paste and Clear All An example This is an example that calls procedures in the Delphi library This is how the finished form for the example should look Figure 5 2 A sample form for the Cut Copy Paste and Clear All example Form Start by opening a new project choose the Blank form template if necessary and adding a memo control and four buttons to a form Use the Object Inspector to change these property settings e Name the buttons Cut Copy Paste and ClearAll by changing their Name properties Be sure you change the Name property and not the Caption property or the event handlers Delphi creates for you won t have the same names as they do in this example e Delete the text in the Text property of the memo control e Set the WordWrap property of the memo control to True e Set the Scr
114. on the right hand side Elements not visible upon starting Delphi The following elements of the Delphi interface are not visible when you first start Delphi but you can access them quickly from the menu bar Project Manager Remove file from project View unit View form Add file to project Projecti a Project Update Status line i HM ainform AboutBox Unit name Project column actions Form name column Unit file path The Delphi Project Manager lists the files that make up your application and enables you to easily navigate among them You can use buttons on the Project Manager SpeedBar to generate new forms and units to view files in the current project and to 12 Delphi User s Guide save modifications to all opened project files Units are discussed in more detail on page 24 for more detailed information about the Project Manager see Chapter 4 To display the Project Manager choose View Project Manager Menu Designer Form1 MainMenul Menu item Menu commands appear below menu items The Delphi Menu Designer enables you to easily add menus to your forms You open the Menu Designer by double clicking on a MainMenu or PopupMenu component found on the Standard page of the Component palette after placing the component on a form Once the Menu Designer is opened you can create your own custom menus or use the predefined menu templates provided with Delphi to insert ready made menus into your applicat
115. open the Gallery Options dialog box choose Options Gallery Specifying the default new project The default new project opens whenever you choose New Project from the File menu on the Delphi menu bar In a new Delphi installation the Blank Project template is the default You can specify any other Project Template including a project you have created and saved as a Project Template as the default new project Alternatively you can designate a Project Expert to run by default when a new project is begun Specifying a Project Template E To specify a Project Template as the default new project 124 Delphi User s Guide Choose Options Gallery to display the Gallery Options dialog box Choose the Project Templates page tab Select the project template you want as the default new project Aa Ga N With the template you want selected choose the Default Project button The folder icon appears in the box for the selected default project 5 Choose OK to register the new default setting Specifying a Project Expert A Project Expert is a program that enables you to build a project based on your responses to a series of dialog box options Instead of opening a Project Template by default when you begin a new project you can run a Project Expert instead To specify a Project Expert as the default new project 1 Choose Options Gallery 2 Choose the Project Experts page tab 3 Select the box displaying the Project Expert you w
116. picture You ve created the placeholder but haven t given it anything to display If the control will always hold a particular picture you can set the image control s Picture property at design time The control can also load its picture from a file at run time as described later in this chapter If you just need a blank bitmap for drawing however you should create it at run time To create a blank bitmap when the application starts attach a handler to the OnCreate event for the form that contains the image create a bitmap object and assign it to the image control s Picture Graphic property For the graphics example the image is in the application s main form Form1 so attach a handler to Form1 s OnCreate event procedure TForml FormCreate Sender TObject var Bitmap TBitmap temporary variable to hold the bitmap begin Bitmap TBitmap Create construct the bitmap object Bitmap Width 200 assign the initial width Bitmap Height 200 and the initial height Image Picture Graphic Bitmap assign the bitmap to the image control end Assigning the bitmap to the picture s Graphic property gives ownership of the bitmap to the picture object It will therefore destroy the bitmap when it finishes with it so you should not destroy the bitmap object You can assign a different bitmap to the picture as you ll see later in this chapter on page 353 at which point the picture disposes
117. predesigned 10 robust 231 sample 267 scrollable regions 348 server See DDE applications OLE applications specifying icons 94 starting 119 testing 141 143 248 version control 94 144 word processing 280 Archive Manager command Workgroups 144 arcs 318 arguments See parameters arranging icons child windows 287 array types 199 203 432 Delphi User s Guide arrays 199 203 See also indexes accessing elements 199 character 200 203 debugging 260 263 declaring 200 as types 199 defined 199 initializing 200 multidimensional 200 pixel 314 315 string 171 270 zeroing 199 as modal form 86 as operator 238 as reserved word 228 ASCII characters 156 debugging 262 ASCII text files reading from 95 saving forms as 94 assigning icons to forms 94 assigning types 157 constants 158 variables 154 assigning values 151 153 See also setting property values fields in records 205 functions 161 186 placing limits 197 to strings 200 type compatibility and 157 zeros to arrays 199 assignment operator 151 equal operator vs 158 assignment statements 151 153 199 enumerated types and 195 function calls 161 object variables 226 type compatibility 157 AssignPrn procedure 305 307 associating bitmaps with strings 275 276 366 at reserved word 245 attributes See also properties file 371 373 376 reading 371 setting 373 AutoActivate property 412 414 auto creating forms at run time 113 114 automatically opening files 375
118. previously saved by checking for an existing value of Filename Recall that the code written so far assigns a value to Filename if the user opens an existing file Otherwise Filename remains empty If the user selects Save for an existing file Save1Click calls the nested procedure CreateBackup which creates a backup version of the file This is described in the next section The remaining code inSave1Click then saves the file by calling the SaveToFile method If Filename is empty or null Save1Click calls the event handler for the Save As menu item click SaveAs1Click SaveAs1Click saves the file using the file name that the user specifies in the Save As dialog box Note The user must enter a file name or the Save As dialog box does not close when the user chooses OK This is a function of the dialog box not of the event handler code gt First write the method for the EditForm File Save As click event procedure TEditForm SaveAsiClick Sender TObject begin SaveFileDialog Filename Filename display current value of Filename if any if SaveFileDialog Execute then begin Filename SaveFileDialog Filename Caption ExtractFileName Filename SavelClick Sender end end If the file has already been named when the user selects Save As SaveAs1Click displays the existing name in the File Name field of the Save As dialog box Otherwise what s displayed there corresponds to the Filters property of the dialog box
119. related procedures functions and data types If you do want to include initialization code add the initialization reserved word and put the initializing code between between initialization and end When you choose to compile or build your project the new units you added are compiled into files with DCU file extensions When the MYUNIT PAS file is compiled for example the resulting file is MYUNIT DCU This newly created file is machine code that is linked into your project executable file Adding an existing unit to a project If you want to use a unit that is already complete whether it is a unit Delphi created that is associated with a form or whether you or someone else wrote the unit from scratch you can simply add it to your project E To add an existing unit to your project 1 Open the project you want to add the unit to 2 Choose File Open File select the source code the PAS file of the unit you want added and choose OK Summary This chapter presented these topics e Writing readable code It doesn t matter to the compiler how you space indent or capitalize your code or where you break lines of code As long as the syntax of your code is correct the compiler can handle it You should however choose a style that makes your code easily readable by you and others Enclose all comments in your code within braces Q e Writing assignment statements Assignment statements assign the value on the right side
120. rules for naming Object Pascal identifiers If you enter a value that is not consistent with Object Pascal naming requirements the name reverts to its previous value and Delphi displays the following error message lt name gt is not a valid component name For more information about Object Pascal naming conventions see Chapter 5 Caution As mentioned in Chapter 1 so long as you use the Object Inspector to change a component s Name property Delphi maintains your changes in the underlying code This is not the case however if you edit the component name yourself by typing the change directly into the Code Editor If you manually edit a component name Delphi will be unable to load your form Adding components to the form When you add components to the form you can either accept the default component size or resize the component as you add it You can also easily add multiple copies of a component E Toaddacomponent to the center of the form simply double click the component in the Component palette If there are already components in the form additional components are offset lower and to the right as you add them so all the components remain at least partially visible E Toaddacomponent to a specific location in the form 1 Click the component on the Component palette 2 Move the cursor to where you want the upper left corner of the component to appear in the form then click the form 44 Delphi User s Guide
121. s not however there are several ways to prevent this You can e Save the form under a different name and use the renamed form in your project instead of the original This is similar to using a Form Template in your project e Make the changes to the form at run time instead of at design time as discussed in Chapter 2 e Make the shared form a component that can be installed onto the Component palette This has the added advantage of enabling users to customize the form at design time For more information see the Delphi Component Writer s Guide If you expect to be the only user of the form and you don t plan extensive or frequent changes run time customization is probably acceptable If you plan on using the form in many different applications run time customization involves more coding for you and other developers In this case it s usually more convenient whenever possible to make the form a component that other users or developers can install onto their Component palette You can also reuse a form by making it into a DLL For more information see the Delphi Component Writer s Guide Using the Form Templates of the Browse Gallery As mentioned earlier the easiest way to share and reuse forms within and among Delphi projects is to use the Form Templates of the Delphi Browse Gallery The Browse Gallery for Form Tempaltes is enabled in a default Delphi installation but you can choose to disable it Chapter 3 Building
122. save the entire project or just the form E To save just the form and its associated unit file choose File Save File m To save the entire project choose File Save Project gt Choose File Save Project 58 Delphi User s Guide You re prompted for a name for each unit form in the project and for the project file itself If you rely on the form and unit names that Delphi generates automatically you are likely to experience name conflicts when you reuse those forms and units On the other hand if you assign descriptive names like AboutBox you greatly reduce the likelihood of putting two like named forms into the same project You can never be sure what names the forms and units in future projects will have but if you consistently use descriptive names it s much easier for you and other developers using your forms to find and use them without conflicts Use the following names Default name Change to UNIT1 PAS ABOUT PAS UNIT2 PAS MAINFORM PAS PROJECT1 DPR MYPROJ DPR Each file must have a unique prefix even though their extensions can be different For example if you specify About as the file name for both the form and project file Delphi displays the following error message The project already contains a module named About If you see this error message Delphi won t save the project file or whichever file you named secondly Simply rename the file by saving it again with a different name Setting proper
123. scopes 5 6 s Be te P eA Se eS 222 Accessing components on another form 223 Scope and descendants of an object 223 Overriding a method 223 Public and private declarations 224 Accessing object fields and methods 225 Assigning values to object variables 226 Creating nonvisual objects 228 Creating an instance of an object 229 Destroying your object 229 EOIN AY aaa a ed Gi IO eae Save rer 230 Chapter 7 Writing robust applications 231 Protecting blocks of code 231 Responding to exceptions 232 Executing cleanup code 232 Handling the exception 232 Exceptions and the flow of execution 232 Nesting exception responses 233 Protecting resource allocations 234 What kind of resources need protection 234 Creating a resource protection block 235 Handling RTL exceptions 236 What are the RTL exceptions 236 Creating an exception handler 239 Providing default exception handlers 241 Handling classes of exceptions 241 Reraising the exception 242 Handling component exceptions 242 Silent exceptions 4 4 4 see 4 ee Sw a 243 Defining your own exceptions 244 Declaring an exception object type 244 Raising anexception 244 Setting the exception address 244 SUNAY 3s e uoe E
124. settings to place an upper or lower limit on the number of pages the user can specify in the Pages From and To edit boxes Note that any setting you make does not change what s displayed in the dialog box If the user enters a number outside the range you specify and then presses Enter the application displays an error message that says From or To value is below or above the minimum or maximum range Options poPageNums A value of True enables the Pages From and To radio buttons so the user can specify a page range For example you might set this to True at run time once you ve determined that more than one page exists in the current document 306 Delphi User s Guide Options poPrintToFile A value of True adds the Print To File check box to the dialog box Your application code must provide the actual capability of printing to a file Options poSelection A value of True enables the Selection radio button so the user can print selected text For example you might set this to True at run time once you ve determined that selected text exists in the current document PrintRange The Print Range settings specify what appears as the Print Range default when the dialog box first opens For example a setting of PrintRange prPageNums specifies that the Pages radio button is selected instead of the All radio button AllPages is the default setting Note that in order for either of the two non default settings to
125. should deallocate the memory set aside for the OLE initialization information by calling the ReleaseOLEInitInfo procedure To enable the user to select an OLE object from the Insert Object dialog box use the InsertOLEObjectDlg function to call the Insert Object dialog box You ll write the code to do this in the next section but you should first have an understanding of the options available in this dialog box e To embed an object that has already been created and saved in a file by the OLE server the user chooses Create From File specifying the file name and path to the OLE object file e To link an object that has already been created and saved in a file by the OLE server the user follows the previous step also selecting the Link check box e To embed a new object the user chooses Create New and selects an OLE object type from the Object Type list The user cannot link a new object as it has not yet been saved as a file e To display the linked or embedded object as an icon the user checks the Display As Icon check box The Change Icon button appears when Display As Icon is checked e To change the default icon or the label of the OLE object the user chooses Change Icon When the user chooses OK to close the Insert Object dialog box InsertOLEObjectDlg returns True It then stores the information necessary to initialize the OLE container in the data structure pointed to by the PInitInfo parameter Chapter 15 OLE exampl
126. string Row plus the current value of the Row variable in the column 0 once the value of Row is converted to a string for Row 1 to 5 do StringGridl Cells 0 Row Row IntToStr Row Chapter 5 Writing Object Pascal code 173 The fourth for statement is nested within the third for statement Together the two for statements display each cell s column and row coordinates within the cell for Col 1 to 5 do for Row 1 to 5 do StringGrid1 Cells Col Row Col IntToStr Col Row IntToStr Row Col receives the initial value of 1 indicating the first scrolling column of the grid Before the for statement actually does something the second for loop begins Row is assigned the initial value of 1 indicating the first row of the scrolling column of the grid The code then writes a string in the column 1 and row 1 The string consists of the substring Col the string value of the Col variable the substring the substring Row and the string value of the Row variable The actual value in Cells 1 1 is this string Col 1 Row 1 The code continues to execute the nested for loop moving to the next row within the same column as the value of the Col variable is still 1 The nested for loop ends when the value of Row has increased from 1 to 5 and a value is written within each row of column 1 Then the third for loop continues to run as the Col variable is assigned the next highest
127. string lists such as the pages in a notebook already use their associated objects as part of their standard operation The Notebook component uses its Pages string list to store both the names of the pages and the objects that represent those pages Although you can assign any type of objects you want to Objects the most common use is to associate bitmaps with strings for owner draw controls The important thing to remember is that strings and objects in a string list work in pairs For every string there is an associated object although by default that object is nil Chapter 13 includes an example of how to associate objects with strings and use them in an owner draw control Chapter 9 Working with string lists 275 It s important to understand that the string list doesn t own the objects associated with it That is destroying the string list object does not destroy the objects associated with the strings Operating on objects in a string list For each of the operations you can perform on a string list with a string you can perform the corresponding operation with a string and its associated object For example you can access a particular object by indexing into the Objects property just as you would the Strings property The biggest difference is that you cannot omit the name Objects since Strings is the default property of the string list The following table summarizes the properties and methods you use to perform correspond
128. support in place activation are activated in place Chapter 14 Exchanging data with DDE or OLE 391 Linking and embedding Data in a linked OLE object is stored in a file by the OLE server that created it Data in an embedded OLE object is stored in the OLE container application Here are guidelines for when to link or to embed OLE objects When to link You want to be able to make changes to the original object and have those changes reflected in all applications or documents linked to that original The original object is likely to be frequently modified or modified from multiple OLE container applications The original object file is unlikely to be frequently moved and won t be deleted The object is large and you will be distributing it via a network or electronic mail You need to conserve disk space by having only one copy of the object Linked objects When to embed You want to be able to make changes to the object and have those changes reflected only in one particular application or document The original object is unlikely to be frequently modified or modified from only one instance of an OLE container application The original object file is likely to be frequently moved or possibly deleted The object is small or when the object is large but you won t be distributing it via a network or electronic mail You don t need to conserve disk space by having only one copy of the object Linked ob
129. system for you In addition the FMXUtils unit in the directory with the file manager sample application provides some supplementary routines useful for this example Previous versions of the Pascal language perform similar operations on files themselves rather than on file names That is you have to locate a file and assign it to a file variable before you can for example rename the file By operating at the higher level Object Pascal reduces your coding burden and streamlines your applications The lower level functions are still available but you shouldn t need them as often These are the file manipulations that Object Pascal handles for your applications e Deleting a file e Changing a file s attributes e Moving copying and renaming files e Executing an application The file manager example attaches all these operations to items on the File menu Before attaching functions to the menu items though it s a good idea to make sure those items are available only when you have a file selected Otherwise you would have to check whether a file was selected each time you performed one of those functions It s much Chapter 13 File manager example 369 easier and more efficient to ensure that menu items and controls are enabled only when the user can actually use them gt To selectively enable and disable items on a menu attach a handler to the OnClick event for the File item on the main menu bar procedure TFMForm Fi
130. tab AddedIndex DriveTabSet Tabs AddObject DriveLetter Floppy Picture Graphic DRIVE_FIXED add a tab AddedIndex DriveTabSet Tabs AddObject DriveLetter Fixed Picture Graphic DRIVE REMOTE add a tab AddedIndex DriveTabSet Tabs AddObject DriveLetter Network Picture Graphic end if UpCase DriveLetter UpCase DirectoryOutline Drive then current drive DriveTabSet TabIndex AddedIndex then make that current tab end end Drawing owner draw items When you set a control s style to owner draw Windows no longer draws the control on the screen Instead it generates events for each visible item in the control Your application handles the events to draw the items To draw the items in an owner draw control follow these steps The steps are repeated for each visible item in the control but you use a single event handler for all items 1 Size the item If the owner draw items are all the same size for example with a list box style of IsOwnerDrawFixed you don t need to do this step 2 Draw the item Sizing owner draw items Before giving your application the chance to draw each item in a variable owner draw control Windows generates a measure item event The measure item event tells the application where the item will appear on the control Chapter 13 File manager example 367 Windows determines what size the item will probably be generally just large enough to display the item s tex
131. take effect in the dialog box the corresponding Options setting must be True For example if you set PrintRange to prSelection without also setting Options Selection to True the dialog box still opens with the default Print Range setting of AllPages Using the Printer Setup dialog box component ChangeDefault is the only property displayed in the Object Inspector for the Printer Setup dialog box component that interacts with the dialog box in the running application The run time value of this property changes to True when the user selects a different printer setup The remaining settings in this dialog box and in the Options and Advanced Options dialog boxes write to and read from settings in the user s WIN INI file Therefore you won t write much code that interacts directly with this component other than launching it All the functions it provides after that are handled by Windows Handling the File Print Setup OnClick event The File Print Setup OnClick event handler simply calls the Print Setup dialog box Write the following handler for the EditForm File Print Setup OnClick event procedure TEditForm PrintSetUpiClick Sender TObject begin PrinterSetupDialogl Execute end Directing your text file to the printer The next few sections describe the parts of code that make up the File Print OnClick event handler You ll see how to write the complete event handler in Printing the contents of the memo on page 308
132. template applications provided with Delphi For the next sample application you ll start a blank project To start this project choose File New Project Depending upon the configuration of the environment one of two things can happen e Anew instance of the project designated in the environment as the Default New Project is generated This is a blank project unless you or another user have configured the Gallery differently using Options Gallery e If the Projects Gallery is enabled in the environment the Browse Gallery dialog box appears with the Blank Project option selected as illustrated in the following figure Figure 1 4 Browse Gallery dialog box displaying application templates Browse Gallery Blank project MDI Application SDI Application Creates a new blank project Templates Chapter 1 Introducing Delphi 19 gt Choose one of the following options e If you have an existing project open but you are not using the Gallery you ll be prompted to save changes Choose No A blank form is displayed just as when you first opened Delphi e If you are using the Gallery double click the Blank Project selection and choose not to save changes to any open project A blank form is displayed just as when you first opened Delphi For this application you ll use two Button components an Edit component and a ListBox component Add the components to the form and set any properties as noted in
133. than in place Also shifting focus to a menu item does not deactivate an OLE object Another way to deactivate an in place active OLE object is to set the value of the Active property of the OLEContainer component to False In the sample application use the Object Deactivate menu command from the menu bar of OLEObjectForm to do this Recall that the Object menu was given aGroupIndex property value of 2 so it is still available when an OLE server merges menus with the OLE container application Write the following event handler for the OnClick event of the Object Deactivate item on the OLEObjectForm menu bar Chapter 15 OLE example 413 procedure TOLEObjectForm DeactivatelClick Sender TObject begin OLEContainer Active False Deactivate the OLE object end gt Save the project now then run it 1 Choose File New to display an OLE Object window 2 Choose Edit Insert Object to display the Insert Object dialog box 3 Choose an object to link or embed then choose OK 4 If the object is activated in place choose Object Deactivate to deactivate an OLE object If the object is activated in its own window rather than in place choose File Exit or its equivalent in the command structure of the OLE server application to deactivate the object The OLEContainer is initialized and contains a picture representing the OLE object For example if you chose to insert a Windows Paintbrush picture object the OLE Objec
134. the breakpoint is encountered However using the Edit Breakpoint dialog box you can customize your breakpoints so that they are activated only when a specified set of conditions is met Use the integrated debugger to add two types of conditions to your breakpoints e Boolean expressions e Pass counts Setting Boolean conditions The Condition edit box in the Edit Breakpoint dialog box lets you enter an expression that is evaluated each time the breakpoint is encountered during the program execution If the expression evaluates to True or not zero then the breakpoint pauses the program run If the condition evaluates to False or zero then the debugger does not stop at the breakpoint location Conditional breakpoints are useful when you want to see how your program behaves when a variable falls into a certain range or what happens when a particular flag is set For example suppose you want a breakpoint to pause on a line of code only when the variable mediumCount is greater than 10 To do so 1 Seta breakpoint on the line of code you want by moving the text cursor to that line of code in the Code Editor and pressing F5 2 Open the Breakpoint List window by choosing View Breakpoints 3 Highlight the breakpoint just set and choose Edit Breakpoint from the SpeedMenu The Edit Breakpoint dialog box opens Chapter 8 Using the integrated debugger 257 4 Enter the following expression into the Condition edit box mediumCount gt
135. the Component list select the menu you want to edit 3 On the Properties page of the Object Inspector select the Items property for this menu and then either click the ellipsis button or double click Menu Using menu templates Delphi provides several predesigned menus or menu templates that contain frequently used commands You can use these menus in your applications without modifying them except to write code or you can use them as a starting point customizing them as you would a menu you originally designed yourself Menu templates do not contain any event handler code The menu templates shipped with Delphi are stored in the DELPHI BIN directory in a default installation These files have a DMT Delphi menu template extension You can also save as a template any menu that you design using the Menu Designer After saving a menu as a template you can use it as you would any predesigned menu If you decide you no longer want a particular menu template you can delete it from the list E To add a menu template to your application 106 Delphi User s Guide 1 Right click the Menu Designer window The Menu Designer SpeedMenu appears 2 From the SpeedMenu choose Insert From Template If there are no templates the Insert From Template option appears dimmed in the SpeedMenu The Insert Template dialog box opens displaying a list of available menu templates Figure 3 17 Sample Insert Template dialog box for menus
136. the application Each section of this chapter builds upon preceding sections but the steps themselves are modular and can be used in a different context to achieve the same result If you want to learn how to load a text file for example you don t need to read the section on creating an MDI editor window first To see the completed application open the project file TEXTEDIT DPR found in the DELPHI DEMOS DOCS TEXTEDIT directory if you installed Delphi using default directories Figure 10 1 shows the application as it appears the first time a new window is opened Chapter 10 Text editor example 279 Figure 10 1 The finished text editor program TEXTEDIT EXE Text Editor File Edit Character Window Multiple Document Interface MDI applications Multiple Document Interface is a means for applications to simultaneously open and display two or more files within the same application For example you might use MDI to allow a word processing application to open and display several documents simultaneously and provide the user with a way to quickly switch among those open documents Likewise you might use MDI to create a spreadsheet application that enables users to have several spreadsheets open at once for example to compare sales figures or interest charges MDI applications provide a convenient way to view and exchange data among multiple documents that share a common workspace The common workspace is often referred to as the
137. the begin end block is executed whenever the OnClick event occurs For this sample application you ll handle a button click E To generate an event handler 1 Select a component then click the Events tab at the bottom of the Object Inspector 2 Select an event and double click in the right Value column When you double click the Value column for an event Delphi generates an event handler in the Code Editor and places your cursor inside the begin end block 3 Inside the begin end block type the code that you want Delphi to execute when the component receives the event 18 Delphi User s Guide gt Generate an event handler for the button s OnClick event and write the following code inside the begin end block Forml Color clAqua This specifies that when a user clicks the button the form s Color property changes to the new value Aqua This is how your completed event handler should look procedure TForml ButtoniClick Sender TObject begin Forml Color clAqua end Any time you use the Object Inspector to change the name of this event handler Delphi maintains that name everywhere it appears in your source code Try out the event handler you just wrote Run the program again and then click the Color button The form changes color Close the application Starting a new project You can use the New Project command from the File menu to start a new application project or to open any of the
138. the container and the components it contains Design time operations you perform on these container or parent components such as moving copying or deleting also affect any components grouped within them Note The form remains the owner for all components regardless of whether they are parented within another component For more information about the difference between a component s parent and owner see online Help topics Owner Property and Parent Property You generally want to add container components to the form before you add the components you intend to group as it s easiest to add components that you want grouped directly from the Component palette into the container component Once a component is in the form you can add it to a container component by cutting and then pasting it m To group components 1 Add a GroupBox or Panel component to the form 2 Making sure that the container component is selected add components as you normally would As you add components they appear inside the container component When you double click a component in the palette it appears in the middle of whichever eligible receiving component has focus either the form or a container component in the form If you select and then place components the container component needn t be selected so long as you click within it when you place the component m To add multiple copies of a component to a container 1 Press Shift and then s
139. the dialog box 87 Providing command buttons 87 Executing button code on Esc 88 Executing button code on Enter 88 Closing a dialog box when the user choosesabutton 88 Creating standard command buttons 88 Setting the tab order aS Gk Swe SES 90 Testing the tab order 91 Removing a component from the tab order 91 Enabling and disabling components 91 Setting the focus ina dialog box 92 Setting focus at design time 92 Setting focusatruntime 92 Saving aformasatemplate 93 Saving form files as ASCII text 94 Converting text files back to DFM format 95 Sample ASCII Form file 95 MDI and SDI forms 96 Creating formmenus 98 Opening the Menu Designer naaa 99 Building menus s sand ai e tee dan S 100 Namme Menus 6 4 foe Sd eoe e Bod a E 101 Naming the menuitems 101 Adding inserting and deleting menu WEEMS kts on a aa So ed E ee oS 101 Adding separator bars 102 Specifying accelerator keys and keyboard SNOULCUIS 52a gh he web 8 Op eee A 102 Creating nested sub menus 103 Creating nested menus by demoting CXISHN OMENS fs Gace tee gate Sy ae gle A 103 Moving menuitems 104 Viewing the menu naana ees Bo 104 Editing menu items without opening the Menu Jesicnete u s ea aa a a e Sek 104 Using the Menu Designer SpeedM
140. the following table Icon Component Property Setting N A Form1 Caption List Box Demo Button1 Caption amp Add Name AddBtn Default True Button2 Caption amp Clear Name ClearBtn ip Edit1 Text Blank F ListBox SF Note The ampersand amp character is used in button captions and menu items to provide quick keyboard access to the button or menu item by means of accelerator keys This technique is explained in more detail in Chapter 3 Calling procedures and functions from event handlers So far this chapter has discussed how to set properties at design time and run time However setting properties is only a minor aspect of code development in Delphi Procedures and functions also known as routines usually constitute the bulk of your program code Just as every component can respond to specific events components in Delphi also have routines that pertain specifically to them Procedures and functions associated with a component are called methods You call methods at run time the same way you set properties at run time by writing an event handler Unlike properties however methods are never activated at design time To read more about methods refer to Chapter 5 or see the online Help topic Methods This sample application uses the list box s Add and Clear methods to display and remove text in the list box E To call methods from an event handler 20 Delphi User s Guide 1 Generate a handler for the component e
141. the name of the unit in which the component is declared if it does not already appear in the units listed gt For an example of this try the following 1 Start a new blank project Chapter 1 Introducing Delphi 25 2 From the Standard page of the Component palette add a GroupBox component to Form1 3 Run the program 4 Select the Unitl page tab it is not necessary to exit the running program and examine the uses clause It appears as uses SysUtils WinTypes WinProcs Messages Classes Graphics Controls Forms Dialogs Stdctris Delphi added the StdCirls library unit because that is where the GroupBox component is declared Similarly whenever you add a new unit to a project Delphi adds it to the project s uses clause When you add new forms to your project other units in the project might need to reference them or their components or code In this case you need to add the new form s unit to the referencing unit s uses clause The form DFM file The form is the focal point for programming in Delphi Whether you re adding components to the form changing their properties using the Object Inspector or typing code in the Code Editor for the unit associated with the form you re really editing the form The DFM file is a binary file and therefore visible only by its onscreen graphical representation of the form not normally by any code you directly modify Any edits you make to the form s visual prop
142. the pen color assign a value to the Color property of the pen Chapter 12 Graphics example 343 In this example you ll use the color grid on the pen s tool bar to let the user choose a new color for the pen A color grid can set both foreground and background colors for example it s the same control used to pick the syntax highlight colors in Delphi In this case you want only one color so you ll use the foreground color The user chooses a new color by clicking the grid so change the pen s color in response to the OnClick event procedure TForml PenColorClick Sender TObject begin Canvas Pen Color PenColor ForegroundColor end Changing the pen width A pen s width determines the thickness in pixels of the lines it draws Remember that when the thickness is greater than 1 some video drivers always draw solid lines no matter what the value of the pen s Style property E To change the pen width assign a numeric value to the pen s Width property In this example you ll use the scroll bar on the pen s tool bar to set width values for the pen You ll also update the label next to the scroll bar to provide feedback to the user Using the scroll bar s position to determine the pen width you need to update the pen width every time the position changes gt Handle the scroll bar s OnChange event as follows procedure TForml PenWidthChange Sender TObject begin Canvas Pen Width PenWidt
143. the reader of your code including yourself understand its logic Even though you understand how your code works when you write it it might not seem so clear to you when you examine it later Writing assignment statements The most common task you ll encounter when writing code within event handlers is assigning a new value to a property or variable You can use the Object Inspector to change the value of a property while designing the user interface but also you ll often want to change the value of a property while the application is running Some properties can be changed only at run time such properties are noted as run time only in the property reference topics of online Help To change a property or variable at run time you need to write an assignment statement Assignment statements consist of two parts separated by the Object Pascal assignment operator The left side of an assignment statement is a property or variable name while the right side of the statement is the new value for the property or variable The assignment statement like all Object Pascal statements ends with a semicolon Here is a simple assignment statement within an OnClick event handler for a button control This statement assigns the value clRed to the Color property of an edit box control named Edit1 procedure TForml ButtoniClick Sender TObject begin Editl Color clRed end Chapter 5 Writing Object Pascal code 151 Assuming that an edit
144. the string and the object For example Fruits AddObject apple AppleBitmap 276 Delphi User s Guide summary Delphi components use string list objects for a number of purposes Because all string lists share some common properties and methods your applications can easily move entire lists of strings from one component to another In addition you can create your own string lists to store data outside of components either on a short term temporary basis or for the duration of the application s execution Chapter 9 Working with string lists 277 278 Delphi User s Guide Chapter Text editor example This chapter presents the steps involved in building a simple Multiple Document Interface MDI text editor that uses the Windows common dialog boxes to open save and print manipulable text files It assumes you are familiar with the material covered in Part I Fundamental skills For instance you need to know how to set component properties and build a menu You should also be familiar with Object Pascal language constructs as discussed in Part III Programming topics Finally Chapter 9 discusses concepts that you ll encounter as you build the text editor The topics discussed in the context of creating this application are Multiple Document Interface MDI applications Working with open child windows Manipulating text ina Memo component Using common dialog boxes Printing the text file Exiting
145. then resume testing 248 Delphi User s Guide Starting a debugging session Note If you find a program run time or logic error you can begin a debugging session by running your program under the control of the debugger To begin a debugging session 1 Generate debug information when you compile your program 2 Run your program from within Delphi When debugging you have complete control of your program s execution You can pause the program at any point to examine the values of program variables and data structures to view the sequence of function calls and to modify the values of program variables to see how different values affect the behavior of your program You can also use the debugger to watch each step of your program s execution By stepping through your program s source code as described in Stepping through code on page 252 you can monitor your program code as it is executed Generating debugging information Before you can begin a debugging session you need to compile your project with symbolic debug information Symbolic debug information contained in a symbol table enables the debugger to make connections between your program s source code and the machine code that s generated by the compiler This way you can view the actual source code of your program while running the program through the debugger Although Delphi generates symbolic debug information by default you can manually turn on symbol
146. they perform are not the actions you had in mind when you wrote the code For instance logic errors can occur when variables contain incorrect values when graphic images don t look right or when the output of your program is incorrect Logic errors are often the most difficult type of errors to find because they can show up in places you might not expect To be sure your program works as designed you need to thoroughly test all of its aspects Only by scrutinizing each portion of the user interface and output of your program can you be sure that its behavior corresponds to its design As with run time errors the integrated debugger helps you locate logic errors by letting you monitor the values of your program variables and data objects as your program executes Planning a debugging strategy After program design program development consists of a continuous cycle of program coding and debugging Only after you thoroughly test your program should you distribute it to your end users To ensure that you test all aspects of your program it s best to have a thorough plan for your debugging cycles One good debugging method involves breaking your program down into different sections that you can systematically debug By closely monitoring the statements in each program section you can verify that each area is performing as designed If you do find a programming error you can correct the problem in your source code recompile the program and
147. this Chapter 7 Writing robust applications 233 Figure 7 2 Nested exception handlers try rE protected code 2 eS oj Sv try D S specially protected code eas except Bs local exception handling S 8a end a co f except global exception handling end You can also mix different kinds of exception response blocks nesting resource protections within exception handling blocks and vice versa Protecting resource allocations One key to having a robust application is ensuring that if it allocates resources it also releases them even if an exception occurs For example if your application allocates memory you need to make sure it eventually releases the memory too If it opens a file you need to make sure it closes the file later Keep in mind that exceptions don t come just from your code A call to an RTL routine for example or another component in your application might raise an exception Your code needs to ensure that if these conditions occur you release allocated resources To protect resources effectively you need to understand the following e What kind of resources need protection e Creating a resource protection block What kind of resources need protection Under normal circumstances you can ensure that an application frees allocated resources by including code for both allocating and freeing When exceptions occur however you need to ensure that the application still execut
148. this event handler procedure TForml OKClick Sender TObject var Number Integer begin Number StrToInt Edit1l Text case Number of 1 3 5 7 9 Label2 Caption z Odd digit 0 2 4 6 8 Label2 Caption Even digit 10 100 Label2 Caption Between 10 and 100 else Label2 Caption Greater than 100 or negative end end 4 Run the application When you enter a number and choose OK the string representation of the number is converted to an integer and assigned to the Number variable The case statement then uses the value of Number to determine which statement within the case statement runs In this line of code the statement after the colon runs and theLabel2 Caption receives the string Odd digit if the value of Number is 1 3 5 7 or 9 1 3 5 7 9 Label2 Caption Odd digit Like the if statement the case statement has an optional else part Case statements end with the end reserved word If you want to include more than one statement in the statement part of acase statement the part following the colon place the begin and end reserved words around the multiple statements For example case Number of deg Be pe De begin Label2 Caption Odd digit Form Color clBlue end 2 4 6 8 Label2 Caption Even digit Chapter 5 Writing Object Pascal code 167 Writing loops Object Pascal has three statements that execute blocks of code repeatedly e The repeat statem
149. to False 4 Set the Picture property of each image to the correct bitmap 1 Inthe Object Inspector double click the Value column for the Picture property to open the Picture editor 2 Choose Load in the Picture editor to open a file dialog box 3 Choose the bitmap file corresponding to the name of each control FLOPPY BMP for Floppy and so on You should now have three small images on the form as shown in the following figure The image controls will be invisible when you run the application c EG Ce 366 Delphi User s Guide Adding images to a string list Once you have graphical images in an application you can associate them with the strings in a string list You can either add the objects at the same time as the strings or associate objects with already added strings If you have all the needed data available you should generally add strings and objects together For the file manager example that means along with a letter for each valid drive you need to add a bitmap indicating each drive s type so update the OnCreate event handler as follows procedure TFMForm FormCreate Sender TObject var Drive AddedIndex Integer DriveLetter Char begin for Drive 0 to 25 do iterate through all possible drives begin DriveLetter Chr Drive ord a case GetDriveType Drive of positive values mean valid drives DRIVE REMOVABLE add a
150. to distribute DCU files with your completed application Graphical form DFM files As discussed in previous chapters a file with a DFM extension is a binary file that contains information about the graphical properties of a form The visual display of a form at design time and at run time derives its information from this file Delphi maintains a corresponding DFM file for each form associated unit source code file If you develop forms exclusively with the visual tools provided by Delphi you seldom if ever need to deal directly with DFM files Delphi updates them as you save changes Chapter 4 Managing projects files and directories 121 to the visual form image You can however edit a DFM file as text by opening it as a file in the Code Editor using File Open File When you close a DFM file the Code Editor automatically converts it back to binary format For more information on DFM files see Chapter 3 Saving form files as ASCII text on page 94 Beginning new projects As discussed in Chapter 1 you can choose from a number of options that control what occurs when you begin a new project in Delphi In a default installation of Delphi opening a new project displays a blank form based on the Blank Project template You can change this default behavior in several ways By changing Gallery options setting Gallery options is discussed on page 124 you can e Specify the default new project to be one of the oth
151. topic is a file For example if the data you want to share is in the Quattro Pro notebook file NOTEBK1 WB2 the topic would be NOTEBK1 WB2 the full file name is used including the extension If the server is a Delphi application the topic is by default the caption of the form containing the data you want to link For example if you want to link to text in a form with a Caption of MyApp the topic would be MyApp Optionally you could use the name of a DDEServerConv component as explained in Creating DDE server applications on page 388 DDE items The item of a DDE conversation identifies the actual piece of data to link The syntax used for specifying the DDE item depends on the DDE server application Examples of possible DDE items are spreadsheet cells or database fields For example to link to cell A1 on page A in a Quattro Pro notebook the item would be A A 1 A 1 If the server is a Delphi application the item is the name of the linked DDEServerltem component For example to establish a conversation with the DDE server component named DDEServer1 the item would be DDEServer1l DDEServerltems are discussed in Creating DDE server applications on page 388 See the documentation for the DDE server for specific information about specifying the application topic and item of a conversation Creating DDE client applications DDE client applications initiate conversations and typically request to receive data from DD
152. unit Unitl interface uses SysUtils WinTypes WinProcs Messages Classes Graphics Controls Forms StdCtrls type TMyButton class TButton private Private declarations protected Protected declarations public Public declarations published Published declarations end procedure Register implementation procedure Register begin RegisterComponents Samples TMyButton end end You are now ready to write the rest of the Object Pascal code needed to program the new component Using customized libraries During application development you might want to work with your own custom component library file You can create a distinct library file by saving your customizations to the Delphi library file under a new name 72 Delphi User s Guide mM To create anew library file 1 2 3 Choose Options Install Components The Install Components dialog box appears Specify the full path and new file name in the Library Filename box Choose OK to create and compile the new library file Now you can install this customized library whenever you want or specify it as the default component library m To replace the current component library 1 Choose Options Open Library The Open Library dialog box appears Select the library file you want to install and choose OK Delphi replaces the current library with the library file you have chosen and reflects the contents of your library fi
153. updating 364 Directories Conditionals page Project Options 129 directory lists 41 42 Project Manager 133 DirectoryListBox component 41 DirectoryOutline component 42 361 Disable All Breakpoints command Breakpoint List window 256 Disable All Watches command Watch List window 260 Disable Breakpoint command Breakpoint List window 256 Disable Watch command Watch List window 260 disabling borders 289 disabling menu items 292 disabling tool bars 340 342 disk drives See drives display options See preferences displaying bitmaps 39 42 breakpoints 255 258 child windows 287 code 12 79 139 Code Editor window 141 debugger and 251 shared events 65 specific event handlers 63 components 11 data 40 in columns and rows 172 data types 153 directories 42 363 366 files 280 in list boxes 297 project 12 23 25 forms 79 80 139 erids 31 menus 104 105 messages 80 409 non textual information 39 OLE objects as icons 411 414 property values 54 shared 54 55 text 39 in columns and rows 39 tool bars 342 displays flickering 250 distributable libraries 115 distributing applications 22 divide by zero errors 235 237 238 239 DLLs 77 117 creating 134 141 dmAutomatic constant 376 387 dmManual constant 376 387 DMT files 106 108 documentation printing conventions 3 Double data type 156 Down property 333 downloading fonts 306 downto reserved word 172 DP files 116 DPR files 22 24 116 118 119 editing 132 viewin
154. using the tab set control e Exchanging data with DDE or OLE This chapter offers background and conceptual material for understanding Dynamic Data Exchange DDE Object Linking and Embedding OLE versions 1 0 and 2 0 and their implementation within the Delphi programming environment e OLE example This chapter expands on the concepts introduced in Chapter 14 by showing you how to create an MDI application that can use either OLE 1 0 or OLE 2 0 268 Delphi User s Guide Chapter Working with string lists There are numerous occasions when Delphi applications need to deal with lists of character strings Among these lists are the items in a list box or combo box the lines of text in a memo field the list of fonts supported by the screen the names of the tabs on a notepad the items in an outline and a row or column of entries in a string grid Although applications use these lists in various ways Delphi provides a common interface to all of them through an object called astring list and goes even farther by making them interchangeable meaning you can for example edit a string list ina memo field and then use it as the list of items in a list box You have probably already used string lists through the Object Inspector A string list property appears in the Object Inspector with TStrings in the Value column When you double click TStrings the String List editor appears where you can edit add or delete line
155. value at which time the nested for loop begins again with the new Col value For more information about for statements see Delphi s online Help Deciding which loop to use This section has described several kinds of Object Pascal loops How do you decide which kind to use Here are some guidelines to help you decide e Use the for loop if you know how many times you want a loop to repeat Thefor loop is very fast and efficient e Use the repeat until loop if you don t know how many times you want the loop to repeat but you do know it must run at least once e Use the while do loop if you don t know how many times you want the loop to repeat and it s possible you don t want the loop to run at all Object Pascal blocks Blocks are an important concept in Object Pascal They provide the structure of your application and they determine the scope of variables properties and so on You can read about scope in the section Understanding scope on page 177 An Object Pascal block is made up of two parts an optional declaration part and the statement part If there is a declaration part it always precedes the statement part A declaration informs the compiler of the item being declared Object Pascal has e Variable declarations e Constant declarations e Type declarations 174 Delphi User s Guide e Label declarations e Procedure function and method declarations Following the declaration part is the statement p
156. values 335 declaring 157 158 giving a type 157 naming 157 335 constructors 229 contacting Borland 3 container applications See OLE applications container components 47 48 removing components in 49 selecting components in 46 containers panels as 346 control bar See tool bars Control menu 86 removing from forms 87 control variables 170 controls 221 222 See also components labeling 38 owner draw 275 365 369 drawing 367 369 resizing 367 styles 365 scrollable regions 348 sharing events 343 conversations See DDE conversations converting case strings 272 types 155 238 coordinates current drawing position 324 origin 314 Copy command Edit 49 Copy function 201 CopyFile function 373 copying components 47 49 50 to containers 48 files 373 graphics 355 project files 138 strings 272 text 291 with DDE links 389 CopyToClipboard method 291 389 corrupted data preventions 231 Count property 270 counters 170 counting example 171 counting strings 270 Create method 229 Create Submenu command Menu Designer 103 105 CreateChild method 404 creating See also adding backup files 302 303 component libraries 68 72 DDE applications client 383 388 server 388 390 dialog boxes 80 84 85 forms at run time 113 114 file manager example 360 362 MDI applications 281 OLE example 400 401 memos 288 message boxes 43 new projects 19 30 122 123 new units 120 134 209 nonvisual components 52 nonvisual objects 228 229 OLE
157. windows to determine whether they can close If any MDI child form s CanClose value is False then the MDI frame form won t close If every child form closes successfully CanClose returns True then the MDI frame form closes and therefore the application terminates Since both the EditForm and FrameForm File menus have an Exit item you need to write an event handler for each menu s File Exit OnClick event Similar to the handlers for the File New and File Open clicks the handler for EditForm s File Exit click simply calls FrameForm s File Exit click event handler gt Write the following handler for the EditForm File Exit OnClick event procedure TEditForm ExitiClick Sender TObject begin Chapter 10 Text editor example 311 FrameForm ExitiClick Sender end gt Write the following handler for the FrameForm File Exit OnClick event procedure TFrameForm Exit1lClick Sender TObject begin Close end summary Delphi provides tools to help you quickly and easily create Multiple Document Interface applications as well as several text manipulation tools This chapter discussed such text manipulation techniques as cutting copying and pasting text using the Clipboard with text and specifying a text font In addition the chapter presented such application development techniques as creation of MDI frame and child windows and merging frame and child menus 312 Delphi User s Guide Chapter
158. within Delphi Creating an exception handler An exception handler is code that handles a specific exception or exceptions that occur within a protected block of code To define an exception handler embed the code you want to protect in an exception handling block and specify the exception handling statements in the except part of the block Here is an outline of a typical exception handling block try statements you want to protect except exception handling statements end The application executes the statements in the except part only if an exception occurs during execution of the statements in the try part Execution of the try part statements includes routines called by code in the try part That is if code in the try part calls a routine that doesn t define its own exception handler execution returns to the exception handling block which handles the exception When a statement in the try part raises an exception execution immediately jumps to the except part where it steps through the specified exception handling statements or exception handlers until it finds a handler that applies to the current exception Once the application locates an exception handler that handles the exception it executes the statement then automatically destroys the exception object Execution continues at the end of the current block Exception handling statements Each statement in the except part of a try except block defines
159. your current project Because Delphi maintains the DPR file manually editing the DPR file is not recommended To view the DPR file 1 Choose View Units The View Unit dialog box appears displaying a list of the unit s in the project and the single project file Select the name of the project file and choose OK The DPR file appears in a page in the Code Editor Figure 1 6 Default project source code PROJECT1 DPR program Projecti Project name uses Uses clause Forms Uniti in UNITI PAS Formi Form identifiers SR RES Compiler directive hegin Application CreateForm TForml Forml Application Run end 41 Modified Insert ej W _j As you add new forms or units to your project Delphi automatically adds the appropriate code to the DPR file Chapter 1 Introducing Delphi 23 The uses clause in the DPR file To illustrate how Delphi maintains the project file you can view the code Delphi generates when you add a new form to the project Try the following 1 View the project file for Project1 2 Choose File New Form and accept the Blank Form option 3 View the DPR file again by clicking the Project1 page tab in the Code Editor Here s what you should see Figure 1 7 Modified project file source code PROJECT1 DPR program Projecti uses Forms Uniti in UNIT1 PAS Formi Unit2 in UN T2 PAS Form2 New form identifier New unit file name begin New uni
160. your program successfully compiles but fails when you run it you ve encountered a run time error Your program contains valid statements but the statements cause errors when they re executed For example your program might be trying to open a nonexistent file or it might be trying to divide a number by zero The operating system Chapter 8 Using the integrated debugger 247 detects run time errors and stops your program execution if such an error is encountered Without a debugger run time errors can be difficult to locate because the compiler doesn t tell you where the error is located in your source code Often the only clue you have to work with is where your program failed and the error message generated by the run time error Although you can find run time errors by searching through your program source code the integrated debugger can help you quickly track down these types of errors Using the integrated debugger you can run to a specific program location From there you can begin executing your program one statement at a time watching the behavior of your program with each step When you execute the statement that causes your program to fail you have pinpointed the error From there you can fix the source code recompile the program and resume testing your program Logic errors Logic errors are errors in design and implementation of your program Your program statements are valid they do something but the actions
161. 0 creating 68 72 customizing 68 73 deleting components 68 69 rebuilding 42 68 69 70 replacing 73 reverting to previous versions 71 Component list 11 Component palette 37 38 42 adding components 42 customizing 68 deleting components 68 moving components 69 overview 10 pointer icon 38 components 37 60 221 222 See also specific types accessing 223 adding 44 45 209 container 48 multiple 44 47 new 121 overview 15 third party 42 68 69 70 aligning 50 52 with grids 52 copying 47 49 50 to containers 48 customizing 10 11 53 59 71 data aware 40 database 40 default listed 38 42 deleting 49 50 deletion undoing 50 displaying 11 enabling disabling 91 grouping 47 48 locking position 52 moving to different pages 69 naming 44 55 third party 70 nonvisual 37 38 42 52 overview 9 10 parent child relationships 48 49 pasting 49 50 DDE links 384 389 OLE objects 394 415 421 removing from tab order 91 renaming 44 49 218 219 resizing 45 46 58 selecting 38 46 48 setting tab order 90 91 sharing events 65 67 visual 37 38 42 without events 60 compound statements 165 Concat function 201 concatenating strings 201 conditional breakpoints 256 257 258 conditions testing 163 166 174 configuring Delphi 28 32 confirmation dialog boxes 80 374 deleting files 370 371 saving files 310 ConnectMode property 387 const reserved word 157 194 constant parameters 194 constants 153 assigning sequential
162. 10 5 Choose Modify to confirm your settings Note You can input any valid language expression into the Condition edit box but all symbols in the expression must be accessible from the breakpoint s location and the expression cannot contain any function calls Using pass counts The Pass Count edit box enables you to specify a particular number of times that a breakpoint must be passed for the breakpoint to be activated pass counts tell the debugger to pause the program execution the nth time that the breakpoint is encountered during the program run the number n is user specified and is set to 1 by default The pass count number is decremented each time the line containing the breakpoint is encountered during the program execution If the pass count equals 1 when the breakpoint line is encountered the breakpoint activates and pauses the program execution on that line of code Pass counts are useful for example when you think that a loop is failing on thenth iteration Or if you can t tell on which iteration the loop fails you can set the pass count to the maximum loop count and run your program When the program fails calculate the number of times that the program went through the loop by examining the number in the pass count field When pass counts are used in conjunction with Boolean conditions the breakpoint pauses the program execution the nth time that the condition is true the condition must be true for the pass count t
163. 10 5 S Char strings String Shows any non displayable ASCII characters as nn where nn represents the ordinal value of the ASCII character Use only to modify memory dumps see nM For example to display a result in hexadecimal type H after the expression To see a floating point number to 3 decimal places type F3 after the expression Modifying the values of variables Once you ve evaluated a variable or data structure item you can modify its value Modifying the value of data items during a debugging session enables you to test different bug hypotheses and see how a section of code behaves under different circumstances m To modify the value of a data item 1 Open the Evaluate Modify dialog box then enter the name of the variable or data item you want to modify in the Expression edit box 2 Click Evaluate to evaluate the data item 3 Type a value into the New Value edit box or choose a value from the drop down box then click Modify to update the data item Note When you modify the value of a data item through the debugger the modification is effective for that specific program run only the changes you make through the Evaluate Modify dialog box do not effect your program source code or the compiled program To make your change permanent you must modify your program source code in the Code Editor then recompile your program 262 Delphi User s Guide Keep these points in mind when you modify program data values
164. 16 PVCS PAGO ct tsi dle aie eh Sn ok Gok wht 18 Browse Gallery dialog box displaying application templates 19 A default Delphi project 22 Default project source code 23 Modified project file source code 24 Default unit source code 25 Form type declaration 27 Modified type declaration 27 Environment Options dialog box Preferences page esa bows pale Ree 29 The Forms Gallery 30 The Projects Gallery ace iy tar a 30 The Compiling dialog box 32 ABOUT DOL sra a aea oe a ees GS GS 43 AboutBox with BitBtn component 45 JANE handles saaa tne a a ook Bae a 46 Form with Panel component 47 AboutBox with Panel and Label COMPONCING 2 suea 4 E O S 49 Panel with Labels and Image components 50 Alignment palettes syok EEA ER 51 Alignment dialog box 51 Aligned Label components 52 Forn end ci 4 oc ka Haale dow eae es Be SS 52 Form2 with two Button1 component CAPUONIS 4 08 bb te ck dy eat cee Ae a ae A 56 Picture Editor dialog box 57 Image displayed in Picture Editor dialog DOr pae ead hd aaah eee ae N 57 About box with image 57 About box with sized image 58 Run time About ox 62 About box displaying program name in form atle bare er aeea u ae me e Ea 64 About box with run time icon 67 The Component Expert dialo
165. 163 Using an else part in an if statement 164 Writing multiple statements within an if SIALE MCI 4 co ares Aue e Bot Sone Ge oes A 165 Nesting if statements 165 The Case statement 6 4 pag Say Gok ye a E 166 Writing Oops siete he BOG ee ae A 168 The repeat statement 168 The while statement 169 The for statement 0 170 A counting example 171 Using nested for loops 172 Deciding which loop touse 174 Object Pascal blocks 174 Blocks within event handlers 175 Blocks within units 175 Blocks within blocks 176 Understanding scope 177 Accessing declarations that are not within SCOPE 3 laste amp wie heats Aa Ae ae oe 178 iV Ascope examples ces Pee wo Ba ee 178 Redeclaring identifiers in a different scope 181 Using a global variable 181 Writing a procedure or function 183 Writing a procedure or function header 185 Writing a procedure or function block 185 Declarations within a procedure or function blocks y s ears seei 2044 185 Type declarations oaaae 185 Variable and constant declarations 186 Ordering the declaration parts 186 Writing the statement part 186 Assigning a return value in a function 186 Positioning a procedure or function in your COGS hat yg sti bit tira Oe a geek aS 187
166. 200 203 StringGrid component 39 string handling routines 201 strings 200 See also string lists substrings accessing characters 201 450 Delphi User s Guide allocating memory 201 assigning values 200 associating graphics with 367 concatenating 201 debugging 262 finding length 201 inserting strings 201 null terminated 156 size 201 291 returning 201 starting position 201 291 Strings property 270 StrPCopy function 387 StrToFloat function 238 StrToInt function 238 Style property brushes 316 344 owner draw variants 365 366 pens 315 343 subrange types 166 197 199 subranges 197 subroutines 158 substrings deleting specific 201 finding 201 returning position 201 string lists and 272 swap files 238 symbol tables 249 symbolic debugging information 249 250 symbols 13 154 local 249 Syntax Check command Compile 142 syntax errors 154 158 159 System menu 86 removing from forms 87 System page Component palette 41 system resources preventing loss 231 protecting 233 234 236 releasing 234 235 SysUtils unit 236 372 T Tab key 54 90 91 tab order 90 91 changing 90 testing 91 Tab Order command Edit 90 TabbedNotebook component 39 47 tabbing through dialog boxes 90 91 tabbing through forms and components 54 Table component 40 TabOrder property 90 tabs 39 See also notebooks changing 363 364 default width 368 draw item events 369 file manager application 362 363 364 measure item events 368 naming 26
167. 22 initializing 336 instatiating 217 229 nonvisual 228 229 OLE See OLE objects properties 216 225 string lists and 275 276 type defining 217 218 224 226 228 Objects property string lists 275 276 368 Objltem property 395 OK buttons 88 89 OLE applications 390 397 421 accessing data 41 392 adding text 419 422 building 399 427 closing 404 container 393 395 399 adding menus 402 408 creating 401 defined 390 initializing 412 413 415 422 DDE applications vs 396 editing data 392 merging menus 111 registering as drop target 421 422 saving data 395 server defined 390 displaying messages 409 status bars adding 409 410 tool bars adding 408 409 version differences 391 OLE objects 390 activating 391 400 adding 393 395 401 410 413 421 class defined 393 Clipboard formats 416 418 420 registering 417 418 returning 419 creating 391 400 deactivating 412 413 414 displaying as icons 411 414 document defined 393 dragging and dropping 395 421 423 initializing 412 item defined 393 linking vs embedding 392 loading 396 424 426 multiple 401 pasting 394 415 421 restricting access to 392 run time properties 407 saving 392 396 424 selecting 411 updating 395 OLE DPR 399 OLEContainer component 41 393 401 adding OLE objects 410 initializing 412 413 415 422 OLEFrame unit 403 OLEObj unit 406 OnChange event list boxes 364 outlines 364 OnClick event 334 buttons 217 222 334 menus 109 370 tab s
168. 3 editing forms and units 140 overview 12 SpeedBar buttons 131 SpeedMenu 130 starting 130 viewing forms and units 140 Project Manager command View 130 Project Manager window 130 Project Options dialog box 127 129 Project Templates 10 29 30 115 122 123 See also Projects Gallery adding to galleries 126 127 saving 136 specifying as default 124 Project Templates page Gallery Options 125 126 projects 22 28 115 145 See also project files adding forms 76 220 224 to multiple 59 adding units 25 27 119 209 210 building 14 22 133 135 143 new 19 30 122 123 compiling See compiling current composition 132 debugging See debugging projects default 118 119 120 specifying 124 125 defined 115 main program 116 moving among forms and units 140 options 116 123 129 overview 115 118 predesigned 10 saving 58 115 135 139 Projects Gallery 19 30 properties 9 49 116 See also property editors brushes 316 canvases 313 changing 54 55 56 225 design time 16 27 run time 151 debugging 261 displaying 54 shared 54 55 multiple components 54 55 objects and 216 222 225 overriding 59 pens 315 read only 153 setting 16 43 55 design time 53 56 in code 151 152 157 run time 59 60 Properties page Object Inspector 11 property editors 56 58 protected blocks 231 232 233 syntax 235 protecting system resources 233 234 236 prototypes 14 prPageNums constant 307 prSelection constant 307 public standard directive 22
169. 4 225 PVCS Version Manager 144 Q qualifying identifiers 152 method calls 159 197 property names 222 queries 40 Query component 40 R SR directive 119 120 199 radio buttons 38 39 RadioButton component 38 RadioGroup component 39 raise reserved word 244 raising exceptions 235 239 242 defined 232 syntax 244 245 range checking 157 199 exceptions and 237 241 Range Checking option 199 RC files 112 README TXT 1 read only properties 153 Real data type 156 real types 156 exception handling 237 rebuilding libraries 42 68 69 70 record types 204 205 records 216 assigning fields to 205 debugging 262 defined 204 recovering from error conditions 232 Index 447 RECT BMP 333 Rectangle method 317 rectangles 39 317 recursion 189 redeclaring identifiers 181 redistributable files ii redrawing images 316 references third party books 429 referencing forms 77 referencing units 26 286 regenerating images 317 RegisterClipboardFormat function 418 RegisterFormAsOLEDropTarget function 421 422 registering Clipboard formats 417 418 registering OLE applications 421 422 relational operator 164 assignment operator vs 158 ReleaseOLEInitInfo function 412 releasing memory 229 234 235 273 releasing mouse buttons 324 See also mouse events releasing system resources 234 235 remote database servers 40 Remove button Project Manager 131 Remove File command Project Manager 131 removing See deleting RenameFi
170. 54 255 after execution begins 255 conditional 257 258 stepping over statements 252 stepping through code 252 253 statement by statement 252 to first executable statement 253 strategy 248 turning off breakpoints 256 viewing function calls 263 264 decimal numbers 156 262 declarations 174 177 186 206 arrays 200 as types 199 begin end blocks 175 constants 157 158 forward 189 190 functions 161 185 189 identifiers 153 157 189 as enumerated types 196 not within scope 178 object types 188 objects 217 222 224 228 exception 244 procedures 158 185 189 type 26 185 186 195 205 enumerated 335 336 variables 154 157 217 character arrays 200 example 226 for statements and 170 procedures and 160 text editor example 299 decrementing values 172 default buttons 88 Default property 88 defaults 123 127 brushes 316 component names 55 components 38 42 form names 55 forms 86 pens 315 restoring 127 defining new types 185 186 195 205 DEFPROJ OPT 127 Delete All Breakpoints command Breakpoint List window 256 Delete All Watches command Watch List window 260 Delete Breakpoint command Breakpoint List window 256 Delete command Edit 50 Delete command Menu Designer 105 Delete method strings 271 276 Delete procedure 201 Delete Templates command Menu Designer 105 107 Delete Templates dialog box 107 Delete Watch command Watch List window 260 DeleteFile function 370 deleting borders 289 breakpoints 256 comp
171. 6 client 41 383 388 defined 382 executing macros 387 updating data 386 388 390 items defined 383 linking data 383 384 386 389 at run time 383 385 388 OLE applications vs 396 poking data 386 server 41 388 390 activating disconnected 387 connecting to 384 386 defined 382 receiving data 386 services defined 382 topics defined 383 DDE conversations 382 383 initiating 41 383 DDE Info dialog box 384 DDE links 385 pasting 384 389 testing 389 DDEClientConv component 41 383 384 385 DDEClientItem component 41 383 DDEConv property 383 DDEItem property 385 DDEServerConv component 41 388 DDEServerltem component 41 388 DDEService property 385 DDETopic property 385 436 Delphi User s Guide deallocating memory 229 234 235 273 debugger 13 247 exception handing 238 restarting 253 264 standalone 249 starting 249 250 debugging options 32 249 debugging projects 247 265 bugs types 247 248 changing breakpoint properties 257 258 coloring breakpoints 258 editing code 255 262 264 examining variables 258 263 disabling watches 260 setting watches 259 261 values changing 261 262 263 execution point 251 253 258 flickering screens 250 generating debugging information 249 250 handling exceptions 264 invalid breakpoints 255 258 releasing system resources 254 running applications 250 251 pausing execution 253 254 264 to breakpoints 253 254 258 to specific locations 251 254 setting breakpoints 2
172. 62 80 viewing bitmaps 39 42 breakpoints 255 258 child windows 287 code 12 79 139 Code Editor window 141 debugger and 251 shared events 65 specific event handlers 63 components 11 data 40 172 data types 153 directories 42 363 366 files 280 in list boxes 297 project 12 23 25 forms 79 80 139 grids 31 menus 104 105 messages 80 409 non textual information 39 OLE objects as icons 411 414 property values 54 shared 54 55 text 39 in columns and rows 39 tool bars 342 Visible property Enabled property vs 292 menus 110 tool bars 342 Visual Basic controls 42 70 Visual Component Library VCL 42 adding components 69 70 customizing 68 73 deleting components 69 visual components 37 38 42 W Watch List window 259 261 opening 259 Watch Properties dialog box 259 260 watches 259 261 setting 259 stopping 260 Watches command View 259 while reserved word 169 while statements 169 170 174 for statements vs 170 whole numbers 156 260 262 Width property pens 315 344 Window List command View 140 Window List dialog box 140 Window menu creating 283 287 WindowMenu property 288 windows closing 309 310 flickering 250 moving among IDE 140 temporary 60 Windows applications See applications Windows common dialog boxes See common dialog boxes Windows resources 116 234 with reserved word 205 with statements 225 226 WMF files 117 See also metafiles Word data type 156 word wrapping 290 word processing
173. 62 363 value parameters 191 193 194 values 203 See also constants assigning 151 153 fields in records 205 functions 161 placing limits 197 to properties See setting property values to strings 200 type compatibility and 157 zeros to arrays 199 changing while debugging 261 262 263 comparing 158 164 declaring as identifiers 196 decremental 172 equal 158 incremental 42 171 numeric valid ranges 156 return See functions sequential 335 string 201 True False 156 types returning 195 var reserved word 120 155 193 variable parameters 193 194 variables 26 179 assigning values 151 152 157 control 170 declaring 154 157 character arrays 200 example 217 226 for statements and 170 procedures and 160 text editor example 299 defined 154 examining 258 263 giving atype 154 global 177 181 183 invalid 194 452 Delphi User s Guide local 177 180 naming 154 objects and 222 226 228 229 values limiting 197 watching 259 261 VBX controls 42 70 VBX page Component palette 42 VCL See Visual Component Library VCRs See media players version control 94 144 vertical scroll bars 290 video files See media players View Form button Project Manager 131 View Form command Project Manager 131 View Form dialog box 63 79 View menu 139 View Source command Breakpoint List window 256 View Source command Call Stack 264 View Unit button Project Manager 131 View Unit command Project Manager 131 View Unit dialog box 23
174. 7 Project Manager SpeedBar buttons 131 Object Pascal predefined datatypes 156 String procedures and functions 201 Heap CxCePHONSiga 4 6 2 Gas aes Yi 237 Integer math exceptions 237 Floating point math exceptions 238 Hardware exceptions 238 Expression format specifiers 262 1X 13 2 13 3 13 4 13 5 13 6 Corresponding string and object methods in string lists Text editor property values Child form property settings for the text editor example Frame form menu items Child form menu items a a aa Naming the project files Grouplndex property settings Memo component settings File filter settings for the text editor SaveDialog component properties Mouse event parameters Property settings for pen and brush tool Dats 2 2 reend arda ote oA A Image control properties for GRAPHEX Graphics example File and Edit menus Property values for the file manager example s main form Property values for the main form components in FILMANEX File menu items for the file manager example Fixed vs variable owner draw styles Property values for the file attribute dialog box form Property values for the file attribute dialog box components 360 360 362 366 Figures The Delphi programming environment 8 Object Inspector with Caption property CEELI e ai enna Gay Se a ea oe
175. 8 three dimensional panels 346 tiling child windows 287 time 38 Timer component 38 41 timers 38 41 228 title bars 87 Code Editor 12 Title property 64 titles 38 See also captions TObject type 221 Toggle Breakpoint command Code Editor window 254 256 Toggle Form Unit command View 140 toggles 42 334 TOLEDropNotify objects 422 423 tool bars 39 47 331 adding buttons 331 334 displaying 342 hiding 340 342 multiple 342 OLE example 408 409 status bars vs 345 tools 9 10 121 See also drawing tools topics defined 383 See also DDE conversations TPrinter object 209 305 Trace Into command Run 252 tracking text changes 300 transactions SQL 40 triangles 318 try reserved word 232 except reserved word and 239 finally reserved word and 235 TStrings type 274 Turbo Debugger 249 tutors 2 3 two dimensional arrays 200 type checking 103 153 ranges 157 199 type declarations 228 type reserved word 120 185 335 typecasting exceptions 238 string lists 368 types 153 See also specific predefined array 199 203 assigning 157 constants 158 variables 154 compatibility 157 converting 155 238 declaring 26 185 186 195 205 enumerated 195 197 declaring 335 336 exception handling 237 mismatch errors 155 naming 186 335 object 188 205 244 objects and 217 218 224 226 228 predefined listed 156 record 204 205 returning values 195 scope 186 set 203 204 string 200 203 subrange 197 199 typography 3 U unde
176. 9 owner draw styles 365 TabSet component 39 TabStop property 90 91 TCheckBox component 222 TComponent type 221 TDragDropEvent type 422 technical support 3 templates 29 30 adding to projects 78 79 forms 10 adding to galleries 93 126 127 opening for reference 79 specifying as default 125 MDI applications 281 menus 100 106 109 loading 106 projects 10 115 122 123 adding to galleries 126 127 saving 136 specifying as default 124 saving forms as 93 94 user defined 126 127 Templates page Browse Gallery 78 temporary windows 60 terminating applications 350 file manager example 362 OLE example 404 text editor example 309 312 testing applications 141 143 248 testing forms 112 text 200 381 See also lists memos outlines aligning 289 in panels 346 changing 300 copying 291 with DDE links 389 deleting 291 292 displaying 39 in columns and rows 39 editing 38 entering 38 83 269 MDI applications 288 295 OLE applications 419 422 owner draw controls and 365 printing 305 309 specified 307 searching for in string lists 270 271 276 selecting 291 status bars 346 word wrapping 290 text editors 279 See also Code Editor text files See files text gauges 42 Text property DDE items 385 388 text strings See string lists strings TEXTEDIT DPR 279 TextOut method 323 TForm class 76 TForm component 216 219 instantiating 217 third party books 429 third party components 42 68 69 70 naming 70 third party help compilers 11
177. Change the main form for MyProj to MainForm 1 Choose Options Project 2 Select the Forms page tab 3 Open the drop down list next to Main form and select MainForm For more information about changing the application s main form see Chapter 3 In this example you ll write one line of code that enables you to open the About box at run time A quick way to do this is to add a button to the main form and write code to open the dialog box when the user clicks the button In a real application you d usually open an About box in response to a click on a menu item but for a quick test it s easier to add a command button Since you ve already added buttons to MainForm all you need to do is generate the event handler and write the code that displays the dialog box To test the dialog box 1 Double click Button1 in MainForm to generate the default event handler 2 Inside the begin end block add the following line of code to execute the dialog box by calling its ShowModal method AboutBox ShowModal The ShowModal method displays the About box modally meaning the user must explicitly close this dialog box before performing any other action For more information about modal versus modeless dialog boxes see Chapter 3 3 Add the About unit to MainForm s uses clause For detailed information see Chapter 1 4 Compile and run the application The main form appears 5 Click Button Chapter 2 Using components an
178. Chapter 3 When the text editor first opens and no child window is open only the FrameForm menu items are available Once the user opens a child window by choosing File New the EditForm menu items merge into the frame form s menu bar This happens automatically in a Delphi MDI application The way that menu items merge is determined by the GroupIndex property 284 Delphi User s Guide gt Set the GroupIndex property for each form s menu titles as noted in Table 10 6 To do so either open the Menu Designer or select each menu item from the Object selector in the Object Inspector Table 10 6 Grouplndex property settings Form Menu title GroupIndex setting FrameForm File 0 FrameForm Window 9 EditForm File 0 EditForm Edit 1 EditForm Character 1 Assigning both File menu titles a GroupIndex value of 0 causes the EditForm File menu to replace the FrameForm File menu at merge time and ensures that the File menu always appears first whether or not the menus are merged Assigning the Window menu title a GroupIndex a value of 9 ensures that the Window menu always appears last because the number 9 exceeds the total number of merged menu items Assigning the Edit and Character menu items identical GroupIndex values maintains their order in the merge and the value of 1 in this case inserts them after the File menu If the frame form had a menu item with a value of 1 the Edit and Character menu items would as a unit replace it
179. Click Sender TObject SR type TValidentry 1100 var Entry TValidEntry begin Entry StrToInt Editi Texti Label2 Caption Excellent end 4 Run the application enter a number in the edit box and click the button 198 Delphi User s Guide Try putting a number greater than 100 in the edit box You ll get a run time error that informs you a range check error has occurred If you enter a number within 1 to 100 the application runs as expected Note the use of the R directive R turns on range checking while the event handler runs If you omit the R directive the compiler won t catch out of range errors To read about compiler directives see the Compiler Directives topic in the Help system You can also turn on range checking by choosing Options Project Compiler Options and selecting Range Checking Array types An array is an ordered collection of a data type with each element of the collection specified by its numeric position within the collection When the array is created the elements don t contain useful values at first but you can fill them with data and manipulate that data as you need to For example here is a variable declaration for an array of Double types var Check array 1 10 of Double This declaration tells Delphi that the variable Check refers to a list of ten variables of type Double each with a number called its index from 1 to 10 Each item of an array is referred to
180. Component palette E To add multiple copies of the same component 1 Press and hold the Shift key 2 Click the component in the palette then click in the form once for each copy you want of the component You don t need to hold down the Shift key after the component is selected 3 Click the pointer icon to clear the selected component Clicking in the form continues to add the component to the form as long as the component remains selected in the palette Add two Label components to the lower portion of AboutBox to the right of the bitmap button Grouping components Besides the form itself Delphi provides several components the GroupBox Panel Notebook TabbedNotebook and ScrollBox that can contain other components These are often referred to as container components You can use these container components to group other components so that they behave as a unit at design time For instance you might group components such as speed buttons and check boxes that provide related options to the user You often use container components such as the Panel component to create customized tool bars backdrops status lines and so on For more information about creating tool bars and status lines see Chapter 12 or search online Help under tool bars or status lines Chapter 2 Using components and code 4 7 When you place components within container components you create a new parent child relationship between
181. Convl PokeData DDEClientIteml DDEItem TheText The text string Hello is inserted into the DDE item specified in the DDEltem property of DDEClientItem1 StrPCopy simply copies a Pascal style string into a null terminated PChar string Just as you need to provide an area and a means to display DDE data in your application so you also need to provide a source for the data you want your application to poke In the previous example the text string itself was passed as a parameter but in most of your real world applications the DDEClientConv control probably obtains this data from another control Controlling other applications All DDE client applications can control server applications in one particular way clients attempt to run servers when necessary When your DDE client tries to establish a link with a DDE server that isn t running the client attempts to activate the server and load the conversation topic specified in the DDETopic property of the DDEClientConv component To activate a DDE server when the client form is created set the value of the ConnectMode property of a DDEClientConv component to dmAutomatic If the value of ConnectMode is dmManual your application must execute the OpenLink method of the DDEClientConv component Another way to control other applications is to execute macro commands To execute a macro in the DDE server from within the DDE client use the ExecuteMacro or ExecuteMacroLines metho
182. Count 1 Counter Text IntToStr Counter end The problem is that each time one of the event handlers runs Count is reset to 0 and then incremented by one Your application would never display the number of calculations as greater than one In this case your application really needs a global variable to function as you want it to gt Declare Count outside of the scope of the event handlers and within the scope of the unit in the unit s implementation part implementation SR DFM var Count Integer procedure TForml MultiplyClick Sender TObject Because you don t want to reset Count to 0 each time you click the Multiply or Divide button initialize Count in the initialization part of the unit To create an initialization part add the reserved word initialization and the code that initializes Count above the final end reserved word at the bottom of the unit The block should look like this initialization Add initialization reserved word here Count 0 Initializes Count to 0 end gt Now run your application and enter values in Edit1 and Edit2 Each time you click one of the buttons one is added to the number of calculations Because both event handlers need to access and change the value of Count you need to declare Count as a global variable to the event handlers Note A more object oriented way of accomplishing the same goal would be to make Count a field of the form object All
183. DE server e Requesting data e Poking data e Controlling other applications Establishing a link with a DDE server If you have access to the DDE server application and data you can establish a DDE link by pasting it from the Clipboard at design time E To paste a DDE link from the Clipboard at design time 1 Activate the server application and select the data to link to your client application gt For example to link to a cell in a Quattro Pro notebook called C NOTEBK1 WB2 run Quattro Pro load the notebook and select the cell 2 Copy the data and DDE link information to the Clipboard from the server application Typically you do this by choosing Copy from the Edit menu of the server gt For example in Quattro Pro choose Edit Copy 3 Activate Delphi and select the DDEClientConv component 4 Click either the DDEService or the DDETopic property in the Object Inspector then click the ellipsis button The DDE Info dialog box appears Figure 14 2 The DDE Info dialog box DDE Info Topic 5 Choose Paste Link 384 Delphi User s Guide Note The App and Topic boxes are filled in with the correct values automatically If the Paste Link button is disabled then the application you intended to be the server does not support DDE or the DDE information was not successfully copied to the Clipboard For example if you copy from the Quattro Pro notebook C NOTEBK1 WBz2 App is QPW and Topic is C NOTEBK1
184. Dialog m To specify a Help context for the dialog box component enter a number in the HelpContext property This number must correspond to a Help topic in the application s Help file For more information on developing Help files see the online Help topic Creating Windows Help 296 Delphi User s Guide E To specify the application Help file 1 Choose Options Project The Project Options multi page dialog box appears 2 Choose the Applications page tab 3 Inthe Auxiliary files section specify a Help file Use the Browse button if necessary to locate the Help file For more information see Help file and Icon on page 128 of Chapter 4 Using the OpenDialog component In the text editor application the handler for the FrameForm File Open menu item OnClick event interacts with the Open dialog box to load a file By setting initial values for several properties of the OpenDialog component and writing a few lines of code you can provide users with an interface consistent with other Windows based applications so they can easily view a list of available files and select a file to open OpenDialog component properties The properties for the OpenDialog component correspond to areas of the dialog box as shown in Figure 10 6 Figure 10 6 OpenDialog component properties w S O F i e N ame File Name Directories DefaultExt c appbuild demos notepad E gt cA l Cancel _ gt appbuild gt demos g
185. E servers Client applications can also send data to servers which is called poking data They can also execute macros of servers with macro capabilities To create a DDE client to be automatically updated by a DDE server 1 Adda DDEClientConv and a DDEClientItem component to a form 2 Assign the name of the DDEClientConv component to the DDEConv property of the DDEClientItem component To establish a link at design time choose this value from a list of possible conversations for DDEConv in the Object Inspector To establish a link at run time your application should execute code that assigns the value to the DDEConv property Chapter 14 Exchanging data with DDE or OLE 383 gt For example the following code links an DDEClientItem component named DDEClientItem1 to a DDEClientConv component named DDEClientConvi DDEClientIteml DDEConv DDEClientConvl E To create a DDE client to be manually updated by a DDE server add only a DDEClientConv component to a form To be updated your client application must execute code that calls the Request Data method of the DDEClientConv component See Requesting data on page 386 for more information Of course no DDE conversation is yet taking place because the DDEClientConv component has not yet been connected to a DDE server Nonetheless you have set the stage for this conversation to take place from your Delphi application The next sections explain e Establishing a link with a D
186. EPE DEE EY 245 Chapter 8 Using the integrated debugger 247 DP OL OU Se eer e ee tat ee ee 247 RUMUME COS e etna a a ads 247 LOGI CITORS i suei Kanaa a a BON hee E e E 248 Planning a debugging strategy 248 Starting a debugging session 249 Generating debugging information 249 Pefore VOU Degine sa ake ce S SE ew 250 Running your program 250 Specifying program arguments 250 Controlling program execution 251 Running to the cursor location 251 The execution point 0 251 Stepping through code 252 Taceo 2 35 Og oan at oe ek a a a oe 252 DIED OVEl 2 245 Weed Ard ore Sea ee 252 Debugging your application startup code 253 Running toa breakpoint 253 Pausing the program 253 Restarting the program 253 Using breakpoints 254 Setting breakpoints 254 Invalid breakpoints 255 Setting breakpoints after starting a POCTA 4 vig cre Sor Oe we Headey Sod ee A 255 Working with breakpoints 255 Viewing and editing code at a breakpoint 255 Disabling and enabling breakpoints 256 Deleting breakpoints 256 Modifying breakpoint properties 257 Creating conditional breakpoints 257 Setting Boolean conditions 257 Using pass counts 2 40 64 4 hee 44 258 Customizing the breakpoint and execution POM COONS o a 0
187. Form menu bar simply call the corresponding event handlers of the OLEFrameForm menu bar To be able to call methods of OLEFrameForm the unit where OLEFrameForm is declared must be referenced by the OLEObj unit Add a uses clause to the implementation part of the OLEOD unit and refer to the OLEFrame unit implementation uses OLEFrame Refer to unit OLEFRAME PAS Do not add OLEFrame to the uses clause in the interface section of OLEObj This would cause a circular unit reference error at compile time Write the following event handler for the OnClick event of the File New item on the OLEObjectForm menu bar procedure TOLEObjectForm NewlClick Sender TObject begin OLEFrameForm New1lClick Sender Call OLEFrameForm s File New handler end Write the following event handler for the OnClick event of the File Exit item on the OLEObjectForm menu bar procedure TOLEObjectForm ExitiClick Sender TObject begin OLEFrameForm Exit1Click Sender Call OLEFrameForm s File Exit handler end The OnClick event handlers for the Tile Cascade and Arrange Icons menu items on the Window menu of the OLEObjectForm menu bar call the corresponding method of OLEFrameForm These methods simply control the appearance of the OLEObjectForm MDI child window s Write the following event handler for the OnClick event of the Window Cascade item on the OLEObjectForm menu bar procedure TOLEObjectForm CascadelClick Sender TObject begin O
188. FormStyle property The FormStyle property determines whether the form is a frame or child form or a non MDI application form You set the FormStyle property only at design time To create an MDI frame form select the main form and use the Object Inspector to set its FormStyle property to fsMDIForm There can be only one MDI frame form per application You can set any form s FormStyle property to fsMDIForm but your application will not be compiled correctly if you do so for a form that is not specified as the application s main form To verify or change the application s main form choose Options Project and select the Forms page For the purposes of the text editor application set the values of the FormStyle Caption and Name properties as indicated in Table 10 1 Table 10 1 Text editor property values Property Value Name FrameForm Caption Text Editor FormStyle fsMDIForm Creating the MDI child form You create child forms at design time as templates for the appearance of each instance of the child window that the user opens at run time Since child windows are visible by default your code needs to explicitly create them at run time rather than allowing Delphi to automatically create them when the application first runs The section Creating child windows at run time on page 285 discusses how to do so The text editor application for example creates an instance of the text editor child form every time the user
189. I add a numeral to the list if I 7 then Abort abort after the seventh one end end Defining your own exceptions In addition to protecting your code from exceptions generated by the run time library and various components you can use the same mechanism to manage exceptional conditions in your own code To use exceptions in your code you need to understand these steps e Declaring an exception object type e Raising an exception Declaring an exception object type Because exceptions are objects defining a new kind of exception is as simple as declaring a new object type Although you can raise any object instance as an exception the standard exception handlers handle only exceptions descended from Exception It s therefore a good idea to derive any new exception types from Exception or one of the other standard exceptions That way if you raise your new exception in a block of code that isn t protected by a specific exception handler for that exception one of the standard handlers will handle it instead For example consider the following declaration type EMyException class Exception If you raise EMyException but don t provide a specific handler for EMyException a handler for Exception or a default exception handler will still handle it Because the standard handling for Exception displays the name of the exception raised you could at least see that it was your new exception raised Raising an e
190. LEFrameForm Cascade Cascade the MDI children of OLEFrameForm end 406 Delphi User s Guide Write the following event handler for the OnClick event of the Window Tile item on the OLEObjectForm menu bar procedure TOLEObjectForm TilelClick Sender TObject begin OLEFrameForm Tile Tile the MDI children of OLEFrameForm end Write the following event handler for the OnClick event of the Window Arrange Icons item on the OLEObjectForm menu bar procedure TOLEObjectForm ArrangelIconsiClick Sender TObject begin OLEFrameForm Arrangelcons Arrange the icons of the MDI chilren of OLEFrameForm end You ll write the OnClick event handlers for the Edit and Object menu items as well as for File Open and File Save As later in the example The OLE object menu item The Edit Object menu command of the OLEObjectForm menu bar is a special menu item It will be the OLE object menu item This item enables the user to open edit or convert an OLE object when an OLE container containing an object is selected at run time You don t program your OLE container application for this functionality it comes from OLE itself To designate a menu item as the OLE Object menu item assign the name of the menu item to the ObjectMenultem property of the form that owns the menu item To make the Edit Object menu command the OLE object menu item 1 Open the Menu Designer for the menu of OLEObjectForm 2 Change the value of the Name propert
191. List window 255 The Edit Breakpoint dialog box 257 The Watch List window 259 The Watch Properties dialog box 260 The Evaluate Modify dialog box 261 Call Stack window 263 The finished text editor program TEX TEDIDEXE s cura is bin ale Be 280 Text editor application menu with no child windows open 282 Text editor application menu with child WINKOW OPEN sis dow ke bw a a eee 283 Open child window 286 Font dialog box component options 296 OpenDialog component properties 297 The Filtereditors 2 4 ergoter ebb oot 298 Font dialog box component properties 304 Print dialog box component properties 306 The finished graphics program GRAPHEX EXE 610i no hence Sap ten 321 Drawing text at the point clicked 324 Graphics application with lines drawn 325 Graphics application following the mouse 326 Line with lost origin 328 xi 12 6 Straight line with intermediate drawing 329 12 7 Persistent intermediate lines 330 12 8 Line after rubber banding 331 12 9 The tool bar with 6 buttons 332 12 10 The tool bar buttons with glyphs assigned 333 12 11 The pen and brush toolbars 341 12 12 Bitmap dimension dialog box from the BPMPD GDE a o s e Sete hoe 354 13 1 The complete file manager example 359 13 2 File manager form with controls 361 13 3 Confirming a file d
192. MouseMove Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin Canvas LineTo X Y draw line to current position end Note that if you run the application moving the mouse over the form causes drawing to follow the mouse even before you press a mouse button as shown in Figure 12 4 Chapter 12 Graphics example 325 Figure 12 4 Graphics application following the mouse Graphics example Mouse move events occur even when you haven t pressed the mouse button You need to add code so the application acts on mouse move events only when the mouse button is down To track whether there is a mouse button pressed you need to add an object field to the form object Adding a field to a form object When you add a component to a form Delphi also adds a field that represents that component to the form object and you can refer to the component by the name of its field Component fields are explained in Chapter 6 You can also add your own fields to forms by editing the type declaration at the top of the form s unit In this example the form needs to track whether the user has pressed a mouse button To do that you can add a Boolean field and set its value when the user presses the mouse button E To add a field to an object edit the object s type definition specifying the field identifier and type after the public directive at the bottom of the declaration Delphi owns any declarations befo
193. Multiply button the third statement multiplies the two numbers together and displays the result in the third edit box Add another button to the form and rename it Divide Figure 5 14 A form for a scope example Form Create this event handler procedure TForml DivideClick Sender TObject begin FirstNumber StrToInt Editl Text SecondNumber StrToInt Edit2 Text Edit3 Text IntToStr FirstNumber div SecondNumber end Try to compile or run your application You get an Unknown Identifier error message Even though you already declared the FirstNumber and SecondNumber variables in the MultiplyClick event handler the DivideClick event handler can t use them Code in your application can t access variables outside the event handler in which they were declared In fact these variables cease to exist in memory when code execution continues outside the event handler This is true for all identifiers declared within any routine whether it is an event handler procedure function or method Such identifiers are called local in scope You can choose one of these two methods to make your application run correctly Chapter 5 Writing Object Pascal code 179 e You can redeclare the FirstNumber and SecondNumber variables in the DivideClick event handler Again the variables are local in scope procedure TForml DivideClick Sender TObject var FirstNumber SecondNumber Integer begin FirstNumber StrTolIn
194. NoFaceSel False fdNoOEMFor False fdNoSimulatic False fdNoSizeSel False fdNoStyleSel False fdNoVectorFe False fdShowHelp False fdwysiwyg False Tag e roperties MEvents y Y Oe The following sections discuss several of the options for the dialog box components you ll use as you build the text editor application Most of these options are unique to each dialog box All the common dialog boxes share at least one option in common however which deserves special mention For each dialog box you can specify whether to display a Help button If you choose to display a Help button you need to enable it so that when the user chooses the Help button at run time the application s Help file is opened to a relevant topic The following section describes how to do this Enabling the Help button from a common dialog box There are three steps to enabling a Help button from a common dialog box 1 Display the button in the dialog box 2 Specify a Help context for the dialog box component 3 Specify the application Help file E To display a Help button in a common dialog box set the Options ShowHelp property to True The ShowHelp setting is a nested property under the Options property for most common dialog box components For each dialog box component the ShowHelp property is prefaced with initials particular to the component For example in the Font dialog box component the ShowHelp property is called fdShowHelp for Font
195. O BUNARA 1557 Origin 27 163 Current 196 124 The main steps involved in creating the program are Responding to the mouse Adding a field to a form object Refining line drawing Adding a tool bar to a form Adding speed buttons to a tool bar Responding to clicks Chapter 12 Graphics example 321 Drawing with different tools Customizing pens and brushes Adding a status bar Drawing on a bitmap Adding a menu Printing graphics Working with graphics files Using the Clipboard with graphics The basic graphics skills used in this chapter are explained in Chapter 11 Responding to the mouse There are four kinds of mouse actions you can respond to in your applications Three of these are uniquely mouse actions mouse button down mouse moved and mouse button up The fourth kind of action a click a complete press and release all in one place is a bit different as it can also be generated by some kinds of keystrokes such as pressing Enter in a modal dialog box In this example you ll respond to the unique mouse actions You ll also see how clicks work when responding to tool bar commands In this example your application will draw shapes in response to clicks and drags pressing a mouse button starts drawing and releasing the button ends the drawing You ll also have the application draw a temporary rubber band image of the drawing while the user moves the mouse with the button pressed Initially yo
196. OC directory and is called FILMANEX DPR Figure 13 1 shows the completed application Figure 13 1 The complete file manager example File Manager Example C autoexec bat command com The topics presented in this example include e Creating the file manager form e Building the drive list e Creating an owner draw control Chapter 13 File manager example 359 e Manipulating files e Dragging and dropping The file manager example makes use of a number of routines in a unit called FMXUtils located in the same directory with the project file The implementation of those routines is outside the scope of this chapter but you can look at the source code to see examples of routines that for example copy and move files or return the size of a specified file Creating the file manager form The first step in creating the file manager application is designing the form The following sections describe briefly how to lay out the form place the controls and design the menu Laying out the form Start by creating a new project Then use the Object Inspector to set the following properties on the project s main form Table 13 1 Property values for the file manager example s main form Property Value Caption File Manager Example Name FMForm Position poDefault Placing the controls gt Next you need to add controls to the form Because you ll align all the controls to each other it s important that you place them and se
197. Paste Special dialog box 415 Using OLE objects with the Clipboard 417 Registering Clipboard formats 418 Specifying OLE formats aaan aaa 418 Pasting the OLE object 420 Dropping obe ss oan tow bw oar ie ae HM 421 Registering a form as an OLE drop target 421 Dropping an OLE object onto the OLE example application 422 Working with objects in files 423 Saving objectstofiles 424 Loading objects from files 424 DUIMIMALY 4 a5 ator Sa aa aaa a aa 426 Appendix A Selected Bibliography 429 Index 431 Tables Typefaces and symbols in these manuals 3 Components on the Standard page 38 Components on the Additional page 39 Controls on the Data Access page 40 Components on the Data Controls page 40 Components on the Dialogs page 41 Components on the System page 41 Components on the VBX page 42 Components on the Samples page 42 AboutBox component properties 53 MessageDlg parameters 81 Alternate form settings 87 Delphi s predefined bitmap button types 89 Property settings for demonstrating ACUVECOMWOls 4 6 2 A224 GS AEG K ESS 93 FormStyle property settings 97 Sample captions and their derived names 101 Menu Designer SpeedMenu commands 105 Design time project files 116 Compiler generated project files 11
198. Pasting objects To register new Clipboard formats for OLE objects call the Windows API function RegisterClipboardFormat To register the Clipboard formats for OLE objects or any other data type you want to be able to drop in the same way as when pasting objects call RegisterClipboardFormat and specify an array of BOLEFormat elements To enable the user to use the Paste Special dialog box to paste an OLE object into the 426 Delphi User s Guide OLEContainer component call PasteSpecialDlg To specify what types of objects to allow to be pasted specify an array of BOLEFormat elements one element for each type of object This array should be passed in the Fmts parameter of PasteSpecialDlg To initialize the OLEContainer component in the same way as when inserting objects assign a pointer modified by PasteSpecialDlg to the PInitInfo property Dropping objects To register a form for object drag and drop call RegisterFormAsOLEDropTarget To use the dropped object as an OLE object typecast the Source object as a TOLEDropNotify object in the OnDragDrop event handler of the form To initialize the container when an OLE object is dropped assign the value of the PInitInfo property of the Source object to the PInitInfo property of an OLEContainer component Working with objects in files To save objects to files call the SaveToFile method To load objects from files call the LoadFromFile method Chapter 15 OLE example 427 428 Delphi Us
199. PopupT emplatel Templatel Zo 3 Select the menu template you want to insert then press Enter or choose OK This inserts the menu into your form at the cursor s location For example if your cursor is on a menu item in a list the menu template is inserted above the selected item If your cursor is on the menu bar the menu template is inserted to the left of the cursor To delete a menu template 1 Right click the Menu Designer window The Menu Designer SpeedMenu appears 2 From the SpeedMenu choose Delete Templates If there are no templates the Delete Templates option appears dimmed in the SpeedMenu The Delete Templates dialog box opens displaying a list of available templates Figure 3 18 Delete Templates dialog box for menus fe Delete Templates PopupT emplatel Templatel 4o Chapter 3 Building forms and menus 107 3 Select the menu template you want to delete and press Del Delphi deletes the template from the templates list and from your hard disk Saving a menu as a template Any menu you design can be saved as a template so you can use it again You can use menu templates to provide a consistent look to your applications or use them as a starting point which you then further customize The menu templates you save are stored in your DELPHI BIN directory as DMT files m To save a menu as a template 1 Design the menu you want to be able to reuse This menu can contain as many items comman
200. Project Manager SpeedBar 131 Project Manager statusbar 131 Project Manager file list 2 nnau 132 Project Manager Pathcolumn 132 Integrating forms and units into a project 133 Creating new form units 134 Creating new source code units 134 Creating new component units 134 Sharing files from other projects or directories 93 4 a aot ith wile te Ee Coe OS 134 Using Borland Pascal source code units 135 Removing constituent files from a project 135 Saving projects and individual project files 135 Savine a projectes 4 s 4 4 68 Ee Soe wk 136 First project save 24 aw ye e364 Sew 136 Subsequent saves 0 136 Naming unit and project source code Mesh We ara wine te ae es Se ekg hE he 136 Saving a separate version of the project TGs fa Gate ie GO Ol Sarg wo Gis ee 137 DAVIE ACS 4 3 cc 4 Agee st ae Se oe te A ak Hee 138 File Save versus File Save As 138 Creating a backup of an entire project 139 Navigating among project components 139 Viewing forms and units 139 Toggling between form image and unit SOUTCO CODE paea 0 6 ea eaa Bs 140 Bringing a window to the front 140 Using the Project Manager to view or edit WADI CS secs sane e Tet cat lt 8 ee Vee Seat SEA a a dean Saad 140 Viewing the project source code DPR ES 2095 2s seit ona tn et es A wees dah A ee 141 Compiling building and running projects
201. Provide a rectangular area of the form to be painted xX FileListBox Provide a list box that displays the files in the current directory and enable users to scroll among them at run time Y DirectoryListBox Provide a list box that displays the directories on the current drive and enable the user to switch among them at run time Y DriveComboBox Provide a combo box that displays the current drive and enable the user to choose a different drive from the drop down list at run time Y FilterComboBox Provide a combo box that displays the current file filter for example and enable the user to select from a list of available filters at run time MediaPlayer Display a VCR style control panel for playing and recording multimedia video and sound files xX OLEContainer Create an Object Linking and Embedding OLE client area in the form mE N DDEClientConv Establish a client connection to a Dynamic Data Exchange Ta SAR DDE server application E N DDEClientItem Specify the client data that will be transferred during a DDE conversation E N DDEServerConv Establish a server connection to the DDE client om application El N DDEServerItem Specify the server data that will be transferred during a z DDE conversation Chapter 2 Using components and code 41 Table 2 7 Components on the VBX page Icon Visual Componentname Use to Y BiSwitch Provide a visual toggle switch similar to a check box Y BiGauge Provide a prog
202. SIWYG menu items as you build the menu File Edit Menu Designer Form MainMenul A TMenultem object is created and the Name property set to the menu item Caption you specify minus any illegal characters and plus a numeric suffix Figure 3 14 Menu Designer for a pop up menu Menu Designer Form1 PopupMenul Placeholder for first menu item Building menus You add a menu component to your form or forms for every menu you want to include in your application You can build each menu structure entirely from scratch or you can start from one of the Delphi predesigned menu templates This section discusses the basics of creating a menu at design time For more information about Delphi menu templates see Using menu templates on page 106 100 Delphi User s Guide Note Naming menus As with all components when you add a menu component to the form Delphi gives it a default name for example MainMenu1 You can give the menu a more meaningful name that follows Object Pascal naming conventions For more detail on the Object Pascal language see Chapter 5 Delphi adds the menu name to the form s type declaration and the menu name then appears in the Component list Naming the menu items In contrast to the menu component itself you need to explicitly name menu items as you add them to the form You can do this in one of two ways e Directly type in the value for
203. Save the project now then run it 1 If you have access to an OLE server application that supports drag and drop of OLE objects open a file within that server application 2 Grab an OLE object from the OLE server and drag it over the OLE Example application window Notice that the mouse pointer changes to the default no drop pointer when over a surface such as the Windows desktop that doesn t accept dragged OLE objects When the mouse pointer is over the OLE example application window it should change back to the drag and drop mouse pointer to indicate that the object can be dropped To change the appearance of the mouse pointer during drag and drop operations modify the DragCursor property For this example however don t modify the default settings of DragCursor 3 Release the mouse button to drop the OLE object An OLE object window is created and its OLE container component is initialized to contain the dropped OLE object 4 Choose File Exit to close the application Working with objects in files Saving OLE objects in files and restoring OLE objects from files was discussed in the section OLE data in files in Chapter 14 This application will use theSaveDialog and OpenDialog components to work with OLE data in files This section describes the following steps involved in working with OLE objects in files e Saving objects to files e Loading objects from files Chapter 15 OLE example 423 Saving o
204. Str function 155 161 238 Invalid Breakpoints dialog box 255 invalid component names 44 invalid drives 362 invalid identifiers 101 invalid types 153 invalid variable references 194 invisible images 366 is reserved word 227 228 items defined DDE conversations 383 OLE objects 393 iterating strings in lists 272 K keyboard shortcuts 43 accessing property values 54 adding to menus 102 103 menu commands 12 viewing Code Editor pages 62 keywords See reserved words Kind property bitmap buttons 88 L Label component 38 labels 38 40 See also captions lavender exit doors 89 Length function 201 libraries 42 adding components 69 70 application icons 128 backing up 68 creating 68 72 customizing 68 73 deleting components 68 69 distributable 115 dynamic link DLLs 77 117 creating 134 141 multiple versions 68 rebuilding 42 68 69 70 replacing 73 reverting to previous versions 71 run time 158 exceptions 236 242 saving 71 Library page Environment Options 71 line breaks in code 150 LINE BMP 333 lines drawing 315 316 317 328 331 changing pen width 344 event handlers 324 325 erasing 330 Lines property DDE items 385 388 memos 308 LineTo method 316 linker options 128 249 Linker page Project Options 128 linking database tables 40 linking DDE items 383 384 386 389 See also DDE links atrun time 383 385 388 linking OLE objects 392 list boxes 38 41 See also combo boxes data aware 40 draggi
205. Style bsNone ScrollBars ssBoth WordWrap False 288 Delphi User s Guide You now have a form with an area that can receive text By setting several properties you ve ensured that the Memo component remains indistinguishable from the form at run time Setting the memo s Align property to a value of alClient ensures that the memo always fills the client area or working space of the form The bsNone value of the BorderStyle property removes any border from within the Memo component Note Because the Memo component has been aligned to fill the client area when you edit the form itself later in this chapter you will access it by using the Object selector in the Object Inspector Manipulating text in a Memo component Once the user can open a new text file you want to provide some basic text manipulation operations such as alignment word wrapping and cutting copying and pasting This application uses event handlers for the EditForm menu items to provide these options Depending on the current condition of the text these menu items might change during run time for example a check mark might appear next to a menu item to indicate whether an option is selected or a menu item might appear dimmed when it s not available The text editor application also provides a local or pop up menu that contains text manipulation commands such as Cut Copy and Paste This section discusses the following topics e Setting text alignment and w
206. TForml class TForm private Line column indicator Modified indicator Priveate declarations public Pubic declaz Mode indicator Page tab The Delphi Code Editor is a full featured editor that provides access to all the code in a given application project The Code Editor includes many powerful features such as Brief style editing color syntax highlighting and virtually unlimited Undo For information about using the editor refer to the online Help topic Code Editor Chapter 1 Introducing Delphi 11 When you open a new project Delphi generates a page in the Code Editor for the unit source code PAS file To view the source code for a particular unit simply click that file s page tab The Code Editor title bar displays the name of the file in the active page of the Code Editor SpeedBar Select unit from list Select form Add file from list Save project tO Project Run Open project Ee a Am Open file g HE Toggle Save file eaen Trace into Remove file from project New form The Delphi SpeedBar in its default state provides you with shortcuts to some of the more common commands from the File Edit View and Debug menus You can configure the SpeedBar to include icons for most Delphi menu commands For information about customizing the SpeedBar right click it and choose the Help command then refer to the online Help topic SpeedBar You can resize the SpeedBar by dragging the separator
207. The component appears in its default size in the position you clicked on the form gt From the Additional page of the Component palette add a BitBtn component to the lower center portion of AboutBox Figure 2 2 AboutBox with BitBtn component J Unit AUinit As discussed in Chapter 1 when you add a component to a form Delphi generates an instance variable or field for the component and adds it to the form s type declaration You ve seen how adding a component changes the form s type declaration type TAboutBox class TForm BitBtnl TBitBtn this is the code that Delphi added end some additional code omitted for brevity Similarly when you delete a component Delphi deletes the corresponding type declaration For more information see Deleting event handlers on page 67 Sizing a component as you add it The next component you ll add an Image component needs to be larger than its default size You can resize and move components after they re on the form or as you place them E To resize a component as you add it 1 Select the component on the Component palette 2 Place the cursor where you want the component to appear in the form then drag the mouse pointer before releasing the mouse button As you drag an outline appears to indicate the size and position of the control 3 Release the mouse button when the outline appears as you want it Add an Image component on the Additional page of
208. The following section describes how to create your application s child windows at run time Creating child windows at run time Now that you have created the child form and its menus you re ready to write the code that generates an instance of EditForm at run time You do this by calling the Create method of EditForm In the text editor application when the new child window is created to contain a new document or to display an existing one the EditForm File menu replaces the FrameForm File menu This is part of the menu merging mentioned previously Because of this you need to handle the File New and File Open events separately for each menu gt Write the following event handler for the OnClick event of the File New item on the FrameForm menu bar be sure to name the handler NewChild rather than accepting the default name Delphi generates procedure TFrameForm NewChild Sender TObject var EditForm TEditForm declare the child form as a variable begin EditForm TEditForm Create Self create the new child window end Opening a new document won t vary much you can simply point back to the original event handler in FrameForm Opening an existing file involves a bit more and is discussed under Using the OpenDialog component on page 297 Chapter 10 Text editor example 285 gt Write the following event handler for the EditForm File New click procedure TEditForm NewlClick Sender TObject beg
209. When you click the While button once again the numbers 1 through 10 are written This time they appear 50 character spaces to the left of the edge of the form Note When you try the following suggested steps your application might appear to be in an endless loop Be patient a moment and the code will stop running Change the statement I 0 to I 10 in the RepeatButtonClick handler Then change the statement J 0 toJ 10 in the WhileButtonClick handler Finally run the application and click one of the buttons If you click the Repeat button the statements within the repeat statement run even though I already equals 10 This happens because the Boolean expression isn t evaluated until the end of the repeat statement The loop keeps running until I 10 once again If you click the While button the statements within the while statement don t run at all Because J already equals 10 the Boolean expression is True and the while statement stops running For more information about while statements see Delphi s online Help The for statement So far this section has discussed two kinds of loops the repeat statement and the while statement The repeat statement runs until a condition is True and the while statement runs while a condition is True The for statement is the third type of loop in Object Pascal The code within a for loop runs a specific number of times The value of a control variable which is really just a co
210. a previously entered expression from the drop down list Chapter 8 Using the integrated debugger 259 Formatting watch expressions You can format the display of a watch expression using the Watch Properties dialog box By default the debugger displays integer values in decimal form However by checking the Hex Integer button in the Watch Properties dialog box you can specify that an integer watch be displayed as hexadecimal Figure 8 4 The Watch Properties dialog box Watch Properties Repeat count fo e Digits ju X Enabled C Character C Hex integer C Record String Ordinal Default C Decimal integer C Pointer Memory dump If you re setting up a watch on an element in a data structure such as an array you can display the values of consecutive data elements For example suppose you have an array of five integers named xarray Type the number 5 in the Repeat Count box of the Watch Properties dialog box to see all five values of the array However to use a repeat count the watch expression must represent a single data element To format a floating point expression indicate the number of significant digits you want displayed in the Watch List window by typing this number in the Digits edit box Disabling a watch If you prefer not to watch an expression that you ve entered in the Watch List window but you don t want to delete it because you might need to use it later you can disable the watch Dis
211. a filter name for example Text and an associated file name extension for example TXT for each filter you want to use gt Specify filters for the Open dialog box of the text editor as shown in the following table Table 10 8 File filter settings for the text editor Filter name Filter Text files TXT TXT All files ue Note The order in which you enter filters is the order in which they then appear in the List File Of Type list box Opening an existing text file Your application can already present a new window where the user can enter and manipulate text Now you can continue by providing the ability to open existing files in a child window In the text editor application you ll write event handlers for both the FrameForm File Open click and the EditForm File Open click As mentioned earlier the event handler for the EditForm File New click simply pointed to the event handler for the FrameForm File New click In a similar way the EditForm File Open click points back to the FrameForm File Open click Then the FrameForm File Open event handler calls an Open method that exists in the new child form By writing a generic handler at the application FrameForm level you can reuse the event handler For example if you wanted to load other types of files you could simply write a different Open method in the child form You wouldn t have to modify the FrameForm event handler 298 Delphi User s G
212. ab list contains a tab for each valid drive on the system procedure TFMForm FormCreate Sender TObject var Drive AddedIndex Integer begin for Drive 0 to 25 do iterate through all possible drives if GetDriveType Drive gt 0 then positive values mean valid drives begin AddedIndex DriveTabSet Tabs Add Chr Drive ord a add a tab if Chr Drive ord A FileList Drive then if it s current drive DriveTabSet TabIndex AddedIndex make that current tab end end Of course just putting drive letters on tabs doesn t provide a very large target to click and doesn t provide any information on what kind of drive each tab represents In the next section you ll make the tab set into an owner draw tab set which will provide graphical information for each drive Connecting the controls Now that you have controls to represent disk drives directories and files you need to connect them so that they all represent their different aspects of the file and directory information That is when you choose a different drive with the tab set you want the directory outline to reflect the directory structure of that drive and the file list to display the contents of selected directory In order to connect the controls you need to handle events caused by tab selections and outline changes Note that in one case the tab set you handle clicks while the others have changes Responding to tab s
213. abling watches speeds up the response of the debugger because it won t have to monitor the watch as you step or run through your program In the Watch List window the Enable check box lies to the left of each watch listing When you set a watch the debugger enables the watch by checking this box To disable a watch do one of the following e Double click a watch in the Watch List window to open the Watch Properties dialog box then uncheck the Enabled check box e Select the watch in the Watch window and choose Disable Watch from the SpeedMenu You can also disable all current watches by choosing Disable All Watches from the SpeedMenu To reenable a watch recheck the Enabled check box or select it in the Watches window then choose Enable Watch or Enable All Watches from the SpeedMenu Deleting a watch To delete a watch expression select the expression in the Watch window then choose Delete Watch from the SpeedMenu You can also delete all the watches by choosing Delete All Watches from the SpeedMenu 260 Delphi User s Guide Caution Note The delete watch commands cannot be reversed Evaluating and modifying expressions You can evaluate expressions and change the values of data items using the Evaluate Modify dialog box The Evaluate Modify dialog box has the advantage over watches in that it enables you to change the values of variables and items in data structures during the course of your debugging session T
214. ach deleting files however would provide a chance for the user to confirm that the application should delete the file You can use a message dialog box to tell the user which file the application is about to delete providing the option to cancel the operation Add the following handler attached to the File Delete menu item s OnClick event The MsgDIg unit must appear in the uses clause for the unit containing this handler 370 Delphi User s Guide procedure TFMForm DeletelClick Sender TObject begin with FileList do if MessageDlg Delete FileName mtConfirmation mbYes mbNo 0 mrYes then if DeleteFile FileName then Update end The application now displays a message dialog box and requests confirmation from the user before deleting any files This gives the user a chance to cancel the deletion if necessary Figure 13 3 shows the message dialog box generated by this example Figure 13 3 Confirming a file deletion TT a Q Delete fmxutils dcu Changing a file s attributes Every file has various attributes stored by the operating system as bitmapped flags File attributes include such items as whether a file is read only or a hidden file Changing a file s attributes requires three steps 1 Reading file attributes 2 Changing individual file attributes 3 Setting file attributes You can use the reading and setting operations independently if you only want to determine a file s attribu
215. ad the MYFILE TXT file into the lines of a memo control Memol Lines LoadFromFile MYFILE TXT Instead of directly specifying a string value you could use a variable or expression of type string var Name string begin Name MYFILE TXT Memol Lines LoadFromFile Name end Finally you could specify a property value of type string In this example the code first calls the Execute method of the Open dialog box displaying the dialog box in your application When you select a file name in the dialog box that file name is specified as the parameter of the LoadFromFile method begin OpenDialogl Execute Memol Lines LoadFromFile OpenDialogl FileName the user specifies the parameter end 160 Delphi User s Guide You can read more about using the open dialog box the TOpenDialog component and the FileName property of an open dialog box in Delphi s online Help To read more about parameters see Passing parameters on page 190 Calling functions Like a procedure a function executes code that performs a specific task Also like a procedure a function that is declared within an object component or control is called a method The difference between a function and procedure is that a function returns a value when it stops running and a procedure doesn t Your code then uses the value returned by the function to do one of two things e Assign it to a property or variable e Use the value to determine
216. ages for each state if you prefer You normally assign glyphs to speed buttons at design time although you can assign different glyphs at run time E Toassign a glyph to a speed button at design time 1 Select the speed button 2 In the Object Inspector select the Glyph property 3 Double click the Value column beside Glyph Delphi opens the Picture editor 332 Delphi User s Guide 4 Choose Load in the Picture editor Delphi opens a file open dialog box 9 Select the BMP file that contains the image you want on the button and choose OK The file open dialog box closes and the Picture editor displays the selected bitmap image 6 Choose OK to close the Picture editor Assign the appropriate glyphs to each speed button Figure 12 10 shows the graphics example s tool bar with the file names for the glyphs for all the speed buttons These files are all located in the same directory as the project files Figure 12 10 The tool bar buttons with glyphs assigned LINE BMP BRUSH BMP RECT BMP PEN BMP ELLIPSE BMP ROUNDREC BMP Setting the initial condition of a speed button Speed buttons use their appearance to give the user clues as to their state and purpose Because they have no caption it s important that you use the right visual cues to assist users e To make a speed button appear pressed set its Down property to True e To make a speed button appear disabled set its Enabled property to False Since the default dra
217. ain later in the same session without having to exit Delphi Once you correct the error you must reopen the Install Components dialog box to rebuild the library If you don t want to recompile you can choose Revert to restore the unit list to match the state of the currently installed library Choosing Revert works only before you successfully rebuild the library You cannot use Revert to specify a previous version of the library after it s been successfully rebuilt Saving library source code After making changes to the library you can save the code for the library project file using the DPR extension To save library source code 1 Choose Options Environment then click the Library page tab 2 Check the Save Library Source Code check box The uses clause of this library source file lists all the units DCU that are used to build the Component palette Using the Component Expert Sometimes you might encounter a programming situation for which you want to create anew custom component rather than simply using one of the components provided with Delphi or available from third party vendors Writing your own components generally requires a more in depth knowledge of Object Pascal and object oriented programming than using pre built components Creating a new component requires you to e Create anew unit file e Derive the new component object from an existing class e Register the new component Once you are familiar with comp
218. alue and the function returns True If the edit box isn t empty the edit box color is set to the Windows system window color thereby changing the edit box color back to normal if it happened to be red and the function returns False gt Call the NoValue function from the two event handlers Here is the call actually two of them from the MultiplyClick event handler procedure TForml MultiplyClick Sender TObject var FirstNumber SecondNumber Integer begin if NoValue Editl or NoValue Edit2 then This line calls NoValue twice EXITS If an edit box 1s empty quit this event handler FirstNumber StrTolInt Editl Text SecondNumber StrToInt Edit2 Text Edit3 Text IntToStr FirstNumber SecondNumber COUNT Count Counter Text IntToStr Count end If either function call returns True one or both of the edit boxes are empty the Exit procedure runs Exit is a routine in the run time library that stops executing the code in the current block This means that none of the remaining lines of code in the MultiplyClick event handler run gt Run your application 184 Delphi User s Guide Now when either edit box is left empty the user is notified A procedure or function consists of e A procedure or function heading e A block of code Writing a procedure or function header Every procedure or function begins with a header that identifies the procedure or function and lists the par
219. ame property So long as the form Caption and Name begin with the same value a subsequent change to the Name property is reflected in the Caption If the Caption differs from the Name changes to the Name do not affect the Caption While the Caption property can contain any alphanumeric character of your keyboard including spaces this is not the case for the Name property The Name property must conform to standard Object Pascal naming conventions For more information on naming conventions see Chapter 5 Running the program Whenever you add components to a form Delphi generates supporting code in the background Likewise whenever you choose the Run command Delphi creates a complete standalone EXE file that runs without any run time interpreted DLLs As a result you can actually compile and run the form just as it is Try it now from the Run menu choose Run Notice that the components in the compiled program behave as you would expect them to The button appears to push in when you click it and you can resize and move the form Such behaviors are native to each component you don t have to program them Of course nothing useful happens when you click the button in this form That s where your code comes in In Delphi you write code that specifies what your program should do when it detects user interactions such as a button click or a drag and drop In programming terms such user interactions are called events
220. ameter no buttons appear in the box HelpCtx Link to a Help topic Not required You need to pass an integer into the HelpCtx parameter even if you don t have an application Help file In this case pass 0 zero If you do have an application Help file Chapter 3 Building forms and menus 8l you should include a Help button in the dialog box and pass the Help context that corresponds to the topic you want users to view for this dialog box If the integer you pass is not a valid Help context users will get an error message when they choose the Help button For more information on connecting your application to a Help system see Help file on page 128 of Chapter 4 To create a sample message dialog box try the following 1 Start a new blank project 2 Add a button to Form1 and generate the following event handler procedure TForml ButtoniClick Sender TObject begin MessageDlg Save changes mtConfirmation mbYesNoCancel 0 end 3 Run the program The message box illustrated here appears when you click Button1 Figure 3 3 Confirmation message dialog box Confirm Save changes Note MessageDlg displays the message box in the center of the screen by default You can use the MessageDIgPos function to create a message box that appears at a screen location you specify For more information about MessageDlg and MessageDI Pos look up the references in online Help and see the Help topic Displaying a Message B
221. ameters the routine uses if any A procedure begins with the procedure reserved word A function begins with the function reserved word The parameters are listed within parentheses Each parameter has an identifying name and usually has a type Parameters in a parameter list are separated from one another by a semicolon For example procedure ValidateDate Day Integer Month Integer Year Integer You can combine parameters of the same type like this procedure ValidateDate Day Month Year Integer You can read more about using parameters in the section Passing parameters on page 190 Functions have one additional element in their headers a return value type Specify the type of the value returned by the function separated from the rest of the header with a colon For example this function returns a value of type Double function CalculateInterest Principal InterestRate Double Double End all headers with a semicolon Writing a procedure or function block As discussed in the section Object Pascal blocks on page 174 all blocks have two parts an optional declaration part and a statement part Declarations within a procedure or function block Declaration parts within a procedure or function block can contain e Type declarations e Variable declarations e Constant declarations Type declarations Delphi applications can create new types beyond the predefined data types that are part of the Object Pascal
222. ample 379 380 Delphi User s Guide Chapter Exchanging data with DDE or OLE Exchanging data among applications is an important feature of multitasking environments such as Microsoft Windows You re probably already familiar with one way to share data the Windows Clipboard With Clipboard objects and methods such as CopyToClipboard Delphi enables you to take advantage of the Clipboard See Chapter 10 for an example that uses the Clipboard or search online Help forTClipboard for more information about using Clipboard objects Data sharing methods such as Dynamic Data Exchange DDE and Object Linking and Embedding OLE are even more powerful With them you can automatically reflect changes in one data file to many users using many instances of your application You can create a front end that integrates the data and functionality of a word processor spreadsheet and database all in one application You can even run and control other applications from within your application This chapter discusses e Using DDE e Using OLE e Comparing DDE and OLE Using DDE Dynamic Data Exchange DDE sends data to and receives data from other applications With Delphi you can use this data to exchange text with other applications You can also send commands and macros to other applications so your application can control other applications Here s a typical way to use DDE a link between two applications is established either by your app
223. and that their alignment takes care of assuring that they stack properly at the top of the frame Now that you ve got tool bars for the pen and brush the next sections describe using them to customize your drawing tools Changing the pen style A pen s style determines what kind of lines the pen draws such as solid dashed or dotted Note that some video drivers do not support different styles for pens with a pixel width greater than one Those drivers generally make all larger pens solid no matter what style you specify 342 Delphi User s Guide E Tochange the style of a pen set the pen s Style property to the value corresponding to the effect you want psSolid psDash psDot psDashDot psDashDot Dot or psClear For this example you could add click event handlers for each of the pen style buttons on the pen s tool bar but instead let s see how you can share one event handler for all the pen style buttons Sharing an event handler Different controls can all use the same event handler to handle events as long as the events are compatible meaning their handlers take the same parameters in the same order The most common use of this is to provide different entry points to do the same action such as attaching the click events for a menu item and a button to the same handler which gives a user multiple ways to perform the same action But you can also have several different controls share a handler that does different thing
224. and to open the Project Options dialog box where you can configure project default settings You access the Project Manager window by means of the View menu Chapter 4 Managing projects files and directories 129 If you share files among different projects using the Project Manager is recommended because you can quickly and easily tell the location of each file in the project This is especially helpful to know when creating backups that include all files the project uses See page 139 for more information on making backups Displaying the Project Manager You need to have a project open in order to view the Project Manager E To view the Project Manager window with a project currently open choose View Project Manager The Project Manager window The Project Manager window displays information about the status and file content of the currently open project It also provides quick access to project management functions easy navigation among the constituent files and access to project options through the SpeedBar and SpeedMenu Figure 4 1 Project Manager window Remove file View unit View form Updat Add file to DUPA _ project _ Pro SRH m N i Projet E SpeedBar status bar contains six SpeedButtons it name Unit si BN RAEAN EEEE oes Project options Form name column Unit file path As shown in the preceding figure the main elements of the Project Manager window are e The SpeedBar e The proj
225. andard components raise and respond to exceptions By handling exceptions in your applications you can ensure that you don t lose system resources when your application must unexpectedly shut down or you can enable the application or the user to correct the error condition and retry the operation In either case exceptions provide information necessary to the application and a mechanism you can use to respond to error conditions Chapter 7 Writing robust applications 245 246 Delphi User s Guide Chapter Using the integrated debugger No matter how careful you are when you write code a newly completed program is likely to contain errors or bugs that prevent it from running as it was designed to Debugging is the process of locating and fixing the errors in your programs Delphi contains an integrated debugger so you can debug programs without leaving Delphi integrated development environment The following topics are discussed in this chapter Types of bugs Planning a debugging strategy Starting a debugging session Controlling program execution Restarting the program Using breakpoints Examining program data values Viewing function calls Handling hardware and language exceptions You can access the integrated debugger through either of two menus Debug or View Types of bugs The integrated debugger can help find two basic types of programming errors run time errors and logic errors Run time errors If
226. ange the fill color assign a value to the brush s Color property Again you can set the brush color just as you did the pen color in response to a click on the color grid on the brush s tool bar procedure TForml BrushColorClick Sender TObject begin Canvas Brush Color end Adding a status bar A status bar is much like a tool bar except it usually occupies the bottom of a window instead of the top and instead of having controls on it the status bar usually displays text Delphi s panel component makes an excellent status bar BrushColor ForegroundColor Often you want to subdivide the status bar into multiple status areas and provide each with a three dimensional bevel effect To do this you can use panel components nested within the status bar panel Adding a status bar to an application involves the following tasks Placing a status bar panel Subdividing a panel Creating 3 D panels Updating the status bar Placing a status bar panel In general status bars appear at the bottom of a form Aligning the status bar panel to the bottom of the form takes care of both placement and resizing for you m To add a status bar panel to a form 1 Place a panel component on the form 2 Set the panel s Align property to alBottom 3 Clear the panel s caption Chapter 12 Graphics example 345 Once you ve added the status bar panel you can subdivide it into separate status panels If you re not going to su
227. ant to run when a new project is opened 4 With the Expert you want selected choose the Default Project button The folder icon displays in the box for the selected Expert 5 Choose OK to register the new default setting Specifying the default new form The default new form opens whenever you choose File New Form or use the Project Manager to add a new form to an open project In a new Delphi installation the Blank Form template is the default You can specify any other Form Template including a form you have created and saved as a Form Template as the default new form Or you can designate a Form Expert to run by default when a new form is added to a project To specify the default new form for new projects 1 Choose Options Gallery to display the Gallery Options dialog box 2 Choose the Form Templates page tab 3 Select the Form Template you want as the default new form 4 With the template you want selected choose Default New Form The form icon appears in the box for the selected default form 5 Choose OK to register the new default setting Specifying the default main form Just as you can specify the Form Template to be used whenever a new form is added to a project you can also specify which Form Template should be used as the default main form whenever you begin a new project Chapter 4 Managing projects files and directories 125 E Tospecify the default main form for open projects 1 Choose Options Gallery
228. applications 280 WordWrap property 290 writing units 206 208 209 begin end blocks 175 176 headers 206 User s Guide Delphi Borland International Inc 100 Borland Way P O Box 660001 Scotts Valley CA 95067 0001 Redistributable files For a list of redistributable files please see the REDIST TXT file in the DELPHI DOC directory Borland may have patents and or pending patent applications covering subject matter in this document The furnishing of this document does not give you any license to these patents COPYRIGHT 1995 Borland International All rights reserved All Borland products are trademarks or registered trademarks of Borland International Inc Other brand and product names are trademarks or registered trademarks of their respective holders Printed in the U S A 1E0R195 9596979899 987654321 W1 Contents Introduction Installing Delph araras dace oso aces 1 Documentation overview 5 2 Using this manual aoaaa aaaea 2 Using TCO w si tse te ow Be ee es 2 Using Interactive Tutors 0o lt i0 vara eae es 2 Manual conventions 3 Contacting Borland 0 3 Part I Getting started with Delphi 5 Chapter 1 Introducing Delphi 7 The Delphi programming environment i Stating Delp isos t det dd oe det ed aes 8 Elements of the Delphiinterface 8 Elements visible upon starting Delphi 9 FOE sss E a Eat his es a aed Gags GE 9 FOI TOOS nea ae ak e
229. ar procedure TOLEFrameForm OpenlClick Sender TObject var 424 Delphi User s Guide NewChild TOLEObjectForm begin if OpenDialog Execute then begin NewChild CreateChild NewChild OLEContainer LoadFromFile OpenDialog FileName end end Write the following event handler for the OnClick event of the File Open item on the OLEObjectForm menu bar procedure TOLEObjectForm OpenlClick Sender TObject begin OLEFrameForm OpeniClick Sender end Save the project now then run it 1 Drop an OLE object or display a new OLE Object window and insert or paste an object onto the child window Edit the object then deactivate it An OLE Object window now contains an inactive OLE object Choose File Save As to display the SaveAs dialog box as in 3 Figure 15 8 The Save As dialog box rr savea O File Name Directories ole d pk Read Only Save File as Type Drives OLE files ole ET Choose a file name then choose OK The OLE object in the OLE Object window that had focus when you chose File Save As is saved to a file Close the OLE Object window The main OLE Example frame form now contains no OLE Object windows Choose File Open to display the Open dialog box as in Select the previously saved file and choose OK Chapter 15 OLE example 425 A new OLE Object window appears displaying the object Figure 15 9 The Open dialog box EmO open File Name Directories ole d pk
230. ard and loading and saving operations for bitmap files Chapter 12 Graphics example 347 Adding a scrollable region The are many times when an application needs to display more information than will fit in a particular area Some controls such as list boxes and memos can automatically scroll their contents But other controls and sometimes even forms full of controls need to be able to scroll Delphi handles these scrolling regions with a control called ascroll box A scroll box is much like a panel or a group box in that it can contain other controls but a scroll box is normally invisible However if the controls contained in the scroll box cannot all fit in the visible area of the scroll box it automatically displays one or two scroll bars enabling users to move controls outside the visible region into position where they can be seen and used E To create a scrolling region place a scroll box control on a form and set its boundaries to the region you want to scroll You often use the Align property of a scroll box to allow the scroll box to adjust its area to a form or a part of a form For this example you ll create a scrollable region covering the entire area between the tool bar and the status bar which can then be used for drawing large images Place a scroll box component on the form and set its Align property to alClient assuring that it fills the entire portion of the form between the top and bottom aligned panels
231. are objects as they all descend from TObject e Object scope All data fields properties and methods of an object are within the scope of the object Any time you refer to a data field property or method within the scope of the object you can omit the object qualifier An object s scope extends to all descendants of the object You can use the public part of an object to declare data fields you want to be able to access from methods in objects in other units and to declare methods you want other objects in other units to be able to use You can use the private part of an object to restrict access to an object s data fields and methods You can access the fields and methods of an object using a with statement e Assigning values to object variables You can assign one object variable to another object variable if the variables are of the same type or are assignment compatible Using the reserved word is you can determine which specific object is assigned to a variable Also instead of specifying a particular object you can use the as reserved word and specify any object of a particular type in your code e Creating nonvisual objects You can create your own nonvisual objects Write the object type declaration in the type declaration part of the unit Before you can use the object you need to instantiate it with a call to the Create method When you have finished using the object you must destroy it and release its allocated
232. ared files you might have added to the project See Sharing files from other projects or directories earlier in this chapter After you name the unit file s Delphi prompts you to name the project source code DPR file before saving it to disk This processing order ensures that the unit and form file names you just specified are correctly registered in the project file s source code Subsequent saves If you have previously saved the project all open files that reside in the project directory are saved to disk if they have been modified If you have opened any new forms or units in the project since the last save the Save Unit As dialog box appears and prompts you to name those unit files before saving them The DPR project file is then updated to reflect any new units and any newly shared files that you might have specified for the project to use Naming unit and project source code files As you open new units in a project Delphi supplies them with default names such as UNIT1 PAS UNIT2 PAS UNIT3 PAS and so on You will soon run into confusion if 136 Delphi User s Guide Important you use these default names when saving the project It is highly advisable to supply a meaningful name for each unit in a project as you save it When naming the project source code file you need to supply a name not previously used by any of the unit files listed in the uses clause of the DPR file If you attempt to give the project th
233. art of the block The statements of a block describe algorithmic actions that can be executed If a block contains a declaration part the statement part uses the items declared in the declaration part of the same block Blocks within event handlers One of the most common kinds of blocks you encounter in Delphi are the blocks within event handlers The following simple event handler doesn t have a declaration part but it does have a statement part procedure TForml ButtoniClick Sender TObject begin The block starts here with the statement part Editl Text Welcome to Delphi end The block ends here at the end of the statement part The beginning of the statement part is marked with the reserved word begin The end of the statement part is marked with the reserved word end Blocks can contain optional declaration parts This is a revised version of the event handler that now includes a variable declaration part procedure TForml ButtoniClick Sender TObject var The block begins here with the start of the declaration part Name string begin The statement part of the block begins Name Editl Text Edit2 Text Welcome to Delphi Name end The end of the block As shown in this event handler the variable declaration part starts with the reserved word var and continues until the beginning of the statement part As described earlier event handlers are Object Pascal pro
234. as RoundRect Origin X Origin Y X Y Origin X X div 2 Origin Y Y div 2 end end MovePt Point X Y end Canvas Pen Mode pmCopy end You probably notice that there is a lot of repeated code in those methods In fact the code to draw each shape appears three different times This is a good example of a time when you should move repeated code into a separate routine In the next section you ll move all the shape drawing code into a single method that both mouse event handlers can call 338 Delphi User s Guide Adding a method to a form Any time you find that a number of your event handlers use the same code you can make your application more efficient by moving the repeated code into a method that all the event handlers can share To add a method to a form 1 Add the method declaration to the form object You can add the declaration in either the public or private parts at the end of the form object s declaration If the code is just sharing the details of handling some events it s probably safest to make the shared method private Write the method implementation in the implementation part of the form unit The header for the method implementation must match the declaration exactly with the same parameters in the same order To get rid of repetitive shape drawing code from mouse event handlers you can add a method to the form called DrawShape and call it from each of the handlers 1 Add th
235. ass Library VCL e Building form and menus This chapter explains how to design and create forms for maximum reusability both within the same project and across multiple projects Additional topics include how to use the Delphi Menu designer to create and modify Form menus for both Single Document Interface SDI and Multiple Document Interface MDI applications e Managing projects files and directories This chapter explains how to use the Delphi Project Manager to view and administer the files making up your Delphi project Additional topics include how to set project and programming environment options and how to streamline your programming tasks by using Delphi templates Part Il Fundamental skills 35 36 Delphi User s Guide Chapter Using components and code This chapter introduces many of the fundamental tasks you ll perform as you build user interfaces with Delphi components It expands on the concepts introduced in Chapter 1 by showing you how to create a dialog box that you can reuse in different applications While building the dialog box you ll find out more about manipulating components in the form arranging copying and so on and working with code in the Code Editor The About box you build in this chapter is available in its completed state as a template in the Delphi Forms Gallery If you like you can refer to the completed About box as you learn how to build your own To open the template choo
236. assigning values to the DDEService and DDETopic properties of a DDEClientConv component does not establish a link at run time You need to use the SetLink method to property initiate a DDE conversation For example execute the following line of code to link to a Quattro Pro notebook named C NOTEBK1 WB2 DDEClientConvl SetLink QPW C NOTEBK1 WB2 After using the SetLink method you need to assign the DDE item of the conversation to the DDEltem property of the DDEClientItem component For example execute the following line of code to link to cell A1 on page A of the Quattro Pro notebook DDEClientIteml DDEItem SA SA 1 SA 1 When a DDE link has been established the linked data appears in the Text and Lines properties of the DDEClientItem component Text specifies a string and Lines specifies a Chapter 14 Exchanging data with DDE or OLE 385 TStrings object Text can contain up to 255 characters of linked text data If the text data from the DDE server is longer than 255 characters use Lines to access the data The data is continuously updated by the DDE server and an OnChange event of the DDEClientItem component occurs whenever the data changes E One way to process linked text data is to display it in an edit box Edit component To do this you assign the value of the Text property of the DDEClientItem to the Text property of the edit box or for larger bodies of text you could assign the Lines property of the DDECli
237. at statement evaluates a condition at the end of the loop the while statement evaluates a condition at the beginning of the loop It starts with thewhile reserved word and the tested condition which must always be aBoolean expression If the condition is met the expression is True the code in the while statement runs until it reaches the end of the statement and the expression is tested again As soon as the expression is False the while statement stops running and execution continues after the while loop This example of a while loop uses the same sample form as the repeat loop did This is how the finished form appears Figure 5 7 A form for a while statement example Form1 To create this application 1 Add another button to the form and make these changes with the Object Inspector e Rename the second button to WhileButton e Change the caption of the button to While 2 Create this event handler that runs when you click the While button procedure TForml WhileButtonClick Sender TObject var J Integer begin i s 07 while J lt 10 do begin J J 1 Writeln J 50 end end Chapter 5 Writing Object Pascal code 169 3 Run the application and click the While button The following Boolean expression is examined first J lt 10 If it is True the remainder of the code within the while statement runs and then the expression is evaluated again If the expression is False the while statement stops running
238. at stores the results of the Boolean begin Pastel Enabled Clipboard HasFormat CF_TEXT enable or disable the Paste menu item HasSelection Memol SelLength lt gt 0 assign the value of the Boolean variable based on whether any text is selected in the Memo Cutl Enabled HasSelection enable the menu items if HasSelection evaluates to True Copyl Enabled HasSelection Deletel Enabled HasSelection end The HasFormat method of the Clipboard returns a Boolean value based on whether the Clipboard contains objects text or images of a particular format By checking the value of the Boolean expression for HasFormat of type text CF_TEXT the UpdateMenus procedure enables the Paste menu item if the Clipboard contains any text and disables the Paste item if the Clipboard does not contain text For more information about the HasFormat method refer to online Help For information about using the Clipboard object with graphics refer to Chapter 12 Declaring a method If you compile the program now Delphi generates a Method identifier expected error message Because UpdateMenus wasn t generated by using the Object Inspector Delphi didn t create the method declaration In order for the program to recognize UpdateMenus as a valid method of the TEditForm class you need to declare it yourself Add the following line to the private part of the TEditForm type declaration in the interface part of the MDIEdit unit proce
239. at the selected components have in common Notice however that the Name property is no longer visible 2 With the components still selected use the Object Inspector to set the property To view this in the About box try the following 1 Select the bitmap button component Notice the properties displayed in the Object Inspector including the Name property 2 Press Shift then select the Panel component The bitmap button component remains selected Notice how the properties displayed in the Object Inspector change to reflect only properties present in all the selected components Notice also that the Name property is no longer visible For information about more ways to set properties at design time see Setting Properties in online Help Scope of the Name property Because every component in a given form and every form in a project must have a unique name Delphi assigns default names to the forms and components in your project and numbers them sequentially as you add them For example if you add three buttons to the form Delphi names them Button1 Button2 and Button3 respectively The default names that Delphi generates are defined within thescope of each form In other words if you have two forms in your application each form could have aButton1 If however you add a button named Button to a form that already contains a Button1 Delphi renames it to the next available sequential number For an illustration of this idea
240. atts 277 Chapter 10 Text editor example 279 sae Document Interface MDI APDMCAMONS 2 422 Ss Bog Boose wg wa a ase 280 Creating the MDI frame form 281 The FormStyle property 281 Creating the MDI child form 281 Creating the application menus 282 Creating the frame formmenu 283 Creating the child form menu 283 Merging the application menus 284 Creating child windows atruntime 285 Referencing other units 286 Working with open child windows 287 Arranging and accessing open child WINKOWSie 555 o ee Sa te ee Dee ee A 287 Coding the Window menu commands 287 Including a list of open documents in a MCN Ae OR eS Ee ee ae eG 288 Providing an area for text manipulation 288 Adding the Memo component 288 Manipulating text ina Memo component 289 Setting text alignment and word wrapping 289 Setting text alignment 289 Adding scroll bars dynamically 290 Using the Clipboard with text 291 Selecting LEXA cca wee Oe i OS Aer ae 291 Cutting copying and pasting text 291 Deleting text without changing the contents of the Clipboard 292 Dimming menuitems 292 Declaringamethod 293 a a procedure from an event handler sra tae Gs Se has o 293 Providing apop upmenu 294 Handling the OnPopupevent 294 Specifying the pop up menu for the form 295 Usi
241. automatically saving files 31 Autosave options 31 123 AutoSize property 58 B backdrops 47 backgrounds repainting 317 backing up files 139 302 303 backup files 116 117 bar gauges 42 BatchMove component 40 begin reserved word 165 167 175 begin end blocks 174 177 case statements 167 if statements 165 nesting 176 BeginDrag method 376 Bevel component 39 beveled panels 346 BevelInner property 346 bibliography 429 BiGauge component 42 biMazimize constant 87 biMinimize constant 87 binary files 116 saving as text 94 BiPict component 42 BiSwitch component 42 biSystemMenu constant 87 BitBtn component 39 88 bitmap buttons 39 adding to dialog boxes 88 89 custom 89 Bitmap property brushes 316 bitmapped flags 371 bitmaps 117 347 350 See also graphics as form icon 94 associating with strings 275 276 366 blank 349 destroying 354 displaying 39 42 editing 14 file manager example 366 367 draw item events 369 measure item events 368 scrolling 348 temporary 348 349 bitwise operators file attributes and 372 bkAbort constant 89 bkAll constant 89 bkCancel constant 89 bkClose constant 89 bkCustom constant 89 bkHelp constant 89 bkIgnore constant 89 bkNo constant 89 bkOK constant 89 bkRetry constant 89 bkYes constant 89 Blank Form template 125 Blank Project template 115 124 blocks 174 177 185 event handlers 175 multiple statements 165 167 protected 231 232 233 syntax 235 protecting 231 234 within blocks 176
242. ay any path information e Files in subdirectories beneath the project directory appear with no preceding backslash character e Files in other locations display full path information In this case the ARSplash unit resides on a different drive If it resided on the same drive as the project directory the path column would display the information as SPLASH Using the Project Manager is highly recommended because it enables you to track the location of everything in your project Integrating forms and units into a project You can use either the Project Manager or commands on the Delphi File menu to create new forms or new unit files in a project or to add existing files from locations outside the project directory In order for any form or unit to belong to a project the project Chapter 4 Managing projects files and directories 133 must be open so that Delphi can update the project source code DPR file as new or shared unit files are added As you build a project you can e Create new form units e Create new source code units e Create new component units e Use files from a different project or location shared files e Use existing Borland Pascal source code units This section discusses each of these topics Creating new form units Opening a new form unit in a project is one of the tasks you probably do most frequently For information on creating new forms in a project see Chapter 3 Creating new sourc
243. bar to a form A tool bar is a panel usually across the top of a form below the menu bar that holds a number of controls especially buttons Tool bars provide an easy visible way to present options to users of your applications and Delphi makes it easy to add tool bars to your forms E To add a tool bar to a form 1 Add a Panel component to the form 2 Set the panel s Align property to alTop When aligned to the top of the form the panel maintains its height but matches its width to the full width of the form s client area even if the window changes size 3 Add speed buttons or other controls to the bar You can add as many tool bars to a form as you want If you have multiple panels aligned to the top of the form they stack vertically in the order added Adda tool bar to the graphics example form and delete its caption In the next section you ll add buttons to the tool bar Later in this example you ll add more tool bars to the form and see how to show and hide them at run time Adding speed buttons to a tool bar Delphi provides buttons called speed buttons specially designed to work on tool bars A speed button usually has no caption only a small graphic called a glyph which represents the button s function Chapter 12 Graphics example 331 Speed buttons have three possible modes of operation They can e Act like regular pushbuttons e Toggle on and off when clicked e Act like a set of radio butto
244. bdivide you probably want to set the BevelInner and BorderWidth properties to create a 3 D effect as explained later Panels that just serve as containers for smaller panels generally don t change those properties You also want to decide how to align the text within a panel By default panels center their captions but often in a status bar you want to set Align to alLeft gt For this example add a status bar panel to the form and name it StatusBar Subdividing a panel Often you want to divide a panel particularly one used for a status bar into multiple independent areas Although you can achieve a similar effect by carefully formatting the text in a single panel it s more efficient to use individual panels instead E To create panels within another panel Place a new panel within the panel Set any 3 D effects you want for the new panel Set the Align property of the new panel to alLeft Move the right side of the new panel to adjust its width Clear the new panel s caption Repeat steps 1 to 5 as needed for additional panels on GND As you add new left aligned panels to the original panel they align to each others right sides For the last panel you probably want to set Align to alClient rather than alLeft so that the last panel takes up all remaining space in the original panel gt For this example add two panels to the status bar named OriginPanel and CurrentPanel Align OriginPanel to the left a
245. bjects to files E Tosave an OLE object ina file use the SaveToFile method of the OLEContainer component For this example use a SaveDialog component to enable the user to specify a file name and location gt Adda SaveDialog component from the Dialogs page of the Component palette to OLEObjectForm and use the Object Inspector to set the following properties of the SaveDialog component Property Value Name SaveAsDialog DefaultExt ole FileName OLE Filter OLE files OLE OLE gt Write the following event handler for the OnClick event of the File Save As item on the OLEObjectForm menu bar procedure TOLEObjectForm SaveasiClick Sender TObject begin if SaveAsDialog Execute then OLEContainer SaveToFile SaveAsDialog FileName Save the object to FileName end Loading objects from files E To load an OLE object in a file use the LoadFromFile method of the OLEContainer component For this example use an OpenDialog component to enable the user to specify a file name and location gt Add an OpenDialog component from the Dialogs page of the Component palette to OLEFrameForm not OLEObjectForm and use the Object Inspector to set the following properties of the Open common dialog box component Property Value Name OpenDialog DefaultExt ole FileName OLE Filter OLE files OLE OLE Write the following event handler for the OnClick event of the File Open item on the OLEFrameForm menu b
246. blem with the OnMouseMove event handler as currently written is that while it draws a line to the current position of the mouse it draws that line from the last mouse position not from the original position Now that the application tracks the origin however that s easy to correct Move the drawing position to the origin point then draw to the current point procedure TForml FormMouseMove Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin if Drawing then begin Canvas MoveTo Origin X Origin Y move pen to starting point Canvas LineTo X Y end end That s better in that you now get lines to the current mouse position Unfortunately the lines don t go away so you can hardly find the final line Chapter 12 Graphics example 329 Figure 12 7 Persistent intermediate lines Graphics example The trick is to erase each line before you draw the next one and that means you need to keep track of where the previous one was That s the purpose of the MovePt field you added earlier gt Set MovePt to the endpoint of each intermediate line so you can use MovePt and Origin to erase that line the next time a line is drawn procedure TForml FormMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin Drawing True Canvas MoveTo X Y Origin POLUO A MovePt Point X Y keep track of where this move was end lt a s procedure TFor
247. bout adding units to a uses clause see How units are used on page 209 A scope example This is an example that illustrates local and global scope Your finished form should look something like this Figure 5 13 A form for multiplying two numbers together Form1 Each time the user enters two numbers in the first two edit boxes and chooses Multiply the application multiplies the two numbers together and displays it in the The Answer edit box gt To create this application 1 Put three edit box controls and a button control on a form 2 Place a label control above each of the three edit boxes 3 Using the Object Inspector change these property settings e Change the caption of Labell to First Number Change the caption of Label2 to Second Number Change the caption of Label3 to The Answer Change the value of the Name property of Button1 to Multiply Delete the text in all the edit boxes 178 Delphi User s Guide 4 Create this OnClick event handler for the Multiply button procedure TForml MultiplyClick Sender TObject Multiplies two numbers together var FirstNumber SecondNumber Integer begin FirstNumber StrTolInt Editl Text SecondNumber StrToInt Edit2 Text Edit3 Text IntToStr FirstNumber SecondNumber Displays answer in Edit3 end 5 Run your application You can put one integer in the first edit box and a second integer in the second edit box When you click the
248. briefly describes the primary kinds of data types you can create Enumerated types Subrange types Array types Set types Record types Object types Object Pascal has other user defined data types that aren t discussed in this chapter file pointer and procedural types For more information about these types see the corresponding topics in online Help Enumerated types An enumerated type declaration lists all the values the type can have These are some examples of enumerated type declarations type TDays Monday Tuesday Wednesday Thursday Friday Saturday Sunday TPrimaryColor Red Yellow Blue TDepartment Finance Personnel Engineering Marketing MIS TDog Poodle GoldenRetriever Dachshund NorwegianElkhound Beagle These are some variables of those enumerated types var DayOfWeek TDays Hue TPrimaryColor Department TDepartment DogBreed TDog Each value listed in parentheses in an enumerated type declaration has an underlying integer value determined by the position of the value in the list For example Monday in the TDays type declaration has the value 0 Tuesday has the value 1 and so on You could achieve the same result by declaring the DayOfWeek variable to be of type Integer and then assign an Integer value to represent each day of the week While this system might work in an orderly and predictable series such as days of the week or months of the year it s less useful when the or
249. bugging check box if necessary this box is checked by default 3 If you want check the Minimize On Run check box to specify that the Delphi environment be minimized when you run your program Running your program Once you ve compiled your program with debug information you can begin a debugging session by running your program from Delphi The debugger takes control whenever you run trace or step through your program code When you run your program under the control of the debugger it behaves as it normally would your program creates windows accepts user input calculates values and displays output In the time that your program is not running the debugger has control and you can use its features to examine the current state of the program By viewing the values of variables the functions on the call stack and the program output you can ensure that the area of code you re examining is performing as it was designed to As you run your program through the debugger you can watch the behavior of your application in the windows it creates For best results during your debugging sessions arrange your screen so you can see both the Code Editor and your application window as you debug To keep windows from flickering as the focus alternates between the debugger windows and those of your application arrange the windows so they don t overlap tile the windows With this setup your program s execution will be quicker and smoother du
250. by the name of the array followed by its index enclosed in brackets So the array Check contains the ten variables Check 1 Check 2 Check 3 Check 4 and so on up to Check 10 You can use any of these variables wherever you would use a regular Real variable Also the index value doesn t have to be a constant It can be any expression that yields an integer in the range 1 to 10 For example J Ses Check J 0 0 These statements assign the value 0 0 to variable Check 5 Because Check is an array of type Double the value you assign must be Real and contain a decimal point Also all Double values must begin with a digit not a decimal point so you can t write 0 0 as 0 If you want to assign a value of zero to all the Check variables in the array you could use a for loop to do it Because an index can be a variable afor loop is easier to use than assigning a value to each item in an array with separate assignment statements Thisfor loop assigns the 0 0 amount to all ten checks for J 1 to 10 do Check J 0 0 You can define arrays as types For example type TCheck array 1 100 of Double You can then declare variables of the array type For example this code declares a CheckingAccount to be a variable of type TCheck which is an array of 100 real numbers Chapter 5 Writing Object Pascal code 199 var CheckingAccount TCheck Multidimensional arrays The arrays discussed so far are one dimensiona
251. can help you learn how to develop a consistent and efficient user interface design This chapter presents techniques and tips for building usable forms but it is up to you to incorporate the forms you design into an overall user interface that presents your application to its best advantage Sharing forms Before you begin designing and building the forms for your applications think about whether these forms will be available to other developers or users Delphi is designed around the principle of reusable components and this encompasses larger elements such as forms or even entire projects The easiest way to share a form is simply to add an existing form to a project The About box you created in Chapter 2 is an example of a form that s broadly reusable Delphi provides the About box as a Form Template for just that purpose Form Templates are predesigned forms that you can easily reuse in your projects When you share forms among projects there are several considerations to keep in mind e As discussed in Chapter 1 to make the forms you add visible to other forms in the project you need to add their unit identifier to the uses clause of those other forms e When forms reference each other you need to avoid creating a circular reference e When you modify a shared form the modifications will show up in every project that uses the form not just the project where the form was originally created These considerations are discussed
252. cations 231 rounded rectangles 39 318 ROUNDREC BMP 333 RoundRect method 318 routines 20 121 338 See also functions methods procedures accessing 209 file operations 369 string handling 201 visibility in units 207 208 RowHeights property 368 Run command Run 17 Run Parameters dialog box 250 Run to Cursor command Run 251 running applications 17 143 250 251 375 376 pausing execution 253 254 264 to breakpoints 253 254 258 to specific locations 251 254 run time errors 247 248 run time graphics 313 319 run time libraries 158 exceptions 236 242 run time properties OLE objects 407 setting 59 60 S sample applications 267 Samples page Component palette 42 Save As command File 138 Save As dialog box 136 302 Save as Form Template dialog box 94 Save as Template command Menu Designer 105 108 Save command File 138 Save common dialog box 41 301 303 Save File command File 58 Save Project As command File 137 Save Project command File 58 Save Project Template dialog box 126 Save Template dialog box 108 Save Unit As dialog box 136 SaveDialog component 41 301 424 SaveToFile method 353 OLE objects 396 424 strings 273 276 SaveToStream method 426 saving 71 component libraries 71 desktops 31 files 301 303 310 353 automatically 31 forms 58 as ASCII text 94 as templates 93 94 graphics 353 menus as templates 105 106 108 OLE objects 392 396 424 projects 58 115 135 139 s
253. cedures Procedures that aren t event handlers also have blocks that look exactly like the blocks in event handlers You can read more about procedures and also about functions which are very similar to procedures in the section Writing a procedure or function on page 183 Blocks within units Units also have blocks that are made up of a declaration part and a statement part While units have a few unique parts of their own the notion of a block is still present For example unit Unitl interface uses WinTypes WinProcs Classes Graphics Forms Controls Apps type Beginning of the declaration part and the unit block TForml class TForm Chapter 5 Writing Object Pascal code 175 Edit1 TEdit Edit2 TEdit Button1 TButton procedure Button1Click Sender TObject private Private declarations public Public declarations end var Forml TForml The end of the declaration part implementation SR DFM procedure TForml ButtonlClick Sender TObject Beginning of the event handler block var Name string begin Name Editl Text Edit2 Text Welcome to Delphi Name end End of the event handler block end The end of the unit block For more information about units see Understanding Object Pascal units on page 206 You can also read about units and study the accompanying syntax diagrams in online Help Blocks within blocks Blocks can contain other block
254. characters can be letters underscores or the digits 0 9 e Identifiers can t contain any other symbols such as and so on For example identifiers called Do Noon or Gross Return result in a syntax error e You cannot use an Object Pascal reserved word for naming an identifier Reserved words have special meaning to the compiler If you use one of these reserved words to name an identifier Delphi displays an error message You can find a list of Object Pascal reserved words in online Help under the Reserved Words topic All reserved words are boldfaced in the Delphi documentation e Avoid using identifiers already defined in the Object Pascal language to name your identifiers For example the words Boolean and Integer are predefined data types see the section Data types on page 156 to read about predefined data types You can use either of these words to name a variable without generating an error message but if you do you won t be able to use the Boolean and Integer types in your code Giving a variable a type When declaring a variable you must state its type The type of a variable defines the set of values the variable can have In general you declare a variable where you want to use it For example if you want to use a variable in an event handler you declare the variable within the event handler For 154 Delphi User s Guide more details about where to declare variables read the sections Object Pascal b
255. checked Delphi loads the last project you worked on and displays any forms that were open at that time If the Editor files option is checked Delphi saves all modified files in the Code Editor when you choose from the Run menu Run Trace Into StepOver or Run To Cursor or when you exit Delphi By default these boxes are unchecked Thus when you start Delphi the default new project opens Gallery The Gallery check boxes specify whether Delphi displays the Browse Gallery dialog box when you choose File New Project or File New Form When checked e Use On New Form displays the Browse Gallery dialog box whenever you choose File New Form e Use On New Project displays the Browse Gallery dialog box whenever you choose File New Project If you check an option that causes the Browse Gallery dialog box to be used its appearance and defaults are controlled by the settings specified in the Gallery Options dialog box Gallery options The settings in the Gallery Options dialog box affect the behavior of Delphi when you begin a new project or create a new form in an open project This is where you specify e Default Project The Project Template or Expert to be used whenever you open a new project e Default New Form The Form Template Form Expert to be used when the Gallery is disabled in the environment and you open a new form e Default Main Form The Form Template used as the main form for a blank project only m To
256. checked by default 3 Begin your debugging session If you check Break On Exception the IDE displays an Error dialog box whenever an exception occurs When you choose OK to close this dialog box Delphi opens the Code Editor with the execution point positioned on the code that caused the exception At this point you can examine the program code to determine why the exception occurred If you continue the program run from this point the VCL displays an exception dialog box Note Because certain hardware exceptions can place your system in an unstable condition it is usually best to terminate your program run after an exception occurs Resolve the program error then resume the debugging session 264 Delphi User s Guide summary You can use the integrated debugger to debug your Delphi applications without leaving the IDE You can control the execution of your program by pausing the execution at any code location Once you pause the program you can examine the program state by reviewing the current values of program data values and the routines that are currently on the program call stack Controlling program execution means that you control when the program should be executed and when or where the program should pause You can use the integrated debugger to control the program execution by e Running to the cursor location e Stepping and tracing e Running to a breakpoint e Pausing your program While you re debugging a program
257. code to execute to handle a particular kind of exception The form of these exception handling statements is as follows on lt type of exception gt do lt statement gt You can define for example an exception handler for division by zero to provide a default result function GetAverage Sum NumberOfItems Integer Integer begin try Result Sum div NumberOfItems except on EDivByZero do Result 0 end end Note that this is clearer than having to test for zero every time you call the function Here s an equivalent function that doesn t take advantage of exceptions Chapter 7 Writing robust applications 239 function GetAverage Sum NumberOfItems Integer Integer begin if NumberOfItems lt gt 0 then Result Sum div NumberOfItems else Result 0 end The difference between these two functions really defines the difference between programming with exceptions and programming without them This example is quite simple but you can imagine a more complex calculation involving hundreds of steps any one of which could fail if one of dozens of inputs were invalid By using exceptions you can spell out the normal expression of your algorithm then provide for those exceptional cases when it doesn t apply Without exceptions you have to test every single time to make sure you re allowed to proceed with each step in the calculation Using the exception instance Most of the time an exception handler doe
258. command View 63 79 form components 38 77 Form Designer options 31 Form Experts 10 125 440 Delphi User s Guide form files 116 129 backup 117 sharing 134 135 form grid 52 Form SpeedMenu 93 Form Templates 10 29 See also Forms Gallery adding to galleries 93 126 127 adding to projects 78 79 loading 29 opening for reference 79 specifying as default 125 Form Templates page Gallery Options 125 126 formal parameters 191 193 194 actual parameters vs 191 formats Clipboard 416 418 420 registering 417 418 returning 419 OLE registration 422 formatting data 39 forms 9 38 48 75 adding fields 326 328 adding to projects 26 59 76 220 224 assigning icons to 94 auto creating at run time 113 114 borders 44 86 resizable 87 building 80 98 changing 26 in text files 94 shared 77 child See child windows customizing 59 75 defaults 86 defined 76 deleting 135 designing 15 17 displaying 79 80 139 editing as ASCII text 94 95 frame See MDI applications main form input 82 83 instantiating 207 main 9 changing 112 dialog boxes as 60 85 93 file manager application 360 362 MDI applications and 280 281 OLE example 400 401 403 specifying at run time 112 specifying default 125 moving among 79 140 multi page 39 naming 17 55 59 objects and 216 218 OLE objects and 393 395 401 predesigned 10 referencing 77 resizing 44 reusing 38 76 saving 58 as ASCII text 94 as templates 93 94 sharing 76 94 source code
259. command button for example whether changes are processed or not By setting properties of the Button component you can call a button s event handler code when the user presses Enter or Esc and you can specify that the dialog box closes when the user chooses a command button without writing any additional code Chapter 3 Building forms and menus 87 Executing button code on Esc Delphi provides a Cancel property for Button components When your form contains a button whose Cancel property is set to True pressing the Esc key at run time executes any code contained in the button s OnClick event handler E To designate a button as the Cancel button set its Cancel property to True Executing button code on Enter Buttons have a Default property that operates similarly to the Cancel property When your form contains a button whose Default property is set to True pressing Enter at run time executes any code contained in the button s OnClick event handler unless another button has focus when the Enter key is pressed Even if your form contains a default button another button can take focus away at run time Pressing the Enter key calls the OnClick event handler code of the button with focus overriding any other button s Default property setting The button with focus is indicated by a darker thicker border than that of other buttons in the dialog box Note Although other components in a form can have focus only button componen
260. cratch since you ll undoubtedly want to design your own This section discusses the most common considerations when designing any dialog box including Making a dialog box modal or modeless Setting form properties for a dialog box Providing command buttons Creating standard command buttons Setting the tab order Testing the tab order Removing a component from the tab order Enabling and disabling components Setting the focus in a dialog box Making a dialog box modal or modeless At design time dialog boxes are simply customized forms At run time they can be either modal or modeless When a form runs modally the user must explicitly close it before working in another running form Most dialog boxes are modal When a running form is modeless it can remain onscreen while the user works in another form for example the application main form You might create a modeless form to display status information such as the number of records searched during a query or information the user might want to refer to while working If you want a modeless dialog box to remain on top of other open windows at run time set its FormStyle property to fsStayOnTop Forms have two methods that govern their run time modality To display a form in a modeless state you call its Show method to display a form modally you call its ShowModal method The following two procedures use the Delphi About box Form Template to demonstrate the Show and ShowModal me
261. create and register their own graphic file formats so that picture objects can store them as well To save the contents of an image control in a file call the SaveToFile method of the image control s Picture object The SaveToFile method requires the name of a file to save into If the picture is newly created it might not have a file name or a user might want to save an existing picture in a different file In either case the application needs to get a file name from the user before saving as shown in the next section The following pair of event handlers attached to the File Save and File Save As menu items respectively handle the resaving of named files saving of unnamed files and saving existing files under new names procedure TForml SavelClick Sender TObject begin if CurrentFile lt gt then Image Picture SaveToFile CurrentFile save if already named else SaveAsiClick Sender otherwise get a name end procedure TForml SaveasiClick Sender TObject begin if SaveDialogl Execute then get a file name begin CurrentFile SaveDialogl FileName save the user specified name SavelClick Sender then save normally end end Replacing the picture You can replace the picture in an image control at any time If you assign a new graphic to a picture that already has a graphic the new graphic replaces the existing one To replace the picture in an image control assign a new graphic to
262. create your own user defined data types in Object Pascal The user defined data types are e Enumerated types a list of values a variable or property of this type can assume Code can refer to these values by name rather than by position in the list e Subrange types a range of values of any of these types integer Boolean Char or enumerated types e Array types an ordered collection of a specified data type with each element of the collection accessible by its numeric position within the collection e Set types a collection of elements of one type either an integer Boolean Char enumerated or subrange type e Record types collections of data that your application can refer to as a whole Records contain fields each with its own type that contain data e Object types collections of typed fields that contain data and methods procedures and functions that act on the data in the fields Understanding Object Pascal units Units are collections of constants data types variables procedures and functions that can be shared by several applications Delphi comes with a large number of predefined units your code can use Your Delphi applications are composed of a collection of units You create units as you design an application and write code in Delphi You can also write your own units that are not associated with forms Units always have an interface part which includes all the declarations that are accessible to ot
263. cts as templates using the Form Templates page of the Gallery Options dialog box instead of the Project Templates page Project options The settings in the Project Options dialog box affect only the current open project If you modify any of the defaults a configuration file with a file extension OPT is created in the project directory the next time you save the project When you reopen the project in future work sessions the project options as saved in the OPT file are in effect To display the Project Options dialog box choose any of these methods e In the Project Manager choose the Options button on the SpeedBar e In the Project Manager choose the Options SpeedMenu command e Choose Options Project from the Delphi menu bar The next sections point out the options in the Project Options dialog box that pertain to project management Detailed information for each option in the dialog box can be found in online Help Default check box The Project Options dialog box displays a check box control labeled Default This control enables you to modify some of Delphi s default project configuration properties Checking this control writes the current settings from the Compiler Linker and Directories Conditionals pages of the Project Options dialog to a file called DEFPROJ OPT Delphi creates this file when you check the Default box and choose OK in the Project Options dialog box Delphi then uses the project options settings stored in
264. d code 61 The About box appears as designed in the center of the screen Figure 2 16 Run time About box About Product Name Version Copyright Comments 6 Click OK Clicking OK closes the dialog box automatically because at design time you set the button s Kind property to bkOK and the border style to bsDialog Working with the Code Editor Using the Delphi Code Editor you can easily view and modify your source code You can also open related data files inside the Code Editor When you open a new project Delphi automatically generates a page in the Code Editor for the initial form unit file When you add a new form unit or other file to the project Delphi adds a new Code Editor page to contain the associated source code or other data Viewing pages in the Code Editor When a page of the Code Editor is displayed you can scroll through all the data it contains not just particular sections of your code When entering and editing your source code you can easily switch between viewing the form and viewing code to see how your design changes your code and vice versa E To view a page in the Code Editor choose from the following methods e Click the tab for the page you want to view e Press Ctrl Tab to move forward through the Editor pages and Shift Ctrl Tab to move backward e Choose View Units to open the View Unit dialog box and choose the unit you want to view e Use SpeedBar buttons to display
265. dEmployee Position Senior technical writer you could assign the values like this with PromotedEmployee do begin LastName Jeffries FirstName Richard YearHired 1990 Salary 100000 Position Senior technical writer end A few words about objects Objects are user defined data types that are very important in programming for Delphi Like records objects are structured data types that contain fields that hold values Objects however also contain methods Methods are procedures and functions that act on the data in the object s fields Each time you time you add a new component to a form you are adding a field to a form object Each component is also an object and each time you create an event handler so the component can respond to an event you are automatically creating a method within the form object All this happens automatically when you build the user interface for your application and create event handlers using the Object Inspector Nevertheless it is helpful to understand how Delphi uses objects to build your application You can read more about objects in Chapter 6 Chapter 5 Writing Object Pascal code 205 Understanding Object Pascal units This section explains what a unit is how you use it and how to write your own units that aren t associated with forms What is a unit A unit is a collection of constants data types variables and procedures and fu
266. dPerfect Document 6 0 C Display As Icon WP Chart 2 1 Result 3 Inserts a new Package object into your document 3 Ifyou want to insert an object that has already been created and saved in a file by the OLE server choose Create From File Specify the file name and path to the OLE object file To link the object select the Link check box If you want to embed a new object choose Create New and select an OLE object from the Object Type list You cannot link a new object since it has not yet been saved as a file 4 Choose OK If you are creating a new object the OLE server becomes active From the OLE server you can edit the OLE object When you have finished creating the OLE object update the OLE server and close the OLE object in your OLE container application Typically do this by choosing File Close or File Update within the OLE server application 5 The ObjClass property now contains the appropriate value for the OLE class and the OLEContainer component contains a picture representing the OLE object If the OLE object was created from an existing file and you inserted a linked object the ObjDoc property contains the appropriate value for the OLE document m If you have access to the OLE server application and data you can paste an OLE object containing an OLE item at design time 1 Activate the server application and select the item to be contained in the OLE object by your OLEContainer component 2 Copy the da
267. de in the Code Editor This is explained more fully under Handling events on page 18 and in Chapter 2 m To modify a property at design time 1 Inthe form select the component whose property you want to change The Component List displays the name of the selected component 2 From the Properties page of the Object Inspector select the property that you want to change 3 Modify the property by entering a new value Most property changes you make at design time are reflected immediately in the form For more information about setting properties refer to the online Help topic Setting Properties Change the Caption property for Form1 to My Demo Then change the Caption property for Button1 to Color Notice that as you type the Caption property for Form1 and Button display their changing value in the title bar of the form and on the button The Name property The Name property identifies the component to the underlying program and is the name shown in your code It s good practice to change the Name property so that it is 16 Delphi User s Guide Note gt descriptive of the component s function rather than relying on default names likeForm1 or Button You can change the Caption property by changing the default value of the Name property before specifying a caption The value of the Name property is then reflected in the caption By contrast changes to the Caption property are never reflected back into the N
268. de the correct drive and path 3 Restart Delphi then choose Workgroups Archive Manager to display the main team development window For information on using the team development support features of Delphi look up PVCS or Version Control in Delphi s online Help 144 Delphi User s Guide summary This chapter has discussed these primary topic areas What is a project Beginning new projects Customizing project options Managing project content Compiling building and running projects Managing multiple project versions and team development Chapter 4 Managing projects files and directories 145 146 Delphi User s Guide Part Programming topics The chapters in this part discuss how to program using the Object Pascal language The four chapters making up this part are e Writing Object Pascal code This chapter explains how to write code to create Delphi applications e Programming with Delphi objects This chapter explains what you need to know about objects and how to use them to create Delphi applications e Writing robust applications This chapter explains how to anticipate recognize and handle exceptions in your Delphi applications e Using the integrated debugger This chapter explains how to debug Delphi applications using the Delphi integrated debugger Part Ill Programming topics 147 148 Delphi User s Guide Chapter Writing Object Pascal code Previous chapte
269. dead code as invalid Setting breakpoints after starting a program While your program is running you can switch to the debugger by accessing the Code Editor and set a breakpoint When you return to your application the new breakpoint is set and your application halts when it reaches the breakpoint Working with breakpoints The Breakpoint List window lists all breakpoints by their file name and line number In addition each breakpoint listing shows any condition and pass count associated with the breakpoint If a breakpoint is either disabled or invalid then the breakpoint listing is dimmed in the Breakpoint List window To open the Breakpoint List window choose View Breakpoint Figure 8 1 The Breakpoint List window Breakpoint list Filename Line Condition Pass FONTLIST PAS 40 4 FONTLIST PAS 55 Index gt 5 0 i FONTLIST PAS 49 Use the Breakpoint List window to view and maintain all your breakpoints you don t need to search through your source files to find the breakpoints you ve set Also using the commands on the Breakpoint List SpeedMenu you can view or edit the code at any breakpoint location Viewing and editing code at a breakpoint If a breakpoint isn t displayed in the Code Editor window you can use the Breakpoint List window to quickly find the breakpoint s location in your source code Chapter 8 Using the integrated debugger 255 m To use the Breakpoint List window to locate a breakpoint
270. der of represented values is arbitrary Most people are not very good at remembering what a number stands for For example the assignment DogBreed Dachshund Chapter 5 Writing Object Pascal code 195 means much more to people than DogBreed 2 When you list a value in an enumerated type you are declaring the value as an identifier If the previous enumerated type declarations and variable declarations were in your application you could not therefore declare a Finance variable because a Finance identifier already exists gt To experiment using an enumerated type 1 Create this form containing four radio buttons in a group box a label and a button Figure 5 21 A form for an enumerated type example Form Select a course History Literature Biology Psychology 2 Change these properties using the Object Inspector e Change the group box caption to Select A Course e Name the first radio button HistoryButton and change the caption to History e Name the second radio button LiteratureButton and change the caption to Literature e Name the third radio button BiologyButton and change the caption to Biology e Name the fourth radio button PsychologyButton and change the caption to Psychology e Change the caption of the button to Display Selected Course 3 Declare a Course type below the implementation reserved word and the resource directive R DFM and declare a SelectedCours
271. design time 1 Select the form then use the Object Inspector to select the form s ActiveControl property 2 From the property s drop down list select the component you want to have focus when the form first opens If no component is specified as the form s active component Delphi gives initial focus to the component that is first in the tab order excluding e Disabled components e Components that are not visible at run time e Components whose TabStop property is set to False Setting focus at run time Focus changes automatically at run time when the user tabs among components You often want to actively specify a focus change Taking the previous example if you are designing a data entry form you might want to specify that focus change from field to field each time the user presses an arrow key You specify that a component gets focus by using the SetFocus method E Tochange the active component during run time type the following code in the appropriate event handler where lt componentn gt is the name of the component for example Button1 lt componentn gt SetFocus 92 Delphi User s Guide Note For more information see the online Help topic SetFocus method If you set a button as the active control for the form at design time that setting overrides at run time any default button you might have specified However you ll often find ways to use an active control together with a default button to process user inpu
272. dialog box For more information see Chapter 4 Associating an event with an existing event handler Delphi emphasizes reuse at all levels of application development from the project to the form to components and code You can reuse code by writing event handlers that handle more than one component event You can do this in the case of generic event handlers that for example are called by both a menu command and an equivalent button on a SpeedBar Once you write one such event handler you can easily associate other compatible events with the original handler To illustrate this concept you ll add anif then else statement to the OnClick event handler for MainForm Button1 Then you ll associate the event handler with MainForm Button2 Using the Sender parameter The Sender parameter in an event handler informs Delphi which component received the event and therefore called the handler You can write a single event handler that responds to multiple component events by using the Sender parameter in an if then else statement For another example of code that uses the Sender parameter see Chapter 10 For more information about these and other Object Pascal language statements see Chapter 5 gt Add anif then else statement to the existing OnClick handler for MainForm Button1 so that it looks like the following procedure TMainl ButtoniClick Sender TObject begin if Sender Buttonl then this is the first l
273. dialog box containing the text you specify in theMsg parameter and an OK button that closes the dialog box To display a message box with the ShowMessage procedure try this 1 Create a new blank project and place a Button component on Form1 2 Inthe button s OnClick event handler write the following code ShowMessage Delphi delivers When you run the program and click the button a modal dialog box appears with the name of the executable file in the title bar the text from the Msg parameter and an OK button as shown in the following figure Figure 3 2 Example ShowMessage message box Ge PROJECTI EXE Delphi delivers MessageDlg function The MessageDlg function displays a message box that contains text you specify and optionally various captions symbols and buttons Here is the syntax of the function function MessageDlg const Msg string AType TMsgDlgType AButtons TMsgDlgButtons HelpCtx LongInt Word The following table summarizes what each parameter specifies See online Help for detailed information regarding each parameter Table 3 1 MessageDlg parameters Parametername Specifies Comments Msg Text displayed in the dialog box If you omit this parameter no text appears in the dialog box AType Caption on title bar and If you omit this parameter no caption accompanying symbol in dialog box appears on the message box title bar AButtons Type of button s in the dialog box If you omit this par
274. dling for exceptions in special cases without losing or duplicating the existing handlers Handling component exceptions Delphi s components raise exceptions to indicate error conditions Most component exceptions indicate programming errors that would otherwise generate a run time error The mechanics of handling component exceptions are no different than handling RTL exceptions 242 Delphi User s Guide A common source of errors in components is range errors in indexed properties For example if a list box has three items in its list 0 2 and your application attempts to access item number 3 the list box raises an Index out of range exception The following event handler contains an exception handler to notify the user of invalid index access in a list box procedure TForml ButtoniClick Sender TObject begin ListBoxl Items Add a string add a string to list box ListBoxl Items Add another string add another string ListBoxl Items Add still another string tj evand a third string try Caption ListBoxl Items 3 set form caption to fourth string in list box except on EListError do MessageDlg List box contains fewer than four strings mtWarning mbOK 0 end end If you click the button once the list box has only three strings so accessing the fourth string Items 3 raises an exception Clicking a second time adds more strings to the list so it no longe
275. ds and submenus as you like everything in the active Menu Designer window will be saved as one reusable menu 2 Right click in the Menu Designer window to open the SpeedMenu 3 From the Menu Designer SpeedMenu choose Save As Template The Save Template dialog box appears Figure 3 19 Save Template dialog box for menus Template Description Form1 MainMenul 4 Inthe Template Description edit box type a brief description for this menu and then choose OK The Save Template dialog box closes saving your menu design and returning you to the Menu Designer window Note The description you enter is displayed only in the Save Template Insert Template and Delete Templates dialog boxes It is not related to the Name or Caption property for the menu Naming conventions for template menu items and event handlers When you save a menu as a template Delphi does not save its Name property since every menu must have a unique name within the scope of its owner the form However when you insert the menu as a template into a new form by using the Menu Designer Delphi then generates new names for it and all its items 108 Delphi User s Guide For example suppose you save a File menu as a template In the original menu you name it MyFile If you insert it as a template into anew menu Delphi names it File1 If you insert it into a menu with an existing menu item named File1 Delphi names it File2 Delphi also does not save any OnClick
276. ds of the DDEClientConv component to send text containing one or more macro commands to the server The server then processes the macro ExecuteMacro sends a PChar string while ExecuteMacroLines sends a TStrings object For example you could tell Microsoft Word 6 0 to close its active worksheet by executing the following code in your client application assuming that TheMacro is of type PChar StrPCopy TheMacro FileClose 2 DDEClientConvl ExecuteMacro TheMacro False Chapter 14 Exchanging data with DDE or OLE 387 In this example the second parameter is a wait flag It specifies whether your client application should wait for the server application to indicate that it has finished processing the macro before sending any more DDE data to the server If False your application sends more data to the server if you execute another ExecuteMacro ExecuteMacroLines PokeData or PokeDataLines method If True subsequent calls to these methods before the server has indicated the completion of the first macro do not send data Search online Help for ExecuteMacro or ExecuteMacroLines for more information about these methods Note Not all DDE servers can process macros See the documentation for the server application to determine whether it supports macros and for its macro syntax Creating DDE server applications DDE server applications respond to DDE clients Typically they contain data to which the client application needs acce
277. dure TForml CountButtonClick Sender TObject var Col Integer begin for Col 5 downto 1 do StringGridl Cells Col 1 IntToStr Col end gt Run the application and click the Count button Although the end result is the same as before the handler displays the numbers beginning with column 5 and proceeding to column 1 As the code runs theCol variable is assigned the initial value of 5 which is then decremented until the value of Col is less than the final value 1 Using nested for loops Writing a for loop within another for loop is very useful when you want to display data in a table or a grid This example uses the string grid The code displays simple column and row titles in the nonscrolling or fixed regions of the grid and then displays the column and row coordinates for each cell When you click the Show Coordinates button this appears in the grid Figure 5 9 A form with string grid displaying column and row coordinates Formi Joa o o oa o o Col 1 Row 1 Col 2 Row 1 Col 3 Row 1 Col 4 Row 1 Col 5 Row 1 Col 1 Row 2 Col 2 Row 2 Col 3 Row 2 Col 4 Row 2 Col5 Row 2 Col 1 Row 3 Col2 Row 3 Col 3 Row 3 Col 4 Row3 Col5 Row 3 Col 1 Row 4 Col 2 Row 4 Col 3 Row 4 Col 4 Row 4 Col5 Row 4 Col 1 Row5 Col2 Row5 Col3 Row5 Col 4 Row5 Col5 Row5 gt To set up the example 1 Place a string grid control and a button control on the form 2 With the Object Inspector change these pr
278. dure UpdateMenus Declaring the method in the private part keeps other units from accessing this method Because the MDIFrame unit has no reason to use this method since it contains no such menus it s good programming practice to keep it separate from the MDIEdit unit s sharable methods Calling a procedure from an event handler The handler for the Edit menu item OnClick event consists of one line of code a call to the UpdateMenus method you ve just written The OnClick event handler for the pop up menu component which you ll add later calls this same method Write the following handler for the Edit menu item s OnClick event procedure TEditForm SetEditItems Sender TObject begin Chapter 10 Text editor example 293 UpdateMenus end Providing a pop up menu Pop up or local menus are a common ease of use feature for any application They enable users to minimize mouse movement by simply right clicking anywhere in the application workspace to access a list of frequently used commands In the text editor application for example a pop up menu repeats the Cut Copy and Paste commands These pop up menu items use the same event handlers as the items on the application s main Edit menu Adda PopupMenu component to EditForm and use the Menu Designer to create the Cut Copy and Paste menu items You don t need to create any accelerator or shortcut keys for pop up menus Then attach the pop up menu items t
279. e What is a project Beginning new projects Customizing project options Managing project content Compiling building and running projects Managing multiple project versions and team development What is a project The Delphi application development process centers around the concept of projects A Delphi project is a collection of all the files that together make up a Delphi application or distributable library Some of these files are generated as you work on a project at design time Others are created when you compile the project source code Project directories Normally you should store each Delphi project you create in its own directory If you begin a project using any Project Template other than the Blank Project template Delphi prompts you for a directory path and then if necessary creates the specified directory for the project If you begin with the Blank Project template Delphi saves it by default in the BIN directory unless you specify otherwise To avoid cluttering this directory and potentially overwriting files create the project directory from the Windows operating environment before saving the new project for the first time See Beginning a project with a Project Template on page 122 for more information about Project Templates Chapter 4 Managing projects files and directories 115 Note Projects can reside in any network or local drive location that your computer can access Delphi doesn t requ
280. e If you try to assign a value to a constant parameter you ll receive an Invalid Variable Reference message because the value of a constant isn t allowed to change Deciding which kind of parameter to use Keep these points in mind when you use parameters e Use a value parameter when you don t want the value of the actual parameter to change Because the formal parameter is only a copy of the actual parameter the value of the actual parameter never changes Remember the actual parameter is the parameter specified in the procedure or function call The formal parameter is the parameter specified in the called routine e Use a variable parameter when you do want the called routine to change the value of the passed parameter Because both the actual and the formal parameters refer to the same value the value of an actual variable parameter can change when it is processed in the called routine e Use a constant parameter as the formal parameter in the called routine when the routine never changes the formal parameter This protects you from inadvertently 194 Delphi User s Guide assigning a new value to the formal parameter when you really don t want the formal parameter to change Defining new data types The Object Pascal language comes with a number of predefined data types see Table 5 1 for a list of them You can use these data types to create new data types that meet the specific needs of your application This section
281. e 209 non resizeable borders 87 non textual information 39 nonvisual components 37 38 42 52 nonvisual objects 228 229 Notebook component 39 47 notebooks 39 See also tabs adding pages 39 as containers 47 changing pages 363 null terminated strings 156 numbers 156 See also constants debugging 260 262 overflow errors 237 238 range checking 157 237 241 subranges 197 O ObjClass property 394 ObjDoc property 394 Object Browser 13 Object Inspector 54 218 See also property editors accessing properties 54 displaying components 11 editing code 19 overview 11 renaming components 44 selecting menus 106 setting properties 54 55 writing event handlers 18 60 Object Linking and Embedding See OLE applications Object Pascal language 149 214 Object selector 11 object types 205 244 declaring 188 ObjectMenultem property 407 object oriented programming 215 230 accessing components 223 adding fields and methods 224 225 constructors 229 declarations 217 222 224 228 defined 215 destructors 229 event handlers 218 219 222 22 renaming components 218 scope 222 226 startup code 216 objects 120 215 230 234 376 See also components accessing 222 226 allocating memory 229 ancestor vs descendant 221 223 226 Clipboard 291 customizing 220 debugging 262 defined 215 destroying 229 240 242 events and 218 219 222 227 exception 232 240 242 244 fields in 205 form 216 218 hierarchies viewing 13 inheritance 219 2
282. e Assign method For this example you can assign the image control s Picture property to the Clipboard in response to a click on the Edit Copy menu item procedure TForml CopylClick Sender TObject begin Clipboard Assign Image Picture end Cutting graphics to the Clipboard Cutting a graphic to the Clipboard is exactly like copying it but you also erase the graphic from the source To cut a graphic from a picture to the Clipboard first copy it to the Clipboard then erase the original In most cases the only issue with cutting is how to effect the erasure of the original image Setting the area to white is a common solution For this example you can attach the following event handler to the OnClick event of the Edit Cut menu item procedure TForml CutiClick Sender TObject var ARect TRect begin CopylClick Sender copy picture to Clipboard with Image Canvas do begin CopyMode cmWhiteness copy everything as white ARect Rect 0 0 Image Width Image Height get bitmap rectangle CopyRect ARect Image Canvas ARect copy bitmap over itself CopyMode cmSrcCopy restore normal mode end end Pasting graphics from the Clipboard If the Windows Clipboard contains a bitmapped graphic you can paste it into any image object including image controls and the surface of a form To paste a graphic from the Clipboard 1 Call the Clipboard s HasFormat method to see wh
283. e 411 Initializing the OLE container In order to contain an OLE object in an OLEContainer component you need to initialize the component Initializing the component means the OLE class is specified as well as the OLE document if the object is linked and the OLE item if the object is a more specific unit of data than is specified by the OLE document After initialization the OLEContainer component contains the OLE object E To initialize an OLEContainer component notify the OLEContainer where the OLE initialization information exists Assigning the pointer passed in the PInitInfo parameter of InsertOLEObjectDlg to the PInitInfo property of the OLEContainer component initializes the component The ObjClass ObjDoc and ObjItem properties of the component is specified automatically When you initialize the OLE container component the OLE object is activated The OLE server will take control and the user can edit the object through the OLE server After you deactivate the OLE object an initialized OLE container component contains a picture representing the OLE object or an icon The object can be reactivated in the manner specified by the AutoActivate property of the OLEContainer component By default activate the OLE object by double clicking the OLEContainer component Next you will write code to initialize the OLEContainer You will write code to specify the Info parameter later with a call to InsertOLEObyectDlg in the OnClick event
284. e About box is an example of the most simple kind of dialog box It doesn t accept any input from the user other than a button click but it does provide useful information A message box that displays a warning or error message is also a kind of dialog box More intricate dialog boxes require input from the user before the application can continue Delphi provides many such fully designed dialog boxes as components and you can also develop your own custom dialog boxes by using Delphi components Using routines to display dialog boxes The Delphi Dialogs unit provides several simple routines that display predesigned dialog boxes to the user based on the parameters you specify This section discusses how to use those routines to perform the following tasks in Delphi e Displaying message boxes e Creating simple input forms e Masking input characters Displaying message boxes Message boxes display text to the user and must be manually cleared from the screen before the application can continue Message boxes can be used for a variety of purposes including e Displaying warning information to the user 80 Delphi User s Guide e Displaying error messages e Requesting confirmation before closing a file or exiting the application ShowMessage procedure The ShowMessage procedure is the simplest way to display a brief message to the user The syntax of the procedure is ShowMessage const Msg string This procedure displays a modal
285. e Number variable in the OnClick event handler Because the Number actual parameter and the formal CalcNo parameter now refer to the same variable the Number value changes in the second edit box when Calculate runs These drawings demonstrate what happens When Calculate is called the value of Number and the value of CalcNo are the same because both the actual and the formal parameters refer to the same memory location Chapter 5 Writing Object Pascal code 193 Figure 5 19 The value of Number and CalcNo when Calculate begins running Value of Number Value of CalcNo actual parameter actual parameter E After the Calculate procedure runs the Number and CalcNo parameters still refer to the same value even though that value has changed Figure 5 20 The value of Number and CalcNo after Calculate runs Value of Number Value of CalcNo actual parameter formal parameter 100 Constant parameters If a formal parameter never changes its value when a procedure or function runs you should consider using a constant parameter instead of a value parameter Make a formal parameter a constant parameter by typing the reserved word const before the name of the parameter in the parameter list Like a value parameter a constant parameter can be any expression Using a constant parameter instead of a value parameter however protects you from accidentally assigning a new value to the parameter when you don t want the parameter to chang
286. e See the documentation for the OLE server for information about whether it attempts menu merge during in place activation The GroupIndex property of each of the container application s menus determines where merging menu items appear in the container s menu bar Merged menu items from the OLE server might replace those on the main menu bar or they might be inserted beside existing container application menu items The OLE server will merge up to three groups of menu items the Edit View and Help groups Each group is distinguished by a unique group index and can contain any number of menu items The following table summarizes which menu item groups the OLE server application will merge Source when OLE Group Index Description active File 0 Menu item s for using files and exiting the OLE container application application Edit 1 Menu item s for editing the active OLE object OLE server application Object 2 Menu item s for manipulating the deactivated OLE container application OLE object View 3 Menu item s for modifying the view of the OLE OLE server application object Window 4 Menu item s for manipulating windows OLE container application Help 5 Menu item s for accessing the server s online Help OLE server application Any menu items in your container application that have a GroupIndex property value of 1 3 or 5 will be replaced by the menu items with corresponding index values from the OLE server application when an OLE object
287. e The first component in the tab order should have the TabOrder value of 0 Keep in mind the following points when manually setting your tab order you needn t be concerned with these points if using the Edit Tab Order dialog box e Each TabOrder property value must be unique If you give a component a TabOrder value that has already been assigned to another component on this form Delphi renumbers the TabOrder value for all other components accordingly 90 Delphi User s Guide Note e If you attempt to give a component a TabOrder value equal to or greater than the number of components on the form because numbering starts with 0 Delphi does not accept the new value instead entering a value that ensures the component is last in the tab order e Components that are invisible or disabled are not recognized in the tab order even if they have a valid TabOrder value When the user presses Tab the focus skips over such components and goes to the next one in the tab order For more information see Enabling and disabling components on page 91 Testing the tab order You can test the tab order you ve set by running the application At design time focus always moves from component to component in the order that the components were placed on the form Changes you make to the tab order at design time are reflected only at run time To test the tab order 1 Run the application 2 Use the Tab key to view the order in which focus moves
288. e and access the context topic if appropriate For further information consult your Windows Help documentation or the online Help file Creating Windows Help Caution Be aware that the Help file for your distributed application might not reside in the same location relative to the executable file as it does on your development system Avoid specifying a drive name unless you know for certain that the finished application s Help file will always reside on a drive with that name Consult your Windows Help documentation for further information on how WINHELP EXE attempts to locate Help files Icon Delphi supplies a default icon for all projects which appears whenever the running application is minimized or when the application s EXE is specified in creating a program item for the Windows Program Manager You ll probably want to use a different icon for your applications The Delphi Image Library supplies some icon files that you can use directly or modify by using the Delphi Image editor You can specify any standard Windows icon file ICO residing in any location The specified icon is compiled into the project s executable file Compiler page The options on this page enable you to specify compiler options Modified settings affect only the current project unless the Default box is checked Checking the Default box preserves the settings on this page as the default compiler settings for all new projects see Default check b
289. e appears in the form s type declaration All the event handlers you write in Delphi are methods of the form object Each time you create an event handler a method is declared in the form object type The TForm1 type now contains a new method the Button1Click procedure declared within the TForm1 type declaration The actual code for the Button1Click method appears in the implementation part of the unit The method is the same as the empty event handler you created with Delphi and then filled in to respond when the user clicks the button as the application runs Changing the name of a component You should always use the Object Inspector to change the name of a component For example when you change the default name of a form from Form1 to something else by changing the value of the Name property using the Object Inspector the name change is reflected throughout the code Delphi produces If you wrote the previous application but named the form ColorBox this is how your code would appear 218 Delphi User s Guide unit Unitl interface uses WinTypes WinProcs Classes Graphics Forms Controls Apps type TColorBox class TForm Changed from TForml to TColorBox Buttonl TButton procedure ButtoniClick Sender TObject private Private declarations public Public declarations end var ColorBox TColorBox Changed from Forml to ColorBox implementation SR DFM procedure TColorBox Button
290. e code units If you want to write a custom Object Pascal procedure function or DLL as a stand alone program callable from any unit you need to save it in a new source code unit If you want to create this type of unit and not have it be part of a project you can open the new unit without having a project open E To open anew source code unit choose File New Unit from the Delphi menu bar If you have a project open you can also choose New Unit from the Project Manager SpeedMenu When you create a unit in an open project by means of the New Unit command the new unit is registered in the project DPR file when you save the project or new unit file Creating new component units You need to create anew component unit only if the purpose of your project is to write a new Delphi component For information on opening a new component unit see Using the Component Expert on page 71 Complete information on writing Delphi components is contained in the online Help system Sharing files from other projects or directories A project can use existing form and unit files that it did not create and which don t reside in the current project directory or any subdirectory of that directory When you compile your project it does not matter whether the files that make up the project reside in the project directory a subdirectory of the project directory or any other location If you add a shared file to a project bear in mind that the file i
291. e declaration of DrawShape to the form object s declaration type TForml class TForm many fields and methods omitted for brevity public Public declarations procedure DrawShape TopLeft BottomRight TPoint AMode TPenMode end Write the implementation of DrawShape in the implementation part of the unit implementation SR FRM many other method implementations omitted for brevity procedure TForm1 DrawShape TopLeft BottomRight TPoint AMode TPenMode begin with Canvas do begin Pen Mode AMode case DrawingTool of dtLine begin MoveTo TopLeft X TopLleft Y LineTo BottomRight X BottomRight Y end tRectangle Rectangle TopLeft X TopLeft Y BottomRight X BottomRight Y tEllipse Ellipse TopLeft X TopLeft Y BottomRight X BottomRight Y tRoundRect RoundRect TopLeft X TopLeft Y BottomRight X BottomRight TopLeft X BottomRight X div 2 TopLeft Y BottomRight Y div 2 Q Qu Y end end end Chapter 12 Graphics example 339 3 Modify the other event handlers to call DrawShape procedure TForml FormMouseUp Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin DrawShape Origin Point X Y pmCopy draw the final shape Drawing False end procedure TForml FormMouseMove Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin
292. e purpose of this section is to introduce the file loading and file saving capabilities of the graphics objects including e Loading a picture from a file e Saving a picture to a file e Replacing the picture Before you start to load or store files add three things to the application e An open file dialog box e Asave file dialog box e An object field named CurrentFile of type string to the form object Adding common dialog boxes is part of the sample application in Chapter 10 Adding object fields is covered in this chapter on page 326 Loading a picture from a file The ability to load a picture from a file is important if your application needs to modify the picture or if you want to store the picture outside the application so a person or another application can change the picture without changing code To load a graphics file into an image control call the LoadFromFile method of the image control s Picture object Attach the following handler to the OnClick event of the File Open menu item procedure TForml OpenlClick Sender TObject begin if OpenDialogl Execute then begin CurrentFile OpenDialogl FileName Image Picture LoadFromFile CurrentFile end end 352 Delphi User s Guide Saving a picture to a file When you have created or modified a picture you often want to save the picture in a file for later use The Delphi picture object can save graphics in several formats and application developers can
293. e result by adding a comma Chapter 8 Using the integrated debugger 261 and one or more format following specifiers to the end of the expression entered in the Expression edit box Table 8 1 details the legal format specifiers Table 8 1 Expression format specifiers Character Types affected Function H or X Integers Hexadecimal Shows integer values in hexadecimal with the 0x prefix including those in data structures C Char strings Character Shows special display characters for ASCII 0 31 By default such characters shown using the appropriate C escape sequences n t and so on D Integers Decimal Shows integer values in decimal form including those in data structures Fn Floating point Floating point Shows n significant digits where n is in the range 2 18 and 7 is the default nM All Memory dump Shows n bytes starting at the address of the indicated expression If n is not specified it defaults to the size in bytes of the type of the variable By default each byte shows as two hex digits The C D H S and X specifiers can be used with M to change the byte formatting p Pointers Pointer Shows pointers as seg ofs instead of the default Ptr seg ofs It tells you the region of memory in which the segment is located and the name of the variable at the offset address if appropriate R Records classes and Records Classes Objects Shows both field names and values objects such as X 1 Y 10 Z 5 instead of 1
294. e running application 286 Delphi User s Guide The application as it s written doesn t provide any way to easily navigate among multiple open child windows The following section discusses how to accomplish this Working with open child windows Now that your application can respond to the File New menu command by creating a new child window you can begin writing code that works with open child windows In the text editor application when a child window is opened the EditForm menu bar merges into the FrameForm menu Commands from the EditForm File menu such as printing saving and closing files become available Commands on the FrameForm Window menu provide a way to arrange and navigate among the open child windows This section describes the following topics e Arranging and accessing open child windows e Providing an area for text manipulation Arranging and accessing open child windows MDI applications provide the ability to open several child windows within one common workspace the frame window Because of this MDI applications should always include a Window or other menu item that contains e Tile Cascade and Arrange Icons commands to offer users an easy way to arrange their open documents in the client area of the frame window e A list of the open document windows which enables users to quickly switch among them The window that currently has focus appears in the list with a check mark next to it You
295. e same name as one of these units Delphi displays an error message similar to the following The project already contains a module named Customer If this occurs respond OK to the error message box and supply a different name for the DPR file in the Save As dialog box As with unit files Delphi supplies a default name PROJECT1 DPR for the unit source code DPR file Again you should supply a more meaningful name when saving the file for the first time All unit and project file names must conform to DOS naming conventions Saving a separate version of the project file Delphi enables you to save a separate version of an open project in a directory other than the project directory The File Save Project As command initiates the process However because the open project might use shared files in addition to files that were created as part of the current project the Save Project As command saves only a copy of the project source code DPR file project options settings OPT file and the project resource RES file to the new location No unit files are saved to the new location When you open the copied version the Project Manager displays all units in the copied project as shared files that is none of them reside in the project directory of the currently open project To save a separate copy of the project DPR file in another location 1 Choose File Save Project As from the Delphi menu bar to display the Save
296. e variable declaration part of the unit you need to declare a variable of the new type var Employee TEmployee Creating an instance of an object TEmployee is just an object type An actual object doesn t exist in memory until the object is instantiated or created by a constructor call A constructor is a method that allocates memory for the new object and points to the new object which is called aninstance of the object type Calling the Create method the constructor assigns this instance to a variable If you want to declare an instance of the TEmployee type your code must call Create before you can access any of the fields of the object Employee TEmployee Create In the TEmployee type declaration there isn t a Create method but because TEmployee is derived from TObject and TObject has a Create method TEmployee can call Create to create a TEmployee instance which is assigned to the Employee variable Now you are ready to access the fields of an Employee object just as you would any other Delphi object Destroying your object When you are through using your object you should destroy it which releases the memory the object used You destroy an object by calling adestructor a method that releases the memory allocated to the object Delphi has two destructors you can use Destroy and Free You should almost always use Free In its implementation the Free method calls Destroy but only when the instance pointer
297. e variable of type TCourse type TCourse Nothing History Literature Biology Psychology var SelectedCourse TCourse 4 Create an OnClick event handler for each radio button When you have finished your code should look like this implementation SR DFM 196 Delphi User s Guide type TCourse Nothing History Literature Biology Psychology var SelectedCourse TCourse procedure TForml HistoryButtonClick Sender TObject begin SelectedCourse History end procedure TForml LiteratureButtonClick Sender TObject begin SelectedCourse Literature end procedure TForml BiologyButtonClick Sender TObject begin SelectedCourse Biology end procedure TForml PsychologyButtonClick Sender TObject begin SelectedCourse Psychology end procedure TForml ButtoniClick Sender TObject begin case SelectedCourse of History Labell Caption You are taking history Literature Labell Caption You are taking literature Biology Labell Caption You are taking biology Psychology Labell Caption You are taking psychology else Labell Caption You are taking nothing end end 5 Run the application When you select a radio button to choose a course an enumerated value is assigned to the SelectedCourse variable The OnClick event handler for the button uses a case statement to display an appropriate message based on the value of the SelectedCour
298. ecause TForm1 is derived from TForm all the elements that belong to a TForm type automatically become part of the TForm1 type If you look up TForm in online Help you can click the form itself and press F1 you see lists of all the properties methods and events in the TForm object type You can use all the elements inherited from TForm in your application Only the elements you specifically add to your TForm1 type such as components you place on the form or event handlers methods you write to respond to 220 Delphi User s Guide events appear in the TForm1 type declaration These are the things that make TForm1 different from TForm The more broad based or generic object from which another more customized object inherits data and code is called the ancestor of the customized object The customized object itself is a descendant of its ancestor An object can have only one immediate ancestor but it can have many descendants For example TForm is the ancestor type of TForm1 and TForm1 is a descendant of TForm All form objects are descendants of TForm and you can derive many form objects from TForm Figure 6 2 Inheriting from TForm Objects components and controls When you look up TForm in online Help you ll notice that TForm is called a component Don t let this confuse you All components and controls are also objects The terminology used in the documentation comes from the inheritance hierarchy of the Delphi Visual Compone
299. ecifies which other units and forms in your project they need to access For example if you want UnitA to be able to access methods or forms declared in UnitB you need to add UnitB to the appropriate uses clause in UnitA Whenever you add a new unit to your application however whether or not it has an associated form Delphi adds the unit name to the uses clause in the DPR file Setting environment preferences Delphi provides developers with a wide array of options for configuring the integrated development environment IDE References to the behavior and appearance of the IDE in this book are based upon the default configuration created by the Delphi installation program If you are not working with a default installation of Delphi bear in mind that another user might have modified parts of the IDE configuration The Environment Options dialog box provides several pages of configuration options that you can control Some settings control behind the scenes elements such as the path to library files while others directly affect the appearance and behavior of the Delphi interface the Grid Gallery and Editor options for example This section discusses the Preferences page of the Environment Options dialog box because the settings on this page directly affect the appearance and behavior of the IDE when you first start Delphi and when you open new projects and forms Other pages from this dialog box are discussed elsewhere in this book t
300. ect Some of these files might be common to multiple projects The most common examples of non Delphi files used in Delphi projects are e Image files The bitmaps BMP WMF files that you use in TImage type components or as glyphs on TBitBin components can reside anywhere on your system When specified as properties of these graphical components Delphi takes a snapshot of the disk file and stores this in the binary form DFM file They are eventually compiled into the project executable file Once the image has been stored in the form file the original image file is no longer required by Delphi e Icon files The icons ICO files that you specify in the Icon property of forms and in the Project Options dialog box can also reside anywhere They are integrated into the project in the same way as bitmap image files After being included in the project the original icon file is no longer required by Delphi BMP and ICO files can also be created with the Delphi Image Editor or you can choose from the bitmaps and icons Chapter 4 Managing projects files and directories 117 available in the Delphi Image Library For more information on the Image editor and the Delphi Image Library see online Help e Help files The online Help HLP file that you specify for the project in the Project Options dialog box can also reside anywhere The HLP file can be compiled using either the Microsoft Help Compiler shipped with Delphi or anothe
301. ect status bar e The project file list The Project Manager also has a SpeedMenu which you can display by right clicking anywhere inside the window 130 Delphi User s Guide Table 4 3 Button Add Remove View Unit View Form Options Update Project Manager SpeedBar The SpeedBar has six buttons that provide commonly needed functionality Project Manager SpeedBar buttons PM SpeedMenu command Add File Remove File View Unit View Form Options Update Delphi menu command File Add File File Remove File View Units Ctrl F12 View Forms Shift F12 Options Project Project Manager status bar This area immediately below the SpeedBar displays information about the location of the main project source code DPR file and a summary of the number of forms and units registered in the DPR file Function Adds a shared or non shared file to the project The Path column of the Project Manager s constituent file list reflects the location of any shared file Removes the selected file s from the current project Opens if necessary and displays the selected file in the Code Editor If multiple files are selected in the Project Manager window displays the most recently selected file Displays the visual image of the currently selected form unit If the currently selected file is not a form unit this button is disabled and the SpeedMenu command is dimmed D
302. ecution 253 254 264 to breakpoints 253 254 258 to specific locations 251 254 executing code repeatedly 168 exiting applications 350 file manager example 362 OLE example 404 text editor example 309 312 exiting dialog boxes 87 Experts See Component Expert Form Experts Project Experts expressions 155 defined 259 evaluating 261 262 format specifiers 262 returning current value 259 Extended data type 156 ExtractFileName function 300 EZeroDivide exception 238 F fatal application errors 240 faults 238 fields 26 204 accessing 224 225 adding to forms 326 328 objects and 205 216 218 222 224 file lists 41 dragging items 377 378 dropping items 378 executing files 375 376 filtering 41 297 298 getting current drive and directory 362 365 updating 364 File menu 133 creating 283 361 369 filenames 59 118 119 137 changing 353 373 375 default 136 returning 364 file types project 116 118 file attribute dialog box 373 creating 371 372 FileGetAttr function 371 FileListBox component 41 file manager application 359 379 adding menus 361 362 369 building drive lists 362 365 creating main form 360 362 drag and drop operations 376 379 manipulating files 369 376 responding to events 363 365 377 files 234 352 383 See also file lists accessing 117 237 attributes 371 373 376 reading 371 setting 373 backing up 139 302 303 binary 116 converting to binary formats 95 copying 373 deleting 135 370 371 dis
303. ed objects only the OLE class should be specified OLE items The item of an OLE object determines what portion of an OLE document contains the data to link or embed Items are used when you want the OLE object to contain a smaller piece of data than an entire document file For example if the OLE object is linked to the cell range B4 to B5 of the page titled GasCosts in a Quattro Pro notebook the OLE document would be GasCosts B 4 B 5 The OLE item must be specified only for linked objects For embedded objects only the OLE class should be specified You don t need to use the OLE item if the OLE object will not contain a piece of data more specific than the file specified in the OLE document Creating OLE container applications OLE container applications simply hold OLE objects To create an OLE container application add an OLEContainer component to a form for every OLE object you want the form to contain To insert the OLE object at design time if you have access to the OLE server and data you specify the OLE class and optionally the document and item Chapter 14 Exchanging data with DDE or OLE 393 1 Select the OLEContainer component on your form 2 Click the ellipsis button for either the OljClass or OlbjDoc property in the Object Inspector The Insert Object dialog box appears Figure 14 4 The Insert Object dialog box Object Type Create New Create from File Quattro Pro Notebook Sound TextArt Wor
304. edure TForml OKClick Sender TObject begin if Editl Text Saturday then Label2 Caption Why are you working today end In this event handler the equal sign operator is used as a relational operator It compares the value of the constant Saturday with the value of the Edit1 Text property gt Run the application and enter a day of the week in the edit box The if statement in this handler is of the simplest form Theif statement begins with the reserved word if and is followed by an expression that results in a Boolean value True or False If the expression is True the code following the reserved word runs So if you type the word Saturday into the edit box control and click the OK button on the form a message appears in the second label Using an else part in an if statement The logic for this simple application has a flaw What if you typeSaturday in the edit box and click the OK button one time but then type Monday and click the OK button again The Saturday message still remains in the second label You could add anelse part to the if statement to handle strings other than Saturday typed in the edit box For example modify the event handler to look like this procedure TForml OKClick Sender TObject begin if Editl Text Saturday then Label2 Caption Why are you working today else Label2 Caption end gt Run the application enter a day of the week in the edit box and click OK This
305. edure or function itself above all routines that use them whether they are event handlers or routines you write entirely on your own In other words a routine can t use another routine unless the second routine has already been declared This is in keeping with the Object Pascal rule that states you can t use an identifier until you have declared it Forward declarations There is an exception to this rule however that allows routine A to call routine B and then while routine B is running routine B calls routine A This type of calling is called mutual recursion To make such mutual recursion possible you need to declare a routine as aforward declaration When you declare a routine using the forward standard directive you can place the implementation of the procedure or function anywhere you choose between event handlers after other procedures and functions that call the routine and so on If the NoValue declaration is declared as a forward declaration it looks like this function NoValue AnEFditBox TEdit Boolean forward A forward declaration uses the forward standard directive The declaration doesn t include the implementation of the procedure Instead the NoValue implementation has to appear somewhere after the forward declaration The implementation of NoValue can appear after other procedures functions event handlers and methods that might call it however This is an example of two procedures that call each o
306. either the program is running or it is paused at a program code location When the program is paused you are free to examine the current values of the program data items Program data items include program variables items in data structures class fields and object properties The integrated debugger enables you to examine the values of these data items with the following e The Watch List window e The Call Stack window e The Evaluate Modify dialog box In addition to examining program data values you can also change the values of single data items using the Evaluate Modify dialog box Modifying program data values during a debugging session provides a way to test hypothetical bug fixes during a program run If you find that a modification fixes a program error you can exit the debugging session fix your program code accordingly and recompile the program to make the fix permanent Chapter 8 Using the integrated debugger 265 266 Delphi User s Guide Part Sample applications The chapters in this part show several complete examples of building applications with Delphi Although each of the sample applications is a complete and useful application the primary purpose of these chapters is to explain how to perform typical application building tasks in Delphi within a realistic context For example the text editor example describes how to manipulate menu items and the graphics example shows how to create and use tool bars You will
307. elect a component from the palette 2 Click anywhere in the container component Each subsequent click continues to place the component in whatever eligible receiving component including the form is clicked 3 Select the pointer icon when you have finished adding components Add two Label components to the Panel component as shown in Figure 2 5 48 Delphi User s Guide Note Figure 2 5 AboutBox with Panel and Label components Panell Label3 Cutting copying and pasting components You can cut copy and paste components between forms or between a form and a container component such as a panel or group box The container component can be on the original form or in another form When you copy components you copy their property settings and event handler associations as well For example copying a button with a Caption property of Button and an event handler called TForm1 Button1Click creates another button with the same Caption property and an OnClick event handler that calls the code in TForm1 Button1Click However Delphi renames the copied button so that each button maintains a unique identifier For an example of this see Scope of the Name property on page 55 Three general rules apply to all cut copy and paste operations e You can select multiple components to be cut or copied but the selection can include only those components within a single parent That parent can be either a form or a contai
308. eletion 371 13 4 The file attribute dialog box 372 13 5 The change file dialog box 374 14 1 A DDE conversation between a Delphi application and Microsoft Word 6 0 382 14 2 The DDE Info dialog box 384 14 3 The WordPerfect Paste Special dialog box 389 14 4 The Insert Object dialog box 394 14 5 The Paste Special dialog box 395 15 1 The completed OLE container application 399 15 2 The OLEFrameForm and OLEObjectForm WINDOWS iador de dod ey techy And inia Ss 405 15 3 The OLE container application menu 408 15 4 The OLE container application tool bar and status DAN as eps te te ese de ot Rang eS de 410 15 5 The Insert Object dialog box 410 15 6 A Paintbrush picture OLE object 414 15 7 The Paste Special dialog box 415 15 8 The Save As dialog box 425 15 9 The Open dialog box 426 xii
309. elp In Multiple Document Interface MDI and Object Linking and Embedding OLE applications you can also merge menu items into an existing menu bar The following section discusses this in more detail 110 Delphi User s Guide Merging menus For MDI applications such as the text editor sample application and for OLE client applications your application s main menu needs to be able to receive menu items either from another form or from the OLE server object This is often calledmerging menus You prepare menus for merging by specifying values for two properties e Menu a property of the form e GroupIndex a property of menu items in the menu Specifying the active menu Menu property The Menu property specifies the active menu for the form Menu merging operations apply only to the active menu If the form contains more than one menu component you can change the active menu at run time by setting the Menu property in code For example Forml Menu SecondMenu Determining the order of merged menu items Grouplndex property The GroupIndex property determines the order in which the merging menu items appear in the shared menu bar Merging menu items can replace those on the main menu bar or can be inserted The default value for GroupIndex is 0 Several rules apply when specifying a value for GroupIndex e Lower numbers appear first farther left in the menu For instance set the GroupIndex property to 0 zero fo
310. em in the menu list m To delete a menu item or command place the cursor on the menu item you want to delete then press Del Note You cannot delete the default placeholder that appears below the item last entered in a menu list or next to the last item on the menu bar This placeholder does not appear in your menu at run time Adding separator bars Separator bars insert a line between menu items You can use separator bars to indicate groupings within the menu list or simply to provide a visual break in a list E To make the menu item a separator bar type a hyphen for the caption Specifying accelerator keys and keyboard shortcuts Accelerator keys enable the user to access a menu command from the keyboard by pressing Alt the appropriate letter indicated in your code by the preceding ampersand The letter after the ampersand appears underlined in the menu Keyboard shortcuts enable the user to perform the action without accessing the menu directly by typing in the shortcut key combination E To specify an accelerator add an ampersand in front of the appropriate letter For example to add a Save menu command with theS as an accelerator key type amp Save E To specify a keyboard shortcut use the Object Inspector to enter a value for the ShortCut property or select a key combination from the drop down list 102 Delphi User s Guide Caution This list is only a subset of the valid combinations you can type in When yo
311. en RenameFile FromFile ToFile FileList Update end end Because all three operations are so similar the file manager application can share much of the code involved In particular you can create a dialog box that prompts the user for an original name and a destination name and use the same dialog box no matter which operation the user requests Figure 13 5 shows the dialog box and the names of its components Figure 13 5 The change file dialog box aa OPY eee CurrentDir CAWINDOWS FromFileName Eem winin SCS X Cancel I ToFileName___2 SSS Once you ve designed the dialog box you can open it from an event handler shared by the Move Copy and Rename items on the File menu by doing the following 1 Double click the main menu component not the File menu itself on the main form to open the Menu Designer In the Menu Designer window choose File Move Choose the Events page in the Object Inspector Click in the Handler column next to the OnClick event ao Aa Gd N Type in FileChange and press Enter Delphi generates an event handler called FileChange 6 In the Menu Designer window choose File Copy and set its OnClick handler to FileChange 7 Repeat step 6 for File Rename 374 Delphi User s Guide gt You can then fill in the empty FileChange handler as follows procedure TFMForm FileChange Sender TObject begin with ChangeDlg do begin if Sender Movel then Caption Mo
312. en you no longer need to examine the code at a breakpoint location you can delete the breakpoint from the debugging session You can delete breakpoints using either the Code Editor or the Breakpoint List window m Use the following methods to delete breakpoints e From the Code Editor place the text cursor in the line containing the breakpoint and press F5 or choose Toggle Breakpoint from the Speed Menu e Click the stop sign glyph in the Code Editor window to delete the associated breakpoint e From the Breakpoint List window highlight the breakpoint you want removed then choose Delete Breakpoint from the SpeedMenu e To delete all currently set breakpoints choose Delete All Breakpoints from the Breakpoint List SpeedMenu Caution The breakpoint delete commands are not reversible 256 Delphi User s Guide Modifying breakpoint properties To view and modify the properties of a breakpoint double click the breakpoint in the Breakpoint List window or select it and choose Edit Breakpoint from the SpeedMenu The Edit Breakpoint dialog box appears Figure 8 2 The Edit Breakpoint dialog box M In addition to examining a breakpoint s properties you can use the Edit Breakpoint dialog box to change the location of a breakpoint set a conditional breakpoint and set a pass count for the breakpoint Creating conditional breakpoints When a breakpoint is first set by default it pauses the program execution each time
313. enced from the OLEObj unit type TOLEFrameForm class TForm private public Fmts array 0 1 of BOleFormat Declare the array of OLE formats end Chapter 15 OLE example 419 Attach the following code to the OnCreate method of OLEFrameForm after the calls to RegisterClipboardFormat procedure TOLEFrameForm FormCreate Sender TObject begin FEmbedClipFmt RegisterClipboardFormat Embedded Object FLinkClipFmt RegisterClipboardFormat Link Source Fmts 0 fmtId FEmbedClipFmt Embedded OLE object Clipboard format Fmts 0 fmtMedium BOLEMediumCalc FEmbedClipFmt Medium for embedded objects Fmts 0 fmtIsLinkable False No linking to OLE server StrPCopy Fmts 0 fmtName s Name from OLE server StrPCopy Fmts 0 fmtResultName s Result name from OLE server Fmts 1 fmtId FLinkClipFmt Linked OLE object Clipboard format Fmts 1 fmtMedium BOLEMediumCalc FLinkClipFmt Medium for linked objects Fmts 1 fmtIsLinkable True Allows linking to OLE server StrPCopy Fmts 1 fmtName s Name from OLE server StrPCopy Fmts 1 fmtResultName s Result name from OLE server end Pasting the OLE object Before pasting the OLE object you should determine if there is an OLE object on the Clipboard m To determine if the Paste Special dialog box is enabled call PasteSpecialEnabled This function determines if any
314. ent Refer to Figure 10 6 For the purposes of the text editor application you ll set the Filter property which you also set for the OpenDialog component You ll also set the Options property so that the Read Only check box isn t displayed in the dialog box since setting read only attributes would prevent users from saving the file and so that read only files cannot be overwritten Add a SaveDialog component to EditForm and set the properties as noted in Table 10 9 Table 10 9 SaveDialog component properties Property Value Filter Text Files TXT TXT All Files Name SaveFileDialog Options ofHideReadOnly ofNoReadOnlyReturn To set the Options property 1 Double click Options to view the members of the set 2 Double click in the Values column to change the Boolean value or choose the value you want from the drop down list For the purpose of the text editor application change the value forofHideReadOnly and of NoReadOnlyReturn to True Saving the text file In the text editor application saving a file is handled with three procedures e SavelClick which is called when the user selects File Save whether for a new or existing file e SaveAs1Click which is called when the user selects File Save As and e CreateBackup which is nested and called within Save1Click Chapter 10 Text editor example 301 The outer block of the nested procedure Save1Click determines whether the file has been
315. ent e The while statement e The for statement The repeat statement The repeat statement repeats a statement or series of statements until some condition is True The statement begins with the repeat reserved word and ends with the reserved word until followed by the condition that is evaluated The condition is always a Boolean expression To see the syntax of the repeat statement look up the repeat reserved word topic in online Help This is the finished form for an application that uses arepeat statement Figure 5 6 A form for a repeat statement example Form1 gt To create this application 1 Create a new form with one button on it 2 Using the Object Inspector change these properties e Change the button name to RepeatButton e Change the caption of the button to Repeat 3 Create this event handler that runs when you click the button procedure TForml RepeatButtonClick Sender TObject var I Integer begin i se repeat I I Writeln I until I 1 end is i 0 I 168 Delphi User s Guide 4 Run the application and click the Repeat button The numbers 1 through 10 are written down the edge of the form The Boolean expression I 10 isn t evaluated until the end of the repeat until block This means that the statements within the repeat until block always run at least one time For more information about repeat statements see Delphi s online Help The while statement While the repe
316. entlItem to the Lines property of a memo Attach the assignment statement to the OnChange event handler of the DDEClientItem For example if the DDEClientItem component is named DDEClientItem1 and the edit box is named Edit1 execute the following code Editl Text DDEClientItem1 Text Requesting data Some DDE items aren t passed automatically in a DDE conversation Instead the client must explicitly request a specific item to be updated by the DDE server Also you might want your client application to obtain data from a DDE server once and not be continually updated by the DDE server In these cases your DDE client should request to be updated with the RequestData method Note To determine if your DDE client must explicitly request to be updated see the documentation of the DDE server application m To request data use the RequestData method of a DDEClientConv component Specify the item to request as a parameter of RequestData The item is the simply a DDE item RequestData returns a PChar null terminated string containing the requested text The requested data is given to the DDE client only in the return value of RequestData Even if the DDEClientConv component is connected to a DDEClientItem component RequestData won t update the values of the Text or Lines properties of the DDEClientItem Search online Help for RequestData for more information about this method For example to request the data from cell A1 on page A
317. enu 105 Commands on the SpeedMenu 105 Switching among menus at design time 106 Using menu templates 106 Saving amenuasatemplate 108 Naming conventions for template menu items and event handlers 108 Associating menu events with code 109 Menu component events 109 Handling menu itemevents 109 Associating a menu item with an existing event handlers sa pie urges are aed ee oa 110 Adding menu items dynamically 110 Mergim MCNUS s Je aia ve ya 8 Bae ds Wie Fea 111 Specifying the active menu Menu Prope so re ar Pek eae A 111 Determining the order of merged menu items GroupIndex property 111 Importing resource RC files 2 2 112 Managing run time behaviors of forms 112 Specifying a form as the project main form 112 Specifying forms to auto create 113 Controlling the form auto create order 113 SUMMAN seo sw ee Se ee oe A 114 Chapter 4 Managing projects files and directories 115 Whatisa Proe oeri eiea EE REA 115 Frojectdirectories eeart eeg a Gh ae 115 Constituent files of a project 116 Files generated at designtime 116 Compiler generated project files 117 Non Delphi resource files aaa 117 Understanding the files in a project 118 The project source code DPR file 118 Unit source code PAS files 119 Form associated unit files
318. er Then the user updates the OLE object within the OLE container and closes the OLE server Note Not all applications support OLE To determine whether an application supports OLE refer to its documentation This section explains e OLE 1 0 and OLE 2 0 e Design time and run time object creation e Linking and embedding e OLE classes 390 Delphi User s Guide Note Note e OLE documents e OLE items OLE 1 0 and OLE 2 0 There are two versions of OLE at the time of this writing OLE 1 0 and OLE 2 0 When the user activates an OLE object that was created with an OLE 1 0 server application the server application opens in its own window in the foreground and receives focus The OLE container application exists in a separate window in the background When the user activates an OLE object that was created with an OLE 2 0 server application the object might try to activate in place In place activation means the OLE server s menu is merged with the OLE container s menu The server s tool bar replaces the container s tool bar and the server might try to use the container s status bar The object is edited from within the OLE container application window but all the processing is handled by the OLE server The mode of activation depends upon the server with which the OLE object was created not the container application in which it is linked or embedded If an OLE 1 0 object is opened within an OLE 2 0 compliant application
319. er Delphi Project Templates including any project you have created and saved as a Project Template Saving a project as a Project Template is discussed on page 126 e Specify the default new project be started from one of the Delphi Project Experts For more information about Project Experts search the online Help system under Experts e Specify that the default new form be one of the Delphi Form Templates including any form you have created and saved as a Form Template Saving a form as a Form Template is discussed on page 126 e Specify that the default new form be one of the Delphi Form Experts The following section discusses how to begin a new project from one of the non default Delphi Project Templates Customizing project options on page 123 describes how to set your preferred project options or modify project options set by another Delphi user Beginning a project with a Project Template Delphi s Project Templates provide you with predesigned projects that you can use as a starting point for your applications Project Templates are part of the Gallery located in the DELPHI GALLERY directory which also provides Form Templates and Experts When you begin a project from a Project Template other than the Blank Project Template you are prompted to specify a project directory a unique subdirectory in which to store the new project files If you specify a directory that doesn t currently exist Delphi creates it for yo
320. er s Guide Appendix Selected Bibliography The following third party titles are available to help you learn more about Delphi and the Object Pascal programming language For details concerning availability of any of these books please consult your local bookseller The Delphi Programmer Explorer by J Duntemann J Mischel D Taylor Coriolis Group ISBN 1 883577 25 X 39 99 A new type of tutorial Theory and practice alternate in short chapters with the emphasis on creating useful software starting on the very first page Delphi for Dummies by Neil Rubenking IDG Press ISBN 1 56884 200 7 19 99 Readers will learn about Borland s new language in the easy to understand style of the Dummies series Teach Yourself Delphi by Devra Hall MIS Press ISBN 1 55828 390 0 27 95 Here is a complete self guided tour to the new development environment from Borland encompassing all the features of the language and all the tools tricks and advantages of Delphi Delphi Nuts and Bolts by Gary Cornell and Troy Strain Osborne McGraw Hill Software Engineering with Delphiby Edward C Webber J Neal Ford and Christopher R Webber Prentice Hall Professional Trade amp Reference A guide to developing client server applications with an emphasis on Delphi s object oriented tools Delphi by Example by Blake Watson Que ISBN 1 56529 757 1 29 99 Appendix A Selected Bibliography 429 Aimed at the beginning programmer who has no prior exp
321. erience with other languages or development products this book presents basic concepts of programming along with a clear explanation of the key development tools that are part of Delphi e Using Delphi Special Edition by Namir Shammas and John Matcho Que ISBN 1 56529 823 3 29 99 This 3 part tutorial on the most important Delphi features covers how to install the product and develop applications using Delphi s visual tools explores the Windows application development process and deals with some advanced programming topics e Developing Client Server Applications with Delphi by Vince Killen and Bill Todd Sams Publishing e Delphi Developer s Guide by Xavier Pacheco Steve Teixeira Sams Publishing ISBN 0 672 30704 9 45 00 Intermediate to advanced guide to developing applications using Delphi e Mastering Delphi by Charlie Calvert Sams Publishing 9 6 45 00 Comprehensive tutorial reference for intermediate programming with Delphi e Teach Yourself Delphi in 21 Days by Andrew Wozniewicz Sams Publishing e Mastering Delphi by Marco Cantu Sybex e Delphi How To by Gary Frerking Waite Group Press Presents large collection of programming problems and their solutions in standard easy to use reference format including unique solutions that use VBX controls and easy ways to build multimedia projects with Delphi e Developing Windows Applications Using Delphi by Paul Penrod John Wiley ISBN 0 471 11017 5 29 95 This introduction
322. ering Clipboard formats If the data on the 416 Delphi User s Guide Clipboard is not an OLE object Format will be modified to specify some other format of data such as CF_TEXT for text data Handle is modified by PasteSpecialDlg to specify the handle of the data on the Clipboard Use Handle to access the Clipboard data if it is of some type other than an OLE object such as text Pass a handle variable in the Handle parameter For this example you will only process the pasting of OLE objects so the value of the Handle parameter is not important PInitInfo is a pointer to an internal OLE object initialization information structure which is required to initialize the OLE container in the same way as described in Initializing the OLE container You should pass a pointer in the Info parameter PasteSpecialDlg modifies this pointer so that it points to a valid data structure containing initialization information for the OLE object selected in the Paste Special dialog box To enable the user to paste an OLE object from the Paste Special dialog box use the PasteSpecialDlg function to call the Paste Special dialog box You ll write the code to do this in the following section but you should first have an understanding of the options available in this dialog box To insert the contents of the Clipboard into the OLE container application so that the data is embedded the user chooses Paste To create a link between the OLE serve
323. ers text in this dialog box at run time only the asterisk character is displayed so that the user s password is not visible onscreen You can enter any single character you choose as the PasswordChar property value gt To see the Password entry Form Template at run time try the following 1 Add a button to Form1 and write the following OnClick event handler procedure TForml ButtoniClick Sender TObject begin PasswordDlg ShowModal end 2 Add Password to the uses clause in Unit1 and run the application 3 Choose Button to display the Password dialog box Figure 3 6 Password dialog box at run time Enter password LE 7a 4 Type some text into the edit box Only asterisks appear Figure 3 7 Password dialog box displaying masked characters Enter password Zax 84 Delphi User s Guide Note Developing custom dialog boxes In addition to routines that display simple predesigned dialog boxes and Form Template dialog boxes such as the Password Dialog Template Delphi provides a number of fully designed dialog boxes as components These appear on the Dialogs page of the Component palette and include components that encapsulate the Windows common dialog boxes You can specify different options for these dialog boxes such as whether a Help button appears in the dialog box but for the most part you cannot change their overall design It s useful therefore to know how to build a dialog box from s
324. erties Font Font Style fdTrueTypeOnly c 5 fdFixedPitchOnly LE ere fdNoSizeSelect Times FY Times New Roman fdEffects Strikeout Underline AaBbYyZz fdNoStyleSelect Color MMM Black Effects B You can also edit the initial settings for the dialog box by selecting the Font property in the Object Inspector and clicking the ellipsis button next to TFont This opens the dialog box in a design time state For the purposes of the text editor application you won t set any properties for the Font dialog box component at design time For more information about the properties of the Font dialog box component not discussed here refer to online Help Changing the font in the Memo component The event handler for the Character Font click creates a reflexive relationship between the Memo component and the Font dialog box it ensures that the value of the memo s Font property is reflected in the dialog box and that settings made from within the dialog box are reflected back into the memo The first time the user opens the Font dialog box in the text editor application the default settings are displayed To change this change the Font property for the Memo component not for the Font dialog box Note Any settings you make at design time to the Font dialog box are overridden by the Character Font event handler This is by design because you generally don t want the dialog box to display anyt
325. erties such as changing the height color border and so forth are stored in the DFM file and reflected in the form Note You can if you choose view and edit the form file as text by directly opening it in the Code Editor The type declaration in the DFM file Just as Delphi generates an instance variable for the form it also generates an instance variable or field for every component you add to the form In this case though the form contains the component so the component declaration appears inside the form s type declaration The same is true for methods event handlers of the form As you add components and event handlers to the form the form s type declaration expands to include the declarations for each component and method For an illustration of this try the following 1 Arrange Form1 and Unit1 on your screen so that both are visible resize the form if necessary 26 Delphi User s Guide 2 Scroll in the Code Editor window until the type declaration for Form1 is visible Figure 1 9 Form type declaration UNIT1 PAS type TFormi class TForm private Private declarations public Public declarations end var Formi TFormil implementation Modified insert 3 Add a button component to the form while watching what happens to the type declaration Figure 1 10 Modified type declaration UNIT1 PAS type TFormi class TForm Buttoni TButton Instance variable code Delphi pr
326. erty 111 menu templates 100 106 109 loading 106 menus 98 109 adding 38 100 104 350 351 drop down 103 file manager example 361 362 369 from other applications 112 MDlapplications 282 284 288 294 OLE example 402 408 pop up 38 294 displaying 104 105 handling events 108 109 110 merging See merging menus moving among 106 naming 101 reusing 105 110 saving as templates 105 106 108 merging menus 111 283 284 402 See also MDI applications Index 443 message boxes 80 82 310 374 See also status bars confirming file deletions 370 371 creating 43 predefined 209 MessageDlg function 81 82 310 MessageDlgPos function 82 messages 81 See also message boxes exception handling 240 242 243 modeless forms as 85 status bar 409 metafiles 39 42 348 methods 20 339 340 See also functions procedures routines accessing 224 225 constructor 229 defined 158 deleting event handlers and 67 destructor 229 objects and 205 216 218 222 224 overriding 223 Microsoft Help Compiler 118 MIDI sequencers See media players Minimize button 44 86 removing from forms 87 minimum numeric ranges 197 MinPage property 306 mismatch errors 155 modal dialog boxes 81 85 86 ModalResult property 88 Mode property pens 315 modeless dialog boxes 85 86 Modified property memos 300 310 modifying See changing mouse buttons 323 326 clicking 323 324 326 334 mouse events 322 326 defined 322 dragging and dropp
327. erty names in the Object Inspector Forms and components often have lengthy lists of properties which can make scrolling through the list in the Object Inspector a bit unwieldy You can jump directly to a property by pressing the Tab key followed by any alphabetic character This causes the cursor to jump to the Property column of the first property beginning with the typed letter The Object Inspector lists property names alphabetically Try using the tab jump feature now 1 Select the form 2 In the Object Inspector select the form s AutoScroll property 3 Press Tab W to jump directly to the Width property 4 Press Tab again to place the cursor in the Value column where you can begin entering your edits Pressing Tab acts as a toggle between the Value column and the Property column Whenever you are in the Value column as you are by default when you select a property with the mouse pressing Tab moves you to the Property column Whenever you are in the Property column pressing an alphabetic character jumps you to the first property starting with that character 54 Delphi User s Guide Displaying and setting shared properties You can set shared properties to the same value without having to individually set them for each component To display and edit shared properties 1 Inthe form select the components whose shared property you want to set The Properties page of the Object Inspector displays only those properties th
328. es the resource freeing code Some common resources that you should always be sure to release are Files Memory Windows resources Objects The following event handler for example allocates memory then generates an error so it never executes the code to free the memory 234 Delphi User s Guide procedure TForml ButtoniClick Sender TComponent var APointer Pointer AnInteger ADividend Integer begin ADividend 0 GetMem APointer 1024 allocate 1K of memory AnInteger 10 div ADividend this generates an error FreeMem APointer 1024 it never gets here end Although most errors are not that obvious the example illustrates an important point When the division by zero error occurs execution jumps out of the block so the FreeMem statement never gets to free the memory In order to guarantee that the FreeMem gets to free the memory allocated by GetMem you need to put the code in a resource protection block Creating a resource protection block To ensure that you free allocated resources even in case of an exception you embed the resource using code in a protected block with the resource freeing code in a special part of the block Here s an outline of a typical protected resource allocation allocate the resource try statements that use the resource finally free the resource end The key to the try finally block is that the application always executes any statements in
329. espects the same as choosing File Save you re prompted to name any unsaved units and forms before saving the DPR file Once all project files have been named File Save and File Save As both prompt you to name only new not modified units and both then save any modifications to previously named project files The distinction between the two commands is that the 138 Delphi User s Guide File Save As command expects you to save the PAS file to a new location If you do not specify either a new name or new location for the PAS file Delphi prompts you to specify whether you want to overwrite the existing PAS file Creating a backup of an entire project Backing up a project can be a simple matter of copying directories or can involve some additional steps This depends upon how your project directories are structured and whether the project uses files from outside its own directory tree The project directory isn t encoded into the project DPR file The project file does however record the location of all constituent project files If these files reside in subdirectories of the main project directory than all path information is relative which makes backup easy as shown in figure Figure 4 3 Figure 4 3 Example project directory tree Cod Lm ar divl Main project directory Chin 0 dialogs C forns Ey lib You could back up this entire project simply by copying the directory tree to another
330. et changes When the user selects a tab in a tab set control by clicking a tab or using the keyboard the tab set generates an OnClick event Any other controls that depend on the setting of the tab set need to have their values updated in response to those click events For example with a tab set that contains tabs for each valid disk drive a click on a different tab indicates a change of drive selection Other controls such as directory lists need to respond to the change To respond to changes in a tab set attach an event handler to the tab set sOnClick event The following code attached to the OnClick event of a tab set named DriveTabSet sets the Drive property in a directory outline control to the first letter of the clicked tab procedure TFMForm DriveTabSetClick Sender TObject begin Chapter 13 File manager example 363 with DriveTabSet do DirectoryOutline Drive Tabs TabIndex 1 end If you select a tab on the drive list now it causes the directory outline to display the directory structure of the specified drive Responding to outline changes When the user selects an item in an outline by clicking it or using an arrow key the outline generates a click Any controls that depend on the currently selected item in the outline need to update themselves in response to those clicks For example in a directory outline a click usually indicates a change in the current directory Other controls such as file lists
331. ether the Clipboard contains a graphic Chapter 12 Graphics example 355 HasFormat is a Boolean function It returns True if the Clipboard contains an item of the type specified in the parameter To test for graphics you passCF_BITMAP 2 Assign the Clipboard to the destination gt Inthis example you can paste a bitmap from the Clipboard into the image control s picture in response to a click on the Edit Paste menu item procedure TForml PasteButtonClick Sender TObject var Bitmap TBitmap begin if Clipboard HasFormat CF_BITMAP then check to see if there s a bitmap on the clipboard begin create a bitmap to hold the contents on the clipboard Bitmap TBitmap Create try Get the bitmap off the clipboard using Assign Bitmap Assign Clipboard Copy the bitmap to the Image Image Canvas Draw 0 0 Bitmap finally Bitmap Free end end end The graphic on the Clipboard could come from this application or you could have copied it from another application such as Windows Paintbrush summary The sample application described in this chapter covers quite a number of issues but leaves several others unresolved In particular a polished version of the application would likely display the name of the current bitmap file in the main form s caption and would track whether the user makes changes to a picture prompting the user whether to save the changes before loading or creating ano
332. ets 363 OnCloseQuery event 311 OnDb Click event 334 OnDragDrop event 378 OLE example 422 423 OnDragOver event 377 OnDrawltem event 369 OnEndDrag event 378 online help 2 118 data types 153 error messages 142 OnMeasureltem event 368 OnMeasureTab event 368 OnMouseDown event 323 parameters passed to 322 OnMouseMove event 325 parameters passed to 322 OnMouseUp event 324 parameters passed to 322 OnPaint event 316 OnPopup event 109 294 OnStatusLineEvent event OLE applications 409 OOP See object oriented programming Open common dialog box 41 297 300 Open Library command Options 73 Open Library dialog box 73 Open method 298 300 OpenDialog component 41 297 424 openin files 297 300 automatically 375 project 134 templates for reference 79 OpenLink method 387 operators assignment 151 158 bitwise file attributes and 372 relational 158 164 OPT files 116 optimizing code 183 339 Options button Project Manager 131 Options command Project Manager 127 131 Options property dialog boxes 296 printing 306 307 Outline component 39 outlines 39 269 directory See directory lists events 364 file manager application 364 378 outlining shapes 315 out of range errors 157 199 237 indexes 243 output 250 exception handling 237 incorrect 248 overflow errors 237 238 overriding methods 223 overriding property settings 59 Index 445 owner draw controls 275 365 369 drawing 367 369 events and 367 369 resizing 367
333. etting 28 32 EOutOfMemory exception 237 EOverflow exception 238 EPageFault exception 238 EProcessorException exception 238 equal sign as relational operator 164 constant declarations 158 type declarations 186 equal values 158 ERangeError exception 237 242 erasing images 355 erasing lines 330 error codes 237 error messages 141 disabling 243 generating 240 242 getting help with 142 ErrorAddr variable 244 errors 231 244 See also exceptions checking 232 clearing conditions 232 divide by zero 235 237 238 239 fatal application 240 logic 248 out of range 199 237 243 overflow 237 238 range 199 run time 247 248 syntax 154 158 159 type mismatch 155 undefined forward 67 Esc key 88 ESingleStep exception 238 EStackFault exception 238 EUnderflow exception 238 Evaluate Modify command Run 261 Evaluate Modify dialog box 261 263 event handlers 49 60 188 218 allocating memory 235 associating events with 64 67 shared events 65 calling procedures and functions 20 21 changing tabs in notebooks 363 defined 158 deleting 67 68 drawing lines 324 325 editing 63 66 locating specific 63 menus 109 110 as templates 108 handling events 294 naming 66 overview 18 19 redrawing images 316 renaming files 353 responding to button clicks 334 336 reusing 64 65 saving files 353 selecting items in lists 364 sharing 339 343 writing 18 60 62 222 code blocks and 175 shared events 66 events 64 67 components without 60
334. ever use the name of a method within an ancestor object to declare a method within a descendant object This is how youoverride a method You would most likely want to override an existing method if you want the method in the descendant object to do the same thing as the method in the ancestor object but the task is accomplished in another way In other words the code that implements the two methods differs It s not often that you would want to override a method unless you are creating new components You should be aware that you can do so though and that you won t receive any warning or error message from the compiler You can read more about overriding methods in the Delphi Component Writer s Guide Chapter 6 Programming with Delphi objects 223 Public and private declarations When you build an application using the Delphi environment you are adding data fields and methods to a descendant of TForm You can also add fields and methods to an object without putting components on a form or filling in event handlers but by modifying the object type declaration directly You can add new data fields and methods to either the public or private part of an object Public and private are standard directives in the Object Pascal language Treat them as if they were reserved words When you add a new form to the project Delphi begins constructing the new form object Each new object contains the public and private directives that mark locatio
335. examining the program continue debugging by running as usual If your program assumes control and won t allow you to return to the debugger for example if it runs into an infinite loop you can press Ctrl Alt Sys Req to stop your program However be aware that you might need to press this command several times before your program actually stops the command doesn t work if Windows kernel code is executing Restarting the program Sometimes while debugging you will find it necessary to restart the program from the beginning For example you might need to restart the program if you step past the location of a bug or if variables or data structures become corrupted with unwanted values E Toend the current program run and reset the program choose Run Program Reset or press Ctri F2 Chapter 8 Using the integrated debugger 253 Resetting a program closes all open program files releases resources allocated by calls to the VCL and clears all variable settings However resetting a program does not delete any breakpoints or watches that you have set which makes it easy to resume a debugging session Note Resetting a program might not release all Windows resources allocated by your program In most cases all resources allocated by VCL routines are released However Windows resources allocated by the code you have written might not be properly released If your system becomes unstable through either multiple hardware or langua
336. f Filename then SaveAsiClick Sender else begin CreateBackup Filename Memol Lines SaveToFile Filename Memol Modified False end end The SaveToFile filename parameter takes the value of the Filename variable whenever the user saves the file gt Run the application and choose File Open The Open File dialog box appears displaying the file filters you specified at design time gt Select a text file and choose OK The text file you specified opens inside the child window Using the Font dialog box At design time you can use the Font property of the Memo component or of the Font dialog box component to set an initial font for text in the memo Primarily however you need to provide a way for the user to select a font at run time You might for example provide a menu list that interacts with the Font dialog box to provide a list of available fonts In the text editor application the Character Font command opens the Font dialog box where the user can then select a font Adda Font dialog box component to EditForm Font dialog box component properties The properties available in the Object Inspector for the Font dialog box consist mainly of the settings in the Options drop down list These settings correspond to several areas of the Font dialog box in the running application as shown in the following illustration Chapter 10 Text editor example 303 Figure 10 8 Font dialog box component prop
337. field to the form to keep track of its drawing tool type TDrawingTool dtLine dtRectangle dtEllipse dtRoundRect TForml class TForm method declarations public Drawing Boolean Origin MovePt TPoint DrawingTool TDrawingTool field to hold current tool end Since objects including forms initialize all their fields to zero the drawing tool when you start the application is dtLine Changing the tool with speed buttons Since you have already seen how to respond to speed button click events you can set up OnClick event handlers for all the drawing tool buttons on the tool bar Attach the following event handlers to the OnClick events of the four drawing tool buttons on the tool bar setting DrawingTool to the appropriate value for each procedure TForml LineButtonClick Sender TObject LineButton begin DrawingTool dtLine end procedure TForml RectangleButtonClick Sender TObject RectangleButton begin DrawingTool dtRectangle end procedure TForml EllipseButtonClick Sender TObject EllipseButton begin DrawingTool dtEllipse end procedure TForml RoundedRectButtonClick Sender TObject RoundRectButton begin DrawingTool dtRoundRect end Now that you can tell the form what kind of tool to use the only step left is to teach it how to draw the different shapes The only methods that do any drawing are the mouse move and mouse up handlers and the only drawing code d
338. fields you added to track the starting and intermediate points Refining line drawing Now that you have fields in place that can track various points you can correct some of the problems introduced in the application The first step is to track the line origin so you can draw the final line Tracking the origin point The most important thing to track when drawing lines is the point where the line starts As you saw earlier you know where the line ends because that s where the mouse up event occurs The OnMouseUp event handler needs to know where the line started too That s where the Origin field comes in gt Set Origin to the point where the mouse down event occurs so the mouse up event handler can use Origin to place the beginning of the line procedure TForml FormMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin Drawing True Canvas MoveTo X Y Origin POLOLO Y record where the line starts end procedure TForml FormMouseUp Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin Canvas MoveTo Origin X Origin Y move pen to starting point Canvas LineTo X Y 328 Delphi User s Guide Drawing False end Those changes get the application to draw the final line again but what about the intermediate drawing Figure 12 6 Straight line with intermediate drawing Graphics example Tracking movement The pro
339. file PAS is open you are prompted to save changes and close it before the DFM file opens in the Code Editor 3 Choose File Save File As 4 Inthe Save As dialog box rename the file using a TXT file extension 94 Delphi User s Guide Using the TXT file extension automatically causes the DFM file to convert to ASCII text 5 Repeat these steps for any other DFM files you want to convert to ASCII Note You cannot have the same form open simultaneously in both visual and text formats Converting text files back to DFM format After editing an ASCII form file you can convert the text based form back into its regular binary DFM format Once you understand the structure and content of a form file it s even possible for you to create a form by writing its structure as a text file and converting that to binary format However it s normally far more efficient to create forms with the visual tools that Delphi provides E Toconvert an ASCII based form file back into binary DFM format 1 Choose File Open File You need not have a project open 2 Select the text file you want to convert to binary DFM format The file opens in the Code Editor 3 Choose File Save File As 4 Inthe Save File As Type combo box choose Form File DFM 5 Name the file with a DFM extension in the File Name edit box 6 Repeat this process for any other files you want to convert to binary DFM format Sample ASCII Form file Here is the tex
340. fined forward errors 67 undefined instructions 238 Undelete command Edit 50 underlining letters in menu commands 102 uninitialized memory 238 unit files 24 116 117 119 121 129 associating with projects 119 120 backup 116 naming 119 opening 134 sharing 134 135 unit reserved word 206 units 119 187 206 210 accessing 206 207 209 adding to projects 25 27 119 209 210 browsing 13 creating new 120 134 209 custom components 71 defined 206 deleting 135 moving among 79 140 predefined 206 210 preexisting 135 private vs public 225 referencing 26 286 restricting access 209 source code viewing 12 23 25 139 140 visibility of routines 207 208 without forms 27 121 writing 206 208 209 begin end blocks 175 176 headers 206 Units command View 23 62 79 unknown identifiers 159 179 until reserved word 168 untyped pointers 156 Update button Project Manager 131 Update command Project Manager 131 updating data DDE applications 386 388 390 OLE objects 395 updating file lists 364 uppercase characters 272 user interactions 17 See also events user interfaces 76 testing 248 user options 39 331 mutually exclusive 38 333 user defined exceptions 244 245 user defined templates 126 127 Index 451 user defined types 185 186 195 205 uses reserved word 76 77 207 implementation reserved word and 209 interface reserved word and 208 V valid characters in identifiers 154 valid drives getting 3
341. for traditional C programmers who want to make the transition to rapid application development also provides detailed instructions for building sophisticated Windows applications and for creating graphical interfaces e Instant Delphi by Dave Jewell Wrox Press ISBN 1 874416 57 5 19 95 Instant Delphi is the fast paced tutorial guide for the programmer who wants to get up to speed on the Delphi product as quickly as possible Look for announcements of other books based on Borland Delphi 430 Delphi User s Guide Symbols amp ampersand character 20 102 plus sign concatenating strings 201 period declarations not within scope 178 identifiers and 152 method calls 159 subrange types 197 ellipsis in Value column 56 colon function declarations 161 variable declarations 155 assignment operator 151 equal operator vs 158 semicolon end of statements 151 165 if statements 165 equal sign as relational operator 164 constant declarations 158 type declarations 186 braces enclosing comments 150 apostrophe in strings 200 Numerics 3 D panels 346 A Abort procedure 243 About dialog box 37 43 76 86 as modeless form 61 85 ABOUT PAS 37 accelerators 102 103 See also menu items access keys See accelerators accessing array elements 199 characters in strings 201 components 223 data DDE applications 41 385 386 OLE applications 41 392 declarations not within scope 178 f
342. from component to component Removing a component from the tab order In some cases you might want to prevent users from being able to tab to a component on a form For example there s usually no need for users to access a Panel component because they can t modify it You might want in such a case to remove the component from the tab order altogether When the user presses the Tab key in the running application the focus will skip over this component and go to the next one in the tab order This is true even if the component has a valid TabOrder value To remove a component from the tab order 1 Select the component in the form 2 Use the Object Inspector to set the value of the TabStop property to False Removing a component from the tab order doesn t disable the component Enabling and disabling components You often want to prevent a user from accessing certain components in a dialog box or form either initially when the dialog box opens or in response to changing conditions with the dialog box at run time For instance in file handling dialog boxes you might want to disable the OK button unless a file name is first specified When a component is disabled it appears dimmed in the running application and the user cannot tab to it even if its TabStop property is set to True By disabling a component at design time you specify that the component is initially unavailable to the user when the dialog box first opens You can a
343. g stand alone units that have no associated form you can make your specialized procedures and functions easily available to other projects To create a unit file not associated with a form choose File New Unit It is not necessary to have a project open unless you want the new unit to be part of a project Unit files for components If you elect to write a new Delphi component you need to create a unit file for the source code The default structure of the unit source code for a new component differs somewhat from other unit files You begin creating a new component unit file when you choose New Component from the File menu For information on creating a component unit file see Using the Component Expert in Chapter 2 You can find an example of unit file source code for a new component on page 72 The Delphi Component Writer s Guide provides complete information on creating new Delphi components Unit object code DCU files When you compile a project Delphi creates an object code file for each unit The file name is the same as the corresponding unit source file PAS and Delphi adds a DCU extension Thus the object code file for UNIT1 PAS is UNIT1 DCU The DCU file is a binary file maintained by the Object Pascal compiler so you should never need to open or modify this file by any other means DCU files are used to help achieve the high speed and efficiency of the Delphi compilation process You do not need
344. g 141 drag and drop 376 379 example 227 228 OLE objects 395 421 423 DRAGDROP DPR 227 DragMode property 376 DrawGrid component 39 drawing 14 347 current pen position setting 315 324 large images 348 lines 315 316 317 328 331 changing pen width 344 event handlers 324 325 owner draw controls 367 369 painting vs 314 shapes 39 317 318 337 fill patterns 316 344 Drawing flag 351 drawing modes 330 drawing surfaces 314 See also canvases drawing tools 334 340 changing 336 customizing 340 345 testing for 335 336 draw item events 368 369 See also owner draw controls drive lists 41 42 adding bitmaps 366 367 368 369 building 362 365 changing directories 376 updating 364 DriveComboBox component 41 drives returning valid 362 363 Index 437 drop down lists See combo boxes lists boxes drop down menus 38 103 See also menus DSK files 117 duplicate accelerators 103 duplicate identifiers 181 223 Dynamic Data Exchange See DDE applications dynamic link libraries 77 117 creating 134 141 E EAbort exception 243 EBreakpoint exception 238 EConvertError exception 238 edit boxes 38 83 225 See also combo boxes data aware 40 DDE applications and 386 390 incremental values 42 Edit Breakpoint command Breakpoint List window 257 Edit Breakpoint dialog box 257 Edit command Watch List window 259 Edit component 38 Edit Source command Breakpoint List window 256 Edit Source command Call Stack 264 Edit Tab Orde
345. g a new File menu however you ll use the File menu template provided with Delphi To create the EditForm menu add the Delphi File menu template and then create the remaining menu items shown in Table 10 4 For each menu item specify values for the Chapter 10 Text editor example 283 Caption property and accept the default value that Delphi then generates for the Name property For the Edit menu specify values for the ShortCut property Table 10 4 Child form menu items Edit menu amp Edit Shortcut keys amp Character Cu amp t Ctrl X amp Left amp Copy Ctrl C amp Right amp Paste Ctrl V amp Center De amp lete Ctrl D lt hyphen gt lt hyphen gt amp Word Wrap Select amp All lt hyphen gt amp Font In later sections you ll set additional properties for this menu You should now have a frame form and a child form for the MDI application each with its respective menu bar The following section discusses how these two menus interact at run time Save the project now Use the following names Table 10 5 Naming the project files Default name Save as UNIT1 PAS MDIFRAME PAS UNIT2 PAS MDIEDIT PAS PROJECT1 DPR TEXTEDIT DPR Merging the application menus MDI child windows do not always have their own menus but when they do as in this example these menus often interact during run time with the application s main menu bar This is known as merging menus Merging menus is discussed in detail in
346. g box 71 Standard Delphi Form Templates in the Browse Gallery 0 00 78 Example ShowMessage message box 81 Confirmation message dialog box 82 Sample input box in running form 83 Password Dialog Template at design time 84 Password dialog box atruntime 84 Password dialog box displaying masked CHARACUCIS 294 yf bar og inte ca ents Ase EE G 84 Edit Tab Order dialog box 90 3 9 5 19 5 20 5 21 5 22 5 23 Save Form Template dialog box 94 Sample MDI child and parent forms 9y Delphi menu terminology 99 MainMenu and PopupMenu components 99 Menu Designer foramainmenu 100 Menu Designer for a pop up menu 100 Nested menu structures 103 Select Menu dialog box 106 Sample Insert Template dialog box for MENUS Pot G8 hs 8 os OE OS 107 Delete Templates dialog box for menus 107 Save Template dialog box for menus 108 Project Manager window 130 Example Project Manager project listing 133 Example project directory tree 139 The Window List dialog box 140 Syntax or compile error display 142 A sample form for assigning a property value to another property 152 A sample form for the Cut Copy Paste and Clear All example 159 A form for an example that uses the Execute MUMCHON e isi g cee Son om oe ed 162 A sample form to il
347. g methods e Press F12 e Choose View Toggle Form Unit e In the Project Manager double click in the Unit column of the unit you want to display its source code or the Form column to display the form image Bringing a window to the front If you have a number of windows open such as the Delphi Project Manager or Object Browser you can easily get to the window you want by selecting it in the Window List dialog box This dialog box displays a list of all open windows and enables you to bring any of them to the front m To display the Window List dialog box and bring a window to the front 1 Press Alt 0 zero or choose View Window List from the menu 2 Double click the name of the window you want to bring to the front Figure 4 4 The Window List dialog box Delphi Projecti File Edit Search View Compile Run Options Tools Help Object nso UNIT3 PAS al procedure TBtnRightDlq FormClick Sender TObject ActiveControl be E a a Iel Din S A AutoS croll a Se pee Pees neler Double click to bring window PTE ee ee ee IT3 to the front Using the Project Manager to view or edit units E To view or edit a unit in the Project Manager window select the unit you want to view or edit and then choose from the following methods On the SpeedBar choose the View Unit button Press the Enter key From the SpeedMenu choose the View Unit command Double click the unit fi
348. g statement calls the CutToClipboard method of the memo control called Memo1 Memol CutToClipboard You can pass parameters to procedures and functions Parameters are surrounded by parentheses in a procedure or function call For example this statement calls the LoadFromFile procedure of a memo control named Memo and passes it the string MYFILE TXT Memol Lines LoadFromFile MYFILE TXT To call a function you assign the return value of the function to a variable or property in your code For example Editl Text IntToStr Sum In this example the compiler executes the IntToStr function passing it the value in the Sum parameter IntToStr converts the Sum value to a string and this string return value is assigned to the Text property of an edit box named Edit1 e Controlling the flow of code execution Chapter 5 Writing Object Pascal code 211 Object Pascal has several statements that direct the flow of code execution e The if statement evaluates an expression and determines the flow of your code based upon the result of that evaluation For example if Edit1 Color clLime then Editl Text Lime green An if statement can contain an else part For example if Fditl Color clLime then Editl Text Lime green else Fditl Text Some shade of blue An if statement can be nested within other if statements e The case statement can be used to branch to code in place of a series ofif statements
349. ge exceptions or through a loss of system resources as a result of resetting your program it is best to exit Delphi before restarting your debugging session Using breakpoints You use breakpoints to pause the program execution at designated source code locations during a debugging session By setting breakpoints in potential problem areas of your source code you can run your program at full speed knowing that its execution will pause at a location you want to debug When your program execution encounters a breakpoint the program pauses and the debugger displays the line containing the breakpoint in the Code Editor You can then use the debugger to view the state of your program Setting breakpoints Breakpoints are flexible in that they can be set before you begin a program run or at any time that the integrated debugger has control For a breakpoint to be valid it must be set on an executable line of code Breakpoints set on comment lines blank lines declarations or other non executable lines of code are invalid and become disabled when you run your program E To seta breakpoint select the line of code in the Code Editor where you want the breakpoint set then do one of the following e Click the left margin of the line in the Code Editor where you want the breakpoint set e Press F5 default key mapping e Choose Toggle Breakpoint from the Code Editor SpeedMenu e Choose Run Add Breakpoint then choose New in the Edit Brea
350. ghted in the Code Editor The Code Editor status bar displays an error message Context sensitive help regarding the error message is available by pressing F1 Figure 4 5 Syntax or compile error display UNIT1 PAS Public declarations end var Formi TForml implementation SR DFM a procedure TForml ABug Line with error highlights Begin Status bar Formil Caption Bugga Boo displays message end Unit with error Error 150 Method identifier expected eomes tome tep lt Compiling a project E Tocompile all the source code files that have changed since the last time you compiled them choose Compile Compile from the Delphi menu bar When you choose this command this is what happens e The compiler compiles source code for each unit if the source code has changed since the last time the unit was compiled This creates a file with a DCU Delphi Compiled Unit extension for each unit If the compiler can t locate the source code file for a unit the unit isn t recompiled e If the interface part of a unit s source code has changed all the other units that depend on it are recompiled To learn about the interface section of a unit see Unit source code PAS files on page 119 e Ifa unit links in an OBJ file a file containing assembly language code and the OBJ file is newer than the unit s DCU file the unit is recompiled e Ifa unit contains an include INC file and the
351. ghts properties For a tab set the default width of each tab is the width of the text it contains To accommodate bitmaps next to the text you need to handle the measure item event increasing the tab width value to include enough space for both the graphic and the text The following code attached to the OnMeasureltem event of an owner draw tab set increases the width of each tab to accommodate its associated bitmap procedure TFMForm DriveTabSetMeasureTab Sender TObject Index Integer var TabWidth Integer note that TabWidth is a var parameter var BitmapWidth Integer begin BitmapWidth TBitmap DriveTabSet Tabs Objects Index Width increase tab width by the width of the associated bitmap plus two Inc TabWidth 2 BitmapWidth end Note You must typecast the items from the Objects property in the string list Objects is a property of type TObject so that it can hold any kind of object When you retrieve objects from the array you need to typecast them back to the actual type of the items Drawing each owner draw item When an application needs to draw or redraw an owner draw control Windows generates draw item events for each visible item in the control E To draw each item in an owner draw control attach an event handler to the draw item event for that control The names of events for owner drawing always start with OnDraw such as OnDrawltem OnDrawTab or OnDrawCell 368 Delphi User s
352. h Position set the pen width directly PenSize Caption IntToStr PenWidth Position convert to string for caption end Changing the brush style A brush style determines what pattern the canvas uses to fill shapes The predefined styles include solid color no color and various line and hatch patterns E Tochange the style of a brush set its Style property to one of the predefined values bsSolid bsClear bsHorizontal bs Vertical bsF Diagonal bsBDiagonal bsCross or bsDiagCross For this example you can set brush styles just as you did pen styles sharing a click event handler for all the brush style buttons Select all eight brush style buttons and type in SetBrushStyle for the OnClick handler name procedure TForml SetBrushStyle Sender TObject begin with Canvas Brush do begin if Sender SolidBrush then Style bsSolid else if Sender ClearBrush then Style bsClear 344 Delphi User s Guide else else else else else else end end if Send if Sen if Sen if Sen if Send if Send Q Q Q Oo 0 MO MO MO o K KR RKR K KBB HorizontalBrush then Style bsHorizontal VerticalBrush then Style bsVertical FDiagonalBrush then Style bsFDiagonal BDiagonalBrush then Style bsBDiagonal CrossBrush then Style bsCross DiagCrossBrush then Style bsDiagCross Changing the brush color A brush s color determines what color the canvas uses to fill shapes E To ch
353. he directory to use as the startup directory The last parameter should be one of Windows constants used for the ShowWindow API function For example SW_SHOW shows the window normally SW_SHOWMINIMIZED shows the window initially as an icon and so on A file list box contains all the information you need to execute a file in the list The following code shows a simple use of ExecuteFile to execute the currently selected file in the file list box procedure TFMForm OpeniClick Sender TObject begin with FileList do ExecuteFile FileName Directory SW_SHOW end Chapter 13 File manager example 375 gt Ifyou add the Open1Click method to handle the File Open menu item s click event you can execute the selected file You can attach the same handler to the file list box s double click event so that double clicking an item executes it Of course it doesn t always make sense to execute a file If the selected item is a directory for example instead of executing it you probably want to open it or change to that directory The following code shows another version of Open1Click that handles directories differently from files procedure TFMForm OpeniClick Sender TObject begin with FileList do begin if HasAttr FileName faDirectory then DirectoryOutline Directory FileName else ExecuteFile FileName Directory SW_SHOW end end HasAttr is a Boolean function in the FM XUtils unit that returns Tr
354. he following event handler for the OnClick event of the File New item on the OLEFrameForm menu bar procedure TOLEFrameForm NewlClick Sender TObject begin CreateChild Call the CreateChild method end The code to create an OLEObjectForm child window was put in a separate method because it will also be called from the OnDragDrop event handler of OLEFrameForm discussed in Dropping objects as well as from the OnClick event handler for the File Open menu item discussed in Working with objects in files This way the child window creation code can be shared Next you ll write the code to exit the application gt Write the following event handler for the OnClick event of the File Exit item on the OLEFrameForm menu bar procedure TOLEFrameForm ExitiClick Sender TObject begin Close close the main form which terminates the application end 404 Delphi User s Guide You ll write the event handler for the File Open item later in the example in the section Loading objects from files gt Save the project now then run it 1 Choose File New to create a new OLE Object window The application should resemble 2 2 Choose File Exit to close the application Figure 15 2 The OLEFrameForm and OLEObjectForm windows OLE Example OLE Object Creating the child form menu The menu items in OLEObjectForm provide users with ways to manipulate the object and object window in the running applicati
355. he functionality of the source application OLE can exchange more complex forms of information such as documents and allows the user to activate the source application to make changes to the data More advanced features of OLE such as run time creation and drag and drop of OLE objects are covered in Chapter 15 398 Delphi User s Guide Note Chapter OLE example Now that you have read the material in Chapter 14 you re ready to practice exchanging data with Object Linking and Embedding OLE by building a simple application This chapter assumes you are familiar with basic OLE terms such as objects linking embedding and OLE servers It presents the steps involved in building a simple OLE container application that allows the user to insert paste and drop OLE objects into Multiple Document Interface MDI child windows The application uses Windows common dialog boxes to save and open OLE objects The material presented in this chapter assumes you are familiar with the MDI application and common dialog material discussed in Chapter 10 The OLE example is also an MDI application that uses Windows common dialog boxes but this example focuses on creating an OLE container application If you are unfamiliar with creating MDI applications or using common dialog boxes read Chapter 10 first The complete application appears under the DEMOS DOC directory and is called OLE DPR Figure 15 1 shows the application as it appears the first
356. he length of the string you entered in the edit box is reported in the Label2 control The text you entered in the edit box is assigned to the UserString variable UserString Editl Text Because UserString is of type TEditString it can contain as many as 255 characters The Length function returns the number of characters in UserString Length UserString 202 Delphi User s Guide Because Length returns an Integer value it needs to be converted to a string value The IntToStr function does this IntToStr Length UserString The string that is assigned to Label2 Caption is a string made up of three substrings e This string is e IntToStr Length UserString e characters in length These substrings are concatenated with the operator into one string The previous example declares a string type and uses a variable of that type You could write the event handler more concisely procedure TForml FindLengthClick Sender TObject begin Label2 Caption This string is IntToStr Length Edit1 Text characters in length end Set types A set is a collection of elements of one type That one type must be either an integer Boolean Char enumerated or subrange type Sets are useful for checking if a value belongs to a particular set Here is a simple application that uses a new set type This is the finished form Figure 5 24 A form for a set type example Form1 To create this application
357. he list box SS 3 Choose the Clear button or press Alt C Any text in the list box is cleared Chapter 1 Introducing Delphi 21 Distributing your application This chapter has shown how easy it is to build and run a simple Delphi application and the same fundamental techniques apply when you create larger and more sophisticated applications as well When you run your program Delphi generates a fully distributable executable EXE file Unless your application uses dynamic link libraries DLLs you have written or database files you have created for the application all you need to distribute the application is just that the EXE file There is no run time DLL file required Overview of Delphi projects When you create a Delphi application you can start with a blank project an existing project or one of Delphi s application or form templates A project consists of all the files needed to create your target application This section introduces you to the core files in a Delphi project It discusses the following topics e The project DPR file e The unit PAS file e The form DFM file e Source code for units without forms When you first start Delphi a blank project named Project1 opens Figure 1 5 A default Delphi project Form Unit source code page tab Code Editor is behind the form A blank Delphi project initially contains one unit PAS file and one associated form DFM file The
358. he same or a different name Chapter 4 Managing projects files and directories 135 You can also save your project as a Project Template which adds it to the Gallery so that you or others can reuse it For more information see Adding templates to the Gallery on page 126 You are not limited to saving a project as a whole Delphi enables you to save individual constituent files of a project including saving a copy of a file to a different directory or under a different file name Saving a project This section explains how to save an open project to the directory created to store it that is the project directory Note Ifthe project was begun from a Project Template the Gallery selection process creates the project directory Otherwise Delphi saves projects by default to the BIN directory unless you specify otherwise E Tosave all open project files to the project directory use one of the following methods e Choose File Save Project e Choose the Save Project button on the Delphi SpeedBar e Choose the Save Project command on the Project Manager SpeedMenu From here the save process for projects varies somewhat depending upon whether or not the project has been saved First project save If you have not previously saved the project Delphi displays the Save As dialog box This dialog box prompts you to supply a name for each open unit file that has been created in the current project You are not prompted for any sh
359. height with that height bOwnerDrawFixed determined by the ItemHeight property csOwnerDrawFixed Variable Each item might have a different height IbOwnerDrawVariable determined by the data at run time csOwnerDrawVariable tsOwnerDraw For this example set DriveTabSet s Style property to tsOwnerDraw Adding graphical objects to a string list Every Delphi string list has the ability to hold a list of objects in addition to its list of strings That is in addition to its indexed Strings property which contains strings a string list also has an Objects property Adding objects to a string list on page 275 explains more about using objects with string lists For the file manager example you need to add bitmaps indicating the type of drive along with the letter of the drive To do that you need to add the bitmap images to the application then copy those images into the proper places in the string list Adding images to an application An image control is a nonvisual control that contains a graphical image such as a bitmap You use image controls to display graphical images on a form but you can also use them to hold hidden images that you ll use in your application For example you can store bitmaps for owner draw controls in hidden image controls For this example 1 Add three image controls to the main form 2 Set their Name properties to Floppy Fixed and Network 3 Set the Visible property for each image control
360. her True or False It tests if the first character in the Text string is in the Vowels set Record types Records are collections of data that your application can refer to as a whole For example your application could use a TEmployee record type that is declared like this type TEmployee record LastName string 20 FirstName string 15 YearHired 1990 2000 Salary Double Position string 20 end Records contain fields that hold data values Each field has a data type The fields of a TEmployee type are LastName FirstName YearHired Salary and Position You can access these fields individually or you can refer to the record as a whole For example here are the declarations of two record variables 204 Delphi User s Guide var NewEmployee PromotedEmployee TEmployee Your code can refer to the Salary field of a NewEmployee record like this NewEmployee Salary 43500 00 Or your code can manipulate the record as a single entity PromotedEmployee Newkmployee When you refer to a field within a record you need to type the name of the record a period and the name of the field PromotedEmployee Position If you are going to assign values to fields within a record you can use thewith statement Instead of writing this code PromotedEmployee LastName Jeffries PromotedEmployee FirstName Richard PromotedEmployee YearHired 1990 PromotedEmployee Salary 100000 00 Promote
361. her to draw you should set it to True when the user presses the mouse button and False when the user releases it procedure TForml FormMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin Drawing True set the Drawing flag Canvas MoveTo X Y end procedure TForml FormMouseUp Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin Canvas LineTo X Y Drawing False clear the Drawing flag end gt Then you can modify the OnMouseMove event handler to draw only when Drawing is True procedure TForml FormMouseMove Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin if Drawing then only draw if Drawing flag is set Canvas LineTo X Y end Now you get drawing only between the mouse down and mouse up events but it s still not very useful You still get a scribbled line that tracks the mouse movements instead of a nice straight line and no final line from the original point when you release the mouse button as shown in Figure 12 5 Chapter 12 Graphics example 327 Figure 12 5 Line with lost origin Graphics example The problem is that each time you move the mouse the mouse move event handler calls LineTo which moves the pen position so by the time you release the button you ve lost the point where the straight line was supposed to start In the next section you ll use the Origin and MovePt
362. her units as well as the current one Units always have an implementation part which contains the bodies of the procedures functions and methods the coded logic of the unit Chapter 5 Writing Object Pascal code 213 An optional uses clause lists the units that the code in this unit can access A uses clause can appear in either the interface or implementation part of a unit or in both places Units can also have an optional initialization part 214 Delphi User s Guide Chapter Programming with Delphi objects Object oriented programming OOP is a natural extension of structured programming OOP requires that you use good programming practices and makes it very easy for you to do so The result is clean code that is easy to extend and simple to maintain Once you create an object for an application you and other programmers can then use that same object in other applications Reusing objects can greatly cut your development time and increase productivity for yourself and others Together Delphi and the Object Pascal language make programming with objects easier than ever before This chapter explains what you need to know about objects to use Delphi effectively If you want to create new components and put them on the Delphi Component palette see the Delphi Component Writer s Guide These are the primary topics discussed in this chapter What is an object Inheriting data and code from an object Object scope Ass
363. hing other than default settings unless the user makes modifications from within the dialog box at run time gt Write the following handler for the Character Font OnClick event procedure TEditForm SetFont Sender TObject begin FontDialogl Font Memol Font if FontDialogl Execute then Memol Font FontDialogl Font end Test the event handler by running the application opening a new file and then choosing Character Font to change the font 304 Delphi User s Guide Printing the text file The Delphi Printers unit contains routines that provide your application with all the printing capabilities users expect The printing functionality written into the text editor represents only a subset of what you can provide in your Delphi applications In the text editor application you ll enable users to print the contents of the text file or to print selected text When printing a selection the first line of selected text will be printed left aligned even if for example the selected text starts mid line Subsequent lines will be printed left aligned as expected The following printing features are beyond the scope of the text editor application WYSIWYG printing Printing multiple copies Collating multiple copies Printing page ranges Printing multiple fonts Printing word wrapped text The Printers unit declares an object TPrinter that acts as an interface between a print job and the output printer The AssignPrn pr
364. his can be useful if you think you ve found the solution to a bug and you want to try the correction before exiting the debugger changing the source code and recompiling the program Evaluating expressions Choose Run Evaluate Modify to open the Evaluate Modify dialog box Figure 8 5 The Evaluate Modify dialog box a EV aluate Modify Expression A E Listbox Demo l New value ee By default the word at the cursor position in the current Code Editor is placed in the Expression edit box You can accept this expression enter another one or choose an expression from the history list of expressions you ve previously evaluated To evaluate the expression click the Evaluate button at the bottom of the Evaluate Modify dialog box Using this dialog box you can evaluate any valid language expression except those that contain e Local or static variables that are not accessible from the current execution point e Function and procedure calls The Evaluate Modify dialog box lets you view and modify the values of object properties while running the program However to view a property you need to explicitly specify the property name For example you can enter the following expression to evaluate the Caption property of Button1 Buttonl Caption When you evaluate an expression the current value of the expression is displayed in the Result field of the dialog box If necessary you can format th
365. hods for an object that is a field in a form object you can use the with statement to simplify your code The with statement is as convenient to use with objects as it is with records For example this is an event handler that makes several changes to a list box when a user clicks the button on the form procedure TForml ButtoniClick Sender TObject begin ListBoxl Clear ListBoxl MultiSelect True ListBoxl Items Add One ListBoxl Items Add Two ListBoxl Items Add Three ListBoxl Sorted True ListBoxl Font Style fsBold ListBoxl Font Color clPurple ListBoxl Font Name Times New Roman ListBoxl ScaleBy 125 100 end Chapter 6 Programming with Delphi objects 225 If the code uses a with statement it looks like this procedure TForml ButtoniClick Sender TObject begin with ListBoxl do begin Clear MultiSelect True Items Add One Items Add Two Items Add Three Sorted True Font Style fsBold Font Color clPurple Font Name Times New Roman ScaleBy 125 100 end end By using the with statement you don t have to qualify each reference to a ListBox1 property or method with the ListBox1 identifier Within the with statement all the properties and methods called are local in scope to the ListBox1 object variable Assigning values to object variables You can assign one object variable to another object variable if the var
366. however uses the most local variable to which it has access each time it encounters a FirstNumber variable in code Using a global variable Suppose you wanted to keep track of the number of calculations performed while your application was running You could modify your form to look like this Figure 5 15 A form that uses a global variable Form1 To create this application 1 Add a fourth edit box to the form and a label to the left of the new edit box 2 With the Object Inspector make these changes e Change the value of the edit box Name property to Counter e Change the caption of the new label to Number of Calculations 3 Add these lines of code to each event handler Count Count 1 Counter Text IntToStr Count These lines of code add one to the Count variable each time you click one of the buttons on the form and display the result in the Counter edit box Chapter 5 Writing Object Pascal code 181 If you try to run your application now Delphi reminds you that you haven t declared the Count variable yet You could declare Count in each of the event handlers and give it an initial value of 0 This is how the DivideClick event handler would look procedure TForml DivideClick Sender TObject var FirstNumber SecondNumber Count Integer begin Count 0 FirstNumber StrToInt Editl Text SecondNumber StrToInt Edit2 Text Edit3 Text IntToStr FirstNumber div SecondNumber Count
367. i generates an error message e It can appear immediately after the reserved word implementation Only declarations in the current unit can use the declarations in the interface parts of the units specified here Any other units that use the current unit won t be able to use the units listed in this uses clause For example if unit C is in a uses clause in the implementation part of unit B and unit B is in a uses clause of unit A unit A can use only the declarations in the interface parts of unit B Unit A can t access the declarations in unit C unless unit C is in a uses clause of unit A If unit B is in the uses clause in the implementation part of unit A unit A can be in the uses clause in the implementation part of unit B While circular unit references are not allowed in the interface part they are fine in the implementation part Interface part The interface part of a unit begins with the reserved word interface which appears after the unit header and ends at the reserved word implementation The interface determines what is visible accessible to any application or other unit using this unit In the unit interface part you can declare constants data types variables procedures and functions If Delphi builds a unit for you as you design a form the form data type the form variable that creates an instance of the form and the event handlers are declared in the interface part You can see examples of these in Chapte
368. iables are of the same type or assignment compatible just as you can assign variables of any type other than objects to variables of the same type or assignment compatible types For example if objects TForm1 and TForm2 are derived from type TForm and the variables Form1 and Form2 have been declared you could assign Form1 to Form2 Form2 Forml You can also assign an object variable to another object variable if the type of the variable you are assigning a value to is an ancestor of the type of the variable being assigned For example here is a TDataForm type declaration and a variable declaration section declaring two variables AForm and DataForm type TDataForm class TForm Buttonl TButton Edit TEdit DataGridl TDataGrid Databasel TDatabase TableSet1 TTableSet VisibleSessionl TVisibleSession private Private declarations public Public declarations end var 226 Delphi User s Guide AForm TForm DataForm TDataForm AForm is of type TForm and DataForm is of type TDataForm Because TDataForm is a descendant of TForm this assignment statement is legal AForm DataForm You might wonder why this is important Taking a look at what happens behind the scenes when your application calls an event handler shows you why Suppose you fill in an event handler for the OnClick event of a button When the button is clicked the event handler for the OnClick event is called Each e
369. ialize the OLE container was put in a separate method because it will also be called from the OnClick event handler for Edit Paste Special discussed in Pasting objects This way the OLE container initialization code can be shared Deactivating objects If the OLE object was created by an OLE 1 0 server it is activated in the OLE server s window Focus and control transfer to the OLE server when an OLE object is activated within its own window To deactivate an OLE object created by an OLE 1 0 server choose the OLE server s File Exit command or its equivalent in the command structure of the OLE server If the OLE object was created by an OLE 2 0 server it might activate in the OLE container application s window if the OLE server application supports in place activation and you ve added a MainMenu component to the main form of your container application The File Exit command from the OLE server isn t available because the available File menu or any menu with a GroupIndex of 0 is from the OLE container application To deactivate an OLE object created by an OLE 2 0 server focus must shift to a control in the OLE container application other than the OLEContainer component containing the active OLE object You can also deactivate the object by clicking in the client area of the form that contains the OLEContainer Shifting focus to another control does not deactivate an OLE object activated in its own window rather
370. ibe the value of the constant The actual value of the constants which can t change while the application runs are 3 14159 342 and Delphi respectively When naming constants follow the same rules for naming variables and other identifiers given on page 154 Chapter 5 Writing Object Pascal code 157 Like variables constants also have types Unlike variables however constants assume the type of the value declared in the constant declaration part For example the constant Pi is of type Real because the value 3 14159 is real number Answer is of type Integer because 342 is an integer and ProductName is of type string because Delphi is a text string Note that the equal sign in a constant declaration is different from the assignment operator in assignment statements The equal sign in a constant declaration states that the left side and the right side of the declaration are equal values It s acommon mistake to misuse an equal sign operator in Object Pascal code When the compiler finds an equal sign rather than an assignment operator it expects that the left side of the statement is a constant or that two values are being compared If that isn t how you are using the equal sign Delphi displays a syntax error message If you make the reverse mistake of using an assignment operator in a constant declaration a syntax error occurs and a message appears telling you that the compiler expected an equal sign Call
371. ic debug information for your project with the following steps 1 Choose Options Project to open the Compiler Options dialog box 2 Click the Compiler Options tab to access the debugging options 3 Check the Debug Information and Local Symbols check boxes When you generate symbolic debug information for use with the internal debugger the compiler stores a symbol table in each associated DCU file If you want to use Turbo Debugger the standalone debugger you also need to include symbolic debug information in your final EXE file To include symbolic debug information in your project s compiled EXE file 1 Choose Options Project to open the Compiler Options dialog box 2 Click the Linker tab to access the linker options 3 Check the Debug Info In EXE check box Be aware that including symbolic debug information in your executable file significantly increases the size of the final EXE file Because of this you want to include debug information in your files only during the development stage of your project Once your program is fully debugged compile your program without debug information to reduce the final EXE file size Chapter 8 Using the integrated debugger 249 Before you begin In order to access the integrated debugger commands you need to make sure the integrated debugger is enabled m To enable the integrated debugger 1 Choose Options Environment and click the Preferences page tab 2 Check the Integrated De
372. icking the primary right button will record mbLeft as the value of the Button parameter Responding to a mouse down action Whenever the user presses a button on the mouse an OnMouseDown event goes to the object the pointer is over The object can then respond to the event In this example the user will press the mouse button with the pointer over the form itself at which time the application starts drawing So you need to define the form s response to OnMouseDown events To respond to a mouse down action you attach an event handler to the OnMouseDown event If you re not sure how to create an event handler see Chapter 2 Delphi generates an empty handler for a mouse down event on the form procedure TForml FormMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin end Just to get a feel for writing a mouse event handler try displaying some text at the point where you press the mouse button To do that you use the X and Y parameters sent to the method and call the TextOut method of the canvas to display text there procedure TForml FormMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin Canvas TextOut X Y Here write text at X Y end Chapter 12 Graphics example 323 If you run the application you can press the mouse button down on with the mouse cursor on the form and have the string appear at the point clicked as shown i
373. ield and Calculate function are declared to be private Only objects within the unit can use Number and Calculate Usually this restriction means that only the form object can use them because each Delphi unit contains just one object type declaration of type TForm Because the ChangeColor method is declared to be public code in other units can use it Such a method call from another unit must include the object name in the call Forml ChangeColor The unit making this method call must have Form in its uses clause When adding fields or methods to an object always put the fields before the method declarations within each public or private part Accessing object fields and methods When you want to change the value of a property of an object that is a field in the form object or you want to call a method of an object that is a field in the form object you must include the name of that object in the property name or method call For example if your form has an edit box control on it and you want to change the value of its Text property you should write the assignment statement something like this making sure to specify the name of the edit box in this example Edit1 Edit1 Text Frank Borland was here Likewise if you want to clear the text selected in the edit box control you would write the call to the ClearSelection method like this Edit1 ClearSelection If you want to change several property values or call several met
374. ields 224 225 files 117 237 index menu commands 102 292 methods 224 225 property values 54 activating OLE objects 391 400 412 Active property 413 ActiveControl property 92 actual parameters 191 193 formal parameters vs 191 Add Breakpoint command Run 254 Add button Project Manager 131 Add File command Project Manager 131 Add method menus 110 strings 271 Add Module Browse dialog box 69 Add Module dialog box 69 Add To Project dialog box 135 Add Watch At Cursor command Code Editor window 259 Add Watch command Run 259 adding See also creating buttons 38 39 to dialog boxes 87 89 child windows 281 401 404 at run time 285 common dialog boxes 41 components 44 45 209 container 48 multiple 44 47 new 121 overview 15 third party 42 68 69 70 fields to forms 326 328 forms 26 59 76 220 224 gauges 42 glyphs 332 333 graphics 39 313 321 menus 38 100 104 350 351 drop down 103 file manager example 361 362 369 from other applications 112 MDlapplications 282 284 288 294 OLE example 402 408 pop up 38 294 methods 339 340 non textual information 39 objects to string lists 275 276 366 367 OLE objects 393 395 401 410 413 421 pages to notebooks 39 panels 331 345 346 scroll bars 39 290 scroll boxes 39 status bars 39 345 347 OLE example 409 410 strings to string lists 271 276 strings to strings 201 text 38 83 269 MDI applications 288 295 OLE applications 419 422 tool bars 39
375. ies and methods within that object Using the earlier bicycle analogy if you were to add a headlight only to your customized bicycle object the headlight would belong to that bicycle and to no other If however the basic model bicycle object included a headlight then all bicycle objects would inherit the presence of a headlight The headlight could lie either within the scope of the ancestor bicycle object in which case a headlight would be a part of all descendant bicycle objects or within the scope only of the customized bicycle object and available only to that bicycle Likewise all data fields properties and methods declared within an object declaration are within the scope of the object and are available to that object and its descendants Even though the code that makes up the methods appears outside of the object declaration in the implementation part of the unit those methods are still within the scope of the object because they were declared within the object s declaration When you write code in an event handler of an object that refers to properties methods or fields of the object itself you don t need to preface these identifiers with the name of the object variable For example if you put a button and an edit box on a new form you could write this event handler for the OnClick event of the button procedure TForml ButtoniClick Sender TObject begin Color s cl Fuchsia Editl Color clLime end
376. ieslClick Sender TObject var Attributes NewAttributes Word begin with FileAttrForm do begin FileDirName Caption FileList Items FileList ItemIndex set box caption PathName Caption FileList Directory show directory name ChangeDate Caption DateTimeToStr FileDateTime FileList FileName Attributes FileGetAttr FileDirName Caption read file attributes ReadOnly Checked Attributes and faReadOnly faReadOnly Archive Checked Attributes and faArchive faArchive System Checked Attributes and faSysFile faSysFile Hidden Checked Attributes and faHidden faHidden if ShowModal lt gt mrCancel then execute dialog box begin NewAttributes Attributes start with original attributes if ReadOnly Checked then NewAttributes NewAttributes or faReadOnly else NewAttributes NewAttributes and not faReadOnly if Archive Checked then NewAttributes NewAttributes or faArchive else NewAttributes NewAttributes and not faArchive if System Checked then NewAttributes NewAttributes or faSysFile else NewAttributes NewAttributes and not faSysFile if Hidden Checked then NewAttributes NewAttributes or faHidden else NewAttributes NewAttributes and not faHidden if NewAttributes lt gt Attributes then if anything changed FileSetAttr FileDirName Caption NewAttributes Write the new values
377. if ShowModal lt gt idCancel then continue if user doesn t cancel dialog box begin Bitmap TBitmap Create create fresh bitmap object Bitmap Width StrToInt WidthEdit Text use specified width Bitmap Height StrToInt HeightEdit Text use specified height Image Picture Graphic Bitmap replace graphic with new bitmap CurrentFile indicate unnamed file end end end The important aspect to understand is that assigning a new bitmap to the picture object s Graphic property causes the picture object to destroy the existing bitmap and take ownership of the new one Delphi handles the details of freeing the resources associated with the previous bitmap automatically Using the Clipboard with graphics You can use the Windows Clipboard to copy and paste graphics within your applications or to exchange graphics with other applications Delphi s Clipboard object makes it easy to handle different kinds of information including graphics Before you can use the Clipboard object in your application you need to add theClipBrd unit to the uses clause of any unit that needs to access Clipboard data 354 Delphi User s Guide Copying graphics to the Clipboard You can copy any picture including the contents of image controls to the Clipboard Once on the Clipboard the picture is available to all Windows applications To copy a picture to the Clipboard assign the picture to the Clipboard object using th
378. if the expression being evaluated is an integer type but not Longint a Char type or an enumerated or subrange type The logic of acase statement is usually easier to see and the code runs more quickly e The repeat statement is a looping statement that repeats a statement or a series of statements until some condition is True This condition is evaluated at the end of the loop A repeat statement always runs at least once e The while statement is a looping statement that evaluates a condition at the beginning of the loop Because a while statement doesn t loop if the condition evaluates to True it is possible a while statement might not loop at all e The for statement is a looping statement that runs a specific number of times depending on the value of a control variable For loops are fast and efficient e Object Pascal blocks Blocks are made up of an optional declaration part and a statement part The statement part is made up of code statements The declaration part declares the identifiers that are used by the code in the statement part Blocks can exist within other blocks For example a project block contains one or more unit blocks which contain one or more event handler blocks e Understanding scope The scope of an identifier defines where the identifier is active The identifier is local in scope to the block in which it is declared Once the execution of your code is outside that block the identifier is no longer wi
379. ifier property constant data type variable or routine with the unit name The uses clause in the implementation part Object Pascal allows you to put an optional uses clause in a unit s implementation part If you put it in it must appear immediately following the implementation reserved word A uses clause in the implementation part lets you hide the inner details of a unit because units specified in the implementation part aren t visible accessible to the users of the unit Writing a unit from scratch You are free to add code to any unit that Delphi creates You must not alter the code that Delphi generates however If you want to create a new unit in your project that is not associated with a form Delphi gets you started To create a new unit choose File New Unit A new unit is added to your current project The source code of the new unit looks like this Chapter 5 Writing Object Pascal code 209 unit Unit2 interface implementation end The name Delphi selects for your unit depends on how many units are already in your project You can then fill in this skeleton unit to include the code that you want Note that the end reserved word is not paired with a begin reserved word If you like you can add an initialization reserved word above the find end reserved word to create an initialization part Many of the units you write don t require any initialization code as they are often collections of
380. igning values to object variables Creating nonvisual objects Before reading this chapter you should know how to design a user interface for your application using the Delphi tools how a Delphi project is structured and how to handle events You should also know the fundamentals of the Object Pascal language To review topics in any of these areas refer to the appropriate chapters in this book or use Delphi s online Help What is an object An object is a data type that wraps up data and code all into one bundle Before OOP code and data were treated as separate elements Chapter 6 Programming with Delphi objects 215 Think of the work involved to assemble a bicycle if you have all the bicycle parts and a list of instructions for the assembly process This is analogous to writing a Windows program from scratch without using objects Delphi gives you a head start on building your bicycle because it already gives you many of the preassembled bicycle parts the Delphi forms and components You can begin to understand what an Object Pascal object is if you understand what an Object Pascal record is In Chapter 5 you read that records are made of up fields that contain data and each of these fields has its own data type Records make it easy to refer to a related collection of varied data elements as one entity Objects are also collections of data elements Like records they also have fields each of which has its own data
381. in FrameForm NewChild Sender end Referencing other units If you try to compile the application now Delphi generates an Unknown identifier error message If you want to reference anything declared in another form s unit you need to add the form to the referencing form s uses clause In this case it s actually EditForm itself that FrameForm doesn t recognize gt Add MDIEdit to the uses clause in the interface section of the MDIFrame unit uses Sysutils Menus MDIEdit By the same token if you run the application now you get the same error message for the FrameForm reference in EditForm s New1Click method gt Create the following uses clause in the implementation part of the MDIEdit unit uses MDIFrame Note When two units reference each other placing both unit references in the uses clause of the interface part causes a circular reference That is why you wrote auses clause in the implementation part of MDIEdit instead of editing the existing uses clause in the interface part For more information refer to Chapter 5 gt Try the following 1 Run the application Even though you ve created the child form it doesn t appear initially because you removed it from the Auto create forms list 2 Choose File New Form You ve just called the event handler that instantiates the child form at run time and the child window appears Figure 10 4 Open child window E Text Editor BA 3 Close th
382. in its argument Delphi adds an Application CreateForm statement to the project file for each form you add to the project The statements are listed in the order the forms are added to the project This is the order that the forms will be created in memory at run time If you want to change this order do not edit the project source code Use Options Project on the Delphi menu bar For more information see Chapter 3 e The Application Run statement starts your application Each time you add a new form or unit to the project Delphi adds it to the uses clause in the project source code file For more information see Integrating forms and units into a project on page 133 Because Delphi maintains the DPR file you should not normally need to modify it manually and in general it is not recommended that you do so Unit source code PAS files Units are the main building blocks of Delphi applications Unit files are identified by a PAS file extension They contain the Object Pascal source code for the elements of the Delphi applications you build For example every form has its own unit source code file Unit source code files may initially be created as part of a project but this is not required You can create and save a unit as a stand alone file that any project can use Once you add a unit to a project Delphi registers the unit in the uses clause of the project DPR file If you open and save a default new project the project
383. in your form design from one of the Form Templates provided with Delphi and you can save any form you design as a template that you can reuse in other projects Likewise you can use menu templates as starting points for menus you customize to suit your programming needs This chapter discusses the following topics What is a form Sharing forms Building forms Creating form menus Associating menu events with code Importing resource RC files Managing run time behaviors of forms Chapter 3 Building forms and menus 75 What is a form The term form means different things to different people depending upon what type of programming environment they have previously experienced For the purposes of this book a form is any component of the TForm class and its visual representation onscreen For more information about classes see Chapter 6 For more information about the TForm class press F1 with the form selected Designing usable forms When designing a graphical user interface application developers must be part programmer and part visual designer Good planning and design of forms and their interaction are important for a number of reasons Well designed intuitively usable forms require less documentation and well designed forms and interfaces are easier to support and maintain Teaching you about basic visual and user interface design principles is beyond the scope of this book but there are many good third party books that
384. include file is newer than the unit s DCU file the unit is recompiled 142 Delphi User s Guide Once all the units that make up the project have been compiled Delphi compiles the project source DPR file and creates an executable file or dynamic link library This file is given an EXE or DLL file extension and the same file name as the project source code file This file now contains all the compiled code and forms found in the individual units and the program is ready to run or in the case of a DLL to be redistributed You can choose to compile only portions of your code if you use ifdef conditional directives and predefined symbols in your code For information about conditional compilation see Conditional Directives in online Help Obtaining compile status information You can get information about the compile status of your project by displaying the Information dialog box Choose Information from the Compile menu This dialog box displays information about the number of lines of source code compiled the byte size of your code and data the stack and heap sizes and the compile status of the project You can get status information from the compiler as a project compiles by checking the Show Compiler Status box in the Environment Options dialog box For more information see Environment Options in online Help Building a project To compile all the source code files in your project regardless of when they were last
385. ine of text Y Memo Display an area where the user can enter or modify multiple lines of text Y Button Provide a button that users can choose to carry out an operation for instance stopping starting or cancelling a process Y CheckBox Present Yes No True False or On Off options Check boxes A Boe A Bas lt operate independently of one another the options presented are not mutually exclusive Y RadioButton Present mutually exclusive options Radio buttons are usually used in conjunction with group boxes to form groups where only one of the listed options is available at any one time E ListBox Display a list of choices from which the user can select one or more items aa lt 38 Delphi User s Guide Table 2 1 Oy S E Li Ea iii O Table 2 2 Icon E E w EL le A i be Components on the Standard page continued continued Visual Y Component name ComboBox ScrollBar GroupBox RadioGroup Panel Use to Combine the functionality of an edit box and a list box to display a list of choices Users can either type text into the edit box part or select an item from the list Provide a way to change which portion of a list or form is visible or to move through a range by increments Group other related components on a form Group radio buttons on a form Group other components such as speed buttons on a tool bar also often used to create a statu
386. ine you add AboutBox Caption About Application Title remove the existing semicolon else AboutBox Caption this is the second line you add AboutBox ShowModal end 64 Delphi User s Guide Note Now you ll associate MainForm Button2 s OnClick event with this handler To associate a new component event with an existing event handler 1 Inthe form select the component whose event you want to code 2 Display the Events page of the Object Inspector and select the event to which you want to attach handler code 3 Click the down arrow next to the event to open a list of existing event handlers The list shows only the event handlers in this form that can be assigned to the selected event 4 Select from the list by clicking an event handler name The code written for this event handler is now associated with the selected component event Select Button2 and associate it with Button1Click Delphi doesn t duplicate the event handler code for every component event associated with a shared handler You see the code for shared handlers in the Code Editor only once even though the same code is called whenever any of the associated component events occurs Run the program again and click Button1 The application title appears in the About box caption Now close the About box and click Button2 in the main form The About box opens but does not display the application title Displaying and coding shared events The
387. ing 376 379 OLE objects 395 421 423 handling 322 323 324 325 testing for 326 351 Move method strings 271 276 MoveFile function 373 MoveTo method 315 444 Delphi User s Guide moving components to different pages 69 files 373 input focus 90 92 menu items 104 pens 315 324 strings in lists 271 moving among IDE windows 140 moving among menus 106 moving through Code Editor 62 moving through databases 40 mrOK constant 88 MsgDlg unit 209 multidimensional arrays 200 multimedia players See media players multi page forms 39 See also notebooks multiple components adding 44 47 copying to containers 48 49 removing from containers 49 resizing 46 selecting 46 setting properties 54 55 sharing events 65 67 Multiple Document Interface See MDI applications multiple tool bars 342 multiplication example 178 multitasking 381 mutual recursion 189 mutually exclusive options 38 333 N name conflicts 44 Name property 16 27 44 Caption property vs 17 multiple components and 54 scope 55 naming See also identifiers applications 128 component classes 72 components 44 55 third party 70 event handlers 66 files See file names forms 17 55 59 menu items 101 108 menus 101 tabs 269 nesting begin end blocks 176 exception handlers 233 234 for statements 172 174 if statements 165 166 menu items 103 networks 116 New Component command File 71 new forms 29 New Project command File 19 New Unit command Fil
388. ing information this is normally a location that contains user written code However you can override this behavior and have Delphi step to the first executable statement in the program when you begin a debugging session This feature provides the ability to debug the startup routines of your project m To have Delphi step to the first executable statement in the program 1 Choose Options Environment then click the Preferences page tab 2 Check the Step Program Block check box 3 Run your program by choosing Trace Into or Step Over Running to a breakpoint You set breakpoints on lines of source code where you want the program execution to pause during a run Running to a breakpoint is similar to running to a cursor position in that the program runs at full speed until it reaches a certain source code location However unlike Run To Cursor you can have multiple breakpoints in your code and you can customize each one so it pauses the program execution only when a specified condition is met For more information on breakpoints see Using breakpoints on page 254 Pausing the program In addition to stepping over or tracing into code you can also pause your program while it s running Choosing Run Program Pause causes the debugger to pause your program the next time the execution point enters your code You can then use the debugger to examine the state of your program with respect to this program location When you ve finished
389. ing a particular string The string list has an indexed property called Strings which you can treat like an array of strings for most purposes For example the first string in the list is Strings 0 However since the Strings property is the most common part of a string list to access Strings is the default property of the list meaning that you can omit the Strings identifier and just treat the string list itself as an indexed array of strings E To access a particular string in a string list you refer to it by its ordinal position or index in the list The string numbers are zero based so if a list has three strings in it the indexes cover the range 0 2 E To determine the maximum index check the Count property If you try to access a string outside the range of valid indexes the string list raises an exception For example the following two lines do exactly the same thing setting the first line of text in a memo field Memol Lines Strings 0 This is the first line Memol Lines 0 This is the first line Finding the position of a string Given a string you often want to find out its position in a string list or whether it s in the list at all m To locate a string in a string list you use the string list s IndexOf method IndexOf takes a string as its parameter and returns the index of the matching string in the list or 1 if the string is not in the list Note that IndexOf works only with complete
390. ing operations on strings and objects in a string list Table 9 1 Corresponding string and object methods in string lists Operation For strings For objects Access an item Strings property Objects property Add an item Add method AddObject method Insert an item Insert method InsertObject method Locate an item IndexOf method IndexOfObject method Methods such as Delete Clear and Move operate on items as a whole That is deleting an item deletes both the string and the corresponding object Also note that the LoadFromFile and SaveToFile methods operate on only the strings since they work with text files Accessing associated objects You access objects associated with a string list just as you access the strings For example to get the first string in a string list you access the string list s Strings property at index 0 Strings 0 The object corresponding to that string is Objects 0 Adding associated objects To associate an object with an existing string you assign the object to the Objects property at the same index For example if a string list named Fruits contains the string apple and you want to associate a bitmap called AppleBitmap to it you would use the following assignment with Fruits do Objects IndexOf apple AppleBitmap You can also add objects at the same time you add the strings by calling the string list s AddObject method instead of Add which just adds a string AddObject takes two parameters
391. ing procedures and functions Procedures and functions are modular pieces of code that perform some specific task They are known as subroutines in other languages The Delphi run time library contains many procedures and functions your applications can use You don t need to write the code the procedures and functions are already written While you don t need to understand the logic of the code within the procedures and functions you need to understand what they do When procedures and functions are declared within objects which include components and controls they are called methods An object is a data type you can read about in the next chapter Programming with Delphi objects Calling procedures Perhaps you ve noticed that all event handlers begin with the reserved word procedure All event handlers are procedures subroutines that divide the logic of your application into manageable chunks Each event handler contains just the code you want executed when the event occurs E To use an existing procedure type the name of the procedure as a statement in your code This is called calling a procedure For example the memo control has a CutToClipboard method that removes the text the user has selected within the memo control and stores it in the Clipboard object Because this functionality is built into the method you need to know only what the method does and how to use it This is how you call the CutToClipboard method
392. int The execution point always shows the next line of code to be executed whether you are going to trace step or run your program at full speed Chapter 8 Using the integrated debugger 251 Stepping through code The Trace Into and Step Over commands offer the simplest way of moving through your program code While the two commands are very similar they each offer a different way to step through code When you step you watch your program execute statements one at a time After stepping the program execution is paused and you can use the debugger to investigate the different aspects of your program Trace Into The Trace Into command executes a single program statement at a time If the execution point is located on a call to a function that was compiled with debugging information choosing Trace Into causes the debugger to step into that function by placing the execution point on the function s first statement However if the execution point is located on a function call that doesn t contain debugging information a library function for example then choosing Trace Into runs that function at full speed after which the execution point is positioned on the statement following the function call If the execution point is located on the last statement of a function choosing Trace Into causes the debugger to return from the function placing the execution point on the line of code that follows the call to the function you are returning
393. introduces the form as aclass A class is simply an object which you will recognize if you are familiar with previous versions of Borland Pascal products or another object oriented programming language Chapter 5 discusses classes and objects in more detail All the elements that make up a Delphi application such as buttons labels fonts and so forth are objects Delphi objects encapsulate Windows behaviors enabling you to interact with the object instead of directly with Windows Form unit var declaration The form unit var declaration declares your form as an instance of TForm1 This means it contains all the behaviors and characteristics of a Form object Form unit compiler directive The R compiler directive links the TForm s binary file DFM This adds the DFM file s in your project to the compiled executable 120 Delphi User s Guide Caution Note You can change which form is specified as your application s main form For more information see Gallery options on page 124 Do not remove the R DFM directive from a form unit file Doing so will result in code that will never work correctly Unit files for procedures and functions You can write custom procedures or functions within any source code unit including those associated with a form file You might however want to reuse the routines that you write In this case it s usually better to create a unit specifically to contain those routines By creatin
394. ion The Menu Designer is discussed in more detail in Chapter 3 Integrated debugger Delphi provides a fully integrated debugger so you can debug your source code without exiting the development environment Your debugging sessions take place in the same visual environment that Delphi provides The debugger includes many advanced features including syntactic awareness expression evaluators watches conditional breakpoints and the ability to view the call stack The integrated debugger is discussed in detail in Chapter 8 ObjectBrowser Browsing status line Back Show browsing history Object Browser Forms Show G m a 5 o gt eine A Pu TObject Classinfo Pointer iP PERE n Text Pu TObject ClassName String Q biMaximize TBordericon 2 Pu TObject ClassParent TClas Details G biMinimize TBordericon 1 Pu ee va ie TClass pane c Peda ERT Toen ae Inspector pane Scope page Inheritance page Reference page The Delphi ObjectBrowser enables you to visually examine object hierarchies units and global symbols your program uses You need to compile your application with Symbol Chapter 1 Introducing Delphi 13 Information enabled by default in order to enable the Browser item on the View menu For more information search online Help for the topic ObjectBrowser Image editor Resource selector window Page tabs Eek n provide selection a WINHELP RES BAI among bitmaps icons and cursors
395. ion amp Read Only Check Box Name Archive Caption amp Archive Check Box Name System Caption amp System Check Box Name Hidden Caption amp Hidden Bitmap Button Kind bkOK Bitmap Button Kind bkCancel Figure 13 4 The file attribute dialog box File Attributes Attributes l ReadOnly System l Archive Hidden Changing individual file attributes Because Delphi represents file attributes in a set you can use normal bitwise operators to manipulate the individual attributes Each attribute has a mnemonic name defined in the SysUtils unit For example to set a file s read only attribute you would do the following Attributes Attributes or faReadOnly You can also set or clear several attributes at once For example to clear both the system file and hidden attributes do the following Attributes Attributes and not faSysFile or faHidden 372 Delphi User s Guide Setting file attributes Delphi enables you to set the attributes for any file at any time To set a file s attributes pass the name of the file and the attributes you want to the FileSetAttr procedure The following code reads a file s attributes into a set variable sets the check boxes in the file attribute dialog box to represent the current attributes then executes the dialog box If the user changes and accepts any dialog box settings the code sets the file attributes to match the changed settings procedure TFMForm Propert
396. ire you to store projects in separate directories but you will find it much easier to manage them if you do Constituent files of a project To manage projects effectively you need to understand the various files and file types that constitute a Delphi project Simply opening a new project within Delphi does not create project files on disk Delphi generates the actual files at different times as you work on the project some at design time when you initially save the project or changes to it and some when you compile the project s source code Still other files used in a project might be created by other applications and integrated into your Delphi application at save or compile time Files generated at design time Some project files are generated as you develop a project These are mainly source code configuration and backup files File or project saving operations within Delphi trigger their creation on disk Table 4 1 summarizes these files and their DOS file extensions and explains when they are written to disk Table 4 1 Design time project files File extension Definition Purpose DPR Project file Pascal source code for the project s main program file Lists all form and unit files in the project and contains application initialization code Created when project is first saved PAS Unit source Object One PAS file is generated for each form the project contains Pascal code when the project is first saved Your project
397. ironment from the contents screen of online Help Elements visible upon starting Delphi While many elements are visible as soon as you start Delphi some others are not visible until needed or until you activate them through menu commands or other actions This section describes those interface elements that you can see right away when you start Delphi Forms are the focal point of nearly every application you develop in Delphi You use the form like a canvas placing and arranging components on it to design the parts of your user interface Components are the building blocks of Delphi applications They appear on the Component palette displayed in the top right hand part of the screen see Figure 1 1 You can think of a form as a component that can contain other components Your application s main form and its components interact with other forms and their components to create your application interface The main form is your application s main interface other forms can include dialog boxes data entry screens and so on You can resize the form and move it anywhere on your screen A form includes standard features such as Control menu Minimize and maximize buttons Title bar Resizeable borders You can change these features as well as other properties of the form by using the Object Inspector to edit the form during design time the time during which you are designing rather than running your form Properties define a comp
398. is activated in place In this example you ll 402 Delphi User s Guide create an Edit menu item with a GroupIndex value of 1 it will be replaced by an OLE server s Edit menu item group when the OLE object is activated The menu items from your OLE container that won t be replaced by the server are any that have a GroupIndex value other than 1 3 or 5 To prevent a menu item from an OLE container application from being replaced with menu items from an OLE server application when an OLE object is activated in place assign a value of 0 2 or 4 or greater than 5 to the GroupIndex property of the menu item This section describes the following steps involved in creating the menus for the OLE example e Creating the frame form menu e Creating the child form menu Creating the frame form menu To allow OLE objects to be activated in place the main form of an application must contain a MainMenu component To create the OLEFrameForm menu 1 Adda MainMenu component from the Standard page of the Component palette to OLEFrameForm and open the Menu Designer 2 Create the File menu title and underlying menu items as shown in the following table For each menu item specify the values for the Caption property and accept the values Delphi creates for the Name property amp File amp New amp Open lt hyphen gt E amp xit By default the value of the GroupIndex property for the File menu title is 0 which is what yo
399. isn t nil in other words the pointer still points to the instance For this reason it is safer to call Free than Destroy Also calling Free is slightly more efficient in the resulting code size To destroy the Employee object when you have finished using it you would make this call Employee Free Just as it inherits the Create method TEmployee inherits Free from TObject To follow good programming practices you should place your destructor call in the finally part of a try finally block while placing the code that uses the object in the try part This assures that the memory allocated for your object is released even if an exception occurs while your code is attempting to use the object You can read about exceptions and what a try finally block is in Chapter 7 You can find a more common example of creating a nonvisual object in Chapter 9 String list objects are commonly used in Delphi applications Chapter 6 Programming with Delphi objects 229 summary This chapter presented these topics e What is an object An object is a data type that combines data and code Like a record an object contains data fields Unlike a record an object also contains methods procedures and functions that act on the data and properties e Inheriting data and code from an object An object inherits all the data fields methods and properties of its ancestor object All the controls and components in the Delphi Visual Component Library
400. isplaying the subordinate menu items Associating a menu item with an existing event handler You can associate a menu item with an existing event handler so that you don t have to rewrite the same code in order to reuse it m To associate a menu item with an existing OnClick event handler 1 In the Menu Designer window select the menu item 2 Display the Properties page of the Object Inspector and ensure that a value is assigned to the menu item s Name property 3 Display the Events page of the Object Inspector 4 Click the down arrow next to OnClick to open a list of previously written event handlers Only those event handlers written for OnClick events in this form appear in the list 9 Select from the list by clicking an event handler name The code written for this event handler is now associated with the selected menu item Adding menu items dynamically Sometimes you want to add menu items to an existing menu structure while the application is running to provide more information or options to the user You can insert a menu item by using the menu item s Add or Insert method or you can alternately hide and show the items in a menu by changing their Visible property The Visible property determines whether the menu item is displayed in the menu To dim a menu item without hiding it use the Enabled property For specific code examples that use the menu item s Visible and Enabled properties see Chapter 10 and online H
401. isplays the Project Options dialog box Synchronizes the Project Manager window display with listings in the project unit source code DPR file Comment Non shared files reside in the project directory Shared files still reside outside the project directory they are not copied to the current project directory Any changes to the shared file in any project are reflected in all projects using the file Only the relationship of the selected file s with the current project is removed The file still exists in its current location The DPR file is updated to reflect the change Using the Delphi menu command opens the View Unit dialog box where you can select which unit to view Using the Delphi menu command opens the View Form dialog box where you can select which form to view This button normally remains disabled and its parallel SpeedMenu command dimmed unless you have manually modified the project DPR file which is not recommended The DPR file location can be a useful reference if you are bringing many forms and units that reside in locations other than the main project directory into the current project It can help you track what you are doing as you either add shared files as part of the project or save copies of shared files in the current project directory The form and unit summary information can also be helpful in evaluating the scope of proposed project modifications Chapter 4 Managing pr
402. ist to appear The following procedure describes this process m To include an open document list in a menu 1 Select the frame form and then select the Properties page of the Object Inspector 2 From the drop down list next to the WindowMenu property select the name of the menu item under which you want the open document list to appear for example a Window or View menu Note This name must represent an item that appears on the menu bar not a submenu item because document lists cannot be used in nested menus gt For the text editor application assign Window1 to FrameForm s WindowMenu property Providing an area for text manipulation Once you ve created a child form for text editors and a frame form to contain the child forms and provide a means of navigating them you need to provide an area where the user can manipulate text You do this by adding a Memo component to the child form Adding the Memo component The Memo component can be used in an application to read and display multiple lines of text whether that text is loaded in from an existing file pasted from the Clipboard or entered by the user You can set properties of the Memo component to enable word wrapping provide scroll bars and control the border style and alignment of the memo within the form Add a Memo component to EditForm and set its properties as noted in Table 10 7 Table 10 7 Memo component settings Property Value Align alClient Border
403. isting menus You can create a nested menu by inserting a menu item from the menu bar or a menu template between menu items in a list When you move a menu into an existing menu structure all its associated items move with it creating a fully intact nested menu This pertains to nested menus as well moving a menu item into an existing nested menu just creates one more level of nesting Chapter 3 Building forms and menus 103 Moving menu items During design time you can move menu items simply by dragging and dropping You can move menu items along the menu bar or to a different place in the menu list or into a different menu entirely The only exception to this is hierarchical you cannot demote a menu item from the menu bar into its own menu nor can you move a menu item into its own nested menu However you can move any item into a different menu no matter what its original position is While you are dragging the cursor changes shape to indicate whether you can release the menu item at the new location When you move a menu item any items beneath it move as well E To move a menu item along the menu bar 1 Drag the menu item along the menu bar until the arrow tip of the drag cursor points to the new location 2 Release the mouse button to drop the menu item at the new location E To move a menu item into a menu list 1 Drag the menu item along the menu bar until the arrow tip of the drag cursor points to the new menu
404. it still opens in the OLE 1 0 style not in place Design time and run time object creation This chapter discusses creating OLE objects at design time Chapter 15 discusses creating objects at run time The following table discusses the differences between creating OLE objects at design time and at run time Design time OLE object creation The object is stored in the executable file increasing the size of the compiled application The developer needs access to the OLE server application at design time The OLE object is already created at run time reducing application execution time The OLE object can be edited at design time or run time The application can contain only as many OLE objects as the number of OLEContainer components added at design time Run time OLE object creation The object is stored in a file or exists only at run time reducing the size of the compiled application The developer does not need access to the OLE server application at design time The OLE object must be created at run time increasing application execution time The OLE object can be edited only at run time The application can create new OLEContainer components at run time to contain more OLE objects than were created at design time At design time an object can t be activated in place The OLE server activates in its own window not in place even if the object supports in place activation At run time however objects that
405. ity of the grid that is how far apart the grid dots appear E Toset form grid options choose Options Environment to display the Preferences page of the Environment Options dialog box The next step in creating the About box involves setting properties for the components you ve just arranged Locking the position of components Once you have aligned the components on a form you can prevent components from being moved accidentally m To lock the position of the components on a form choose Edit Lock Controls from the Delphi menu bar Controlling the creation order of nonvisual components When you run your Delphi application Delphi automatically creates or loads into memory all the application forms When a form is created in memory all the components encapsulated in the form are created as well As you will see in Chapter 3 52 Delphi User s Guide you can control the order in which forms are created at run time and whether they are created automatically Similarly you can control the creation order for nonvisual components The MainMenu PopupMenu Database Table and Query are a few examples of nonvisual components For more information about controlling component creation order search online Help for Creation order Setting component properties This section discusses different ways you can set component properties at design time Note in the context of creating the About box Table 2 9 lists the prope
406. ivate added for Button Private declarations public Public declarations end var Formi TForm1 implementation 1 Modified insert f om If you delete Button1 from Form1 Delphi deletes the button s instance variable but not any associated methods For more information see Chapter 2 Note No code is generated when you change a component s design time properties because those values are stored in the DFM file The only exception to this is the Name property as discussed previously When you use the Object Inspector to change a component s Name property Delphi changes its variable declaration for you to reflect the new name in the underlying code This is discussed in more detail in Chapter 5 Source code for units without forms Although most Delphi units are associated with forms you may want to create or use units that have no forms associated with them For example you might create a separately compilable unit of nonvisual objects or import a library of certain mathematical functions This is the only code that Delphi generates when you add a new unit to a project without adding a form Chapter 1 Introducing Delphi 27 unit Unit2 interface implementation end Because there is no need to synchronize the code in these files with an associated form Delphi does not maintain the code for you When you write your own units or import existing units you need to write the uses clause that sp
407. ject declaration and would lie with the scope of Form2 You would write the statement to change the color of the edit box inForm2 from the TForm1 ButtonClick method like this Form2 Editl Color clLime In the same way you can also access methods of a component on another form For example Form2 Editl Clear To give the code of Form1 access to properties methods and events of Form2 you need to add Unit2 to the uses clause of Unit1 assuming the units associated with Form1 and Form2 are named Unit1 and Unit2 respectively For more information about the uses clause see the section Understanding Object Pascal units starting on page 206 in Chapter 5 Scope and descendants of an object The scope of an object extends to all the object s descendants That means all the data fields properties methods and events that are part of TForm are within the scope of TForm1 also because TForm1 is a descendant of TForm Your application won t be able to declare a data field using the same name as a data field in the object s ancestor If Delphi displays a duplicate identifier message it s possible a data field with the same name already exists in the ancestor object such as in TForm If you see the duplicate identifier message and you don t understand why try altering the name of the identifier slightly It might be that you happened to choose the name of a data field in an ancestor object Overriding a method You can how
408. jects are stored in files You can t create a new OLE link unless the OLE object has previously been saved to a file from within the OLE server application The data in an linked OLE object file can be modified by your OLE container application and by other applications The OLE server application and other OLE container applications can all access and modify the OLE object Data can exist in one location but be accessible from multiple applications You can program your OLE container application in Delphi to continually obtain the latest data from the OLE object file When the OLE object data is modified even by other applications the changes will appear in all OLE container applications that contain a link to the file including your own Embedded objects Embedded objects are stored in your OLE container application Other OLE container applications can t access the OLE object The only time the embedded OLE object can be edited is when the user activates the object from your OLE container application Only then can the OLE server edit the OLE object data Embedded OLE objects don t need to exist in files All the data can be stored in your container application This ensures that the OLE data cannot be accidentally deleted modified or corrupted by being stored in an external file The drawback is that the size of your OLE container application increases by the size of the included OLE data If you want to make the changes you ma
409. k with a DDE client Loading a picture fromafile 352 application gcc hat wed oe aah 389 Saving a picture toa ME 4 Ale e ae eee 353 MSO aye ent he ea ied ek ee 390 Replacing the picture 393 What BOLE ios vind mayne ewe ewe 390 vii OLE 1 0 and OLE2 0 391 Design time and run time object creation 391 Linking and embedding 392 Linkedobjects resanse Bate Se Ed 392 Embedded objects o oo 392 OLE classes a rira ea ah SE Gola Bp wo 393 OLE doc metS y roei 6d ease a a a ea EE 393 OCE TEMS a aa da duka Ga Ae eS 393 Creating OLE container applications 393 OLE data in files 6 5 5 0045 395 Comparing DDE and OLE 396 SUNAY te ai of ai EA R EA 397 Chapter 15 OLE example 399 Creating the MDI framework 400 Creating the frame and child forms 400 Adding the OLE container component 401 OLE applicationmenus 402 Creating the frame formmenu 403 Creating the child form menu 405 The OLE object menu item a na 407 OLE tool bars and status bars 408 Setting up tool bars and status bars 408 viii Adding the toolbar 408 Adding the status bar 409 Inserting objects gt s ss ecou ea seeen 410 Using the Insert Object dialog box 410 Initializing the OLE container 412 Deactivating objects aoaaa aaa 413 Pasting objects 64 aaua 415 Using the
410. ke to the embedded OLE object appear the next time you run your application save the OLE data to a file See OLE data in files on page 395 for more information 392 Delphi User s Guide Note Note Note Note OLE classes The class of an OLE object determines the OLE server application that created the OLE object Sometimes you can link or embed more than one type of object from an OLE server application For example you could link or embed an entire spreadsheet a range of cells or a graph from a spreadsheet application The OLE class also determines which type of data the OLE object contains For example if the OLE object is a Quattro Pro notebook the class would be Quattro Pro Notebook The OLE class must be specified for both linked and embedded objects OLE documents The document of an OLE object determines the source file that contains the data for the OLE object The object document must be used for a linked object because linked objects exist in files The object document is used for an embedded object only if you create the object from an existing source file If you create a new embedded object that doesn t yet exist in a file you would not specify an OLE document For example if the OLE object is linked to the Quattro Pro notebook TUTOR WB2 stored in the D OFFICE QPW directory the OLE document would be D OFFICE OQPW TUTOR WB2 The OLE document must be specified only for linked objects For embedd
411. kpoint dialog box to confirm a new breakpoint setting or choose Modify to implement changes to an existing breakpoint e Choose Add Breakpoint from the Breakpoint List SpeedMenu Alternately if you know the line of code where you want the breakpoint set choose Run Add Breakpoint and type the source code line number in the Line Number box When the settings in the Edit Breakpoint dialog box are correct choose New to complete the breakpoint entry 254 Delphi User s Guide Note When you set a breakpoint the line on which the breakpoint is set becomes highlighted and a stop sign glyph appears in the left margin of the breakpoint line Invalid breakpoints If a breakpoint is not placed on an executable line of code the debugger considers it invalid For example a breakpoint set on a comment a blank line or declaration is invalid If you set an invalid breakpoint the debugger displays the Invalid Breakpoint error box when you attempt to run the program To correct this situation close the error box and delete the invalid breakpoint from the Breakpoint List window You can then reset the breakpoint in the intended location However you can also ignore invalid breakpoints the IDE disables any invalid breakpoints when you run your program During the linking phase of compilation lines of code that do not get called in your program are marked as dead code by the linker In turn the integrated debugger marks any breakpoints set on
412. l functions specific to the child window and its contents These menu items merge with the frame form s menu items to present one application menu with options appropriate to the current condition of the application While most MDI applications merge frame and child menus you can also choose to replace menus rather than merging them You ll use the Delphi Menu Designer to create the text editor application menus If you do not know how to use the Menu Designer see Chapter 3 Creating the frame form menu The menu items in the text editor frame form provide users with various ways to manipulate child windows in the running application Create the File and Window menus for the text editor frame form as shown in Table 10 3 For each menu item specify a value for the Caption property and accept the values Delphi then creates for the Name property Table 10 3 Frame form menu items amp File amp Window amp New amp Tile amp Open amp Cascade lt hyphen gt amp Arrange Icons E amp xit Note that specifying a hyphen for the caption below the Open1 menu item on the file menu creates a separator bar In later sections you ll set additional properties for the frame form menu Creating the child form menu The menu items in the text editor child form provide users with ways to manipulate text in the running application At run time the File menu in EditForm completely replaces the File menu in FrameForm Instead of creatin
413. l that Delphi automatically adds the Stdctrls unit to the uses clause of any unit whose form contains a component declared within Stdctrls SelText a run time only property contains a string based on any text selected in the component The SelectAll method selects all the text in the memo or other component The SelLength and SelStart methods return values for a selected string s length and starting position respectively The text editor application uses SelLength to determine whether the Memo component contains any selected text and then sets the condition of the Edit menu items accordingly This is discussed in the section Dimming menu items on page 292 SelStart is discussed in the section Loading the file on page 300 Write the following handler for the Edit Select All OnClick event procedure TEditForm SelectAll Sender TObject begin Memol SelectAll end Cutting copying and pasting text In Delphi the CopyToClipboard method copies all selected text in a memo or edit component to the Clipboard the CutToClipboard method cuts selected text from the memo or edit component and also places it on the Clipboard and the PasteFromClipboard method copies all text currently on the Clipboard back to the location of the insertion point In the text editor application these methods are called with OnClick event handlers for the Edit menu commands Write the following OnClick event handlers for the Edit Cut Edit Cop
414. l lists Arrays can have many dimensions Two dimensional arrays can be used to hold all the values in a table for example This is how you would create a two dimensional array that can hold all the values in a table that contains 20 columns and 20 rows type TTable array 1 20 1 20 of Double Then you can declare a variable of the TTable type var BigTable TTable To initialize all the values in the table to 0 0 you could use nested for loops var Col Row Integer for Col 1 to 20 do for Row 1 to 20 do BigTable Col Row 0 0 String types Arrays of characters Strings such as the text you enter for the caption on a control are actually one dimensional arrays of characters an array of type Char When you declare a variable of type string you specify the size of the string much as you specify the size of an array when you declare an array type These are some string type declarations type MyString string 15 BigString string LittleString string 1 These declarations declare the MyString type to contain 15 characters and the LittleString type to contain 1 character If no size is specified the string contains 255 characters the maximum size as is the case with the BigString type You can then declare variables of these character arrays just as you would with any other data type var MyName MyString Letter Digit LittleString You can assign a value to a string variable or prope
415. l raised The block that contains the protected block can then respond to the exception Handling RTL exceptions When you write code that calls routines in the run time library RTL such as mathematical functions or file handling procedures the RTL reports errors back to your application in the form of exceptions By default RTL exceptions generate a message that the application displays to the user You can define your own exception handlers to handle RTL exceptions in other ways There are also silent exceptions that do not by default display a message The explanation of silent exceptions begins on page 243 To handle RTL exceptions effectively you need to understand the following What are the RTL exceptions Creating an exception handler Providing default exception handlers Handling classes of exceptions Reraising the exception What are the RTL exceptions The run time library s exceptions are defined in the SysUtils unit and they all descend from a generic exception object type called Exception Exception provides the string for the message that RTL exceptions display by default There are seven kinds of exceptions raised by the RTL Input output exceptions Heap exceptions Integer math exceptions Floating point math exceptions Typecast exceptions Conversion exceptions Hardware exceptions 236 Delphi User s Guide Input output exceptions Input output I O exceptions can sometimes occur when the RTL tries t
416. lBottom alLeft or alRight to the Align property of a Panel component which is not locked 408 Delphi User s Guide Note Note Add a Panel component from the Standard page of the Component palette to OLEFrameForm and use the Object Inspector to set the following properties of the panel component Property Value Name ToolBarPanel Align alTop Caption lt Blank gt Locked False default The OLE server will replace ToolBarPanel when an OLE object is activated in place because the control is not locked Adding the status bar You create a status bar for OLE in place activation the same way you create a status bar for anon OLE application If you are unfamiliar with creating status bars see Chapter 12 for information about this process Add another Panel component to the OLEFrameForm and use the Object Inspector to set the following properties of the panel component Property Value Name StatusBarPanel Align alBottom Caption lt Empty string gt Locked True The OLE server cannot replace StatusBarPanel when an OLE object is activated in place because the control is locked When an OLE object is active and the OLE server has a message to display in the status bar an OnStatusLineEvent event of the OLE container component occurs A text string is passed from the OLE server to this event handler The Msg parameter of the OnStatusLineEvent event handler contains the text from the OLE server To display status bar messages
417. lClick Sender TObject begin Forml Color clGreen The reference to Forml didn t change end end Notice that the name of the form object type changed from TForm1 to TColorBox Also note that the form variable is now ColorBox the name you gave to the form References to the ColorBox variable and the TColorBox type also appear in the final begin and end block of code the code that creates the form object and starts the application running If Delphi originally generated the code it updates it automatically when you use the Object Inspector to change the name of the form or any other component Note that the code you wrote in the OnClick event handler for the button hasn t changed Because you wrote the code you have to update it yourself and correct any references to the form if you change the form s name If you don t your code won t be compiled In this case change the code to this procedure TColorBox ButtoniClick Sender TObject begin ColorBox Color clGreen end You should change the name of a component only with the Object Inspector While nothing prevents you from altering the code Delphi produced and changing the name of component variables you won t be able to compile your program Inheriting data and code from an object The TForm1 object described on page 217 might seem quite simple If you create the application TForm1 appears to contain one field Button1 one method Button1Click and Chapte
418. language You can read about creating user defined types in the section Defining new data types on page 195 but here you can see what a type declaration part can look like A type declaration part begins with the reserved word type These are some type declarations Chapter 5 Writing Object Pascal code 185 type TCount Integer TPrimaryColor Red Yellow Blue TTestIndex 1 100 TTestValue 99 99 TTestList array TTestIndex of TTestValue TCharVal Ord A Ord Z TDays Monday Tuesday Wednesday Thursday Friday Saturday Sunday An equal sign follows the type identifier The rest of the declaration defines the values that make up the new type A variable of type TNumber must be an Integer value A variable of type TPrimaryColor can be only red yellow or blue A variable of type TCharVal must fall within the range of values returned by the Ord function on the capital letters A through Z and so on Note that each type has a name that begins with the letter T This isn t necessary but it s the convention the Delphi documentation uses and you ll find it helpful in distinguishing type names from other identifiers if you use it too Just like variable and constant declarations type declarations can be global or local in scope depending on where you place the declaration For example if you declare the type Days within a procedure the TDays type exists only when that procedure runs a
419. le It stores a binary format copy of the DFM file as it existed before the most recent save DSK Desktop settings This file stores information about the desktop settings you have specified for the project in the Environment options dialog box Compiler generated project files Some project files are created on disk at compile time These include the application executable file that you can deploy and distribute when the project is complete and the object code for the project unit files each separately compiled to minimize time required for compilation Table 4 2 summarizes the project files created and or written at compile time Table 4 2 Compiler generated project files File extension Definition Purpose EXE Compiled This is the distributable executable file for your application This executable file file incorporates all necessary DCU files when your application is compiled There is no need to distribute DCU files with your application DCU Unit object code Compilation creates a DCU file corresponding to each PAS file in the project DLL Compiled For information on creating DLLs see the Delphi Component Dynamic link Writer s Guide library Non Delphi resource files Some files that you use in a Delphi project might be files created with applications other than Delphi and need not reside in the project directory When you correctly specify such files in a project Delphi integrates them when you save or compile the proj
420. le function 373 RenameFile method 302 renaming components 44 49 218 219 renaming files 353 373 375 repainting backgrounds 317 repeat reserved word 168 repeat statements 168 169 174 for statement vs 170 while statements vs 169 Replace common dialog box 41 ReplaceDialog component 41 replacing existing libraries 73 Report component 40 ReportSmith 40 RequestData method 384 386 reraising exceptions 242 RES files 116 reserved words 154 at 245 begin 165 167 175 448 Delphi User s Guide case 166 const 157 194 downto 172 else 164 167 241 end 165 167 175 210 232 except 239 241 finally 235 for 170 forward 189 function 161 185 if 163 164 implementation 187 207 208 209 initialization 208 210 interface 187 206 207 private 224 225 procedure 158 185 public 224 225 raise 244 repeat 168 restrictions 154 string 200 try 232 235 239 type 120 185 335 unit 206 until 168 uses 76 77 207 208 209 var 120 155 193 while 169 with 205 resizable borders 87 resizing components 45 46 58 graphics 58 353 owner draw controls 367 resizing forms 44 resource files 112 117 loading 112 resources 116 129 234 system See system resources responding to exceptions 231 232 responding to multiple events 64 restoring deleted components 50 Result variable 187 Retry buttons 89 return values See functions reusing event handlers 64 65 reusing forms 38 76 reusing menus 105 110 Rewrite procedure 308 robust appli
421. le in the Component palette summary This chapter has presented the following topics in the context of developing a reusable About box The Delphi components and the pages of the Component palette on which they can be found Adding and manipulating components in your forms Setting component properties both at design time and at run time Working with code to generate locate and modify event handlers Customizing the Delphi Visual Component Library by using the Component Expert by writing your own customized components or by adding Visual Basic VBX components Chapter 2 Using components and code 73 74 Delphi User s Guide Chapter Building forms and menus Forms are the foundation for all your Delphi applications The previous chapter Using components and code described how to build the simplest of forms a reusable About box This chapter discusses more about how forms work together to provide an integrated user interface An application usually contains multiple forms a main form which is the primary user interface and other forms such as dialog boxes secondary windows for instance those that display OLE 2 0 data and so on You develop your application by customizing the main form and adding and customizing forms for other parts of the interface You customize forms by adding components setting their properties and creating menus to provide user control over the application at run time You can beg
422. le name you want in the Unit column 140 Delphi User s Guide If the source code file for the selected unit is not open a Code Editor page opens to display it Otherwise the appropriate Code Editor page comes to the top m To view or edit a form in the Project Manager window select the form you want to view or edit and then choose from the following methods e On the SpeedBar choose the View Form button e Press Shift Enter e From the SpeedMenu choose the View Form command e Double click the form name in the Form column If the form is already open it comes to the front in design mode Otherwise the form opens and comes to the front Viewing the project source code DPR file As with unit source code files you can also open the project source code DPR file in the Code Editor The main reason to do this is so you can see the units and forms that make up the project and which form is specified as the application s main form As you add forms and units to the project you can see Delphi s updates of the project source code Caution Manually editing the DPR file is not recommended mM To view the DPR file use either of these methods e Choose View Project from the Project Manager SpeedMenu e From the Delphi menu bar choose View Project Source The contents of the DPR file appear in a page in the Code Editor To hide the DPR file again close the page in the Code Editor Note Closing a Code Editor page by
423. led by your program Below this is the listing for the previously called function The listing continues with the first function called in your program located at the bottom of the list Note that only functions in the currently loaded symbol table are listed in this window To view functions located in a different module change symbol tables as described later in this chapter The Call Stack window is particularly useful if you accidentally trace into code you wanted to step over Using the Call Stack window you can return to the point from which the current function was called then resume debugging from there E To use the Call Stack window 1 In the Call Stack window double click the function that called the function you accidently traced into it is the second function listed in the Call Stack window The Code Editor becomes active with the cursor positioned at the location of the function call Chapter 8 Using the integrated debugger 263 2 In the Code Editor move the cursor to the statement following the function call 3 Choose Run To Cursor on the Code Editor SpeedMenu or press F4 Navigating to function calls Using the Call Stack window you can view or edit the source code located at a particular function call E To view or edit the source code of a function call choose either View Source or Edit Source as appropriate from the Call Stack SpeedMenu The View Source and Edit Source commands each cause the Code Edit
424. lelClick Sender TObject var FileSelected Boolean begin FileSelected FileList ItemIndex gt 0 True if there is a file selected Openl Enabled FileSelected Deletel Enabled FileSelected Copyl Enabled FileSelected Movel Enabled FileSelected Renamel Enabled FileSelected Propertiesl Enabled FileSelected end Now whenever the user opens the File menu the application disables all the items except Exit unless there is a file selected in the file list box Deleting a file Deleting a file erases the file from the disk and removes the entry from the disk s directory There is no corresponding operation to restore a deleted file so applications should generally allow users to confirm deletions of files m To delete a file pass the name of the file to the DeleteFile function DeleteFile returns True if it deleted the file and False if it did not for example if the file did not exist or if it was read only The following code handles a click on a File Delete menu item by deleting the selected file in a file list box then updating the list so it reflects the deletion procedure TFMForm DeletelClick Sender TObject begin with FileList do if DeleteFile FileName then Update end The application now deletes the selected file in response to either File Delete or the Del key which is the shortcut for that menu item Confirming file deletions A safer way to appro
425. lication or the other application Once this link called aconversation is established the two applications can continuously and automatically send data back and forth A typical use for DDE is to exchange text data When the text changes in one application DDE automatically updates the text in the other For example in the Chapter 14 Exchanging data with DDE or OLE 381 following figure text changes in the Delphi application are automatically reflected in Word Figure 14 1 A DDE conversation between a Delphi application and Microsoft Word 6 0 El _DDE Server Application Pee ea ena ead Decumet e File Edit View Insert Format Tools Table Window Help jagoan Dizi BR eles Sls ls Sse irst Name Normal Times New Roman fio 2 3 2 Last Name Address City 141 Ln 2 Col 8 Linked text Note Not all applications support DDE To determine whether an application supports DDE refer to its documentation To understand DDE applications you need to become familiar with the concept of DDE conversations DDE conversations In order to have a DDE conversation there must be a DDE client application and a DDE server application The application that requests data is the client The application that provides the requested data and updates the DDE client is the DDE server With Delphi you can create both DDE clients and DDE servers In fact a single Delphi application can be both a DDE clie
426. line displays the value of Number in the second edit box Place this Calculate procedure above the event handler in your code but below the implementation reserved word procedure Calculate CalcNo Integer begin CalGNos Calel 10 end In the Calculate procedure the value in the CalcNo parameter changes By the end of the procedure the value of CalcNo is ten times greater than it was when Calculate began gt Run the application and enter a number in the Edit1 edit box The value you enter in the Edit1 edit box is the value of Number before Number is passed to the Calculate procedure The value that appears in the Edit2 edit box is the value of Number after the Calculate procedure runs The two values of Number are the same Because the CalcNo parameter is only a copy of the Number parameter Number remains unchanged while the value of CalcNo changes considerably The application never displays the value of CalcNo A couple of simple illustrations can demonstrate what is happening Number and CalcNo each have a separate address in your computer s memory The boxes in the following drawings represent memory locations When Calculate is called the value of Number is copied into the CalcNo memory location Figure 5 17 The value of Number and CalcNo when Calculate begins running Value of Number Value of CalcNo actual parameter formal parameter Because the Calculate procedure changes the value of the CalcNo parameter
427. line of pixels connecting two points A polyline is a string of straight lines connected end to end The canvas draws all lines using its pen Drawing straight lines E To draw a straight line on a canvas use the LineTo method of the canvas LineTo draws a line from the current pen position to the point you specify and makes the endpoint of the line the current position The canvas draws the line using its pen For example the following method draws crossed diagonal lines across a form whenever the form is painted procedure TForml FormPaint Sender TObject begin with Canvas do begin MoveTo 0 LineTo ClientWidth ClientHeight MoveTo 0 ClientHeight LineTo ClientWidth 0 end end 0 An OnPaint event occurs whenever Windows determines that a form needs to be redrawn such as when another window covers it and then goes away again FormPaint is the default name Delphi generates for a handler for a form s OnPaint event Handle Delphi User s Guide OnPaint events when you want to paint a background on a form or when you want to regenerate an image The rest of the examples in this chapter also do their drawing inOnPaint event handlers As you construct the sample application in Chapter 12 you ll see how to draw ona canvas interactively Drawing polylines In addition to individual lines the canvas can also draw polylines which are groups of any number of connected line segments m To draw a poly
428. line of text In addition the debugger regards a single statement that s spread over several lines of text as a single line of code Running to the cursor location When beginning a debugging session you often run your program to a spot just before the suspected location of the problem At that point you want to ensure that all data values are as they should be If everything appears to be correct you can run your program to another location and again check to ensure things are functioning correctly m Torun toa specific program location 1 Inthe Code Editor position the cursor on the line of code where you want to begin or resume debugging 2 Run to the cursor location using one of the following methods e Choose Run To Cursor from the Code Editor SpeedMenu e Choose Run Run To Cursor e Press F4 default key mapping When you run to the cursor your program executes at full speed until the execution reaches the location marked by the text cursor in the Code Editor When the execution encounters the code marked by the cursor the debugger regains control and places the execution point on that line of code The execution point The execution point marks the next line of source code to be executed by the debugger Whenever you pause the program execution within the debugger for example whenever you run to the cursor or step to a program location the debugger highlights a line of code marking the location of the execution po
429. line on a canvas call the PolyLine method of the canvas The parameter passed to the PolyLine method is an array of points You can think of a polyline as performing a MoveTo on the first point and LineTo on each successive point The following method for example draws a rhombus in a form procedure TForml FormPaint Sender TObject begin with Canvas do PolyLine Point 0 0 Point 50 0 Point 75 50 Point 25 50 Point 0 0 end This example takes advantage of Delphi s ability to create an open array parameter on the fly You can pass any array of points but an easy way to construct an array quickly is to put its elements in brackets and pass the whole thing as a parameter For more information see online Help Drawing shapes Canvases have methods for drawing four kinds of shapes The canvas draws the outline of a shape with its pen then fills the interior with its brush There are three distinct kinds of shape drawing e Drawing rectangles and ellipses e Drawing rounded rectangles e Drawing polygons Drawing rectangles ellipses and rounded rectangles are quite similar but polygons are a little different Drawing rectangles and ellipses m To draw a rectangle or ellipse on a canvas you call the canvas s Rectangle or Ellipse method passing the coordinates of a bounding rectangle The Rectangle method draws the bounding rectangle Ellipse draws an ellipse that touches all sides of the rectangle The fo
430. lines to your forms see Chapter 12 Creating form menus Menus provide an easy way for your users to execute logically grouped commands The Delphi Menu Designer enables you to easily add a menu either predesigned or custom tailored to your form You simply add a menu component to the form open the Menu Designer and type menu items directly into the Menu Designer window You can add or delete menu items or drag and drop them to rearrange them during design time You don t even need to run your program to see the results your design is immediately visible in the form appearing just as it will during run time Your code can also change menus at run time to provide more information or options to the user This section explains how to use the Delphi Menu Designer to design menu bars and pop up local menus It discusses the following ways to work with menus at design time and run time Opening the Menu Designer Building menus Editing menu items without opening the Menu Designer Using the Menu Designer SpeedMenu Using menu templates Saving a menu as a template Note For specific code samples that demonstrate ways to manipulate menus at run time refer to the example application chapter Chapter 10 98 Delphi User s Guide Figure 3 11 Delphi menu terminology igitiam Edit Search View New Project Open Project Save Project Save Project As Close Project Menu items on the menu bar New Form
431. llowing method for example draws a rectangle filling a form s upper left quadrant then draws an ellipse in the same area Chapter 11 Drawing graphics at run time 317 procedure TForml FormPaint Sender TObject begin Canvas Rectangle 0 0 ClientWidth div 2 ClientHeight div 2 Canvas Ellipse 0 0 ClientWidth div 2 ClientHeight div 2 end Drawing rounded rectangles To draw a rounded rectangle on a canvas you call the canvas s RoundRect method The first four parameters passed to RoundRect are a bounding rectangle just as for Rectangle or Ellipse RoundRect also takes two more parameters that indicate how to draw the rounded corners The following method for example draws a rounded rectangle in a form s upper left quadrant rounding the corners as sections of a circle with a diameter of 10 pixels procedure TForml FormPaint Sender TObject begin Canvas RoundRect 0 0 ClientWidth div 2 ClientHeight div 2 10 10 end Drawing polygons E To draw a polygon with any number of sides on a canvas call the Polygon method of the canvas Polygon takes an array of points as its only parameter and connects the points with the pen then connects the last point to the first to close the polygon After drawing the lines Polygon uses the brush to fill the area inside the polygon To draw a right triangle in the lower left half of a form for example do the following procedure TForml FormPaint Sender TObject begi
432. location as shared files which might or might not be what you want If you don t understand how the new project is using its constituent files you can run into problems later see Project Manager Path column on page 132 for an example Caution Do not use file management tools other than those in Delphi to save a copy of a project to a new location Saving files You can save individual files in a project or non project files such as text files that you may have open in the Code Editor To save a file it must be open E To save an individual file 1 Bring the file to the topmost level of the Code Editor by selecting its tab 2 Choose File Save File If this is the first time you ve saved the file you re prompted to name it 3 If necessary name the file and choose OK Delphi saves the file E To save a file under a different name or location 1 Bring the file to the topmost level of the Code Editor by selecting its tab 2 Choose File Save File As The Save File As dialog box appears 3 Specify the new file name or location or both and choose OK Delphi saves a copy of the file under the name and location you specify Note This changes the name of the file and if it is already part of the project includes the file with the new name in the project The older unit name still exists as a file but isn t included in the project any longer File Save versus File Save As Using the File Save As command is in many r
433. locks on page 174 and Understanding scope on page 177 Precede all variable declarations with the reserved word var The declaration itself is made up of two parts the left side is the name of the new variable and the right side declares what the variable s type is The two parts are separated by a colon This example declares three variables Value Sum and Line var Value Integer sum Integer Line string Because Value and Sum are both of type Integer the variable declaration could look like this with a comma separating the two variables of the same type var Value Sum Integer Line string The following example assumes that there is an edit box named Edit1 and a button named AddButton on the form Three variables X Y and Sum are declared as type Integer When the user clicks the AddButton two variables X and Y are assigned Integer values and added together The result Sum appears in the edit box procedure TForml AddButtonClick Sender TObject var X Y Sum Integer begin R 00 i ee 0s Sum X Y Editl Text IntToStr Sum end This line assigns the value of an expression to a variable Sum X Y An expression is usually two identifiers related to one another through an operator To read about expressions see the Expressions topic in online Help Because the Text property of an edit box is of type string and the Sum variable is of type Integer this line is not permis
434. log box Recall from Chapter 14 that specifying the ObjItem property of an OLEContainer component at design time displays the Paste Special dialog box At run time the PasteSpecialDlg function displays the Paste Special dialog box Figure 15 7 shows this dialog box Figure 15 7 The Paste Special dialog box Paste Special Source Cancel O Paste O Paste Link L Display As Icon Result Result PasteSpecialDlg is an independent function not a method of the OLEContainer component To see the parameters used with PasteSpecialDlg examine its declaration function PasteSpecialDlg Form TForm const Fmts array of BOleFormat HelpContext THelpContext var Format Word var Handle THandle var PInitInfo Pointer Boolean The parameters of PasteSpecialDlg are as follows e Form is the form that owns the Paste Special dialog box You should pass the name of the form that contains the OLEContainer component in the Form parameter e Fmts is the array of object formats to register Each format is specified by an array element of type BOLEFormat For this example you will register two object formats FEmbedClipFmt for embedded OLE objects and FLinkClipFmt for linked OLE objects Chapter 15 OLE example 415 To understand more about object formats examine the declaration of the BOLEFormat record leFormat Record tid Word Clipboard format id tName array 0 31 of char for paste special listbox s if ole fm
435. lorIt Edit1 The corresponding AnEditBox parameter in the called procedure declaration is the formal parameter procedure ColorIt AnEditBox TEdit Value parameters With the exception of the code example in the previous section Forward declarations value parameters are the only type of parameters discussed in this chapter so far A formal value parameter is a copy of the actual value parameter In other words the compiler puts the actual parameter at one memory address and the formal parameter at another memory address Therefore the called procedure or function can change the value of the formal parameter yet the value of the actual parameter remains unchanged To see an example of this 1 Put two edit box controls and a button on a form 2 Using the Object Inspector delete the text specified as the value of the Text property for the two edit box controls Your form should look something like this Figure 5 16 A form for a value parameter example Form1 3 Create this OnClick event handler for the button procedure TForml ButtoniClick Sender TObject var Number Integer Chapter 5 Writing Object Pascal code 191 begin Number StrToInt Editl Text Calculate Number Edit2 Text IntToStr Number end The handler retrieves the number the user enters in the first edit box and assigns it to the Number variable This variable is passed to the Calculate procedure as Calculate is called The last
436. lso dynamically change whether a component is enabled at run time To disable a component at design time use the Object Inspector to set the component s Enabled property to False Chapter 3 Building forms and menus 91 m To disable a component at run time type the following code in an event handler for the component where lt componentn gt is the name of the component for example Button1 lt componentn gt Enabled False For example the following event handler specifies that when Button receives an OnClick event Button2 is disabled procedure TForml ButtoniClick Sender TObject begin Button2 Enabled False end Setting the focus in a dialog box Only one component per form can be active or have the focus in a running application at any given time The component having the focus by default corresponds to the ActiveControl property of the form which can be set at design time or used during run time to access the component that has focus To change focus at run time use the SetFocus method Setting focus at design time When you design a dialog box you usually want to specify which component should have focus when the dialog box first opens For example in a data entry form you might want to give focus to the edit or memo component where users will first be entering data That way the user can begin typing immediately without first having to tab to a certain component E To specify the active component at
437. lt projectname gt As dialog box 2 Select the directory where you want to copy the project file 3 If you want to save the project file under a different name enter the new name in the File Name edit box If a DPR file with the same name exists in the directory you specify you re prompted as to whether you want to overwrite the existing file 4 Choose OK to complete the task The open project is now the project you just saved Delphi saves the DPR file the project options OPT file and the project resource RES file under the name and or new location you specify Delphi also saves any modified Chapter 4 Managing projects files and directories 137 unit files in their current location so you won t be prompted to save these changes again when you close the project When you open either version of the project all changes saved with the Save As operation are reflected in both places If you check the constituent file list in the Project Manager you will see that all the files in the currently open version of the project reside in a directory other than the current project directory If you want separate copies of any of those files in the new project directory you need to save them individually to the new location using File Save File As See Creating a backup of an entire project on page 139 for more information If you leave the new project unchanged it continues to use the files in their present that is old
438. lustrate an if statemen a 6 9 whe ehh Petes el ole amp Ws 163 A form for a case statement example 166 A form for a repeat statement example 168 A form for a while statement example 169 A sample form to illustrate a for loop 171 A form with string grid displaying column and row coordinates 172 A form for a nested for loop example 173 Blocks within blocks 176 Blocks within a simple project 177 A form for multiplying two numbers tgeen Mae oe hy se elt ae Bes 178 A form forascopeexample 179 A form that uses a global variable 181 A form for a value parameter example 191 The value of Number and CalcNo when Calculate beginsrunning 192 The values of Number and CalcNo after CAlCOlale TUS Aa 4 ewe ty eS oak 193 The value of Number and CalcNo when Calculate beginsrunning 194 The value of Number and CalcNo after Calculate Tins utia ee oe a e aa 194 A form for an enumerated type example 196 A form for a subrange example 198 A form for a string handling example 5 24 10 2 10 3 10 4 10 5 10 7 10 8 10 9 12 1 12 2 12 4 12 5 A form fora set type example 203 A SiMPLE TON e poate bg oe yy at Bae ea dee 217 Inheriting from TForm 221 A simplified hierarchy diagram 221 Nested resource protections 233 Nested exception handlers 234 The Breakpoint
439. ly better to let Delphi create them for you O A G PO For the purposes of the text editor application create a new form and set the values of its FormStyle Caption and Name properties as indicated in Table 10 2 Then remove EditForm from the project s Auto Create forms list as described in the previous procedure Table 10 2 Child form property settings for the text editor example Property Setting Name EditForm Caption lt blank gt FormStyle fsMDIChild Creating the application menus The frame form menu bar serves as the main application menu If the child form contains a menu bar any menu items on it merge into the frame form s menu when a child window has focus at run time For example Figure 10 2 shows the text editor menu as it appears when the application first runs with no child windows open Figure 10 2 Text editor application menu with no child windows open Text Editor ja The File and Window menu items exist in the frame form because they control functions of the frame rather than functions specific to a particular child window When the user opens a child window by choosing File New or File Open the application menu changes to include two new menu options as shown in Figure 10 3 282 Delphi User s Guide Note Figure 10 3 Text editor application menu with child window open Text Editor i l The Edit and Character menu items exist in the child form because they contro
440. m and an OnClick event handler for the button that changes the color of the form when the user clicks the button You then have an application that s about as simple as it can be and still actually do something Here is the form for the application Figure 6 1 A simple form Form1 When the user clicks the button the form changes color to green This is the event handler code for the button OnClick event procedure TForml ButtoniClick Sender TObject begin Forml Color clGreen end Chapter 6 Programming with Delphi objects 217 If you create this application and then look at the code in the Code Editor this is what you see unit Uniti interface uses WinTypes WinProcs Classes Graphics Forms Controls Apps type TForml class TForm Buttonl TButton New data field procedure ButtonlClick Sender TObject New method declaration private Private declarations public Public declarations end var Forml TForml implementation SR DFM procedure TForml ButtoniClick Sender TObject The code of the new method begin Forml Color clGreen end end The new TForm1 object now has a Button field that s the button you added to the form TButton is an object type so Button is also an object Object types such as TForm1 can contain other objects such as Button1 as data fields Each time you put a new component on a form a new field with the component s nam
441. matic If you pass False dragging doesn t begin until the user actually moves the mouse a short distance Calling BeginDrag False allows the control to accept mouse clicks without beginning a drag operation You can also place conditions on whether to begin dragging such as checking which button the user pressed by testing the parameters of the mouse down event before calling BeginDrag The following code for example handles a mouse down event on a file list box by beginning dragging only if the left mouse button was pressed procedure TFMForm FileListBoxlMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin if Button mbLeft then drag only if left button pressed with Sender as TFileListBox do treat Sender as TFileListBox begin if ItemAtPos Point X Y True gt 0 then is there an item here BeginDrag False Loh On sara te end end Once you run the program you ll see that you can drag items from the file list box but that the cursor always indicates that you can t drop the item anywhere The cursor never changes from the slashed circle Before you can drop items you have to have controls that accept drops You ll add those in the next section Accepting dragged items When a user drags something over a control that control receives anOnDragOver event at which time it must indicate whether it can accept the item if the user drops it there Delphi changes the d
442. me and type of selected object ActiveContral AutoS croll Borderlcons biSystemMeny BorderStyle bsSizeable Caption Form1 ClientHeight Movable column separator drag horizontally to resize columns Client Width Color E Value column CtI3D l Cursor Nested property double click to view subproperties nin oe Font TFont e FormStyle fsNormal Properties Height page The Delphi Object Inspector enables you to easily customize the way a component appears and behaves in your application The properties and events of the component that is selected in the form are displayed in the Object Inspector You use the Properties page of the Object Inspector to customize components you ve placed on a form or the form itself and the Events page to generate and navigate among certain parts of program code called event handlers Event handlers are specialized procedures To keep the Object Inspector visible at all times right click it and choose Stay On Top from the SpeedMenu Object selector The Object selector the drop down list at the top of the Object Inspector displays the name and type of every component in the current form including the form itself You can use the Object selector to easily switch among components in the form or to switch back to the form Code Editor UNIT1 PAS unit Uniti interface Title bar displays uses WinTypes WinProcs Classes Graphics Form name of file being type viewed
443. memory with a call to the Free method If you are interested in creating your own Delphi components you can learn more about objects by reading the Delphi Component Writer s Guide 230 Delphi User s Guide Chapter Writing robust applications Delphi provides you with a mechanism to ensure that your applications arerobust meaning that they handle errors in a consistent manner that allows the application to recover from errors if possible and to shut down if need be without losing data or resources Error conditions in Delphi are indicated by exceptions An exception is an object that contains information about what error occurred and where it happened To use exceptions to create safe applications you need to understand the following tasks Protecting blocks of code Protecting resource allocations Handling RTL exceptions Handling component exceptions Silent exceptions Defining your own exceptions Protecting blocks of code To make your applications robust your code needs to recognize exceptions when they occur and respond to them If you don t specify a response the application will present a message box describing the error Your job then is to recognize places where errors might happen and define responses particularly in areas where errors could cause the loss of data or system resources When you create a response to an exception you do so on blocks of code When you have a series of statements that all req
444. ment the Cut Copy and Delete items on the Edit menu appear dimmed You specify whether a particular menu command is available to the user by setting the Boolean value for its Enabled property In contrast to the Visible property the Enabled property leaves the item visible a value of False simply dims the menu item As with most properties you can specify the Enabled property s initial value by using the Object Inspector The default value for this property is True In the text editor application the UpdateMenus method sets the Enabled property for the Cut Copy and Delete menu items based on whether any text is selected in the memo By contrast it sets the Enabled property for the Paste command based on whether any text exists on the Clipboard UpdateMenus uses a Boolean variable HasSelection to reflect the value of the memo s SelLength property If SelLength is not equal to zero in other words if the memo contains 292 Delphi User s Guide selected text HasSelection stores True otherwise it stores False The rest of the procedure assigns a value to the menu items Enabled property based on the value of HasSelection gt Open the Code Editor and write the following method in the MDIEdit unit This method will be called by another event handler which you will write shortly so you won t use the Object Inspector to generate it procedure TEditForm UpdateMenus var HasSelection Boolean declare a variable th
445. ments or loops Assigning a return value in a function Because a function returns a value you need to ensure that you assign that return value You can do this in either of two ways 186 Delphi User s Guide e Assign the value to be returned to the name of the function e Assign the value to be returned to the Result variable The following example shows you the first way the value to be returned is assigned to the name of the function function CalculateInterest Principal InterestRate Double Double begin CalculateInterest Principal InterestRate end The next example accomplishes the same thing but the value is assigned to a Result variable that all functions have function CalculateInterest Principal InterestRate Double Double begin Result Principal InterestRate end You don t have to declare the Result variable it is automatically available for you to use Using Result is a shortcut that makes your code just a little easier to understand No matter which method you choose the function call is still the same For example this function call is the same regardless of whether the CalculateInterest function internally assigns a value to CalculateInterest or Result InterestEarned CalculatelInterest 1000 0 08 Positioning a procedure or function in your code Procedures and functions are placed in the implementation part of a unit All identifiers declared in the implementation pa
446. might also contain one or more PAS files not associated with any form Contains all declarations and procedures including event handlers for the form DFM Graphical form file Binary file containing the design properties of a form contained in the project One DFM file is generated along with the corresponding PAS file for each form the project contains when the project is first saved OPT Project options file Text file containing the current settings for project options Generated with first save and updated on subsequent saves if changes were made to project options RES Compiler resource file Binary file containing the application icon and other outside resources used by the project DP Project backup file Generated on the second save of a project and updated on subsequent saves this file stores a copy of the DPR file as it existed before the most recent save PA Unit backup file This file stores a copy of a PAS file as it existed before the most recent save If a PAS file changes this parallel file is generated on the second project save or any save of the PAS unit file after a change has occurred It is updated on subsequent saves if the PAS file has changed 116 Delphi User s Guide Table 4 1 Design time project files continued File extension Definition Purpose DF Graphical form backup If you open a DFM file as text in the Code Editor and make changes this file is generated when you save the DFM fi
447. ml FormMouseMove Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin if Drawing then begin Canvas Pen Mode pmNotXor use XOR mode to draw erase Canvas MoveTo Origin X Origin Y move pen back to origin Canvas LineTo MovePt X MovePt Y erase the old line Canvas MoveTo Origin X Origin Y start at origin again Canvas LineTo X Y draw the new line end MovePt Point X Y record point for next move Canvas Pen Mode pmCopy end Now you get a nice rubber band effect when you draw the line By changing the pen s mode to pmNotXor you have it combine your line with the background pixels When you go to erase the line you re actually setting the pixels back to the way they were By changing the pen mode back to pmCopy its default value after drawing the lines you ensure that the pen is ready to do its final drawing when you release the mouse button 330 Delphi User s Guide Figure 12 8 Line after rubber banding Graphics example You ve come a long way with your line drawing and as you ll see shortly it will all pay off when you want to draw different shapes such as rectangles and ellipses Before you can draw those shapes however you need to add a way for the user to choose which shape to draw In the next section you ll define a tool bar that provides those choices then see how to respond to the tool bar s controls Adding a tool
448. ms are auto created at run time 1 Choose Options Project and select the Forms page of the dialog box The names of all forms in the project are displayed in the Auto Create Forms list 2 Inthe Auto Create Forms list select any form s that you donot want created in memory at run time and choose the gt button To move all form names from one list to the other choose the lt lt or the gt gt button The selected files move to the Available Forms list Forms displayed in this list do not auto create at run time 3 Choose the OK button to save the information and close the dialog box It s usually best to have Delphi create your application forms If you decide not to auto create a form you must specifically create the forms at run time by writing code If you try to reference a form that hasn t first been created for example by calling its Show method Delphi raises an exception For more information on creating forms at run time search online Help for TInstantiating Forms Controlling the form auto create order After the main form the forms you specify in the Auto Create Forms list are created at run time in the order they are displayed in the list You can change the order by changing a form name s position in the list For instance if you ve designed one form that contains dependencies to another form you can ensure the form is available by creating it first To change a form s creation order in the Aut
449. n Canvas Polygon Point 0 0 Point 0 ClientHeight Point ClientWidth ClientHeight end Drawing special parts In addition to all the lines and shapes described in this chapter a canvas also provides some more specialized graphics capabilities such as pie slices arcs and chords You can also flood fill regions and rectangles and copy images from other canvases To see details on all the graphics you can draw on a canvas see TCanvas component in online Help 318 Delphi User s Guide summary Delphi s canvas objects enable you to draw quickly and easily on a form at run time You can use the same techniques to create images in owner draw controls and other custom controls Normally you use the pen and brush properties of the canvas to create lines and shapes but you can also manipulate individual pixels Chapter 11 Drawing graphics at run time 319 320 Delphi User s Guide Chapter Graphics example This chapter presents all the steps to create a simple graphics application that draws lines and shapes on a window s canvas in response to mouse clicks and drags Each section in the chapter builds on the previous sections but the individual sections also explain discrete tasks To see the finished application open the project GRAPHEX DPR in the DEMOS GRAPHExX directory Figure 12 1 shows the completed application Figure 12 1 The finished graphics program GRAPHEX EXE Graphics Example File Edit NOOC m
450. n Use the event caption handler of this button to call your program Help file If the dialog box has a Help context Delphi does this automatically bkIgnore Creates a button A Ignore Caption amp Ignore Use to continue an to ignore Ignore ModalResult mrl operation after an error changes and aed sa i condition has occurred proceed with specified action bkNo Makes a Cancel Caption amp No Red circle with slash button with No No Cancel True appears next to caption aoe Capon ModalResult mrNo bkOK Creates an OK Caption OK Green check mark appears button Default True next to caption ModalResult mrOK bkRetry Creates a button Caption amp Retry Green circular arrow to retry specified ModalResult mrRetry appears next to the caption action bkYes Creates an OK Caption amp Yes Green check mark appears button with Yes Default True next to caption caption ModalResult mrYes Note that setting the Kind property also sets the ModalResult property discussed previously in every case except bkCustom bkHelp and bkClose In these cases ModalResult remains mrNone and choosing the button doesn t automatically close the dialog box Chapter 3 Building forms and menus 89 Setting the tab order Tab order is the order in which focus moves from component to component in a running application when the Tab key is pressed To enable the Tab key to shift focus to a comp
451. n function NoValue AnEditBox TEdit Boolean end procedure TForml MultiplyClick Sender TObject end procedure TForml DivideClick Sender TObject end end If the NoValue function is not declared in the interface part but in the implementation part instead only this unit and no other can use NoValue When Delphi creates an event handler the event handler procedure is declared in the object type declaration Because the object type declaration is in the interface part of the unit any other unit can call the event handler For more information about theinterface and implementation parts of a unit see the section Understanding Object Pascal units on page 206 You can also read more about object type declarations in Chapter 6 The NoValue function as it appears on page 184 is an example of a routine that is not declared separately from its implementation Because you want only the code within the event handlers to be able to use NoValue you would not declare it in the interface part but in the implementation part as the code in the event handlers is in the implementation part 188 Delphi User s Guide Note NoValue appears before the event handlers that use it If the NoValue function is declared and implemented after the event handlers the compiler reports the NoValue call in the handlers to be an unknown identifier Wherever you first declare a procedure or function you should place either the declaration or the proc
452. n Figure 12 2 Figure 12 2 Drawing text at the point clicked Graphics example Here Here Here Here Here Here Here HeHere The application wouldn t be able to draw a line yet because the user would only have pressed the mouse button Pressing the button only tells the application where the drawing will start and for a line you need both a starting point and an ending point For now you can change the mouse down event handler to set the current drawing position to the coordinates where the user presses the button procedure TForml FormMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin Canvas MoveTo X Y set pen position end Pressing the mouse button now sets the pen position setting the line s starting point You just need to draw a line to the point where the user releases the button To do that you ll need to respond to a mouse up event Responding to a mouse up action An OnMouseUp event occurs whenever the user releases a mouse button The event usually goes to the object the mouse cursor is over when the user presses the button which is not necessarily the same object the cursor is over when the button is released This enables you for example to draw a line as if it extended beyond the border of the form E To respond to mouse up actions you define a handler for the OnMouseUp event If you re not sure how to create an event handler see Chapter 2
453. n OLE Object window 2 Activate an OLE server application and copy an OLE object to the Clipboard 3 From the OLE example application choose Edit Paste Special to display the Paste Special dialog box 4 Choose an object to link or embed by pasting then choose OK The OLE container in the OLE Object window is initialized You can activate the OLE object by double clicking the OLE container component 5 Choose File Exit to close the application Dropping objects Note Dragging OLE objects from an OLE server application and dropping them on the OLE container application is an easy way to link or embed an OLE object into the OLE example application By dragging and dropping the user isn t required to use the Insert Object or Paste Special dialog box to specify an OLE object The user simply grabs the OLE object from the OLE server with the mouse drags it over the OLE example application and drops it by releasing the mouse button The material presented in this section assumes you are familiar with the general concepts of drag and drop covered in Chapter 13 The OLE example also uses drag and drop but this example focuses on the registration of OLE object formats If you are unfamiliar with drag and drop in general you should read Chapter 13 first This section describes the following steps involved in dragging and dropping OLE objects onto the OLE example application e Registering a form as an OLE drop target e Droppi
454. n alignment guide 52 Locking the position of components 52 Controlling the creation order of nonvisual COMPONEN ara e E E ete ese a 8 wade 52 Setting component properties 53 How the Object Inspector displays PIOPClUCS a so Cale hE St a eee Sw ee 54 Tab jumping to property names in the Object HASPECUON 2 5 dee Reese tale ee Werth Bek A 54 Displaying and setting shared properties 55 Scope of the Name property 55 Using property editors 56 Dialog box editors 00 0 56 Loading animage 56 SIZING an Image oa ha ee oe ee ee eS 58 Saving your project ar 2 waa yee 58 Setting properties atruntime 59 Using properties to customize forms at run UO e a 2k E e e EIR E oe ea E Se 59 Working with codes serere or URET ERY 60 Generating the default event handler 60 Displaying the form as a dialog box 60 Working with the Code Editor 62 Viewing pages in the Code Editor 62 Locating an existing event handler 63 Locating default event handlers 63 Modifying an existing event handler 63 Associating an event with an existing event PandleT a a 2 9 Wak tan wring ah arden Seo Bon 64 Using the Sender parameter 64 Displaying and coding shared events 65 Modifying a shared event handler 66 Deleting event handlers 67 Customizing the Delphi Visual Component Hiprary VOL exces eit A
455. n in CurrentPanel procedure TForml FormMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin Drawing True Canvas MoveTo X Y Origin POIt Yy MovePt Origin OriginPanel Caption Format Origin d d X Y update status bar end procedure TForml FormMouseMove Sender TObject Shift TShiftState X Y Integer begin if Drawing then begin DrawShape Origin MovePt pmNotXor MovePt Point X Y DrawShape Origin Point X Y pmNotXor end CurrentPanel Caption Format Current d d X Y update status bar end Drawing on a bitmap The times when you want to draw directly on a form are relatively rare More often an application should draw on a bitmap since bitmaps are very flexible for operations such as copying printing and saving Delphi s image control is a component that can contain a bitmap making it easy to put one or more bitmaps into a form In addition the bitmap need not be the same size as the form it can be either smaller or larger By adding a scroll box control to the form and placing the image inside it you can draw on bitmaps that are much larger than the form or even larger than the screen Adding a scrollable bitmap for drawing takes two steps e Adding a scrollable region e Adding an image control Once you move the application s drawing to the bitmap in the image control it is easy to add printing Clipbo
456. n place activation of OLE objects e Creating the frame and child forms e Adding the OLE container component e OLE application menus e OLE tool bars and status bars Creating the frame and child forms The first step in creating the OLE container application is to create an MDI frame form The frame form displays OLE Example in the title bar and will contain multiple MDI child windows Start by creating a new project Then use the Object Inspector to set the following properties of the project s main form Property Value Caption OLE Example 400 Delphi User s Guide Property Value FormStyle fsMDIForm Name OLEFrameForm Next you need to add an MDI child form The MDI child will be displayed within OLEFrameForm at run time Add a new form to the project and use the Object Inspector to set the following properties of the new form Property Value Caption OLE Object FormStyle fsMDIChild Name OLEObjectForm Since this application will create instances of OLEObjectForm dynamically at run time it should not create an instance of OLEObjectForm automatically Remove OLEObjectForm from the Auto create list for the project 1 Choose Options Project to display the Project Options dialog box 2 On the Forms page of the Project Options dialog box move OLEObjectForm from the Auto create forms list box to the Available forms list box 3 Choose OK Save the project now using the following names Default name Save
457. n the Component palette to simultaneously select it and place it in the center of the form The component appears in the center of the form Chapter 1 Introducing Delphi 15 Setting component properties Delphi makes it easy for you to set properties the attributes that define how components are displayed and how they function in the running application You use the Object Inspector to set a component s default initial properties when you design your application during design time and the code you enter in the Code Editor can change properties as the application runs during run time For example you probably want the caption that is the descriptive label for both the form and the button to display something more meaningful than Form1 and Button1 You specify the caption you d like by using the Object Inspector to change the value of the Caption property Figure 1 2 Object Inspector with Caption property selected Object Inspector j Fomt Trom ActiveControl Autos crall True Borderlcons _ biSystemMen BorderStyle bsSizeable Caption Form ClientHeight 269 Clientwidth 423 Property clIBtnFace Value column column True crDefault True Font i TFont EF FormStyle fsNormal Height 300 HelpContext O l A Properties pevenis Page tabs Caption property setting for Form 1 If you wanted the Caption property to change as the application runs you would type the appropriate co
458. nable a control to respond when items have been dragged from it attach an event handler to the OnEndDrag event of the control The most important parameter in an OnEndDrag event is called Target which indicates which control if any accepts the drop If Target is nil it means no control accepts the dragged item Otherwise Target is the control that accepts the item The OnEndDrag event also includes the x and y coordinates on the receiving control where the drop occurs 378 Delphi User s Guide gt In this example a file list box handles an end drag event by refreshing its file list assuming that dragging a file from the list changes the contents of the current directory procedure TFMForm FileListBoxlEndDrag Sender Target TObject X Y Integer begin if Target lt gt nil then FileList Update end summary The sample application in this chapter demonstrates a number of widely useful tasks including specific applications of some outline list box and tab set controls using image controls to store hidden bitmaps dragging and dropping within an application and manipulating files There are a number of other features you would probably want to add to the application for real use such as dragging and dropping to the drive tab set handling of multiple file selections and display of file information other than the size All of these are straightforward extensions to the existing application Chapter 13 File manager ex
459. nces setting 28 32 123 pressing mouse buttons 323 324 326 334 See also mouse events preventing data corruption and loss 231 Print common dialog box 41 305 306 307 PrintDialog component 41 Printer object 305 Printer Setup common dialog box 41 305 307 printers setting up 307 specifying 305 Printers unit 209 305 351 PrinterSetupDialog component 41 printing conventions documentation 3 printing graphics 351 printing text files 305 309 to files 307 PrintRange property 307 private standard directive 224 225 procedure reserved word 158 185 procedures 116 121 183 195 207 as standalone program 134 135 availability 187 calling 20 21 158 161 recursively 189 190 declaring 158 185 189 headers 185 208 short form 208 parameters 160 predefined 158 Program Reset command Run 253 programming See code object oriented programming programs See projects progress indicators 42 Project command Options 127 project directory 122 Project Experts 10 125 Project Experts page Gallery Options 125 project files 22 27 115 116 122 See also projects adding 131 backing up 139 backup 116 117 binary 116 saving as text 94 copying 138 debugging See debugging projects default names 136 displaying 12 23 25 editing 23 132 naming 59 118 137 non Delphi 117 opening 134 removing from project 131 135 caution 135 saving 136 138 139 sharing 134 135 144 storing 115 116 132 types 116 118 Project Manager 129 13
460. nctions that can be shared by several applications Delphi comes with a large number of predefined units you use to construct your Delphi applications The Delphi Visual Component Library is made up of several units that declare the objects components and controls you use to design the interface for your application Each time you add a check box to a form for example you are using the SidCtrls unit automatically because the TCheckBox component is declared in StdCtrls As you design the forms for your application you are automatically creating new units that are associated with the forms Units don t have to be associated with forms however You can use a predefined unit that contains only mathematical routines for example Or you can write your own unit of math functions All the declarations in a unit are related to one another For example the CDialogs unit contains all the declarations for using common dialog boxes in your applications The structure of a unit Regardless of whether a unit is associated with a form the basic structure of a unit is the same The parts of a unit are unit lt identifier gt interface uses lt list of units gt optional public delcarations implementation uses lt list of units gt optional private declarations implementation of procedures and functions initialization optional optional initialization code end The unit header starts with the reserved word
461. nd CurrentPanel to the client area Creating 3 D panels Panel components used for status bar information usually have a 3 D effect By default all panels have an outer bevel to give them a slightly raised appearance Interior text however usually looks better if you set it off by lowering making the panel look like a frame around the text m To create the lowered text effect you change two properties Bevellnner and BorderWidth e To create the engraved look for the panel set BevelInner to buLowered e To change the space between the inner and outer bevels change the BorderWidth property A BorderWidth of 2 gives a good appearance The combination of inner and outer bevels creates a frame around the text gt Set the Bevellnner and BorderWidth properties for both OriginPanel and CurrentPanel to bvLowered and 2 respectively 346 Delphi User s Guide Updating the status bar Once you have a status bar in a form you need to update the status bar information You can set the caption text of a panel at any time to reflect the status of the application m To update a status bar panel set the panel s Caption property to reflect the current status Add this caption changing code to any event handlers that affect the status a particular panel reflects Since the graphics program has two panels you can update the drawing s origin point in OriginPanel when the user presses the mouse button and track the current positio
462. nd ForegroundColor a property of the color grid are of type TColor You can find out the type of a property by looking up the property in online Help or by selecting the property in the Object Inspector and pressing F1 The type is listed at the end of a property declaration For example the Color property declaration declares Color to be of type TColor property Color TColor Note You can t assign new values to all properties Some properties are read only which means you can find out what the value of the property is but you can t change its value in your application Properties that are read only are noted as such in Delphi s online Help Declaring identifiers Identifiers are names you give to any part of a Delphi application including variables types procedures functions methods and so on All identifiers are italicized in the Delphi books except in the code examples Object Pascal requires that you declare identifiers before using them in your code If you haven t used a compiled language before you might wonder why it is necessary to declare identifiers before you use them As with all compiled languages the compiler must be given explicit information about the identifiers before the compiler can create executable code that uses them The compiler can then check your code to ensure that the values you assign to variables or properties are of the correct type If they aren t Delphi displays a syntax error me
463. nd it is therefore local in scope If you place a type declaration at the top of the implementation part all event handlers and other procedures and functions can use it Variable and constant declarations Declaring variable and constants within event handlers is discussed in the section Declaring variables on page 154 and in the section Declaring constants on page 157 Because event handlers are procedures you should already know how to create variable and constant declarations for procedures and functions Ordering the declaration parts Traditionally any type declarations appear in a procedure or function before variable declaration parts and any variable declarations appear before constant declarations This isn t required though and you can mix declaration parts any way you choose You can also have more than one declaration part of the same kind For example you can have two or more variable declaration parts The only rule you must remember is that declarations occur after the procedure or function header and before the statement or code part of the routine Writing the statement part The statement part of a procedure or function begins with the reserved wordbegin and ends with the reserved word end followed by a semicolon All the code within the begin and end block are the statements of a procedure or function As discussed earlier statements can be assignment statements procedure or function calls if or case state
464. ndler The handler is removed when you compile or save the project Customizing the Delphi Visual Component Library VCL You can customize the Delphi component library and therefore what s displayed on the Component palette by adding or deleting components to parallel the functionality you need while developing a particular application You use the Install Components dialog box to modify the contents of the Delphi library DCL file You can develop as many such customized library files as you choose by saving each library configuration with a different file name You can then choose to use a particular library file when building applications so that the Component palette provides you with exactly the components you prefer Note Customizing the Component palette by using the Palette page of the Options Environment dialog box does not affect the DCL library file When you use this dialog page to customize the palette Delphi does not rebuild the library file but merely changes the visual representation of the Component palette This topic is discussed in online Help see the Help topics Palette Options Environment or Customizing the Component Palette When modifying libraries keep the following points in mind e You can work ona project in Delphi only if the current component library contains all the components used in the project If you try to load a project that uses components not currently installed Delphi displays a message
465. ne Outlinel Lines ComboBoxl Items This example adds all the items from the combo box to the end of the outline Out linel AddStrings ComboBoxl Items iterating the strings in a list Many times you need to perform an operation on each string in a list such as searching for a particular substring or changing the case of each string E To iterate through each string in a list you use a for loop with an Integer type index The loop should run from zero up to one less than the number of strings in the list Count 1 Inside the loop you can access each string and perform the operation you want For example here s a loop that iterates the strings in a list box and converts each one to all uppercase characters in response to a button click procedure TForml ButtoniClick Sender TObject var Index Integer begin for Index 0 to ListBoxl Items Count 1 do ListBoxl Items Index UpperCase ListBoxl Items Index end Loading and saving string lists You can easily store any Delphi string list in a text file and load it back again or load it into a different list String list objects have methods to handle both operations Using these methods you can quickly create a simple text editor by loading a file into a memo component as shown in Chapter 10 But you can also use the same mechanism to save lists of items for list boxes or complete outlines E To load a string list from a file call the LoadFromFile method
466. necessary open the project you want added to the Gallery 2 Choose Options Gallery 3 On the Project Templates page choose Add to display the Save Project Template dialog box 4 Specify a DOS compatible file name without extension for the template file By default Delphi suggests the name of the project DPR file 5 In the Title edit box enter a project title The title for the template will appear in the Browse Gallery window 6 In the Description field enter text that describes the template This text will appear in the Gallery window s status panel 7 Choose Browse and select bitmap file to represent this template in the Gallery This can be any Windows compatible bitmap including those you create in Delphi s Image editor but the Gallery displays only the upper left portion of any bitmap too large to fully fit the available space 8 Choose OK to put your choices into effect and save the current project as a Project Template 126 Delphi User s Guide Note Note If you later make changes to a Project Template you will need to resave the projectas a template not merely as a project You can also save your own forms as Form Templates and add them to those already available in the Forms Gallery This is helpful in situations where you want to develop standard forms for an organization s software as in the earlier example To add a form to the Gallery as a Template follow the preceding steps for adding proje
467. need to respond to this change However it is possible that the click was on the directory already selected Instead of handling the OnClick event it is more useful to handle the OnChange event which indicates that something in the directory outline has changed E To respond to changes in an outline attach a handler to the outline sOnChange event gt The following code updates both a file list box and a status bar panel to reflect the current directory in a directory outline every time the directory outline changes procedure TFMForm DirectoryOutlineChange Sender TObject begin FileList Directory DirectoryOutline Directory DirectoryPanel Caption DirectoryOutline Directory end Any change in the directory outline whether caused by changing to a different drive and therefore replacing the entire directory list or changing to a different directory in the same outline now causes the status bar panel to reflect the current directory path and causes the file list box to display the contents of that directory Responding to list box changes When the user clicks an item in a list box or uses an arrow key to move to one that item becomes the selected item and the list box generates an OnChange event The application can handle the change and update any dependent controls m To respond to changes in a list box attach an event handler to the list box sOnChange event For example a file list box can have an associated pa
468. nel that displays information about the selected file or files The following event handler for a file list box s OnChange event updates a status bar panel with the name and size of the file currently selected in a file list box procedure TFMForm FileListChange Sender TObject var TheFileName string begin with FileList do begin 364 Delphi User s Guide if ItemIndex gt 0 then is there a selected item begin TheFileName Items ItemIndex get the file name FilePanel Caption Format s d bytes TheFileName GetFileSize TheFileName set caption to file name size end else FilePanel Caption blank panel if none selected end end GetFileSize is a function in the FMX Utils unit Changing the selected file in the list box now causes the status bar panel to display the name of the current file and its size If there is no selected file the panel is blank The next section of this chapter deals with turning the drive tab set into an owner draw control that shows bitmaps next to the drive letters The application works fully without the owner draw feature however so if you want to skip it for now you can jump right to the section Manipulating files on page 369 Creating an owner draw control Windows list box and combo box controls have a style available called owner draw which means that instead of using Windows standard method of drawing text for each item
469. ner place your cursor where you want the menu to appear The imported menu can be part of a menu you are designing or an entire menu in itself 2 From the Menu Designer SpeedMenu choose Insert From Resource The Insert Menu From Resource dialog box appears 3 In the dialog box select the resource file you want to load and choose OK The menu appears in the Menu Designer window If your resource file contains more than one menu you first need to save each menu as a separate resource file before importing it Managing run time behaviors of forms The main focus of this chapter up to this point has been on the design and construction aspects of forms There are two run time aspects of forms that you might find you want to specify at design time These are designating a form as the project main form and controlling the creation order of forms at run time Specifying a form as the project main form The first form you create and save in a project becomes by default the project s main form which is the first form created at run time For more information about form creation order see Controlling the form auto create order later in this chapter or see online Help As you add forms to your projects you might decide to designate a different form as your application s main form Also specifying a form as the main form is an easy way to test it at run time because unless you change the form creation order the main form is the
470. ner component within the form but not both If you individually select components that have different parents and then attempt to cut or copy them only the components in the parent of the component you first selected are cut or copied For example if you first select a button in the form then select a check box in a panel on the form and then attempt to cut or copy the two selected components only the button is cut or copied e When you paste one or more components they appear in whichever eligible receiving component has focus e When you cut copy or paste a component any associated event handler code is not duplicated but the copied component retains associations to the original event handlers To cut a component or components select the component s then choose Edit Cut To copy a component or components select the component s then choose Edit Copy To paste a component or components assuming you have first placed components on the Clipboard by cutting or copying Chapter 2 Using components and code 49 1 Select the form or other container component where you want the pasted components to appear 2 Choose Edit Paste gt Cut the two Label components remaining in the form and paste them into the panel Then cut the Image component and paste it into the top left corner of the panel Figure 2 6 Panel with Labels and Image components Labell Label2 Panell Label3 Label Deleting and restori
471. ng Clipboard formats e Specifying OLE formats Registering Clipboard formats OLE objects should be registered with Windows as Clipboard formats Before you can paste an OLE object into the OLEContainer component you need to register two new Clipboard formats for linked and embedded OLE objects with the Windows API function RegisterClipboardFormat These formats can then be used in the fmtld field of the BOLEFormat record E To register a Clipboard format for OLE objects call RegisterClipboardFormat Pass a description of the format as a parameter RegisterClipboardFormat returns a Word value that uniquely identifies the newly registered format Next you ll write code to register two new Clipboard formats for linked and embedded OLE objects using RegisterClipboardFormat gt RegisterClipboardFormat returns a Word value identifying the registered Clipboard format Declare FEmbedClipFmt and FLinkClipFmt in the private part of the OLEFrameForm type declaration before the declaration of the CreateChild method type TOLEFrameForm class TForm private FEmbedClipFmt Word Declare the embedded OLE object Clipboard format FLinkClipFmt Word Declare the linked OLE object Clipboard format function CreateChild TOLEObjectForm public Public declarations end gt For this example the OLE object Clipboard formats should be registered as soon as the user runs the application Therefore attach the following code to the OnCreate me
472. ng an OLE object onto the OLE example application Registering a form as an OLE drop target To accept dropped OLE objects a form should be registered with Windows as an OLE drop target Use the RegisterFormAsOLEDropTarget function to do this To see the parameters used with RegisterFormAsOLEDropTarget examine its declaration procedure RegisterFormAsOleDropTarget Form TForm const Fmts array of BOleFormat The parameters of RegisterFormAsOLEDropTarget are as follows e Form is the form to be registered as a possible drop target for OLE objects For this example you should pass OLEObjectForm in the Form parameter Chapter 15 OLE example 421 e Fmts is the array of object formats to register This is an array of type BOLEFormat identical in purpose to the Fmts array used with PasteSpecialDlg in the section Pasting objects Each type of data to be dropped must be registered by having a corresponding BOLEFormat element of the Fmts array For this example you will use the same Fmts array that has been declared in the OnCreate event of OLEFrameForm which registers two formats one for linked objects and one for embedded OLE objects However if you wanted to be able to drop types of data other than OLE objects such as text then Fmts would require an additional element for each other type of data For example if you also wanted to allow the dropping of text Fmts should have a third element with a fmtld field value of CF_TEXT anda c
473. ng common dialog boxes 295 Common dialog box options in the Object SPECE 4 3 4h he 4h Week Ba aay 296 Enabling the Help button from a common CMOS DOM 55 a Raat 8 BS Oe oes 296 Using the OpenDialog component 297 OpenDialog component properties 297 Specifying file filters annaua 297 The Filt r property ok waer ee 298 Opening an existing text file 298 Declaring a form level variable 299 vi Loading the fle ceter cor oa ew nni 300 Using the Save dialog box 301 SaveDialog component properties 301 Savine the textile easca g oa ai eee 301 Creating a backup file 302 Using the Font dialog box 303 Font dialog box component properties 303 Changing the font in the Memo component 304 Prntine the textile rece ania aeea 305 Using the printer object 305 CANVAS 24 Ae SR Ae eee ge ey 305 VOUS 264 ah tern go Pee e Re 305 Using the printer dialog box es 306 Print dialog box component properties 306 MinPage MaxPage 306 Options poPageNums 306 Options poPrintToFile 307 Options poSelection 307 PONRI E e a Yee ache Nan wre Bie oS 307 Using the Printer Setup dialog box COMPONE 4 4 4 4 6 Fc ues eed hile BAG A 307 Handling the File Print Setup OnClick CVCUL 2 be oe eee ste A ee 307 Directing your text file to the printer 307 Downloading the text
474. ng components Deleting components that have been added to a form is simple and if you change your mind after deleting a component you can easily restore that component E To delete a component select the component in the form and press Del or choose Edit Delete E To restore a component that s just been deleted choose Edit Undelete This restores the component just as it was including any customizations you might have made to it such as setting properties or writing code Caution You must choose Undelete before performing any other operation or the component are not restored Aligning components You can align components relative to each other or relative to the form Once you select the component s you want to align you can use the Alignment palette or the Alignment dialog box to set the alignment When aligning a group of components the first component you select is used as a guide to which the other components are aligned E To align components by using the Alignment palette 1 Select the component s 2 Choose View Alignment Palette The Alignment palette appears 50 Delphi User s Guide 3 Select an alignment icon from the palette Figure 2 7 Alignment palette Align horizontal Center horizontally Space equally centers in window horizontally Align left edges Align tops J a4 4 it Align bottoms awe Align vertical Center vertically Space equally centers in window vertically
475. ng items 377 378 dropping items 378 executing files 375 376 file types 297 getting current drive and directory 362 365 items See string lists owner draw controls 365 369 draw item events 369 measure item events 368 variant styles 365 ListBox component 38 lists 365 See also string lists literal values 153 Load Picture dialog box 57 LoadFromFile method 160 graphics 352 OLE objects 396 424 strings 272 276 LoadFromStream method OLE objects 426 loading files See opening files loading images 56 57 loading OLE objects 396 424 426 loading string lists 272 local exception handlers 242 local menus See pop up menus local symbols 249 local variables 177 180 locating event handlers 63 locating specific strings 270 271 276 locating substrings 201 Lock Controls command Edit 52 locking components 52 logic errors 248 Longint data type 156 lookup tables databases 40 273 loop statements 168 174 arrays and 199 debugging 258 losing data preventions 231 machine code 210 249 macros 387 main form 9 changing 112 dialog boxes as 60 85 93 file manager application 360 362 MDI applications 280 281 OLE example 400 401 403 specifying at run time 112 specifying default 125 main menu See menu bars menus MainMenu component 38 99 109 403 MaskEdit component 39 masking input characters 83 math exceptions 237 239 241 Maximize button 44 86 removing from forms 87 maximum numeric ranges 197 MaxPage property 306 MCI drive
476. ns The graphics example uses some of each kind of speed button There are four tasks related to speed buttons on tool bars e Adding a speed button to a tool bar e Assigning a speed button s glyph e Setting the initial condition of a speed button e Creating a group of speed buttons Adding a speed button to a tool bar E To adda speed button to a tool bar just place the speed button component on the panel that represents the tool bar The panel rather than the form owns the speed button so moving or hiding the panel also moves or hides the speed button For the graphics program add six speed buttons to the tool bar arranged as shown in Figure 12 9 and change the Name property of each to the indicated text Figure 12 9 The tool bar with 6 buttons LineButton TAA m RectangleButton EllipseButton BrushButton RoundRectButton PenButton The default height of the tool bar is 41 and the default height of speed buttons is 25 If you set the Top property of each button to 8 they ll be vertically centered The default grid setting snaps the speed button to that vertical position for you Assigning a speed button s glyph Each speed button needs a graphic image called a glyph to indicate to the user what the button does If you supply the speed button only one image the button manipulates that image to indicate whether the button is pressed unpressed selected or disabled You can also supply separate specific im
477. ns for data fields and methods you want to add to the code directly For example note the private and public parts in this new form object declaration that so far contains no fields or methods type TForml class TForm private Private declarations public Public declarations end Use the public part to e Declare data fields you want methods in objects in other units to access e Declare methods you want objects in other units to access Declarations in the private part are restricted in their access If you declare fields or methods to be private they are unknown and inaccessible outside the unit the object is defined in Use the private part to e Declare data fields you want only methods in the current unit to access e Declare methods you want only objects defined in the current unit to access To add data fields or methods to a public or private section put the fields or method declarations after the appropriate comment or erase the comments before you add the code Here is an example type TForml class TForm Editi TEdit Button1 TButton procedure Button1Click Sender TObject private Private declarations Number Integer function Calculate X Y Integer Integer public Public declarations procedure ChangeColor end 224 Delphi User s Guide Note Place the code that implements the Calculate and ChangeColor methods in the implementation part of the unit The Number data f
478. nt If you want to call DoThat whenever ConditionA is False regardless of the value of ConditionB write your code like this if ConditionA True then begin if ConditionB True then DoThis end else DoThat In this case using the begin and end reserved words forces the else part to be linked with the first if statement For more information about writing if statements see Delphi s online Help The case statement Your application can also use a case statement to branch to the appropriate lines of code The case statement is often preferable to a series of if statements when the variable or property being evaluated is an integer type with the exception of Longint a Char type an enumerated type or a subrange type You can read about enumerated and subrange types beginning on page 195 The logic of a case statement is usually easier to see than in complex nested if statements and the code runs more quickly To see the syntax of the case statement look up the case reserved word topic in Delphi s online Help This is the form used for the following case statement example Figure 5 5 A form for a case statement example Form1 166 Delphi User s Guide gt Tocreate this application Note 1 Place a button an edit box and a label on a form 2 Using the Object Inspector modify these properties e Delete the text from the edit box e Change the caption of the label to Enter a day of the week 3 Create
479. nt Library Figure 6 3 is a greatly simplified diagram of the hierarchy omitting some intermediary objects To see a more complete diagram refer to the Delphi Component Writer s Guide Figure 6 3 A simplified hierarchy diagram TObject TComponent TControl TListBox TCheckBox TButton Everything in this hierarchy is an object Components which inherit data and code from a TObject type are objects with additional properties methods and events that make them suitable for specialized purposes such as the ability to save their state to a file Controls which inherit data and code from a TComponent type which in turn inherits elements from TObject have additional specialized capabilities such as the ability to Chapter 6 Programming with Delphi objects 221 display something So controls are components and objects components are objects but not necessarily controls and objects are simply objects This chapter refers to all components and controls as objects Even though TCheckBox isn t an immediate descendant of TObject it still has all the attributes of any object because TCheckBox is ultimately derived from TObject in the VCL hierarchy TCheckBox is a very specialized kind of object that inherits all the functionality of TObject TComponent and TControl and defines some unique capabilities of its own Object scope An object s scope determines the availability and accessibility of the data fields propert
480. nt and a DDE server at the same time A DDE conversation is defined by its service topic and item Note Sometimes DDE clients are called destinations and DDE servers are called sources The terminology is interchangeable This section explains e DDE services e DDE topics e DDE items DDE services The service of a conversation is the name of the DDE server Typically this is the server application s main executable file without the EXE extension For example if you want your application to establish a conversation with Novell Quattro Pro 6 0 QPW EXE the conversation service is QPW Sometimes however the service differs from the main executable file name For example if you want your application to establish a conversation with Borland ReportSmith 2 0 RPTSMITH EXE the DDE service would be ReportSmith 382 Delphi User s Guide Note Note Note If the server is a Delphi application the service is the project name without the DPR or EXE extension For example to establish a conversation with PROJ1 DPR the service is PROJ1 The DDE service depends on the DDE server application Refer to the documentation of the DDE server for specific information about specifying the DDE service Sometimes DDE services are called application names The terminology is interchangeable DDE topics The topic of a DDE conversation is a unit of data identifiable to the server containing the linked information Typically the
481. nt handler You can also generate an event handler for most components simply by double clicking the component in the form This generates a handler for the default event of that component if one exists The default event is the one the component most commonly needs to handle at run time For example a button s default event is the OnClick event To generate a default event handler double click the component in the form Certain components such as the Timer or the Notebook don t need to handle user events For these components double clicking them in the form doesn t generate an event handler Double clicking certain other components such as the Image component or either of the menu components opens a dialog box where you perform design time property edits Displaying the form as a dialog box Unlike the main form of an application dialog boxes are temporary windows that generally remain invisible until the user opens them The main form of an application is 60 Delphi User s Guide generally the form that users first see when they run the application For more information about application forms see Chapter 3 So far you ve been designing the About box as the application s main form so you can run it without writing any code and have it appear immediately To view it as a dialog box as it would probably appear in a real world application you first need to specify another form as the application s main form
482. nterface GDI while maintaining a high degree of compatibility While working through the sample application in Chapter 12 you might find it convenient to refer back to this chapter for specific techniques Chapter 11 Drawing graphics at run time 313 Drawing versus painting When working with graphics you often encounter the terms drawing and painting It s important that you understand the difference between the two e Drawing is the creation of a single specific graphic element such as a line or a shape with code In your code you tell an object to draw a specific graphic in a specific place on its canvas by calling a drawing method of the canvas e Painting is the creation of the entire appearance of an object At certain times Windows determines that objects onscreen need to refresh their appearance so it generates OnPaint events OnPaint events happen when for example a window that was hidden is brought to the front The thing to remember is this painting usually involves drawing That is in response to OnPaint events an object generally draws some graphics An edit box for instance paints itself by drawing a rectangle and then drawing some text inside A shape control on the other hand paints itself by drawing a single graphic The examples in this chapter demonstrate how to draw various graphics but they do so in response to OnPaint events The sample application in Chapter 12 shows how to do the same kind of d
483. nts and code 39 Table 2 3 Icon Sl lf lt wo T Er mi min Table 2 4 Icon Visual 2 H H ai mi W W e ii va 40 Delphi User s Controls on the Data Access page Visual N Z Z hae Z Z Y Y Guide Component name Database Table Query StoredProc DataSource BatchMove Report Component name DBGrid DBNavigator DBText DBEdit DBMemo DBImage DBListBox DBComboBox DBCheckBox DBRadioGroup DBLookupList DBLookupCombo Use to Establish and maintain a connection between a Delphi application and a remote database server Link a database table with a Delphi application Construct then execute an SQL query to a local database or remote SOL server Provide a means to locally store SQL procedures applicable to a remote SQL database Provide a conduit for data between a Query or Table component and data aware components in your application Locally store a queried answer set from a remote database server locally modify add or delete records and write the updated batch back to the server Provide a means for your application to generate and print reports using Borland ReportSmith Components on the Data Controls page Use to Provide a grid in which your application can display data Provide a means for users to navigate or edit data records displayed by your application Provide a data aware version of the Label component Provide a data aware ver
484. ny speed button in a group automatically sets the same property value for all buttons in the group This enables the group to act as a normal group with only one button pressed at a time but also allows the case with no button pressed gt Both the pen and brush buttons in this example are single button groups that act as toggles Make sure each has its AllowAllUp property set to True then set the GroupIndex properties of PenButton and BrushButton to 2 and 3 respectively Responding to clicks When the user clicks a control such as a button on a tool bar the application generates an OnClick event You handle those OnClick events by writing OnClick event handlers for your forms In this section you ll see how to respond to one such click event and do something useful in response Responding to a button click Speed button components have only two events built into them OnClick and OnDbIClick m To respond to the user s click on a speed button you define a handler for the button s OnClick event If you re not sure how to generate an event handler see Chapter 2 By default Delphi generates an OnClick event handler named after the control clicked For example the default OnClick event handler for a speed button named LineButton would be procedure TForml LineButtonClick Sender TObject begin end You then fill in the action you want to occur when the user clicks that button In this example you ll write several kinds
485. o Create list select the form name and drag it to the position you want Chapter 3 Building forms and menus 113 Note The main form and auto create specifications on the Forms page of the Project Options dialog box are reflected in the Application CreateForm statements in the project DPR file summary This chapter has presented the following topics Sharing forms with other units both in the same project and in other projects Using the Browse Gallery to add Form Templates to your project Viewing forms and units Designing forms including setting design time and run time properties specifying the tab order and setting focus Adding and saving forms as ASCII MDI and SDI forms Creating form menus including how to use the Menu Designer to create and name menu items specifying accelerator keys and keyboard shortcuts creating nested menus and moving menu items Setting menu properties through the Object Inspector Using the Menu Designer SpeedMenu Using and saving menu templates Dynamically adding menu items Merging menu items Importing resource RC files Changing the project main form designation Controlling the auto create order of forms 114 Delphi User s Guide Chapter Managing projects files and directories The purpose of this chapter is to help you understand what a Delphi project comprises and how to manage the projects you create as you work with Delphi The topics covered in this chapter includ
486. o access files or I O devices Most I O exceptions are related to error codes returned by Windows or DOS when accessing a file The SysUtils unit defines a generic input output exception called EInOutError that contains an object field named ErrorCode that indicates what error occurred You can access that field in the exception object instance to determine how to handle the exception as shown in Using the exception instance on page 240 Heap exceptions Heap exceptions can sometimes occur when you try to allocate or access dynamic memory The SysUtils unit defines two heap exceptions called EOutOfMemory and EInvalidPointer Table 7 1 shows the specific heap exceptions each of which descends directly from Exception Table 7 1 Heap exceptions Exception Meaning EOutOfMemory There was not enough space on the heap to complete the requested operation EInvalidPointer The application tried to dispose of a pointer that points outside the heap Usually this means the pointer was already disposed of Integer math exceptions Integer math exceptions can occur when you perform operations on integer type expressions The SysUtils unit defines a generic integer math exception called EIntError The RTL never raises an ElntError but it provides a base from which all the specific integer math exceptions descend Table 7 2 shows the specific integer math exceptions each of which descends directly from EIntError Table 7 2 Integer math excep
487. o be decremented Customizing the breakpoint and execution point colors You can customize the colors used to indicate the execution point and the enabled disabled and invalid breakpoint lines m To set execution point and breakpoint colors 1 Choose Options Environment to access the Environment Options dialog box 2 Select the Editor Colors page tab 3 From the Element list select Execution Point Active Break Disabled Break or Invalid Break then set the background and foreground colors as you want Examining program data values Even though you can discover many interesting things about your program by running and stepping through it you usually need to examine the values of program variables to uncover bugs For example it s helpful to know the value of the index variable as you step though a for loop or the values of the parameters passed to a function call 258 Delphi User s Guide The integrated debugger has the following tools to help you examine the data values in your program e The Watch List window e The Evaluate Modify dialog box e The Call Stack window Data evaluation operates at the level of expressions An expression consists of constants variables and values contained in data structures combined with language operators In fact almost anything you can use as the right side of an assignment operator can be used as a debugging expression with the exception of function calls Watching expressions
488. o of type TObject Source is assigned the object that is being dragged The purpose of the Memo1DragOver method is to ensure that only labels can be dragged Accept is a Boolean parameter so it can have only one of two values True or False If Accept is True the control the user has selected to drag can be dragged If Accept is False the user can t drag the selected control Chapter 6 Programming with Delphi objects 227 This expression is assigned to the Accept variable Source is TLabel The is reserved word checks the Source variable to determine if Source is of type TLabel If it is the expression evaluates to True Because the expression becomes True only when the user tries to drag a label Accept becomes True only under the same circumstances The next event handler in the drag and drop demonstration Memo1DragDrop also uses the Source parameter The purpose of this method is to change the font of the text in the memo control to the font of the label dropped on the memo control Here is the method s implementation procedure TForml MemolDragDrop Sender Source TObject X Y Integer begin Memol Font Source as TLabel Font end When writing the assignment statement in this handler the developer didn t know which label the user would drag By referring to the name of the label as Gource as TLabel the font of the label the user dropped is assigned to Memo1 Font because Source contains the name of the control the use
489. o the event handlers for the corresponding menu items from the Edit menu Adding a pop up menu and associating a menu item s OnClick event with an existing handler are explained in Chapter 3 Handling the OnPopup event To complete the pop up menu you need to handle the menu component s On Popup event This event handler calls the UpdateMenus procedure as does the handler for the Edit menu title s OnClick event SetEditItems In both cases you need to call the event handler code when the user activates the menu With a pop up menu however there is no top level menu bar so to prepare the pop up menu commands you code the menu component itself First you need to add a few lines of code to UpdateMenus one for each menu item in the pop up menu You simply duplicate the code you wrote for the equivalent items on the main menu Cut Copy and Paste gt Locate the UpdateMenus procedure in the Code Editor and add the three lines of code as shown procedure TEditForm UpdateMenus var HasSelection Boolean begin Pastel Enabled Clipboard HasFormat CF_TEXT Paste2 Enabled Clipboard HasFormat CF_TEXT Add this line HasSelection Memol SelLength lt gt 0 Cutl Enabled HasSelection Cut2 Enabled HasSelection Add this line Copyl Enabled HasSelection Copy2 Enabled HasSelection Add this line Deletel Enabled HasSelection end Now you could simply associate the pop up
490. objects 391 400 string lists 273 275 current drive and directory displaying 363 366 resetting 376 updating 364 current operation stopping 243 current settings 116 117 cursors editing 14 position in file 300 custom templates 126 127 customer assistance 3 customizing components 10 11 Cut command Edit 49 cutting graphics 355 cutting text 291 292 See also deleting CutToClipboard method 291 D data accessing DDE applications 41 385 386 OLE applications 41 392 corrupted preventing 231 displaying 40 in columns and rows 172 editing 40 392 exchanging 381 formatting 39 initializing 208 210 loss preventing 231 relating varied elements 216 sharing 390 396 updating DDE applications 386 388 390 OLE applications 395 valid characters 39 Data Access page Component palette 40 Data Controls page Component palette 40 data grids 40 data types See types data aware components 40 Database component 40 database components 40 Database Form Expert 10 database links 40 Index 435 database servers 40 databases 40 querying 40 DataSource component 40 DBCheckBox component 40 DBComboBox component 40 DBEdit component 40 DBGrid component 40 DBlmage component 40 DBListBox component 40 DBLookupCombo component 40 DBLookupList component 40 DBMemo component 40 DBNavigator component 40 DBRadioGroup component 40 DBText component 40 DCL files 68 DCU files 117 121 210 DDE applications 381 390 accessing data 41 385 38
491. ocedure also declared in the Printers unit directs your text file to the printer currently selected in the Print Setup dialog box Using the printer object You call methods and set properties declared in the Printer object to control the way your application prints documents These methods and properties interact with the Print and Printer Setup common dialog boxes The code for the File Print OnClick event handler in the text editor application refers to only some of the printer object properties as noted here For information about the other methods refer to online Help Canvas Canvas represents the surface of the currently printing document You assign the contents of your text file to the Canvas property of the printer object The printer object then directs the contents of the Canvas property your text file to the printer Fonts Fonts represents the list of fonts supported by the current printer These fonts appear in the Font list of the Font dialog box As described previously any font selected from the Font dialog box is reflected back into the Font property for Memo1 However the printer object has no such relationship to the Font dialog box or to the Font property for Memo1 Unless your program specifies otherwise the printer uses the default System font that is returned by the Windows device driver to print your text file Chapter 10 Text editor example 305 To change the printer s font simply assign the Font pr
492. ocedure TEditForm FormCloseQuery Sender TObject var CanClose Boolean var DialogValue Integer declare an integer variable to store the user s response to the message dialog FName string declare a string variable to store the value of the file name when saving begin if Memol Modified then begin FName Caption save the value of the Caption property to the FName variable if Length FName 0 then FName Untitled 1f there is no filename use Untitled DialogValue MessageDlg Format SWarningText FName mtConfirmation mbYes mbNo mbCancel 0 produce the message dialog box case DialogValue of id_Yes SavelClick Self Self parameter saves the instance of EditForm open at the time the user chooses Yes in the dialog id_Cancel CanClose False 1f the user chooses Cancel exit the dialog and don t close the form end end end Note that there is no need to provide a response if the user chooses No from the message dialog box because the default value for CanClose is True which means that the dialog box will close without saving the user s changes Exiting the application The File Exit event handler calls the Close method of TForm as does the File Close event handler In an MDI application the Close method closes the window that has focus if the focused window is the application s main form then theCloseQuery method of that form first iterates through all open MDI child
493. ocument view Ct Ct It s probably more common to design an MDI form as such from the beginning but you can change forms you create into MDI or SDI forms simply by changing their FormStyle property 96 Delphi User s Guide The following table displays the possible FormStyle property settings and their purpose Table 3 5 FormStyle property settings FormStyle value Creates Comments fsNormal A standalone SDI form fsMDI Form An MDI parent or frame form This form can contain other forms at run time fsMDIChild An MDI child form This form is contained by the MDI parent at run time fsStayOnTop A standalone form that stays on top of other open forms at run time To demonstrate how MDI parent forms contain child forms try the following 1 2 3 4 Start a new blank project and add a new blank form Set the FormStyle property for Form1 to fsMDIForm and for Form2 to fsMDIChild Add a Panel component to Form1 and change its Alignment property to AlTop Add a SpeedButton component to the panel and generate the following OnClick event handler for it procedure TForml SpeedButtonlClick Sender TObject begin Form2 Show end 5 Add Unit2 to Unit1 s uses clause 6 Run the program and click SpeedButton1 Form2 opens inside Form1 Figure 3 10 Sample MDI child and parent forms Panell You can resize and move either form but the child form always stays within the borders of the paren
494. of responses to speed button clicks For the drawing tool buttons you ll select the appropriate drawing tool For the pen and brush buttons you ll display other tool bars Drawing with different tools Now it s time to put some of the skills explained earlier to good use Earlier sections have described adding fields to keep track of a state and how to respond to speed 334 Delphi User s Guide button clicks In this section you ll respond to clicks on speed buttons by setting the drawing tool for the form The next few sections demonstrate e Declaring an enumerated type e Changing the tool with speed buttons e Using the drawing tools Declaring an enumerated type The graphics program needs a way to keep track of what kind of drawing tool you want it to use at any given time You could assign numbers to each kind of tool but then you would have to remember what each number stands for You can do that more easily by assigning mnemonic constant names to each number but your code won t be able to distinguish which numbers are in the proper range and of the right type Fortunately Object Pascal provides a means to handle both of these shortcomings You can declare an enumerated type An enumerated type is really just a shorthand way of assigning sequential values to constants Since it s also a type declaration you can use Object Pascal s type checking to ensure that you assign only those specific values To declare an enume
495. of the Clipboard formats specified in the Fmts array are on the Clipboard If so the Paste Special dialog box is enabled and PasteSpecialEnabled returns True To paste an OLE object into the OLE example application you need to initialize the OLEContainer component in the same way you did in Initializing the OLE container gt Write the following event handler for the OnClick event of the Edit Paste Special menu item on the OLEObjectForm menu bar procedure TOLEObjectForm PasteSpecialiClick Sender TObject var ClipFmt Word Declare the Windows Clipboard format variable DataHand THandle Declare the Windows Clipboard data handle variable Info Pointer Declare the pointer to the OLE initialization info begin if PasteSpecialEnabled Self OLEFrameForm Fmts then If there 1s something to paste if PasteSpecialDlg OLEObjectForm OLEFrameForm Fmts 0 Paste Special dialog box ClipFmt DataHand Info then InitializeOLEObject Info Initialize the OLE object end You should enable the Edit Paste menu item only when the Paste Special dialog box is enabled Write the following event handler for the OnClick event of the Edit menu item on the OLEObjectForm menu bar 420 Delphi User s Guide gt procedure TOLEObjectForm EditiClick Sender TObject begin PasteSpeciall Enabled PasteSpecialEnabled Self OLEFrameForm Fmts end Save the project now then run it 1 Choose File New to display a
496. of the old bitmap and assumes control of the new one If you run the application now you see that client area of the form has a white region representing the bitmap If you size the window so that the client area cannot display the entire image you ll see that the scroll box automatically shows scroll bars to allow display of the rest of the image But if you try to draw on the image you don t get any graphics because the application is still drawing on the form which is now behind the image and the scroll box Drawing on the bitmap There are two things you need to do to make the drawing code you already wrote apply to the bitmap instead of the form Chapter 12 Graphics example 349 1 Use the image control s canvas instead of the form s canvas The easiest way to make that change is to use the editor s search and replace dialog box to change every instance of Canvas to Image Canvas 2 Attach the mouse event handlers to the appropriate events in the image control In the Object Inspector drop down the handler list next to OnMouseDown for the image control and choose FormMouseDown then do the same for OnMouseMove and OnMouseUp If you want you can also detach the methods from the form s events but it s not necessary Since there are now controls on all parts of the form the form will never receive any mouse clicks or drags Now when you run the application you can draw as before but only on the image
497. of the statement to the property or variable on the left side of the assignment statement The assignment 210 Delphi User s Guide operator is a combination of a colon and an equal sign Assignment statements look like this Edit1 Color clRed Object Pascal statements end with a semicolon e Declaring variables Before you can use a variable you need to declare it To declare a variable you give it a name and a type For example the following code declares the variable named MyVariable to be of type Double var MyVariable Double Variable declaration sections begin with the reserved word var Object Pascal has several data types built into the language You can create variables of any of these predefined types In general you can assign values of a particular type to a variable or property of the same type or within the same category of types e Declaring constants Before you can use a constant you need to declare it To declare a constant you give ita name and a value For example the following code declares the constantMyApp to contain the string Financial Calculator const MyApp Financial Calculator Constants assume the type of the value declared in the constant declaration Constant declaration sections begin with the reserved word const e Calling procedures and functions To call an existing procedure type the name of the procedure as a statement in your code For example the followin
498. ogether and go directly to the next chapter Programming with Delphi objects You ll still want to refer to the Language Definition in Delphi s online Help to learn about the new additions to the language however The primary topics in this chapter are Writing readable code Writing assignment statements Declaring identifiers Declaring constants Calling procedures and functions Chapter 5 Writing Object Pascal code 149 Controlling the flow of code execution Object Pascal blocks Understanding scope Writing a procedure or function Defining new data types Understanding Object Pascal units To use this chapter effectively you need to understand how a Delphi project is structured and how to create event handlers If you are uncertain about these topics review Chapter 1 Chapter 3 and Chapter 4 Writing readable code Although you write code for the compiler to compile and turn into an executable program you want yourself and others to be able to read your code easily Coding style As you prepare for writing your first code statements you should realize that it doesn t matter to the compiler how you space indent or capitalize your Object Pascal code or how you break lines of code to continue on the next line As long as the code is syntactically correct the compiler can handle it properly For example this code compiles just fine PROCEDURE TFORML Button1CLICK SENDER TOBJECT begin Edit1l Color CLRED
499. ogether with the topics that relate to their function Complete information for each page and option is available in online Help for the Environment Options dialog box Accessing environment options preferences To display the Environment Options dialog box choose Options Environment from the Delphi menu bar then choose the Preferences page tab 28 Delphi User s Guide Note Note Figure 1 11 Environment Options dialog box Preferences page Environment Options Autosave options Editor files Desktop contents Desktop only Desktop and symbols Environmen t Desktop Form designer X Display grid Grid size X is Soop to i Grid sze 9 Debugging X Integrated debugging X Break on exception Step program block l Minimize on run Gallery X Use on New Form Compiling l Show compiler progress Use on New Project Gallery options The check boxes in the Gallery group that appear at the bottom of the Environment Options dialog box are some of the most important options because they control what you see when you open a new form or a new project The exercises in this and subsequent chapters assume that the Forms Gallery option is enabled as it is by default when you install Delphi However if you share your installation of Delphi this option might have been disabled by another user See Enabling the Gallery options later in this section The Gallery is a
500. oject 14 Delphi User s Guide For the full fledged applications you ll write once you re more familiar with Delphi you ll perform the additional step of debugging your code Debugging code is discussed in Chapter 8 Designing a form Designing forms is as simple as arranging objects in a window If you re familiar with a graphical user interface GUI environment such as Windows then you already know how to use the mouse to manipulate objects by selecting moving sizing and so forth If you are not familiar with these techniques consult your Microsoft Windows documentation In Delphi the objects you manipulate are components and the window is the Delphi form This section demonstrates the following concepts e Creating a new form e Adding components to the form e Setting component properties e Running the program Creating a new form There are several ways to create a new form When you first start Delphi if you re running under a default configuration a new blank form opens Other ways of generating new forms are discussed in Chapter 3 In the interest of simplicity this section assumes a default Delphi configuration Start Delphi Adding components to the form The first application uses only one component a button component Click the Button component on the Standard page of the Component palette then click the center of the form to place the button Alternatively double click the Button component o
501. oject the template is not compiled or linked into the project It remains open however just like any open file until you close it Viewing forms and units When you re working with several forms at design time it s easy to switch among them by bringing the form you want to work on to the front Similarly it s easy to view the unit source code for the form you re working in E To switch among forms in a project 1 Choose View Forms The View Form dialog box appears 2 Inthe View Form dialog box select the form to which you want to give focus then choose OK m To switch among units in a project 1 Choose View Units Chapter 3 Building forms and menus 79 The View Unit dialog box appears View Unit ik 2 Inthe View Unit dialog box select the unit you want to view then choose OK You can also use the Delphi Project Manager to navigate among the units and forms in your project For more information see Chapter 4 Building forms Delphi provides you with tools for building the forms that will make up your application s user interface By using the Browse Gallery simple function calls and Delphi components it s easy to create a wide variety of forms from the simplest to the most complex One of the most common ways that Windows based applications interact with users is through dialog boxes Dialog boxes supply information about the application and in most cases accept input from the user Th
502. oject settings affect the current project only If you share your installation of Delphi with other users it s possible that another user has modified the default option settings in which case displays or behaviors might differ from those described in the examples and illustrations in this chapter In a shared installation situation it s a good idea to check and modify environment options if necessary as described in the following sections before creating a new project Environment options The settings in the Environment Options dialog box affect all Delphi projects This dialog box contains several pages of options that you can change to customize your installation of Delphi Some of the settings affect the behavior of Delphi when you open a new project or add new forms and units to an open project This section covers those particular settings To open the Environment Options dialog box choose Options Environment For more information on the Environment Options dialog box see Chapter 1 or online Help Environment preferences The options on the Preferences page have the most impact on what occurs when you open a new project reopen an existing project or add forms and units to an open project Autosave options The Autosave options are Editor Files and Desktop The settings of these options affect what you see when you start Delphi Chapter 4 Managing projects files and directories 123 If the Desktop option is
503. ojects files and directories 131 Project Manager file list This area of the Project Manager details the current composition of the project It gets its information from the project source code DPR file If you have modified this file manually that is you edited the source code directly the information in this list might be inaccurate When you open the Project Manager Delphi compares the information in the DPR file to the last saved information for the Project Manager If these are not synchronized the contents of the Project Manager file list become dimmed and the Update button on the SpeedBar becomes enabled so that you can synchronize the information Caution Delphi has mechanisms for automatically tracking the files that make up a project and for keeping the project DPR file updated Avoid editing project files manually unless you have a thorough understanding of this process and its ramifications By editing a DPR file you circumvent Delphi s automated project management mechanisms and risk maintaining inaccurate information about project composition Compilation failures and other problems can result Project Manager Path column If you have an open project that uses files that reside in a location other than the current project directory or if you save a copy of a project to another location the Path column of the constituent file list can be the most important bit of information the Project Manager provides This column
504. ol Lines LoadFromFile FileName loads the file specified in the form variable Memol SelStart 0 Caption ExtractFileName FileName displays the filename in the form caption Memol Modified False end Setting the memo s Modified property to False enables you to track any changes the user makes to the text file This in turn gives you the opportunity to provide messages that prompt the user to save the file before closing 300 Delphi User s Guide Using the Save dialog box Once users have created a new file or modified an existing one your code must enable them to save their work You ll do this by means of a handler for the File Save event In the text editor application the event handler for the FrameForm File Save menu command interacts with the Save As dialog box to save the file If the file has never been saved choosing File Save opens the Save As dialog box prompting the user to enter a file name If the file has been saved and therefore named no dialog box appears when the user chooses File Save but the file is saved and a backup version of the file is created saveDialog component properties You use the Open dialog box to read from files and the Save As dialog box to write to files The properties for both dialog box components are identical It follows that the properties for the SaveDialog component correspond to the areas of the dialog box in the same way as do those for the OpenDialog compon
505. ollBars property of the memo control to sc Vertical For each button create an OnClick event handler Fill in the event handlers as follows procedure TForml CutClick Sender TObject begin Memol CutToClipboard end procedure TForml CopyClick Sender TObject Chapter 5 Writing Object Pascal code 159 begin Memol CopyToClipboard end procedure TForml PasteClick Sender TObject begin Memol PasteFromClipboard end procedure TForml ClearAllClick Sender TObject begin Memol Clear end gt Run the application You can type text into the memo control and cut copy paste and clear text as you want When you click the Cut button the memo s CutToClipboard method runs When you click the Copy button the memo s CopyToClipboard method runs and so on Calling procedures with parameters Many procedures require you to specify parameters The statements of the called procedure use the values passed in the parameters when the procedure s code runs the values are treated as variables declared within the procedure Parameters are surrounded with parentheses in a procedure call For example the LoadFromFile method is declared in a TStrings object like this procedure LoadFromFile const FileName string FileName the sole parameter of the method is of type string When you call the LoadFromFile method you specify which file you want loaded by specifying a string as the FileName parameter This code would re
506. ollowing section describes how to create in one simple step such standard command buttons as the Cancel and OK buttons just described Creating standard command buttons You can quickly create buttons for many standard commands by adding BitBtn components to the form and setting the Kind property for each button The possible Kind property settings and their effect are shown in the following table In addition to the 88 Delphi User s Guide property settings shown the bitmap button displays graphics such as a green check mark for the OK button or a red X for the Cancel button Table 3 3 Delphi s predefined bitmap button types Kind value Effect Equivalent property setting s Comments bkAbort Makes a Cancel Caption Abort Red X appears next to button with ModalResult mrAbort caption Abort as caption bkAll Creates an OK Caption amp All Green double check mark button with All A ModalResult 8 appears next to caption caption bkCancel Makes a Cancel Caption Cancel Red X appears next to button Cancel True caption ModalResult mrCancel bkClose Creates a Close Caption amp Close A lavender exit door button closes FLE appears as the glyph for the window this button bkCustom None N A Use this setting to create a custom command button including specifying a custom Glyph bitmap bkHelp Creates a button Caption amp Help A blue appears next to the with Help as the captio
507. omponent class if necessary Change the name for example if you re installing a VBX control that has the same class name as an existing component in your project 5 Once you have specified the options you want choose OK to return to the Install VBX File dialog box 6 Repeat steps 3 through 5 until you have specified all the VBX controls you want to add They should appear in the Installed Units list 7 Choose OK to close the Install VBX File dialog box and rebuild the component library Note In many cases VBX controls are written so as to require placement in the system path or in the WINDOWS SYSTEM directory If you see a message stating Can t load VBX when you compile or run your application verify that any VBX controls are in the proper location Handling an unsuccessful compilation Before rebuilding the component library Delphi checks to make sure all the specified units are available and compilable If the compilation succeeds Delphi loads the newly built library into the Component palette If Delphi encounters a problem it displays an error message stops building the library and displays the Code Editor so that you can correct the error You may be able to correct the problem simply by adding missing directories to the search path 70 Delphi User s Guide Note gt In the event of an unsuccessful compile Delphi maintains the Unit list with your most recent modifications so that you can try rebuilding ag
508. omponent list and edit its properties without ever opening the Menu Designer To edit a menu item without opening the Menu Designer select the item from the Component list To close the Menu Designer window and continue editing menu items 1 Switch focus from the Menu Designer window to the Object Inspector by clicking the properties page of the Object Inspector 2 Close the Menu Designer as you normally would The focus remains in the Object Inspector where you can continue editing properties for the selected menu item To edit another menu item select it from the Component list Using the Menu Designer SpeedMenu The Menu Designer SpeedMenu provides quick access to the most common Menu Designer commands and to the menu template options For more information about menu templates refer to Using menu templates on page 106 To display the SpeedMenu right click the Menu Designer window or press Alt F 10 when the cursor is in the Menu Designer window Commands on the SpeedMenu The following table summarizes the commands on the Menu Designer SpeedMenu Table 3 7 Menu Designer SoeedMenu commands Menu command Action Insert Inserts a placeholder above or to the left of the cursor Delete Deletes the selected menu item and all its sub items if any Create Submenu Creates a placeholder at a nested level and adds an arrow to the right of the selected menu item Select Menu Opens a list of menus in the current form D
509. omponent selected The Object Inspector has several other behaviors that make it easier to set component properties at design time e When you use the Object Inspector to select a property the property remains selected in the Object Inspector while you add or switch focus to other components in the form provided that those components also share the same property This enables you to type a new value for the property without always having to reselect the property If a component does not share the selected property Delphi selects its Caption property If the component does not have a Caption property Delphi selects its Name property e When more than one component is selected in the form the Object Inspector displays all properties that are shared among the selected components This is true even when the value for the shared property differs among the selected components In this case the property value displayed are either the default or the value of the first component selected When you change any of the shared properties in the Object Inspector the property value changes to the new value in all the selected components There is one notable exception to this when you select multiple components in a form their Name property no longer appears in the Object Inspector even though they all have a Name property This is because you cannot assign the same value for the Name property to more than one component in a form Tab jumping to prop
510. on At run time the File menu from OLEObjectForm replaces the File menu from OLEFrameForm The other menu items from OLEObjectForm will be merged with the menu bar of OLEFrameForm gt To create the OLEObjectForm menu 1 Add a MainMenu component to OLEObjectForm and open the Menu Designer 2 Create the File Edit Object and Window menu titles and underlying menu items as shown in the following table For each menu item specify the value for the Caption property and accept the values Delphi creates for the Name property amp File amp Edit amp Object amp Window amp New amp Insert Object amp Deactivate amp Cascade amp Open amp Paste Special amp Tile amp Save As lt hyphen gt amp Arrange Icons lt hyphen gt amp Object E amp xit 3 Specify the GroupIndex property values for the File Edit Object and Window menu titles as shown in the following table Menu GroupIndex File 0 default Edit 1 Chapter 15 OLE example 405 Note Note Menu GroupIndex Object 2 Window 4 The GroupIndex property of the Edit menu has the same value 1 as the index of the Edit menu group from the OLE server When an OLE object is activated in place the Edit menu item group from the OLE server replaces the Edit menu from OLEObjectForm The other menu item groups from the OLE server are merged with the menu of OLEObjectForm The OnClick event handlers for the New and Exit menu items on the File menu of the OLEObject
511. onent s appearance and behavior Form tools Forms created in Delphi can be reused among Delphi projects and can also be saved as dynamic link libraries DLLs so you can load them into projects built with other applications such as C Paradox dBASE Visual Basic and PowerBuilder Delphi provides several development tools that make generating productive forms and reports easier than ever Chapter 1 Introducing Delphi 9 e Project Templates provide a selection of several application designs that you can use as a starting point when building your own applications You can save your own projects as Project Templates e Form Templates enable you to choose from an array of predesigned forms when developing your user interface You can save your own forms as Form Templates e Project Experts develop projects for you based on your specified preferences according to general project categories e Form Experts develop custom forms for you based on your specified preferences For example the Database Form Expert generates a form that displays data from an external database for more information see the book Building Database Applications with Delphi For more information about creating forms see Chapter 3 for more information about working with projects see Chapter 4 Component palette Components Standard page components shown Placeholders for additional Left scroll arrow additional components available by clicking the page tabs
512. onent on a form the TabStop property of the component must be set to True The tab order is initially set by Delphi corresponding to the order in which you add components to the form You can change this by changing the TabOrder property of each component or by using the Edit Tab Order dialog box mM To use the Edit Tab Order dialog box 1 Select the form or a container component in the form that contains the components whose tab order you want to set 2 Choose Edit Tab Order or choose Tab Order from the form s SpeedMenu The Edit Tab Order dialog box appears displaying a list of components ordered first to last in their current Tab order Figure 3 8 Edit Tab Order dialog box Edit Tab Order Controls listed in tab order BitBtn2 TBitBtn Za 3 Inthe Controls list select a component and press the appropriate arrow button Up or Down or drag the component to its new location in the tab order list 4 When the components are ordered to your satisfaction choose OK Using the Edit Tab Order dialog box changes the value of the components TabOrder property You can also do this manually if you want m To manually change a component s TabOrder property 1 Select the component whose position in the tab order you want to change 2 Inthe Object Inspector select the TabOrder property 3 Change the TabOrder property s value to reflect the position you want the component to have in the tab order Not
513. onent writing you can use the Component Expert to help you get started You supply information about the component you want to create and the Component Expert creates the new unit file with the appropriate declarations to derive and register the new class To open the Component Expert and create a new component unit file 1 Choose File New Component to open the Component Expert dialog box Figure 2 19 The Component Expert dialog box Component Expert Chess Nane eee a Pate Page Samples YJ Chapter 2 Using components and code 71 2 Inthe Class Name edit box enter the name of the new class you are creating Remember that all Object Pascal classes are generally prefaced with a letter T for type For example the name of a new button component type could be TMyButton 3 Use the drop down list of the Ancestor Class combo box to select a base class or enter the name of a base class for your new component Unless you override them in the component declaration your new component will inherit all the properties methods and events from its ancestor class 4 Use the drop down list of the Palette Page combo box to select a page or enter the name of the palette page where you want your new component to appear when you add it to the library 5 Choose OK to create the unit file for the new component you are creating The following code shows an example of component unit file code created by the Component Expert
514. onents 49 50 from libraries 68 69 event handlers 67 68 files 135 370 371 forms from projects 135 graphics 355 menu items 102 105 menu templates 107 strings 271 substrings 201 text 291 292 units from projects 135 Delphi configuring 28 32 installing 1 123 saving desktops 31 starting 8 Delphi Image Library 118 descendant objects 221 223 226 See also inheriting from objects design tools 14 designing forms 15 17 design time properties 53 56 overriding 59 desktop 117 124 saving 31 Desktop Contents option 31 Destroy method 229 destroying objects 229 240 242 destructors 229 developing applications 7 33 7 80 fundamentals 14 22 tools 9 10 121 DF files 117 DFM files 26 27 116 121 122 dialog boxes 80 93 See also common dialog boxes accepting input 87 adding buttons 87 89 specifying default 88 as main form 60 85 93 closing 87 confirmation 310 374 deleting files 370 371 file attribute 371 372 373 labeling 87 masking characters 83 message See message boxes modal 81 85 86 modeless 85 86 predesigned 80 85 property editors as 56 specifying active component 92 tab order 90 91 testing 91 Dialogs page Component palette 41 dialogs See dialog boxes Dialogs unit 80 dimming menu items 292 directives compiler 120 143 199 forward 189 public vs private 224 225 directories 115 116 122 building drive lists 362 365 changing 41 376 displaying structures 42 363 366 project 133 136 specifying 115
515. online Help Nesting if statements You can put if statements within if statements when the logic of your application requires it For example the OKClick handler shown here can now test three conditions procedure TForml OKClick Sender TObject begin if Editl Text Saturday then Label2 Caption Why are you working today else if Editl Text Sunday then Label2 Caption You should be resting else if Editl Text Monday then Label2 Caption Welcome to a new work week else Label2 Caption end As soon as a condition is met the statement part runs and no further testing of conditions occurs In other words if you type Saturday in the edit box the code displays the Saturday message in the label and the rest of the if statement is ignored No semicolon appears until the end of the final else part When you write nested if statements choose a consistent clear indentation style This will help you and anyone else who reads your code see the logic of the if statement and how the code flows when your application runs Chapter 5 Writing Object Pascal code 165 You can also nest if statements containing else parts within if statements that don t have else parts Your nested if statement might have this structure if ConditionA True then if Condition B True then DoThis else DoThat Be aware that if you do this the compiler considers the else part to belong to the inner most if stateme
516. operty for Memo1 to the Font property for the printer object s Canvas This effectively downloads the selected font to the printer For example Printer Canvas Font Memol Font Using the printer dialog box es In the text editor application the File Print command opens the Print dialog box where the user can then select printing options or open the Printer Setup dialog box to change printers The File Print Setup command also opens the Printer Setup dialog box Adda Print dialog box component and a Printer Setup dialog box component to EditForm Print dialog box component properties The properties available in the Object Inspector for the Print dialog box component correspond to several areas of the Print dialog box in the running application as shown in the following illustration Figure 10 9 Print dialog box component properties Printer Default Printer HP LaserJet IIP PostScript on pubs386 rlp3 LPT1 PrintRange FromPage Print Range MaxPage MinPage Options ToPage C Selection Pages properties an fo Go Options Help property Options PrintToEile Print Quality 300 dpi Copies fi Copies property prop erty Print to File Collate Copies Collate property Although Delphi makes it easy to do so you don t usually need to reset the default options for this dialog box at design time There are however a few print options worth mentioning here MinPage MaxPage Use these
517. operty values for the grid e Change RowCount to 6 e Change ColCount to 6 e Change DefaultColWidth to 105 172 Delphi User s Guide You might have to enter a different DefaultColWidth value depending on your screen resolution Make the columns wide enough to display the coordinates of the cells e Change the name of the button to ShowCoordinatesButton e Change the caption of the button to Show Coordinates You probably also want to increase the size of the form and the grid to display all the rows and columns Figure 5 10 A form for a nested for loop example Form 3 Create this event handler that runs when you click the Show Coordinates button procedure TForm1 ShowCoordinatesButtonClick Sender TObject var Col Row Integer begin for Col 1 to 5 do StringGridl Cells Col 0 Col IntToStr Col for Row 1 to 5 do StringGridl Cells 0 Row Row IntToStr Row for Col 1 to 5 do for Row 1 to 5 do StringGridl Cells Col Row Col IntToStr Col Row IntToStr Row end 4 Run the application and click the Show Coordinates button This event handler contains four for statements The first for statement writes the string Col plus the current value of the Col variable in the row 0 once the value of Col is converted to a string for Col 1 to 5 do StringGridl Cells Col 0 Col IntToStr Col The second for statement writes the
518. or printing is that you add the Printers unit to the uses clause of the form that will call the printer The Printers unit declares a printer object called Printer that has a canvas that represents the printed page E To print a graphic image copy the image to the printer s canvas You can use the printer s canvas just as you would any other canvas In particular that means you can copy the contents of a graphic object such as a bitmap to the printer directly Inthis example you ll print the contents of the image control in response to a click on Print item on the File menu procedure TForml PrintiClick Sender TObject begin with Printer do Chapter 12 Graphics example 351 begin BeginDoc start printing Canvas Draw 0 0 Image Picture Graphic draw Image at upper left of page EndDoc Tainen printing end end Working with graphics files gt Graphic images that exist only for the duration of one running of an application are of very limited value Often you either want to use the same picture every time or you want to save a created picture for later use Delphi s image control makes it easy to load pictures from a file and save them again Once you add the ability to load and save files this sample application becomes a much more powerful tool The logic for loading and saving graphics files is the same as for any other files so this chapter doesn t cover the mechanics in great detail Th
519. or to navigate to the selected function However Edit Source gives focus to the Code Editor so you can modify the source code at that function location while View Source does not move the focus from the Call Stack window If you select the top function in the Call Stack window View Source and Edit Source cause the Code Editor to display the location of the execution point in the current function Selecting any other function call causes the debugger to display the actual function call in the Code Editor Handling hardware and language exceptions Delphi provides a mechanism to control the way exceptions are handled while you are debugging In addition Delphi makes the debugging session easier by treating most hardware exceptions as Object Pascal language exceptions This means Delphi traps the hardware exceptions generated by your Delphi application and you can gracefully recover before your program run ends with a system crash If a hardware or language exception occurs during a debugging session the VCL displays a dialog box that notes the exception note that the VCL displays this dialog box regardless of whether you are debugging the program When you choose OK to close the dialog box your program run continues and you can continue to debug your application E To have Delphi pause the program run when an exception occurs 1 Choose Options Environment then click the Preferences page tab 2 Check the Break On Exceptions check box
520. ord wrapping e Selecting text e Using the Clipboard with text e Providing a pop up menu Setting text alignment and word wrapping In the text editor application users set text alignment and word wrapping options by means of commands on the Character menu A check mark appears next to the menu command to indicate which options are in effect Alignment and WordWrap are properties of the Memo component As with all properties you can set their values during run time with a simple assignment statement Checked is a Boolean property for menu items If Checked is True then a check mark appears next to that menu item Setting text alignment An example of using the Sender parameter is discussed in Chapter 3 The text alignment commands on the EditForm Character menu have a single event handler that uses the Sender parameter to check which alignment option was selected Depending on the value of Sender the event handler sets the appropriate alignment and either checks or unchecks the menu items as called for Chapter 10 Text editor example 289 Here is the event handler procedure TEditForm AlignClick Sender TObject begin Leftl Checked False Right1 Checked False Centerl Checked False with Sender as TMenuItem do Checked True with Memol do if Leftl Checked then Alignment taLeftJustify else if Right Checked then Alignment taRightJustify else if Centerl Checked then Alignment taCenter end
521. orresponding BOLEMedium field value of BOLE_MED_HGLOBAL Note The fmtName and fmtResultName fields of BOLEFormat are not used when dragging and dropping OLE objects They are required fields only for pasting objects For this example both pasting and dropping should be enabled so they should be specified as they are in the OnCreate event of OLEFrameForm However if you wanted to allow drag and drop but not pasting in another application you could leave them uninitialized m To register a formas an OLE drop target call RegisterFormAsOLEDropTarget Specify the object types you want to allow to be dropped on the form in the Fmts parameter Note To use RegisterFormAsOLEDropTarget the TOCtrl unit must be referenced in the uses clause of the unit Since you already added this reference for OLEFrame in order to call BOLEMediumCalc nothing needs to be done to the OLE example application For other applications remember to refer to TOCtrl gt Attach the following code to the OnCreate method of OLEFrameForm after the specification of the Fmts array elements procedure TOLEFrameForm FormCreate Sender TObject begin RegisterFormAsOleDropTarget Self Fmts Register form as drop target end Dropping an OLE object onto the OLE example application When an object is dropped onto a form an OnDragDrop event occurs The object is specified as the Source parameter of the TDragDropEvent method which is the event handler of OnDragDrop event
522. ouble clicking a menu name opens the designer window for the menu Save As Template Opens the Save Template dialog box where you can save a menu for future reuse Insert From Template Opens the Insert Template dialog box where you can select a template to reuse Delete Templates Opens the Delete Templates dialog box where you can choose to delete any existing templates Insert From Resource Opens the Insert Menu from Resource file dialog box where you can choose an MNU file to open in the current form For more information about the Menu Designer SpeedMenu see the online Help topic Menu Designer SpeedMenu Chapter 3 Building forms and menus 105 Switching among menus at design time If you re designing several menus for your form you can use the Menu Designer SpeedMenu or the Object Inspector to easily select and move among them E To use the SpeedMenu to switch among menus in a form 1 Right click in the Menu Designer to display the SpeedMenu 2 From the SpeedMenu choose Select Menu The Select Menu dialog box appears Figure 3 16 Select Menu dialog box ET MainMenul PopupMenul This dialog box lists all the menus associated with the form whose menu is currently open in the Menu Designer 3 From the list in the Select Menu dialog box choose the menu you want to view or edit E To use the Object Inspector to switch among menus in a form 1 Give focus to the form whose menus you want to choose from 2 From
523. ow In the text editor application there are two menu items that call the Close method File Close and File Exit File Close closes the child window and File Exit closes FrameForm which terminates the application and indirectly closes all child windows Note that users can also close an application window in any of the following ways e Pressing Alt F4 from an MDI frame window terminates the application e Pressing Ctrl F4 from an MDI child window closes the child window Chapter 10 Text editor example 309 e Double clicking the Control menu box also known as the System menu e Choosing Close from the Control menu All of these occurrences invoke Form Close as well In the text editor application to handle any of these user actions you ll write a handler for the edit form sOnClose event Closing the child window The handler for the File Close OnClick event exists in EditForm so there is no need to specify which form should close gt Write the following handler for the EditForm File Close OnClick event procedure TEditForm CloselClick Sender TObject begin Close end Now you ll write the handler that gets called when the user closes the form without using the File Close command gt Write the following handler for the EditForm OnClose event procedure TEditForm FormClose Sender TObject var Action TCloseAction begin Action caFree end This method closes the form and frees all memory
524. owing procedures describe how to perform the basic tasks involved in building your menu structure Each procedure assumes you have the Menu Designer window open E To add menu items at design time Chapter 3 Building forms and menus 101 1 Select the position where you want to create the menu item If you ve just opened the Menu Designer the first position on the menu bar is already selected 2 Begin typing to enter the caption Or enter the Name property first by specifically placing your cursor in the Object Inspector and entering a value In this case you then need to reselect the Caption property and enter a value 3 Press Enter The next placeholder for a menu item is selected If you entered the Caption property first use the arrow keys to return to the menu item you just entered You ll see that Delphi has filled in the Name property based on the value you entered for the caption See Naming the menu items on page 101 4 Continue entering values for the Name and Caption properties for each new item you want to create or press Esc to return to the menu bar Use the arrow keys to move from the menu bar into the menu and to then move between items in the list press Enter to complete an action To return to the menu bar press Esc E To insert a new blank menu item place the cursor on a menu item then press lns Menu items are inserted to the left of the selected item on the menu bar and above the selected it
525. ox Creating simple input forms Where MessageDlg displays an informational form that requires only a button click from the user the Dialogs unit also provides two functions InputBox and InputQuery that display forms requiring a single line of input from the user For example you might use such a form as a password entry screen Here is the syntax for each function function InputBox const ACaption APrompt ADefault string string function InputQuery const ACaption APrompt string var Value string Boolean Both InputBox and InputQuery create a dialog box with an OK and Cancel button Use InputBox if you simply want the string the user enters returned if the user chooses OK and not returned if the user chooses Cancel or presses Esc to exit the dialog box Use InputQuery if you want to be able to interpret the user s action OK Cancel or Esc as a Boolean variable that the program can recognize gt Foran illustration of how InputBox works try the following 82 Delphi User s Guide 1 Start a new blank project 2 Add a Button component and a Label component to Form1 3 Generate the following OnClick event for Button1 procedure TForml ButtoniClick Sender TObject begin Labell Caption InputBox Password Entry Form Enter Password end Leaving the ADefault parameter string empty means no text initially appears in the input box 4 Run the program and choose Button1 The input box appears
526. ox on page 127 For information on the individual settings on this page see online Help Linker page This page enables you to specify how the link options are configured The two options that relate to project management are Include TDW Debug Info and the Default check box 128 Delphi User s Guide Checking the Include TDW Debug Info check box causes debugging information to be compiled into the project executable file This enlarges the size of that file See online Help for information about using this or other options on the Linker page Checking the Default check box preserves the settings on this page as the default linker configuration for all new projects see Default check box on page 127 Directory and Conditional options On the Directories Conditionals page you can control the location of the project s compiled output and specify the location of resources needed to compile link and distribute the application If you want the compiled project output to be stored in a directory other than the project directory you can enter a path in the Output Directory edit box The specified directory must exist or be accessible at compile time or Delphi generates an error message The Search Path edit box specifies the location s of any non Delphi library file s needed to compile the program The Delphi compiler always includes DELPHI BIN and DELPHIN LIB directories in its search for resources If your program needs to
527. parent or frame In a Delphi MDI application the frame is always the application s main form Within the frame window other windows often called child windows can be opened Each child window appears and behaves the same way The application documents or other data are opened inside the child windows These documents can all be of the same format or they can be a mix of file formats supported by the MDI application At design time you create the MDI frame form as the main application form and you create the child form as a template for the application s child windows You can create more than one type of child form but MDI applications support only one frame form This section describes the following steps involved in creating a basic MDI application for text manipulation e Creating the MDI frame form e Creating the MDI child form e Creating the application menus e Merging the application menus e Creating child windows at run time You ll want to save your work periodically as you follow the steps this chapter outlines 280 Delphi User s Guide Caution Caution Creating the MDI frame form In an MDI application the frame window provides a workspace for the application documents which open inside one or more child windows Creating a frame form is the first step in building the text editor application If necessary start Delphi Then choose File New Project and select the Blank project The
528. pecify the fields of a BOLEFormat record for each object format e fmtld should be the Clipboard format previously registered with RegisterClipboardFormat e fmtMedium should be BOLE_MED_STORAGE for embedded OLE objects or BOLE_MED_STREAM for linked OLE objects Pass the Clipboard format for which you need a BOLEFormat as a parameter of BOLEMediumCalc That function will return the correct value for any valid Clipboard format including the ones you registered for embedded and linked OLE objects e fmtIsLinkable should be False for embedded objects and True for linked objects e fmtName should be s copied into a null terminated string by the StrPCopy function This will be replaced by the object name from the source at run time automatically e fmtResultName should be s also copied into a null terminated string by StrPCopy This will be replaced by the results name from the source at run time automatically Next you will specify an array of BOLEFormat records which you will use with PasteSpecialDlg later The BOLEFormat type is declared in the BOLEDefs unit and the BOLEMediumCalc function is declared in the TOCtrl unit Add these units to the uses clause of the interface part of the OLEFrame unit interface uses BOLEDefs TOCtrl Refer to unit BOLEDefs type Declare the Fmts array in the public part of the OLEFrameForm type declaration Fmts is public instead of private for this example because it is refer
529. perty using as indexes the x and y coordinates of the pixel For example the following event handler responds to a click on a button by changing a random pixel on the form to red For detailed information on the Random function see online Help procedure TForml ButtoniClick Sender TObject begin Canvas Pixels Random ClientWidth Random ClientHeight clRed end Using pens The Pen property of a canvas controls the way lines appear including lines drawn as the outlines of shapes Drawing a straight line is really just changing a group of pixels that lie between two points The pen itself has four properties you can change Color Width Style and Mode The values of these properties determine how the pen changes the pixels in the line By default every pen starts out black with a width of 1 pixel a solid style and a mode called copy that overwrites anything already on the canvas You can set the color of a pen as you would any other Color property at run time Width is an integer number of pixels Style gives you solid lines dashed lines dotted lines and so on Mode lets you specify various ways to combine the pen s color with the colors already in the pixel array The sample program in Chapter 12 demonstrates the effects of each pen property Moving the pen The current drawing position the position from which the pen will draw its next line is called the pen position The canvas stores its pen position in
530. place activation defined 391 See also OLE applications input dialog boxes 87 exception handling 237 masking 83 input focus container components and 48 dialog boxes 88 setting 92 93 moving 90 92 OLE objects 413 input forms 82 83 InputBox function 82 InputQuery function 82 Insert command Menu Designer 105 Insert From Resource command Menu Designer 105 112 Insert from Resource dialog box 112 Insert From Template command Menu Designer 105 107 Insert method menus 110 strings 271 Insert Object dialog box 394 410 411 options 411 Insert procedure 201 Insert Template dialog box 107 inserting a string in a string 201 InsertOLEObjectDlg function 410 411 Install Components command Options 69 442 Delphi User s Guide Install Components dialog box 69 73 Install VBX File dialog box 70 installing component libraries 73 installing Delphi 1 123 installing third party components 42 68 instance variables 26 instantiation forms 207 objects 217 229 instructions undefined 238 Integer data type 156 integer types 156 166 exception handling 237 239 241 integers 156 260 262 See also constants numbers integrated debugger 13 247 exception handing 238 restarting 253 264 starting 249 250 integrated development environment 28 customizing 123 129 minimizing 32 moving among windows 140 starting 8 interactive tutors 2 3 interface reserved word 77 187 206 207 interfaces 76 testing 248 interrupts 238 IntTo
531. playing 280 in list boxes 297 executable 17 117 building 141 DDE applications and 382 including debug information 249 graphics 121 122 352 354 moving 373 OLE applications and 392 opening 297 300 automatically 375 printing 305 309 to files 307 project See project files reading from 301 redistributable ii renaming 353 373 375 resource 112 117 routines 369 Index 439 saving 301 303 310 353 automatically 31 selecting types 297 size returning 364 swap 238 writing to 301 FileSetAttr procedure 373 fill patterns 316 344 FILMANEX DPR 359 Filter editor 298 FilterComboBox component 41 filters 41 297 298 Filters property 298 finally reserved word 235 Find common dialog box 41 FindDialog component 41 finding event handlers 63 finding specific strings 270 271 276 finding substrings 201 flags drawings 351 file attributes 371 flickering screens 250 floating point numbers 260 262 overflow errors 238 floppy disk drives See drives fmtId constant 416 419 fmtIsLinkable constant 416 419 fmtMedium constant 416 419 fmtName constant 416 419 fmtResultName constant 416 419 FMXUtils unit 369 focus container components and 48 dialog boxes 88 setting 92 93 moving 90 92 OLE objects 413 Font common dialog box 41 303 304 Font property 303 304 FontDialog component 41 303 fonts 269 305 downloading 306 setting 303 304 for loops vs 199 for reserved word 170 for statements 170 174 arrays and 199 nesting 172 174 Form
532. ponent in your DDE server application Assign the value of the Text property of an edit box to the Text property of the DDEServerltem or for larger bodies of text you could assign the Lines property of a memo to the Lines property of the DDEClientlItem Attach the assignment statement to the OnChange event of the edit box or memo For example if the edit box is named Edit1 and the DDEServerltem component is named DDEServerltem1 execute the following code DDEServerlIteml Text Editl Text Using OLE This section explains e What is OLE e Creating OLE container applications e OLE data in files What is OLE Object Linking and Embedding OLE is a method for sharing data among applications To use OLE one application must be an OLE server and another application must be an OLE container With Delphi you can create OLE container applications An OLE server is an application that can create and edit an OLE object An OLE container is an application that can contain an OLE object An OLE object is simply the data shared by the two applications Examples of OLE objects are documents spreadsheets pictures and sounds Here s a typical way to use OLE the OLE container application displays a picture representing the OLE object The user activates the OLE object typically by double clicking the picture When the OLE object is activated the OLE server application opens and the user can edit the OLE object using the OLE serv
533. preadsheet Only your OLE container application can use the data saved in this file E Tosave an OLE object call the SaveToFile method of the OLEContainer component For example to store the OLE data in a file called SALES OLE in the C TIPPER directory execute the following code The OLEContainer component is named OleContainer1 OleContainer1 SaveToFile C TIPPER SALES OLE E To obtain OLE data from a file saved with the SaveToFile method use the LoadFromFile method To load the OLE data from the file saved by the previous code execute the following code OleContainer1 LoadFromFile C TIPPER SALES OLE If you attached the code above to the OnCreate event of the form containing the OLEContainer component your application would restore the latest version of the OLE object every time you run your OLE container application For an example that uses SaveToFile and LoadFromFile refer to Chapter 15 Search online Help for more information about SaveToFile and LoadFromFile Comparing DDE and OLE DDE and OLE are both for sharing data between applications When should you use DDE and when should you use OLE DDE is good for exchanging distinct text strings If all you want to know is the bottom line of a profits spreadsheet it makes sense to link the cell that contains the bottom line to a Delphi DDE client application Then you could output the data in an edit box or label DDE protects the data in the spreadsheet b
534. project program Project uses Forms Unitl in UNIT1 PAS Form1 SR ARES begin Application CreateForm TForml Form1 Application Run end 118 Delphi User s Guide Important e Project1 represents the file name of the project source code file For example if you save the project source code file under the name MYNEWAPP DPR the first line of the source code would be program Mynewapp e Unitl represents the unit identifier where UNIT1 PAS represents the actual DOS file name for the unit If the unit identifier is longer than the standard eight character DOS file name convention Delphi creates the file name as a truncated version of the identifier Otherwise these names are identical and must remain so in order for your project to be correctly compiled e The in clause tells the compiler where to find the unit file Form1 represents the variable identifier for the form associated with this unit this would not appear in the clause if this were not a form associated unit This is the same as the Name property of the form Because you use the Object Inspector to name the form Delphi maintains the name in the DPR file e The R compiler directive specifies that the file with a RES extension and the same base name as the project is to be included in the project For more information search online Help for the Resource File Directive topic e The Application CreateForm statement loads the form specified
535. r 6 The procedures and functions visible to any unit or application using the unit are declared in the interface part Their actual bodies their implementations are found in the implementation part You don t need to use forward declarations and they aren t allowed in the interface part The interface part lists all the procedure and function headers the implementation part contains the coded logic of the procedures and functions including those that are event handlers Chapter 5 Writing Object Pascal code 207 An optional uses clause can appear in the interface and must immediately follow the interface reserved word Implementation part The implementation part of a unit begins with the reserved word implementation Everything declared in the interface part is accessible to the code in the implementation part The implementation can have additional declarations of its own although these declarations aren t accessible to any other application or unit These declarations are used by the procedures functions and event handlers declared in this unit An optional uses clause can appear in the implementation part and must immediately follow the implementation reserved word The bodies of the routines declared in the interface part must appear in the implementation part The procedure or function header that appears in the implementation part can be identical to the declaration that appears in the interface part or it can be in
536. r 6 Programming with Delphi objects 219 no properties Yet you can change the size of the form add or delete minimize and maximize buttons or set up the form to become part of a Multiple Document Interface MDI application How is it possible to do all these things with a form that contains only one field and one method The answer lies in the notion of inheritance Recalling the bicycle analogy once you have put together all the objects that make up a complete bicycle object you can ride it because it has all the essentials to make the bicycle useful it has pedals you push to make the wheels go around it has a seat for you to sit on it has handlebars so you can steer and so on Similarly when you add a new form to your project it has all the capabilities of any form For example all forms provide a space to put other components on them all forms have the methods to open show and hide themselves and so on Suppose though that you want to customize that bicycle just as you would customize a form object in Delphi You might adjust a few gear settings add a headlight and provide a horn with a selection of sounds just as you might customize a form by adding or rearranging buttons changing a few property values and adding a new method that allows the form to appear with a plaid background To change the bicycle to make it exactly as you want it you start with the basic model and then customize it You do the same thing wi
537. r a menu that you always want to appear leftmost such as a File menu Similarly specify a high number it needn t be in sequence for a menu that you always want to appear rightmost such as a Help menu e To replace items in the main menu give items on the child menu the same GroupIndex value This can apply to groupings or to single items For example if your main form has an Edit menu item with a GroupIndex value of 1 you can replace it with one or more items from the child form s menu by giving them a GroupIndex value of 1 as well Giving multiple items in the child menu the same GroupIndex value keeps their order intact when they merge into the main menu e To insert items without replacing items in the main menu leave room in the numeric range of the main menu s items and plug in numbers from the child form For example number the items in the main menu 0 and 5 and insert items from the child menu by numbering them 1 2 3 and 4 Additional rules apply for OLE client applications For more information refer to Chapter 15 Chapter 3 Building forms and menus 111 Importing resource RC files Note Delphi supports menus built with other applications so long as they are in the standard Windows resource RC file format You can import such menus directly into your Delphi project saving you the time and effort of rebuilding menus that you created elsewhere To load existing RC menu files 1 Inthe Menu Desig
538. r causes the exception Silent exceptions Delphi applications handle most exceptions that your code doesn t specifically handle by displaying a message box that shows the message string from the exception object You can also define silent exceptions that do not by default cause the application to show the error message Silent exceptions are useful when you don t intend to handle an exception but you want to abort an operation Aborting an operation is similar to using the Break or Exit procedures to break out of a block but can break out of several nested levels of blocks Silent exceptions all descend from the standard exception type EAbort The default exception handler for Delphi applications displays the error message dialog box for all exceptions that reach it except those descended from EAbort m There is a shortcut for raising silent exceptions Instead of manually constructing the object you can call the Abort procedure Abort automatically raises an EAbort exception which will break out of the current operation without displaying an error message The following code shows a simple example of aborting an operation On a form containing an empty list box and a button attach the following code to the button s OnClick event procedure TForml ButtoniClick Sender TObject var I Integer begin for T 1 to 10 do loop ten times begin Chapter 7 Writing robust applications 243 ListBoxl Items Add IntToStr
539. r dialog box 90 editing See also changing code 19 62 as ASCII text 94 event handlers 63 66 while debugging 255 262 264 data 40 392 forms as ASCII text 94 95 graphics 14 menu items 105 project files 23 132 text 38 Editor Colors page Environment Options 258 Editor files option 124 editors 279 Code See Code Editor Filter 298 Image 14 Picture 332 333 property See property editors 438 Delphi User s Guide EDivByZero exception 237 EFault exception 238 EGPFault exception 238 EInOutError exception 237 EIntError exception 237 241 242 EIntOverflow exception 237 EInvalidCast exception 238 EInvalidOp exception 238 EInvalidOpCode exception 238 EInvalidPointer exception 237 Ellipse method 317 ELLIPSE BMP 333 ellipses 39 317 ellipsis in Value column 56 else reserved word case statements and 167 except reserved word and 241 if statements and 164 EMathError exception 237 embedding OLE objects 392 Enable All Watches command Watch List window 260 Enable Breakpoint command Breakpoint List window 256 Enable Watch command Watch List window 260 Enabled property 91 menus 110 292 speed buttons 333 end reserved word 165 167 175 exception handling 232 standing alone 210 Enter key 88 enumerated types 166 195 197 constants vs 335 declaring 335 336 identifiers as 196 environment 232 options 123 124 Environment command Options 28 123 Environment Options dialog box 28 68 123 environment preferences s
540. r dragged and dropped Only if Source is a label does the event handler allow the assignment to occur Creating nonvisual objects Most of the objects you use in Delphi are components you can see at both design time and run time such as edit boxes and string grids A few such as common dialog boxes are components you don t see at design time but they appear at run time Still others such as timers and data source components never have any visual representation in your application at run time but they are there for your application to use Occasionally you might want to create your own nonvisual objects for your application For example you might want to create a TEmployee object that contains Name Title and HourlyPayRate fields You could then add a CalculatePay method that uses the data in the HourlyPayRate field to compute a paycheck amount for a given period The TEmployee type declaration could look like this type TEmployee class TObject Name string 25 Title string 25 HourlyRate Double function CalculatePayAmount Double end In this case TEmployee is derived from TObject TEmployee contains three fields and one method Because it is derived from TObject TEmployee also contains all methods of TObject TObject has no fields Place object type declarations you create without the help of Delphi in the type declaration part of your unit along with the form type declaration 228 Delphi User s Guide In th
541. r source file and the OLE container application so that the data is linked the user chooses Paste Link Recall that linked data must exist in an external file To display the linked or embedded object as an icon the user chooses Display As Icon When this check box is checked the Change Icon button appears To change the default icon or the label of the OLE object the user chooses Change Icon If the data is not one of the registered formats the Paste and Paste Link options are disabled in the Paste Special dialog box The user won t be allowed to paste data from the Clipboard For this example the data on the Clipboard must be of type FEmbedClipFmt embedded OLE object or FLinkClipFmt linked OLE object The user chooses the type of data from the As list Sometimes data might be interpreted in a variety of ways For example if you copy text from some word processor OLE servers you could choose to paste the data as text or as an OLE object The values of the As list are determined by the OLE server application When the user chooses OK to close the Paste Special dialog box PasteSpecialDlg returns True It then stores the information necessary to initialize the OLE container in the data structure pointed to by the PInitInfo parameter Using OLE objects with the Clipboard This section discusses the following steps involved in registering and specifying the object formats for pasting Chapter 15 OLE example 417 e Registeri
542. r third party Help compiling system Only the file name and its path if specified are integrated into the project not the Help file itself This can affect the accessibility of Help when you deploy or distribute your application For more information see Application page under Project options on page 128 Understanding the files in a project As described in Tables 4 1 and 4 2 several different DOS file types work together to create a project specifying project and environment options containing compiled and uncompiled Object Pascal code detailing the appearance and behavior of the project s forms and so on This section discusses the file types within the project that affect the appearance and behavior of your completed application including e The project source code DPR file e Unit source code PAS files e Unit object code DCU files e Graphical form DFM files The project source code DPR file The DPR file is the main program file Delphi uses to compile all other units Delphi updates this file throughout the development of the project When you initially save the project you are prompted to name the project source code file after being prompted to name any unit source code files the project contains Since the project file is stored by the operating system the file name must conform to DOS file naming rules As introduced in Chapter 1 Delphi generates the following source code for a default
543. rag cursor to indicate whether the control can accept the dragged item To accept items dragged over a control attach an event handler to the control s OnDragOver event The drag over event has a variable parameter called Accept that the event handler can set to True if it will accept the item Setting Accept to True specifies that if the user releases the mouse button at that point dropping the dragged item the application can then send a drag drop event to the same control If Accept is False the application won t drop the item on that control This means that a control should never have to handle a drag drop event for an item it doesn t know how to handle The drag over event includes several parameters including the source of the dragging and the current location of the mouse cursor The event handler can use those parameters to determine whether to accept the drop Most often a control accepts or rejects a dragged item based on the type of the sender but it can also accept items only from specific instances Chapter 13 File manager example 377 gt Inthe following example a directory outline accepts dragged items only if they come from a file list box procedure TFMForm DirectoryOutlinelDragOver Sender Source TObject X Y Integer State TDragState var Accept Boolean begin if Source is TFileListBox then Accept True end Dropping items Once a control indicates that it can accept a dragged item i
544. rated type you use the reserved work type followed by an identifier for the type then an equal sign and the identifiers for the values in the type in parentheses separated by commas For example the following code declares an enumerated type for each of the drawing tools in a graphics application type TDrawingTool dtLine dtRectangle dtEllipse dtRoundRect Add the declaration of the TDrawingTool type above the declaration of the form class _ type this is already there TDrawingTool dtLine dtRectangle dtEllipse dtRoundRect you type this TForml class TForm this is already there _ By convention type identifiers begin with the letter T and groups of similar constants such as those making up an enumerated type begin with a 2 letter prefix such asdt for drawing tool The declaration of the TDrawingTool type is equivalent to declaring a group of constants const dtLine 0 dtRectangle dtEllipse dtRoundRect iy I Nl 37 The main difference is that by declaring the enumerated type you give the constants not just a value but also a type which enables you to use Object Pascal s type checking to prevent many errors A variable of type TDrawingTool can be assigned only one of the Chapter 12 Graphics example 335 constants dtLine dtRoundRect Attempting to assign some other number even one in the range 0 3 generates a compile time error gt You can now add a
545. rawing in response to other events Using the pixel array Every canvas has an indexed property called Pixels that represents the individual colored points that make up the image on the canvas You rarely need to access Pixels directly unless you need to find out what color a particular pixel is or to set that pixel s color It s more important to understand that Pixels is the drawing surface of the canvas and that the pen and brush are just convenient ways to manipulate groups of pixels This section describes e Manipulating pixels e Using pens e Using brushes Manipulating pixels You can treat the pixels of a canvas like a two dimensional array with each element in the array having a particular color You can either read or set individual pixels Reading a pixel s color m To retrieve the color of a particular pixel you access the Pixels property of the canvas using as indexes the x and y coordinates of the pixel you want to read The upper left corner of the canvas is the origin of the coordinate system 314 Delphi User s Guide For example the following event handler responds to a click on a check box by changing the color of the text in the check box to the color of the pixel at the point 10 10 in the form procedure TForml CheckBoxlClick Sender TObject begin CheckBoxl Font Color Canvas Pixels 10 10 end Setting a pixel s color To set a pixel s color you assign a color value to the Pixels pro
546. raws lines no matter what tool is selected 336 Delphi User s Guide UY UY UY Using the drawing tools Now that the application has the ability to specify different drawing tools you need to make the event handlers apply the tool the user selects which you ve stored in DrawingTool Your code now needs to choose how to draw based on the selected tool This section describes e Making efficient choices e Drawing the appropriate shapes e Adding a method to a form Making efficient choices If you had only a few choices you d probably just rewrite the drawing methods to look something like this procedure TForml FormMouseUp Sender TObject begin if DrawingTool dtLine then draw a line else if DrawingTool dtRectangle then draw a rectangle oega NG SOOM aan end The comments like draw a line of course represent blocks of statements such as those you wrote earlier to draw a line Once you get more than a few choices though this becomes tedious and inefficient Fortunately Object Pascal and Delphi offer an easier way to switch among alternatives the case statement Among other things case statements make it easier to add new choices later The method shown above could be rewritten using acase statement instead of the if then else statements procedure TForml FormMouseUp Sender TObject begin case DrawingTool of dtLine draw a line dtRectangle draw a rectangle E aas ANG EO O aa
547. re about TForm and objects derived from other objects 216 Delphi User s Guide Recall that an object is like a record in that they both contain data fields but an object also contains methods code that acts on the object s data So far type TForm1 appears to contain no fields or methods because you haven t added to the form any components the fields of the new object and you haven t created any event handlers the methods of the new object As discussed later TForm1 does contain fields and methods even though you don t see them in the type declaration This variable declaration declares a variable named Form of the new object type TForm1 var Forml TForml Form is called an instance of the type TForm1 The Form1 variable refers to the form itself to which you add components to design your user interface You can declare more than one instance of an object type You might want to do this to manage multiple child windows in a Multiple Document Interface MDI application for example Each instance carries its own data in its own package and all the instances of an object use the same code Although you haven t added any components to the form or written any code you already have a complete Delphi application that you can compile and run All it does is display a blank form because the form object doesn t yet contain the data fields or methods to do more Suppose though that you add a button component to this for
548. re information about this event For example to create a link from a DDEServerltem component named DDEServerItem1 to a WordPerfect 6 0 document perform the following steps If you don t have WordPerfect installed this example is worth examining because the steps required are similar for any other DDE client application that can paste links 1 Atrun time your DDE server application should execute the following code DDEServerItem1 CopyToClipboard 2 Activate WordPerfect and choose Edit Paste Special The WordPerfect Paste Special dialog box appears Figure 14 3 The WordPerfect Paste Special dialog box Paste Special Source DDESERY DdeServerConyl Dd 1 eServer Data Type Unformatted Text 3 Choose Paste Link The Paste Special dialog box closes and the linked text from the Text or Lines property of DDEServerItem1 appears at the insertion point in the WordPerfect document When the value of Text or Lines changes the text in the WordPerfect document is updated automatically Chapter 14 Exchanging data with DDE or OLE 389 Note The method for establishing a DDE link depends on the DDE client application See the documentation for the client for specific information about establishing DDE links If the DDE client is another Delphi application refer to Establishing a link with a DDE server on page 384 E One way to process linked text data is to keep the client updated to changes in an edit box Edit com
549. re is another way to share event handlers When components have events in common you can select the components to display their shared events select a shared event and then create a new event handler for it or select an existing one All the selected components will now use this event handler To demonstrate this you ll add a speed button to MainForm that calls the same OnClick event handler as Button1 and Button2 Then you ll modify the shared event handler to display a different icon in the About box Image component To display shared events 1 Inthe form select all the components whose common events you want to view 2 Display the Events page of the Object Inspector The Object Inspector displays only those events that pertain to all the selected components Note also that only events in the current form are displayed To associate a shared component event with an existing event handler 1 Select the components with which you want to associate a shared event handler 2 Display the Events page of the Object Inspector and select an event The Object Inspector displays only those events which the selected components have in common Chapter 2 Using components and code 65 3 From the drop down list next to the event select an existing event handler and press Enter Whenever any of the components you selected receives the specified event the event handler you selected is called E To create an event handler for a shared event
550. re the public directive that s where it puts the fields that represent controls and the methods that respond to events To give a form a field called Drawing of type Boolean you edit the form object s declaration as follows type TForml class TForm procedure FormMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer procedure FormMouseUp Sender TObject Button TMouseButton Shift TShiftState X Y Integer procedure FormMouseMove Sender TObject Button TMouseButton Shift TShiftState X Y Integer public Drawing Boolean field to track whether button was pressed end 326 Delphi User s Guide gt You ll add several more fields to the graphics form as you work on this example In fact you re going to need two fields of type TPoint so go ahead and add one called Origin and one called MovePt in addition to Drawing type TForml class TForm procedure FormMouseDown Sender TObject Button TMouseButton Shift TShiftState X Y Integer procedure FormMouseUp Sender TObject Button TMouseButton Shift TShiftState X Y Integer procedure FormMouseMove Sender TObject Button TMouseButton Shift TShiftState X Y Integer public Drawing Boolean Origin MovePt TPoint fields to store points end gt Now that you have the Drawing field to track whet
551. re the rest of the application runs 208 Delphi User s Guide How units are used To use another unit you need to add the name of that unit to the uses clause of your current unit Delphi does this automatically when you add new components to a form you are designing If you add a component declared in a unit that isn t already in the standard Delphi uses clause Delphi adds the unit name to the uses clause for you For example if you add a color grid to a form Delphi attaches ColorGrd to the end of the unit s uses clause This makes all the declarations in the ColorGrd unit available to the unit associated with the form A few objects declared in units have no corresponding visual components in the Delphi environment however For example if you want to use predefined message boxes in the code within a unit you must add the MsgDig unit to the uses clause yourself The same is true if you want to use the TPrinter object in the Printers unit To add a unit name to the uses clause put the unit name before the semicolon that ends the uses clause separating the unit name from the previous unit name in the clause with a comma To use a routine declared in another unit preface the name of the routine with the name of the unit in which it is declared For example to call a ComputePayment function declared in Unit1 from Unit2 make the call like this Amount Unitl ComputePayment 1000 085 242 You can preface any ident
552. ready checked 3 Choose OK to close the Environment Options dialog box Desktop Contents option The setting of this option in the Environment Options dialog box controls what desktop information is saved when you choose File Save Project or exit Delphi It also affects your ability to use the ObjectBrowser which enables you to step through the object hierarchies units and global symbols in your application For more information on using the ObjectBrowser see online Help Desktop Only Choosing this option saves directory information open files in the Code Editor and open windows Desktop And Symbols Choosing this option saves the same information as the Desktop Only option plus symbol information from the last successful compilation The ObjectBrowser uses this symbol information to construct the object hierarchy of your application If you plan to use the ObjectBrowser to analyze your application you should choose this Environment option Autosave Options These options enable you to specify what files and options are automatically saved when you test run your program from within Delphi and when you exit Delphi Editor Files Choosing this option saves all modified files in the Code Editor The advantage of this option is that changes to your code are saved whenever you test run your program Desktop Choosing this option saves the arrangement of your desktop Subsequent Delphi work sessions display the same desktop as the cu
553. ress indicator for your application Y BiPict Display a bitmap icon or metafile Y Chart Provide charting capability Table 2 8 Components on the Samples page Visual Componentname Use to Icon Y Gauge Display a bar text or pie shaped gauge that serves as a progress indicator Y ColorGrid Enable the user to select colors for the elements in the application y SpinButton Provide a means for the user to quickly increment or decrement a value in an edit box Y SpinEdit Provide an integrated combination of a spin control and an edit box Y DirectoryOutline Provide a hierarchical listing of the current drive s directory structure y Calendar Provide a simple monthly calendar grid Note The components on the VBX and Samples page are not included in the Delphi Visual Component Library VCL They are provided as examples only and are not formally documented as part of the core product All components in the VCL are fully documented in online Help For more information press F1 with a component selected in the form Installing additional components The components displayed in the Component palette reflect the contents of a library file that Delphi maintains initially called COMPLIB DCL You can customize this library and therefore what is displayed on the palette by adding or removing components from the file Whenever you customize the library Delphi rebuilds the library file You can also install components such as Mic
554. ring the debugging session Specifying program arguments If the program you want to debug uses command line arguments you can specify those arguments from within Delphi E To specify command line arguments for your application 1 Choose Run Parameters 2 Inthe Run Parameters dialog box type the arguments you want to pass to your program when you run it under the control of the integrated debugger 3 Choose OK 250 Delphi User s Guide Controlling program execution The most important property of a debugger is that it lets you control the execution of your program you can control whether your program executes a single line of code an entire function or an entire program block By dictating when the program should run and when it should pause you can quickly move over the sections that you know work correctly and concentrate on the sections that are causing problems The integrated debugger lets you control the execution of your program in the following ways Running to the cursor location Stepping and tracing Running to a breakpoint Pausing your program When running code through the debugger all program execution is based on lines of source code The integrated debugger lets you control the rate of debugging to the level of a single line of code However the debugger considers multiple program statements on one line of text to be a single line of code you cannot individually debug multiple statements contained on a single
555. rm Templates 2 On the Templates page use the arrow keys or the mouse to select the template you want to add and choose OK Delphi adds a copy of the template form and its associated unit file to the project you have open You can now use this form the way you would any form ina project You 78 Delphi User s Guide can customize it add components and code to it and so on Any modifications you make do not affect the original template Note With no project open it is still possible to choose File New Form and select a Form Template from the Gallery The form s unit file then opens as a reference file see the following section If you subsequently open a project or create a new project the open template form is not part of that project To save it as part of the project save the open unit file under a different name File Save File As Opening a Form Template for reference only You can open a Form Template or any form in any project as a standalone form for reference purposes only without adding the form to your current project E To open a Form Template as a separate form and unit file 1 Choose File Open File to display the Open File dialog box 2 Switch to the DELPHI GALLERY directory and select the PAS file that corresponds to the template you want to open The Form Template opens and you can view it or its associated unit source code but it is not included in your project When you run your pr
556. rm itself is selected no other components can be selected along with it E To select all components in a form choose Edit Select All Resizing components in the form When a component is selected on a form small squares called sizing handles appear on the perimeter of the component You can use these handles to resize one or more components Figure 2 3 Sizing handles Buttoni Resizes the button horizontally Resizes the button both horizontally and vertically Resizes the button vertically m To resize a single component select the component on the form and drag a sizing handle until you are satisfied with the component s size When you release the mouse button the component is redrawn in the new size E To resize multiple components 1 Select the components you want to resize as a group 2 Choose Edit Size to display the Size dialog box 3 Select appropriate sizing options then choose OK 46 Delphi User s Guide Adda Panel component from the Standard page of the Component palette then resize it so that it fills most of the form without covering the other components as shown in the following figure Figure 2 4 Form with Panel component Panell Adding multiple copies of a component You can easily add more than one copy of the same type of component to a form by pressing the Shift key before selecting the component The component remains selected until you select the pointer icon on the
557. ro Notebook O Create from File Result ja Inserts a new Paintbrush Picture object into your document Note InsertOLEObjectDig is an independent function not a method of the OLEContainer component 410 Delphi User s Guide To see the parameters used with InsertOLEObjectDlg examine its declaration function InsertOleObjectDlg Form TForm HelpContext THelpContext var PInitInfo Pointer Boolean The parameters of InsertOLEObjectDlg are as follows e Form is the form that owns the Insert Object dialog box In the Form parameter pass the name of the form that contains the OLEContainer component e HelpContext is used to identify the Insert Object dialog box for online Help If your application is not programmed for online Help pass 0 zero for HelpContext Then a Help button won t appear in the Insert Object dialog box Pass an integer other than 0 to use HelpContext as the context sensitive online Help identification number for the dialog box e PInitInfo is a pointer to an internal data structure of OLE initialization information necessary to initialize the OLE container The internal details of the data structure are not documented here as this information is meaningful only to the OLE container component InsertOLEObjectDlg modifies this pointer so that it points to a valid structure containing initialization information for the OLE object selected in the Insert Object dialog box After the pointer has been used you
558. rosoft Visual Basic VBX controls and other third party components onto the palette Installing components is described in the section Customizing the Delphi Visual Component Library VCL on page 68 42 Delphi User s Guide Manipulating components in your forms Note This section demonstrates fundamental skills you need as you work with the components in your forms If you re comfortable using controls in a graphical user interface GUI environment much of the material discussed here such as selecting sizing and deleting components and so on might be familiar to you You might not be familiar however with how to perform some of these common operations within the Delphi environment This section shows you how to do so In the context of designing a reusable About box this section describes such skills as Setting form properties Adding components to the form Selecting components in the form Grouping components Cutting copying and pasting components Deleting and restoring components Aligning components Controlling the creation order of nonvisual components Keyboard support is available for many of the tasks documented here For more information about keyboard techniques the online Help topic Form Keyboard Shortcuts Figure 2 1 About box Project Version 1 0 Copyright 1994 Borland International This is atest This is only a test To begin designing the About box start a new project 1
559. rrent session Form Designer options grid These options control whether the form grid is displayed whether components snap to the nearest x y grid position and the spacing of the grid positions For information on using the grid feature search online Help for the topic aligning components Chapter 1 Introducing Delphi 31 Debugging options These options control debugging processes in the environment Integrated Debugging Enables the Delphi integrated debugger in the environment Check this option unless working exclusively with programs that have already been debugged Step Program Block This option causes the integrated debugger to stop at the first unit initialization containing debug information Break On Exception Choosing this option causes a running application to stop if an exception occurs and displays the exception class message and location This provides a means for you to step through the exception handlers as if going through the code sequentially Minimize On Run Choosing this option minimizes the Delphi IDE whenever you run an application from within Delphi The IDE returns to a normal state when the running application terminates Compiling option Delphi can display a dialog box showing the progress of the compiler as it compiles your program To enable this display check the Show Compiler Progress check box in the Environment Options dialog box Enabling this option makes the Cancel button in the
560. rs and name them PenBar and BrushBar Figure 12 11 shows the tool bars and their controls Note that they use other controls in addition to speed buttons a color grid a scroll bar and a label in the case of PenBar and a color grid in BrushBar You can put any kind of controls on a tool bar Add controls to PenBar and BrushBar and name them as shown in the following figure then set the values of properties as shown in Table 12 2 Figure 12 11 The pen and brush tool bars DashDotDotPen DashDotPen DotPen DashPen SolidPen 4 4 4 SolidBrush m ENA ClearBrush DiagCrossBrush HorizontalBrush CrossBrush VerticalBrush BDiagonalBrush FDiagonalBrush Table 12 2 Property settings for pen and brush tool bars Component Property Value SolidPen Glyph SOLID BMP Down True DashPen Glyph DASHED BMP DotPen Glyph DOTTED BMP DashDotPen Glyph DASHDOT BMP DashDotDotPen Glyph DASHDOT2 BMP ClearPen Glyph CLEAR BMP PenColor BackgroundEnabled False GridOrdering g08x2 Height 30 Top 5 Width 144 PenWidth LargeChange 10 Top 12 PenSize FocusControl PenWidth Caption 1 Top 13 SolidBrush Glyph FSOLID BMP Down True ClearBrush Glyph FCLEAR BMP HorizontalBrush Glyph FHORIZ BMP VerticalBrush Glyph FVERT BMP FDiagonalBrush Glyph FDIAG BMP BDiagonalBrush Glyph BDIAG BMP CrossBrush Glyph CROSS BMP DiagCrossBrush Glyph DCROSS BMP Chapter 12 Graphics example 341 Table 12 2 Property settings
561. rs See media players MDI applications 96 98 child windows 280 287 accessing 287 288 adding 281 401 404 at run time 285 closing 309 310 closing 309 312 defined 280 displaying documents 288 298 entering text 288 295 main form 400 401 creating 281 defined 280 menus adding 282 284 288 294 merging 111 283 284 402 specifying active 111 OLE example 399 427 parent child relationships 97 text editor example 279 312 measure item events 367 See also owner draw controls Media Control Interface drivers See media players media players 41 MediaPlayer component 41 Memo component 38 288 memory 52 234 addresses 154 allocating 113 229 234 235 character strings 201 string lists 273 checking 262 deallocating 229 234 235 273 uninitialized 238 memos 38 changing 300 creating 288 data aware 40 entering text 83 269 289 295 loading text 300 printing 305 309 selected text 307 saving 301 310 menu bars 38 See also menus MDI applications 282 288 moving items 104 menu commands See also menu items SpeedMenus accessing 292 shortcuts 12 menu components 99 109 adding 100 Menu Designer 13 99 100 109 SpeedMenu 105 106 menu items 101 103 adding 101 110 check marks and 289 defined 99 deleting 102 105 editing 105 enabling disabling 292 370 grouping 102 moving 104 naming 101 108 nesting 103 placeholders 105 selecting 109 292 separator bars 102 setting properties 104 105 specifying shortcuts 102 103 Menu prop
562. rs discuss how to build a user interface for your application by adding components to forms They describe how to create event handlers for those components so the components can respond to events that occur as your application runs This chapter explains the primary features of the Object Pascal language and shows you how to use it to write code within event handlers and other parts of your application After reading this and the following chapter Programming with Delphi objects you should be able to develop useful and more sophisticated Delphi applications This chapter assumes you already have some programming experience You certainly don t have to be an expert however If you ve programmed successfully in any of the popular programming languages you ll recognize common concepts in Object Pascal While the chapter does show you the most common uses of Object Pascal in a Delphi application it doesn t explain all there is to know about the language You can find in depth information about Object Pascal in Delphi s online Help look up the Language Definition topic The information there includes syntax diagrams of all Object Pascal language constructs You might also want to read one or more of the excellent books published about Pascal especially those that discuss Delphi Turbo Pascal and Borland Pascal If you are familiar with Borland Pascal language already you can probably either skim this chapter rapidly or skip it alt
563. rt can be used only by the code contained within that unit You can set up procedures and functions so that code in other units can use the procedures and functions you write To make a procedure or function available to other units 1 Put the header of the procedure or function in the interface part of the unit By placing the header in the interface part you are declaring the routine in the interface part thereby making the routine available to any unit that uses this unit 2 Place the entire procedure or function repeating the header in the implementation part of the unit 3 Add the name of the unit in which you declared the routine to theuses clause of the unit that needs to access the routine You can read more about units the uses clause and how to use routines declared in other units in the section Understanding Object Pascal units on page 206 For example the NoValue function described on page 184 could be declared in the interface part of the unit Then you could place the body of the routine or its Chapter 5 Writing Object Pascal code 187 implementation in the implementation part of the unit This is a skeleton of how the unit would look unit Uniti interface uses type TForml class TForm Multiply TButton Divide TButton procedure MultiplyClick Sender TObject procedure DivideClick Sender TObject end var Forml TForml function NoValue AnEditBox TEdit Boolean implementatio
564. rties you will set for the About box You can also change property values while an application is running This is discussed in the section Setting properties at run time on page 59 For more information about the properties for each component search online Help for the keyword components or see the topic Visual Component Library Components and select the component whose properties you want to view You can also press F1 with the component selected in the form The components on the VBX and Samples page of the palette are provided as examples only not formally part of the Delphi VCL and therefore are not documented as part of Delphi Table 2 9 AboutBox component properties Component Property Value Panel Name BackgroundPanel BevelOuter buLowered Caption lt Blank gt Image Name ProgramlIcon Label1 Name ProductName Label2 Name Version Label3 Name Copyright Label4 Name Comments AutoSize False WordWrap True bitbtn Name OKButton Kind bkOK Change the Name property for all the components in the form as specified in Table 2 9 Notice that as you move from component to component the Name property remains selected in the Object Inspector Set the remaining properties as noted for BackgroundPanel Comments and OKButton Chapter 2 Using components and code 53 How the Object Inspector displays properties As discussed earlier the Object Inspector dynamically changes the set of properties it displays based on the c
565. rty by enclosing the sequence of characters that make up the string in single quotation marks or apostrophes For example 200 Delphi User s Guide MyName Frank P Land Labell Caption File name Because MyName is a variable of type MyString which holds 15 characters the MyName variable is stored in memory as if the string were Frank P Land If you assigned the string Frank P Borland to the MyName variable MyName would contain the string Frank P Borlan because the MyName variable can hold only 15 characters Object Pascal strings are stored as arrays of characters in memory but the arrays are actually one byte bigger than size of the specified string The first position of the string 0 is a byte that contains the size of the string Because strings are arrays of characters you can access characters within a string with an index value just as you would in an array For example MyName 1 refers to the first letter contained in the MyName string variable You can use Object Pascal s rich assortment of operators procedures and functions to manipulate variables and properties of string types Here are some examples of string handling routines in the run time library Table 5 2 String procedures and functions Routine Description Concat Concatenates multiple strings creating a larger string You can also concatenate strings together using the plus sign Copy Returns a substring within
566. s You can also work with string lists at run time These are the most common types of string list tasks Manipulating the strings in a list Loading and saving string lists Creating a new string list Adding objects to a string list Manipulating the strings in a list Quite often in an Delphi application you need to write code to work with strings in an existing string list The most common case is that some component in the application has a string list property and you need to change it or get strings from it These are the common operations you might need to perform e Counting the strings in a list e Accessing a particular string Chapter 9 Working with string lists 269 Finding the position of a string Adding a string to a list Moving a string within a list Deleting a string from a list Copying a complete string list Iterating the strings in a list Counting the strings in a list E To find out how many strings are in a string list use the Count property Count is a read only property that indicates the number of strings in the list Since the indexes used in string lists are zero based Count is one more than the index of the last string in the list For example an application can find out how many different fonts the current screen supports by reading the Count property on the screen object s font list which is a string list containing the names of all the supported fonts FontCount Screen Fonts Count Access
567. s For example in the previous example the block of the Button1Click event handler exists within the unit block which exists within the project block Here is a visual representation of the blocks within the application so far Figure 5 11 Blocks within blocks Project block Unit1 block Button1Click event handler block 176 Delphi User s Guide All Delphi applications have the same basic structure As your application becomes more complex you are adding new blocks of code such as new event handlers to a unit or new units to a project Understanding scope The scope of a variable constant method type or other identifier defines where the identifier is active The identifier is local in scope to the smallest block in which it is declared When your application is executing code outside the block in which an identifier is declared that identifier is no longer in scope That means the identifier is no longer available to the executing code Only when code execution reenters the same block as the identifier declaration can the code access the identifier again You were introduced to blocks in the previous section Imagine that you have a project that contains two units Each of those units contains three event handlers or procedures Here is your project depicted graphically Figure 5 12 Blocks within a simple project Projectt Unit A nit B U Each rectangle in the diagram represen
568. s If the Source is an OLE object it is a descendant of type TOLEDropNotify TOLEDropNotify objects have a PInitInfo property that corresponds to the PInitInfo property of TOLEContainer components To use the Source OLE object you should typecast it as a TOLEDropNotify object E To initialize an OLEContainer component when an OLE object is dropped assign the value of the PInitInfo property of the Source object typecast as a TOLEDropNotify object to the PInitInfo property of the OLEContainer component in the OnDragDrop event handler Note You don t need to use ReleaseOLEInitInfo to release memory allocated for the PInitInfo property of the Source object Delphi does this for you automatically 422 Delphi User s Guide Attach the following code to the OnDragDrop event handler of OLEFrameForm This code creates a new OLEObjectForm and initializes its OLEContainer procedure TOLEFrameForm FormDragDrop Sender Source TObject X Y Integer var NewChild TOLEObjectForm begin if Source is TOLEDropNotify then begin NewChild CreateChild with Source as TOLEDropNotify do NewChild OLEContainer PInitInfo PInitInfo end end Note To use the TOLEDropNotify object the TOCtrl unit must be referenced in the uses clause of the unit Since you already added this reference for OLEFrame in order to call BOLEMediumCalc nothing needs to be done to the OLE example application For other applications remember to refer to TOCtr1 gt
569. s Line write the contents of the Memo to the printer object CloseFile PrintText end end Your application now has the ability to print a text file gt Save and run the application and test its printing capability Exiting gracefully Applications that enable users to modify and save data into files should include safeguards so that users do not lose their work The text editor application for example creates a backup file every time the user saves an existing file Other important safety measures involve responding to a file or application close event making sure that modified files are not closed without giving the user the option to save changes So far you ve given users the ability to open save and print their text files but not the ability to close them In Delphi closing a child window involves the same process as closing the main MDI application window In both cases you use the Close method of TForm The Close method executes your form s OnCloseQuery event handler code which returns a Boolean value for the CanClose parameter If CanClose returns True then the Close method executes your form s OnClose event handler code You should ensure that the code you write for the OnCloseQuery event handles any changes made to the text file before the window closes This section discusses e Closing a window e Determining whether the file has been modified e Exiting the application Closing a wind
570. s bar Components on the Additional page Visual Y Y Component name BitBtn SpeedButton TabSet Notebook TabbedNotebook MaskEdit Outline StringGrid DrawGrid Image Shape Bevel Header ScrollBox Use to Provide a button that can receive and display a bitmap Provide a button that can be added to a Panel component to create a tool bar Speed buttons have some unique capabilities that allow them to work as a set Create notebook tabs that give your form the appearance of having pages Often used with the Notebook component Provide a stack of multiple pages often used with the TabSet component Create a multi page form with page tabs at the top Format the display of data or limit user input to valid characters Display information in a variety of outline formats Provide a means for handling strings in columns and rows Provide a means for displaying non textual information in columns and rows Display a bitmap icon or metafile Draw geometric shapes an ellipse rectangle or rounded rectangle Provide a rectangle the single lines or entire border of which can appear raised or sunken Provide a sectioned visual control that displays text and allows each section to be resized with the mouse Provide a scrollable display area smaller than the form itself Scroll bars automatically appear at run time if the size of the display exceeds the size of the scroll box Chapter 2 Using compone
571. s depending on which control called it E To share an event handler you assign the same event handler to the events of multiple controls If you need to determine which control actually got the event check theSender parameter In this example you ll create a click event handler for all the pen style buttons on the pen s tool bar attach the handler to each of the controls then use Sender to determine which button to respond to 1 Select all six pen style buttons 2 On the Events page in the Object Inspector select OnClick 3 In the Handler column type Set PenStyle and press Enter Delphi generates an empty click event handler called SetPenStyle and attaches it to the OnClick events of all six buttons 4 Fill in the click event handler by setting the pen s style depending on the value of Sender which is the control that sent the click event procedure TForml SetPenStyle Sender TObject begin with Canvas Pen do begin if Sender SolidPen then Style psSolid else if Sender DashPen then Style psDash else if Sender DotPen then Style psDot else if Sender DashDotPen then Style psDashDot else if Sender DashDotDotPen then Style psDashDotDot else if Sender ClearPen then Style psClear end end Changing the pen color A pen s color determines the color of the lines the pen draws including lines drawn as the boundaries of shapes as well as other lines and polylines E Tochange
572. s have Maximize and Minimize buttons a resizable border and a Control menu that provides additional commands to resize the form While these features are useful at run time for modeless forms modal dialog boxes seldom need them Delphi provides a BorderStyle property for the form that includes several useful values Setting the form s BorderStyle to bsDialog implements the most common settings for a modal dialog box such as e Removing the Minimize and Maximize buttons e Providing a Control menu with only the Move and Close options e Making the form border non resizable and giving it a beveled appearance 86 Delphi User s Guide Note The following table shows other form property settings that can be used individually or in concert to create different form styles Table 3 2 Alternate form settings Property Setting Effect BorderlIcons biSystemMenu False Removes Control System menu biMinimize False Removes Minimize button biMazimize False Removes Maximize button BorderStyle bsSizeable Enables the user to resize the form border bsSingle Provides a single outline non resizable border bsNone No distinguishable border not resizable Changing these settings doesn t change the design time appearance of the form these property settings become visible at run time Specifying a caption for the dialog box In most Windows based applications each dialog box has a caption on its title bar that describes the primary function of
573. s important last minute information about Delphi It s a good idea to read README TXT before running Delphi for the first time Introduction 1 Documentation overview Delphi includes complete documentation to help you learn to use the product quickly and effectively The Delphi documentation consists of three parts e Printed manuals e Online Help e Interactive Tutors Using this manual e Part I Getting started with Delphi introduces you to the kinds of tasks you ll perform when designing and testing applications in Delphi e Part II Fundamental skills presents concepts and techniques you ll use in developing robust and sophisticated Delphi applications These skills are discussed in the context of creating simple but functional examples e Part III Programming topics discusses the language you ll use to write your applications how to work with objects and how to write robust applications by handling exceptions e Part IV Sample applications presents several complete sample applications demonstrating most of the tasks you ll perform when writing your own applications Reference material on Delphi and its component library appear in online Help The Delphi Component Writer s Guide and Database Application Developer s Guide are also printed separately They contain information on how to create your own components for use in Delphi and how to create database applications respectively Using
574. s not copied to the current project directory it remains in its current location Adding the shared file to the current project simply registers the file name and path in the uses clause of the project s DPR file Delphi automatically does this as you add units to the project The compiler treats shared files the same as those created by the project itself E To adda shared file to the current project do one of the following e Choose File Add File from the Delphi menu bar 134 Delphi User s Guide Caution e Choose the Add File button on the Delphi SpeedBar e Choose the Add button on the Project Manager SpeedBar e Choose Add File from the Project Manager SpeedMenu Any of these actions displays the Add To Project dialog box in which you can select the file you want the current project to use The Path column of the Project Manager s file list displays the path to the shared file Using Borland Pascal source code units If you have existing source code units for custom procedures or functions written in Borland Pascal or Turbo Pascal you can use these units in a Delphi project You add these files in the same way as files created in Delphi Removing constituent files from a project You can remove forms and units from a project at any point during project development The removal process deletes the reference to the file in the uses clause of the DPR file Note that using the following procedure to remove a unit that has an a
575. se variable Subrange types A subrange type is a range of values of any of these types integer Boolean Char or enumerated types Subranges are useful when you want to limit the number of values a variable can have To create a subrange specify the minimum and maximum values in the range with two periods in between them For example 1 100 Chapter 5 Writing Object Pascal code 197 Declare the subrange as a new type in a type declaration Here are some examples type TCompassRange 0 360 TValidLetter Arua eG TMonthlyIncome 10000 30000 THours e ee TPrecipitation Drizzle Showers Rain Downpour Thunderstorm an enumerated type TRain Drizzle Downpour a subrange of TPrecipitation Here is a simple application that uses a new subrange type 1 Place an edit box and a button on a form Place a label above the edit box and put a second label beneath the edit box 2 Using the Object Inspector change these properties e Delete the text specified as the value of the Text property for the edit box e Change the Caption value for the Labell label to Enter a number between 1 and 100 e Delete the text specified as the value of the Caption property for the Label2 label e Change the Default property of the button to True Your form should look like this Figure 5 22 A form for a subrange example Form1 3 Create this event handler for the button s OnClick event procedure TForml Buttoni
576. se File Open File and select the ABOUT PAS file in the DELPHI GALLERY directory This chapter discusses the following topics Delphi components Manipulating components in your forms Setting component properties Working with code Customizing the Delphi Visual Component Library VCL Delphi components The pages of the Component palette display the components Delphi provides to enable you to quickly develop powerful and diverse applications A large part of interface design consists of using these components to customize the forms that make up your application Delphi components include both visual and nonvisual types Visual components appear essentially the same in your form at design time as they do at run time Nonvisual components on the other hand are not visible on the form at run time The MainMenu and Timer components are two examples of nonvisual components The MainMenu component appears as an icon in your form at design time to give you access to the Menu Designer but at run time only the menu you ve designed is visible not the Chapter 2 Using components and code 37 component A Timer component on the other hand provides a visual representation at design time of the function that timers provide to your application a means of triggering events at measured intervals while at run time the timer measures the intervals but is not a visible part of your interface The form component The form is a component tha
577. sible and causes a type mismatch error if you try to run or compile it Edit1 Text Sum Instead the last line of the event handler uses the IntToStr function from the Delphi run time library to convert the Sum value to a text string then assigns the value of the Sum variable to the Edit1 Text property This variation avoids the assigning of a value to Sum altogether procedure TForm1 AddButtonClick Sender TObject var X Y Integer Chapter 5 Writing Object Pascal code 155 begin Loe 100s eal Editi Text a IneTosrr 47 end Using functions in your code is discussed in more detail in the section Calling functions on page 161 but it s useful to know that functions return a value of a particular type and that value can then be assigned to a variable or property Data types Object Pascal has several data types built into the language You can create variables of any of these predefined types The following table lists the predefined data types Table 5 1 Object Pascal predefined data types Category Datatype Description Integer Integer Numbers without a fractional part within the range of 32768 to 32767 Requires two bytes of memory Shortint Numbers without a fractional part within the range of 128 to 127 Requires only one byte of memory Longint Numbers without a fractional part within the range of 2147483647 to 2147483647 Requires four bytes of memory Byte Numbers without a fractional part within
578. sion of the Edit component Provide a data aware version of the Memo component Provide a data aware version of the Image component Provide a data aware version of the ListBox component Provide a data aware version of the ComboBox component Provide a data aware version of the CheckBox component Provide a data aware version of the RadioGroup component Provide a list box type lookup list with values from a secondary table Provide a combo box type lookup of values from a secondary table Table 2 5 Components on the Dialogs page Icon Visual Componentname Use to N OpenDialog Make the Windows Open common dialog box available to the application SaveDialog Make the Windows Save File common dialog box available to the application Ege e w e e E a a E E i FontDialog Make the Windows Font common dialog box available to the application ColorDialog Make the Windows Color common dialog box available to the application PrintDialog Make the Windows Print common dialog box available to the application PrinterSetupDialog Make the Windows Printer Setup common dialog box available to the application FindDialog Make the Windows Find common dialog box available to the application an ReplaceDialog Make the Windows Replace common dialog box available to the application Table 2 6 Components on the System page Icon Visual Componentname Use to N Timer Provide a measured time interval that can be tied to events PaintBox
579. sn t need any information about an exception other than its type so the statements following on do are specific only to the type of exception In some cases however you might need some of the information contained in the exception instance To read specific information about an exception instance in an exception handler you use a special variation of on do that gives you access to the exception instance The special form requires that you provide a temporary variable to hold the instance If you create a new project for example that contains a single form you can add a scroll bar and a command button to the form Double click the button and add the following line to its click event handler ScrollBarl Max ScrollBarl Min 1 That line raises an exception because the maximum value of a scroll bar must always exceed the minimum value The default exception handler for the application opens a dialog box containing the message in the exception object You can override the exception handling in this handler and create your own message box containing the exception s message string try ScrollBarl Max ScrollBarl Min 1 except on E EInvalidOperation do MessageDlg Ignoring exception E Message mtInformation mbOK 0 end The temporary variable E in this example is of the type specified after the colon EInvalidOperation in this example You can use the as operator to typecast the exception into a more specific type
580. ss Servers simply update clients E To create a DDE server add a DDEServerltem component to a form The Text or Lines properties of the DDEServerltem component contain the data to link Your server application continuously updates all clients with the value of theText or Lines properties As with the DDEClientItem component Text specifies a string while Lines specifies a TStrings object If the text to exchange is longer than 255 characters use the Lines property to specify the data When either Text or Lines is modified the other is automatically updated to reflect the change The value of Text always equals the value of the first line of Lines Optionally you can add a DDEServerConv component and link the DDEServerltem and DDEServerConv together When you add a DDEServerConv component the DDE topic becomes the name of the DDEServerConv component instead of theCaption of the form containing the DDEServerltem component You should use a DDEServerConv component in the following situations e The value of the Caption property of the form containing the DDEClientItem component might change or might not be unique at run time If this value is not unique or constant the link might not be able to be established e The DDE client might send a macro to your server application for processing If this happens an OnMacroExecute event of the DDEServerConv component occurs The OnMacroExecute event contains a string parameter that specifies the
581. ssage so you can correct the problem Languages that aren t compiled can t protect you from assigning a value of a wrong type a common programming mistake Object Pascal is known as a strongly typed language Also because Object Pascal is a compiled language your Delphi applications will run much faster than applications you build with an interpreted language Declaring Chapter 5 Writing Object Pascal code 153 identifiers before you use them reduces the number of programming errors and increases the efficiency of your code Declaring variables A variable is a name in code that stands for a memory address the contents of which can change as the code runs You need to declare a variable before using it There are two steps in declaring a variable 1 Naming a variable 2 Giving a variable a type Naming a variable When you declare a variable you need to select a name for it You should try to select a name that reminds you of the variable s purpose so your code is easier to read For example Day Name and Total are more memorable names than X Y and Z Beyond choosing meaningful names for your variables you should remember a few rules that apply to variables and all other identifiers e Identifiers can be up to 63 characters in length If your identifiers are longer than 63 characters the compiler ignores the extra characters e Identifiers must begin with either a letter or an underscore _ character e Subsequent
582. ssociated form file removes the form file as well To remove a unit from a project open the project and choose any of these methods e In the Project Manager window e Select the unit or units you want to remove then choose the Remove button on the Speed Bar e Select the unit or units you want to remove then choose Remove File from the SpeedMenu e Choose the Remove File button on the Delphi SpeedBar e Choose File Remove File from the Delphi menu bar Removing a file from the project ends its relationship with the project it does not delete the file from disk Use the Windows File Manager or another utility to delete unwanted files from disk Do not use Windows file management programs or DOS commands to delete Delphi project files from disk until you have performed the preceding removal process in every Delphi project that uses the files Otherwise the project DPR file of each project using the deleted files retains references to them in the uses clause When you open the project again Delphi attempts to find the deleted files and displays error messages for each file it cannot find When the project opens the information about its constituent files in the Project Manager is inaccurate Saving projects and individual project files At any time during project development you can save an open project in its current state to the project directory You can optionally save a copy of the project in a different directory under t
583. starting the debugger 249 250 starting the Project Manager 130 statements 186 assignment 151 153 enumerated types and 195 for loops vs 199 function calls 161 object variables 226 type compatibility 157 blocks 175 branching 162 163 167 case 337 checking 248 compound 165 exception handling 239 loop 168 174 arrays and 199 debugging 258 multiple 165 167 debugger and 251 nested for 172 174 Index 449 nested if 165 166 stepping over 252 stepping through 252 terminating character 151 165 with 225 226 status bars 39 345 347 adding panels 346 aligning text 346 file manager example 360 364 OLE example 409 410 Project Manager 131 subdividing 360 updating information in 347 status lines 47 Stdctrls unit 291 Step Over command Run 252 stepping through code debugger 252 253 statement by statement 252 to first executable statement 253 stopping project execution 253 264 Stored Procedure component 40 storing project files 115 116 132 streams 426 Stretch property 58 string arrays 171 270 string grids 39 269 displaying data 172 string lists 269 277 368 accessing strings 270 276 at run time 274 adding objects 275 276 366 367 copying 272 counting strings 270 creating 273 275 deleting strings 271 inserting strings 271 276 iterating 272 loading 272 locating specific string 270 271 276 manipulating strings 269 272 owner draw controls and 365 366 367 saving 272 string reserved word 200 string types 156
584. strings That is it must find an exact match for the whole string passed to it and it must match a complete string in the list If you 270 Delphi User s Guide want to match partial strings for instance to see if any of the strings in the list contains a given series of characters you must iterate the list yourself and compare the strings Here s an example of using IndexOf to determine whether a given file name is in the list of files in a file list box if FileListBoxl Items IndexOf AUTOEXEC BAT gt 1 then you re in the root directory Adding a string to a list There are two ways to add a string to a string list You can either add it to the end of the list or insert it in the middle of the list To add a string to the end of the list call the Add method passing the new string as the parameter The added string becomes the last string in the list To insert a string into the list call the Insert method passing two parameters the index where you want the inserted string to appear and the string To make the string Three become the third string in a list you would call Insert 2 Three If the list doesn t already have at least two strings Delphi raises an index out of range exception Moving a string within a list You can move a string to a different position in a string list such as when you want to sort the list If the string has an associated object the object moves with the string To mo
585. strings 271 276 clearing error conditions 232 Index 433 ClearSelection method memos 292 clicking mouse buttons 323 324 326 334 See also mouse events client server applications See DDE applications OLE applications Clipboard 291 292 DDE links and 384 389 formats 416 418 420 registering 417 418 returning 419 graphics and 354 356 testing for images 356 OLE objects and 394 415 421 testing for 420 Clipboard object 291 ClipBrd unit 354 Clipbrd unit 291 CLIPBRD PAS 291 clock 38 Close buttons 89 Close method forms 309 311 CloseQuery method 309 310 closing applications 350 file manager example 362 OLE example 404 text editor example 309 312 closing dialog boxes 87 closing windows 309 309 310 code 27 60 68 150 151 219 See also source code browsing 13 case sensitivity 150 comments in 150 controlling flow 163 174 editing 19 62 as ASCII text 94 event handlers 63 66 while debugging 255 262 264 executing repeatedly 168 indenting 150 165 line breaks 150 machine 210 249 optimizing 183 339 protecting 231 234 stepping through 252 253 statement by statement 252 to first executable statement 253 testing conditions 163 166 174 434 Delphi User s Guide viewing 12 79 139 Code Editor window 141 debugger and 251 shared events 65 specific event handlers 63 Code Editor 62 64 124 adding pages 62 closing pages 141 deleting breakpoints 256 event handlers and 60 63 64 65 moving through 62 overvie
586. t For an example of this try the following 1 Ona blank form add an Edit component a Button component and a Memo component 2 Set the component properties as follows Table 3 4 Property settings for demonstrating ActiveControl Component Property Setting Form1 ActiveControl Edit1 Edit1 Text lt blank gt Button1 Default True Button1 Caption OK 3 Write the following OnClick event handler for Button1 procedure TForml ButtoniClick Sender TObject begin Memol Lines Add Editl Text Editl Clear end 4 Run the program When the program starts the cursor is in Edit1 the active control for the form 5 Type some text in Edit1 and press Enter Because Button is the default button pressing Enter activates its OnClick event Saving a form as a template Once you ve designed a custom dialog box you might want to reuse it in other projects One convenient way to do this is to save it as a Form Template Saving a form as a template is similar to saving a copy of the form under a different name When you save a form as a template however it then appears on the list of templates displayed in the Browse Gallery You specify the bitmap and description of the template that appears in this template list To save your current form as a template 1 Right click the form to open the Form SpeedMenu 2 From the Form SpeedMenu choose the Save As Template command Chapter 3 Building forms and menus 93 The Save Form Templa
587. t Here are some rules about MDI parent and child forms e The MDI parent form must always be the application s main form If the MDI parent form isn t specified as the application s main form the application won t be correctly compiled Chapter 3 Building forms and menus 97 e There can be only one form of style fsMDIForm per application e The application s main form can never be of type MDIChild This would also prevent the application from being properly compiled e In general you should remove the MDI child form from the Auto create forms list on the Forms page of the Project Options dialog box This is because for true MDI applications you create multiple instances of a single child form at run time If on the other hand your application uses only one instance of each of several different types of child forms as might be the case in a database application you probably don t need to create each child form at run time In this case you needn t remove the forms from the Auto create list For more information about the Auto create forms list see Specifying forms to auto create on page 113 or search online Help for instantiating forms For more information about MDI applications see Chapter 10 which documents how to write the demo application TEXTEDIT DPR The next section describes the Delphi Menu Designer which you use to add menus to your forms For information about adding tool bars and status
588. t tResultName array 0 31 of char for paste special results box s if ole fmt tMedium BOleMedium based upon clip format id fmtIsLinkable Bool end The fields of BOLEFormat are as follows e fmtld is the Clipboard format ID of the object format fmtId can be the standard Clipboard formats such as CF_TEXT and CF_BITMAP See the HasFormat or Formats property in online Help for more information about standard Clipboard formats For OLE objects however you should register new Clipboard formats to handle OLE objects You do this with the RegisterClipboardFormat Windows API function td Eh Eh Eh Fh I 3 g 3 e fmtName is the name of the object This field specifies the name of the object to appear in the list box of the Paste Special dialog box For this example you should assign s to fmtName The format name from the OLE server application is automatically substituted for os for each object For example if the OLE server is Paintbrush Paintbrush Picture Object will be substituted for s at run time e fmtResultName specifies the name to appear in the Results box of the Paste Special dialog box For this example you should assign s to fmtResultName The format result name from the OLE server application is automatically substituted for s for each OLE object For example if the OLE server is Paintbrush Paintbrush Picture is substituted for os
589. t Editl Text SecondNumber StrToInt Edit2 Text Edit3 Text IntToStr FirstNumber div SecondNumber end e You can move the variable declaration part out of the MultiplyClick event handler to an area above all event handlers but after the implementation line and the R DFM directive Your code should look like this beginning with the implementation part implementation SR DFM var FirstNumber SecondNumber Integer Variables global to the event handlers procedure TForml MultiplyClick Sender TObject Multiplies two numbers together begin FirstNumber StrToInt Editl Text SecondNumber StrToInt Edit2 Text Edit3 Text IntToStr FirstNumber SecondNumber Displays result in Edit3 end procedure TForml DivideClick Sender TObject Divides first number by the second begin FirstNumber StrTolInt Editl Text SecondNumber StrToInt Edit2 Text Edit3 Text IntToStr FirstNumber div SecondNumber Displays result in Edit3 end If you choose the second method First Number and SecondNumber are no longer local in scope to the event handlers Because any event handler can now access these variables even those you might add in the future they are called global in scope or global variables The variables are local in scope to the unit however because the variables are declared within the unit block As stated earlier you should try to keep your variables as
590. t notepad InitialDir Read Only Filte rs List Files of Type Drives Filterlndex Text Files txt For the purposes of the text editor application you ll specify values only for the Filter property For information about the other properties of the OpenDialog component refer to online Help Add an OpenDialog component to FrameForm Name it OpenFileDialog Specifying file filters The List Files Of Type list box displays file types from which the user can select when specifying a file to open Only those files with the specified extension and in the current directory are displayed in the list box These file extensions are also known asfilters To create such a list of filters or valid file extensions you set the Filters property for the Open dialog box For more information about creating file filters see the online Help topic Filter Editor Chapter 10 Text editor example 297 The Filter property The Open dialog box includes a property named Filters which provides a quick way to specify both the types and the listed order of file filters In the Filter editor shown in the following figure you specify a description and the file extension that you want to be associated with each file type Figure 10 7 The Filter editor m Tospecify file filters 1 In the Object Inspector double click the Value column next to the Filter property or click the ellipsis button in the Value column 2 Specify
591. t can contain other components This makes it different from most other components and is what makes it useful to you as an area for designing your application interface There are other Delphi components that can act as containers within a form For more information see Grouping components on page 47 By default the form component doesn t appear on the Component palette However you can reuse a form by making it into a component that can be installed onto the Component palette For more information see the Delphi Component Writer s Guide Default Component palette pages The following tables illustrate the components as they initially appear on each page of the Component palette before any customizing you might choose to perform Note The pointer icon appears on each palette page When the pointer icon is selected the mouse cursor is shaped like an arrow enabling you to select from the components in the palette Table 2 1 Components on the Standard page Visual Componentname Use to N MainMenu Design a menu bar and its accompanying drop down menus for a form N PopupMenu Design pop up local menus available to forms and controls when the user selects the component and clicks the right mouse button Y Label Create a non windowed control that displays text such as titles that the user cannot access Usually this text labels some other control Edit Display an area where the user can enter or modify a single l
592. t environment supporting rapid development of highly efficient Microsoft Windows based applications with a minimum of coding Many of the traditional requirements of programming for Windows are handled for you within the Delphi class library shielding you from complicated or merely repetitive programming tasks Delphi provides design tools such as application and form templates so you can quickly create and test your application prototype Then by using Delphi s rich component set and intuitive code generation you can turn your prototypes into robust applications that fit your business needs Delphi s database tools enable you to develop powerful desktop database and client server applications and reports You can view live data at design time so you know immediately whether your query results are what you want This chapter introduces the following topics e The Delphi programming environment e Elements of the Delphi interface e The Delphi development model e Overview of Delphi projects e Setting environment preferences The Delphi programming environment This section briefly describes the elements of the Delphi programming environment You can also learn about Delphi by e Running the A Quick Look at Delphi Computer based Training choose Help Interactive Tutors from the Delphi menu bar e Viewing Help topics choose Contents or Topic Search from the Help menu Chapter 1 Introducing Delphi 7 e Choosing con
593. t identifier Application CreateForm TFormi Form Application CreateForm TForm2 Formz Application Run end 4 1 Modified Insert niti AProject A Unit2 Delphi added the identifier for the new unit Unit2 its file name UNIT2 PAS and the identifier for its associated form Form2 The unit PAS file The unit file is the Object Pascal source code file saved with a PAS extension Initially the unit file consists of e The default unit name Delphi provides all new units with a default name or unit identifier for example Unit1 or Unit2 The units in a template application have more descriptive identifiers for example MainForm You can change the name when you first save the project or at any time by choosing File Save As e An interface part that contains e The uses clause for the unit e The type declaration for the form e public and private sections e The declaration of an instance variable for the form Just as the uses clause in the DPR file lists the units in the project the uses clause in a PAS file lists all other units that are accessed in turn by this unit Whenever you generate a new default unit Delphi automatically adds the library units needed to the unit s uses clause For more information see page 25 24 Delphi User s Guide e An implementation part where the source code for the form appears e A program block containing initialization code Viewing the PAS file
594. t in the current font Your application can handle the event and change the rectangle Windows chose For example if you plan to substitute a bitmap for the item s text you d change the rectangle to be the size of the bitmap If you want the bitmap and text you adjust the rectangle to be big enough for both E Tochange the size of an owner draw item attach an event handler to the measure item event in the owner draw control Depending on the control the name of the event will vary List boxes and combo boxes use OnMeasureltem Tab sets use OnMeasureTab Grids have no measure item event The sizing event has two important parameters the index number of the item and the size of that item That size is variable the application can make it either smaller or larger The positions of subsequent items depend on the size of preceding items For example in a variable owner draw list box if the application sets the height of the first item to five pixels the second item starts at the sixth pixel down from the top and so on In list boxes and combo boxes the only aspect of the item the application can alter is height of the item The width of the item is always the width of the control In tab sets only the width of the tabs varies since the size of the control fixes the height of the tabs Note Owner draw grids cannot change the sizes of their cells as they draw The size of each row and column is set before drawing by the ColWidths and RowHei
595. t is shared by more than one component is virtually the same as modifying any existing event handler Just remember that whenever you modify a shared event handler you are modifying it forall the component events that call it m To modify the shared event handler 1 Select any of the components whose event calls the handler you want to modify 2 Inthe Events page of the Object Inspector double click the event handler name 66 Delphi User s Guide 3 In the Code Editor modify the handler Now when any of the components that share this handler receive the shared event the modified code gets called The following example demonstrates this notion It also provides an illustration of how run time property settings override those made at design time Modify the Button1 OnClick event handler by adding the following line of code before the the following ShowModal method call where lt path gt equals your Delphi BIN directory About Box ProgramIcon Picture LoadFromFile lt path gt TDW 1CO Run the program and click any of the buttons in MainForm The About box appears with the newly specified icon showing in the Image component Because all of the buttons in MainForm share the same event handler and because the run time property setting overrides deign time values clicking any button produces the same results Figure 2 18 About box with run time icon E AboutMy proj Product Name Version Copyright Comments
596. t output of the Password Dialog Form Template As you can see it is basically a summary listing of the objects that make up the form and the main visual properties of those objects object PasswordDlg TPasswordDlg Left 200 Top 99 ActiveControl Password AutoScroll False BorderStyle bsDialog Caption Password Dialog Font Color clBlack Font Height 11 Font Name MS Sans Serif Font Style f sBold PixelsPerInch 96 Position poScreenCenter ClientHeight 93 ClientWidth 236 object Labell TLabel Lett 28 Top 9 Width 92 Chapter 3 Building forms and menus 95 Height 13 Caption Enter password end object Password TEdit Left 8 TOD 27 Width 220 Height 20 TabOrder 0 PasswordChar end object OKBtn TBitBtn Left 66 Top 59 Width 77 Height 27 TabOrder 1 Kind KOK Margin 2 NumGlyphs 2 Spacing 1 end object CancelBtn TBitBtn Left 152 Top 59 Width 77 Height 27 TabOrder 2 Kind bkCancel Margin 2 NumGlyphs 2 Spacing l end end MDI and SDI forms Any form you design can be implemented in your application as a Multiple Document Interface MDI or Single Document Interface SDI form In an MDI application more than one document or child window can be opened within a single parent window This is common in applications such as spreadsheets or word processors An SDI application by contrast normally contains a single d
597. t should then also define some way to handle the item should it be dropped If a user sees the mouse cursor change to indicate that a control will accept the item being dragged it is reasonable for the user to then expect that dropping the item there will accomplish some task E To handle dropped items attach an event handler to the OnDragDrop event of the control accepting the dropped item Like the drag over event the drag drop event indicates the source of the dragged item and the coordinates of the mouse cursor over the accepting control These parameters enable the drag drop handler to get any needed information from the source of the drag and determine how to handle it For example a directory outline accepting items dragged from a file list box can move the file from its current location to the directory dropped on procedure TFMForm DirectoryOutlinelDragDrop Sender Source TObject X Y Integer begin if Source is TFileListBox then with DirectoryOutline do ConfirmChange Move FileList FileName Items GetItem X Y FullPath end Dragging and dropping now has the same effect as using File Move but the user doesn t need to type in the file name Ending a drag operation When a dragging operation ends either by dropping the dragged item or by the user releasing the mouse button over a control that doesn t accept the dragged item Delphi sends an end drag event back to the control the user dragged m To e
598. t their properties in the order indicated in Table 13 2 Note that DirectoryPanel and FilePanel go inside StatusBar to form a subdivided status bar For more information on creating status bars and their panels see Subdividing a panel in Chapter 12 Table 13 2 Property values for the main form components in FILMANEX Property Panel Align Caption Component Name BevelOuter Panel Align Caption Name Bevellnner BevelWidth Panel Align 360 Delphi User s Guide Value alBottom lt leave blank gt StatusBar buNone alLeft lt leave blank gt DirectoryPanel buLowered 2 alClient Table 13 2 Property values for the main form components in FILMANEX continued Component Property Value Caption lt leave blank gt Name FilePanel Bevellnner buLowered BevelWidth 2 TabSet Align alBottom Name DriveTabSet DirectoryOutline Name DirectoryOutline Align alLeft FileListBox Align alClient Name FileList ShowGlyphs True Note that for the DirectoryOutline component you can use either the DirectoryOutline on the Samples page of the Component palette or the standard DirectoryListBox component from the System page The DirectoryOutline component can display a more detailed view of the directory structure of a disk The form with all its controls now looks like Figure 13 2 Figure 13 2 File manager form with controls fattrdlg dfm DirectoryOutline E adia gas ee C fehngdlg dfm FileList C fehngdlg pas CO filmanex
599. t window contains the object as in Figure 15 6 Note If the Insert As Icon check box of the Insert OLE Object dialog box is checked the OLE object is inserted as an icon representing the server application associated with the object An object inserted as an icon is always activated in its own window rather than in place Figure 15 6 A Paintbrush picture OLE object OLE Example File Edit Object Window OLE Object la 5 Double click the OLEContainer component Because the AutoActivate property of the OLEContainer component has not been changed from its default value aaDoubleClick this reactivates the OLE object 6 Experiment with creating new OLE Object windows and embedding and linking OLE objects with the Edit Insert Object command 7 Choose File Exit to close the application 414 Delphi User s Guide Pasting objects Note Some OLE server applications allow the user to copy or cut OLE objects to the Clipboard If an OLE object is stored on the Clipboard you can initialize an OLEContainer by allowing the user to use the Paste Special dialog box to paste the object into the OLE container application This section describes the following steps involved in pasting OLE objects at run time e Using the Paste Special dialog box e Using OLE objects with the Clipboard e Pasting the OLE object Using the Paste Special dialog box To paste an OLE object into an OLEContainer component use the Paste Special dia
600. t you have a menu it s a good idea to attach a handler to the File Exit item to provide the standard method to terminate the application 350 Delphi User s Guide gt Attach the following event handler to the OnClick event of the File Exit menu item procedure TForml ExitlClick Sender TObject begin Close end You will attach event handlers to the other menu items in the remaining sections of this chapter As you work with the menus you might sometimes notice that the application draws an extra line or shape after the user clicks a menu item Windows sometimes sends a mouse up message to a form that didn t see the mouse down message Because the application always draws in its OnMouseUp event handler these extra mouse up messages can disrupt your drawing The solution is the same one used to filter out unwanted mouse movements on page 326 execute the drawing code only if the Drawing flag is set gt Modify the event handler for OnMouseUp events to check the Drawing field before drawing the shape procedure TForml FormMouseUp Sender TObject Button TMouseButton Shift TShiftState X Y Integer begin if Drawing then begin DrawShape Origin Point X Y pmCopy Drawing False end end Now the application should draw only when the user initiates the drawing by pressing the mouse button Printing graphics Printing graphic images from a Delphi application is a simple task The only requirement f
601. ta and OLE object information to the Clipboard from the server application Typically do this by choosing Edit Copy 3 Activate Delphi and select the OLEContainer component 394 Delphi User s Guide 4 Click the ellipsis button for the ObjItem property in the Object Inspector The Paste Special dialog box appears with the currently available OLE object in the As list Figure 14 5 The Paste Special dialog box Source C OFFICESQPW NOTEBK1 WBIS 4 4 1 491 Paste Link C Display As Icon Result Inserts the contents of the Clipboard into your document so p that you may activate it using the application which a created it 9 Select the OLE object from the As list 6 Select Paste to create an embedded object or Paste Link to create a linked object 7 Choose OK The OLEContainer component is now initialized If you pasted an embedded object the ObjClass property now contains the appropriate value for the OLE object If you pasted a link to an OLE object in a file the ObjClass ObjDoc and ObjItem properties are all specified The OLEContainer component contains a picture representing the OLE object m If you have access to an OLE server application that supports drag and drop of OLE objects you can create an OLE container component and embed an OLE object in a form by dragging the object from the server and dropping it on the form at design time 1 Activate the server application and select the object to be
602. te dialog box appears Figure 3 9 Save Form Template dialog box Save Form Template Forms File Name Formi UNIT1 Title Description Select a bitmap to represent this template ewe 3 In the Title edit box specify a name for the template 4 Inthe Description edit box type a brief description of this template 9 To specify an icon for the template choose the Browse button The Select Bitmap dialog box appears 6 Locate and select the bitmap if any you want to use and choose OK to exit the Select Bitmap dialog box 7 Choose OK to accept your specifications and exit the Save Form Template dialog box The next time you choose File New Form your template appears in the templates list with the bitmap you chose to represent it and the description you entered Saving form files as ASCII text Delphi enables you to save DFM form files as ASCII text You can then modify a form by using any standard text editor to edit the text file Later you can load the ASCII file in the Code Editor and convert it back into the binary DFM format This can be useful when using Delphi projects in a team development environment or whenever version control is an issue since most version control mechanisms depend on a text based comparison E Toconvert a form file to ASCII format 1 Choose File Open File You need not have a project open 2 Select the DFM file you want to convert to ASCII If the form s unit
603. tells you exactly where each file resides on disk regardless of its project affiliation If the Path column is empty for a listed file this means the file resides in the current project directory On the other hand if there is an entry in the Path column you know immediately that the file resides elsewhere If you often share files among different projects this can alert you that this file might be used by another project This is illustrated in the following figure 132 Delphi User s Guide Figure 4 2 Example Project Manager project listing rs WAR OM TAROT OPA 6 units 5 forme D About Aboutbor T FORMS TTT caer Arsplash AA Splash E SPLASH Chkauth Dhaentry TabDE Screens FORMS Files residing in a Login PasswoardD lg FORMS subdirectory of the current Maih Mainwin FORMS project directory Edd t Citin ibin forns forns lardivl 4 ardivl in the project directory A ardivl ardivl chkauth pas Non form unit file residing Notice how this project s directories are structured The project directory contains only project source and configuration files and a BIN directory for compiled output and a FORMS directory for form unit and graphical form DFM files were created This structure is purely optional storing all these files in the project directory D AR_DIV1 would work equally well In the Path column observe that e Files residing in the project directory do not displ
604. tes or if you want to set an attribute regardless of previous settings To change attributes based on their previous settings however you need to read the existing attributes modify them and write the modified attributes Reading file attributes Operating systems store file attributes in various ways generally as bitmapped flags To read a file s attributes pass the file name to the FileGetAttr function The return value is a group of bitmapped file attributes of type Word The file manager example handles a click on the File Properties menu item by opening a file attribute dialog box in which the user can see each attribute represented as a check box as shown in Figure 13 4 Add a new form to the project and set its properties as indicated in Table 13 5 When you save the updated project name the new unit FAttrDlg Table 13 5 Property values for the file attrioute dialog box form Property Value Name FileAttrForm Caption File Attributes Chapter 13 File manager example 371 Table 13 5 Property values for the file attrioute dialog box form continued Property Value Position poScreenCenter BorderlIcons biSystemMenu BorderStyle bsDialog Next add controls as indicated in Table 13 6 and Figure 13 4 Table 13 6 Property values for the file attribute dialog box components Component Property Value Label Name FileName Label Name FilePath Label Name ChangeDate Group Box Caption Attributes CheckBox Name ReadOnly Capt
605. text sensitive help F1 for a particular part of the interface Starting Delphi You can start Delphi the same way you start any Windows based application program default installation this file is located in your DELPHI BIN directory DELPHI EXE path statement Figure 1 1 The Delphi programming environment Component palette Standard page shown additional SpeedBar component pages available by selecting page tabs Delphi Projecti Object Inspector ActiveControl AutoScroll Borderlcons BorderStyle Caption ClientHeight Client width Color CtI3D Cursor Object selector True Form 269 423 clBtnFace True ciDefault True TFont FormStyle fsNormal Height 300 HelpContext 0 Events page tab Properties page tab Elements of the Delphi interface Double click the Program Item for DELPHI EXE that was created by the Install Use File Manager to locate and double click the DELPHI EXE file if you performed a Choose Run from the Program Manager File menu and specify the path to Start Delphi from the command line WIN DELPHI assuming Windows is in your Code Editor The elements of the Delphi programming environment were designed to provide you with the tools you need to quickly and intuitively develop high performance 8 Delphi User s Guide applications This section briefly describes each element For more information choose Programming Env
606. th Delphi forms When you add a new form to your project you ve added the basic model form By adding components to the form changing property values and writing event handlers you are customizing the new form To customize any object whether it be a blank form a form with multiple controls that is used as a dialog box or a new version of the Delphi bitmap button you start by deriving a new object from an existing object When you add a new form to your project Delphi automatically derives a new form object for you from the TForm type At the moment a new form is added to a project the new form object is identical to the TForm type Once you add components to it change properties and write event handlers the new form object and the TForm type are no longer the same No matter how you customize your bicycle it can still do all the things you expect a bicycle to do Likewise a customized form object still exhibits all the built in capabilities of a form and it can still do all the things you expect a form to do such as change color resize close and so on That s because the new form objectinherits all the data fields properties methods and events from the TForm type When you add a new form to an Delphi project Delphi creates a new object type TForm1 deriving it from the more generic object TForm The first line of the TForm1 type declaration specifies that TForm1 is derived from TForm TForml class TForm B
607. the Execute function like this if ColorDialog Execute True then Controlling the flow of code execution Object Pascal has several statements that direct the flow of code execution Two are branching statements and the other three are loop statements e Branching statements e The if statement e The case statement e Looping statements e The repeat statement e The while statement e The for statement The if statement Object Pascal s if statement evaluates an expression and determines the flow of your code based on the result of that evaluation If a certain condition is True the code flow branches one way If the condition is False the flow branches in another direction To see the syntax of an if statement see the if reserved word topic in Delphi s online Help This example uses a simple if statement This is how your finished form should look Figure 5 4 A sample form to illustrate an if statement Form1 To create this sample application 1 Create a form that contains one edit box control two label controls and a button 2 Place Labell above the edit box control and place Label2 below it Chapter 5 Writing Object Pascal code 163 3 Change these properties with the Object Inspector e Change the caption of Labell to Enter a day of the week e Delete the caption of Label2 so the label isn t visible when the application runs e Rename the button OK 4 Create this OKClick event handler proc
608. the Name property e Type in the value for the Caption property first and let Delphi derive the Name property from the caption For example if you give a menu item a Caption property value of File Delphi assigns the menu item a Name property of File1 If you fill in the Name property before filling in the Caption property Delphi leaves the Caption property blank until you type in a value If you enter characters in the Caption property that are not valid for Object Pascal identifiers Delphi modifies the Name property accordingly For example if you want the caption to start with a number Delphi precedes the number with a character to derive the Name property The following table demonstrates some examples of this assuming all menu items shown appear in the same menu bar Table 3 6 Sample captions and their derived names Component caption Derived name Explanation amp File File1 Removes ampersand amp File 2nd occurrence File2 Numerically orders duplicate items 1234 N12341 Adds a preceding letter and numerical order 1234 2nd occurrence N12342 N1 Removes all non standard characters adding preceding letter and numerical order hyphen N2 Numerical ordering of second occurrence of caption with no standard characters As with the menu component Delphi adds any menu item names to the form s type declaration and those names then appear in the Component list Adding inserting and deleting menu items The foll
609. the current unit or to open the View Unit dialog box When viewing a page in the Code Editor you can return to the form associated with the current Code Editor page or to a different form at any time E To return to the form choose from the following methods 62 Delphi User s Guide Note e Click any part of the form that is visible under the Code Editor page e Choose View Form to open the View Form dialog box and choose the form you want to view e Use Speedbar buttons to display the current form or to open the View Form dialog box Remember that simply toggling from viewing a unit to viewing a form returns you to the form associated with the selected page tab in the Code Editor This might not necessarily be the form you were previously viewing Locating an existing event handler Once you ve generated an event handler it s easy to locate it in the Code Editor To locate an existing event handler in the Code Editor 1 Inthe form select the component whose event handler s you want to locate 2 Inthe Object Inspector display the Events page 3 In the Events column double click the event whose code you want to view Delphi displays the Code Editor placing your cursor inside the begin end block of the event handler You can now modify this event handler Locating default event handlers If you generated a default event handler for a component by double clicking it in the form you can locate that event handler in
610. the dialog box By default Delphi displays the Name property value for each form in the form s title bar If you change the Name property of the form prior to changing the Caption property the title bar caption changes to the new name Once you change the Caption property the form s title bar always reflects the current value of Caption Providing command buttons Depending on whether you intend to use your dialog box in a modal or modeless state you ll want to provide certain command buttons in the dialog box For modal dialog boxes you need to provide the user with a way to exit the dialog box It s fairly standard design to provide one or more command buttons for this purpose For simple modal dialog boxes such as a message box one button is often sufficient Such a button might be labeled for instance OK or Close If you have another button in the dialog box labeled No as described in the next paragraph this button might be labeled Yes In cases where the dialog box accepts input from the user you want to provide users with a choice of whether or not to process their input on exiting the dialog box You can do this by means of an additional button labeled for example Cancel or No If your dialog box explicitly asks a question of the user you might want to label this button No otherwise Cancel is usually more appropriate Your code controls what happens when a user chooses a
611. the event handlers of the form could then access the Count field You can read about objects and fields in Chapter 6 182 Delphi User s Guide The next section uses the same sample application so don t delete the work you have just done if you are working through the examples Writing a procedure or function Much of the code you write while developing a Delphi application is contained within event handlers Delphi creates for you Still there are times when you want to write your own procedures and functions that aren t event handlers For example if you find yourself writing the same code over and over to perform some common task within event handlers consider moving that code from the event handlers into a procedure or function outside the handlers Then any event handler can call the procedure or function as it does any other existing procedure or function You derive two benefits you need to write the code only once and the code in your event handlers is less cluttered This example continues with the scope example presented in the previous section Here is the code of the example as it should exist currently beginning with the implementation part implementation SR DFM var Count Integer procedure TForml MultiplyClick Sender TObject var FirstNumber SecondNumber Integer begin FirstNumber StrToInt Edit1 Text SecondNumber StrToInt Edit2 Text Edit3 Text IntToStr FirstNumber SecondNumber
612. the flow of code execution Assigning a function s returned value This code example appears on page 155 procedure TForml AddButtonClick Sender TObject var X Y Sum Integer begin X 0 Y 0 Sum X Y Edit1 Text IntToStr Sum end eae di 1 The example uses the IntToStr function Edit1 Text IntToStr Sum IntToStr converts an integer value of type Longint into a string value This is the declaration of the IntToStr function in Delphi s run time library function IntToStr Value Longint string All functions begin with the reserved word function The word after the final colon in a function declaration is the data type of the value that is returned TheIntToStr function therefore returns a value of type string Once the code in the IntToStr function runs the assignment statement assigns the returned string value to the Text property of an edit box named Edit1 Value is the only parameter of the IntToStr function It has a data type of Longint an integer type To use IntToStr you can specify as the Value parameter e An actual integer value IntToStr 3 Chapter 5 Writing Object Pascal code 161 e A variable or property that is an integer type IntToStr Sum e An expression that is evaluated as an integer value assume X and Y are integer values in this example IntToStr X Y E To calla function assign the returned value to a variable or property that is compatible with the returned
613. the image control s Picture object Creating the new graphic is the same process you used to create the initial graphic see page 349 but you should also provide a way for the user to choose a size other than the default size used for the initial graphic An easy way to provide that option is to present a dialog box such as the one in Figure 12 12 Chapter 12 Graphics example 353 Figure 12 12 Bitmap dimension dialog box from the BMPDlg unit Bitmap Dimensions Width WidthEdit Height HeightEdit Creating a dialog box form is not the focus of this chapter so it doesn t present all the details of creating the bitmap dimensions dialog box here You can create your own or you can use the one in the BMPDIg unit included with the GraphEx project The rest of this section assumes you use the dialog box in the BMPDIg unit gt Add the BMPDIg unit to your project You also need to add BMPDIg to the uses clause in the unit for the main form You can then attach the following event handler to the File New menu item s OnClick event procedure TForml NewlClick Sender TObject var Bitmap TBitmap temporary variable for the new bitmap begin with NewBMPForm do begin ActiveControl WidthEdit make sure focus is on width field WidthEdit Text IntToStr Image Picture Graphic Width use current dimensions HeightEdit Text IntToStr Image Picture Graphic Height as default
614. the palette to the lower left corner of the form Drag before you release the mouse button until the outline is the size you want the image to be Later you ll move the Image component to its final position Chapter 2 Using components and code 45 Selecting components in the form There are several ways to select components in the form most but not all of these methods also apply to components contained by other components such as the Panel or GroupBox component E Toselect a single component do one of the following e Click the component in the form e Choose from the Object selector located at the top of the Object Inspector e With focus in the form tab to the component m To select multiple components do one of the following e First hold down the Shift key and then click the components one at a time e Click the form outside one of the components and drag over the other components you want to select If the components are inside a Panel or GroupBox component press Ctrl and then drag As you drag you surround the components with a dotted rectangle or rubber band When this rectangle encloses all the components you want to select release the mouse button In some cases you might need to rearrange the components before they can be easily enclosed within a rectangle Note Multiple selection applies to all components in the form including container components and any components they contain but when the fo
615. the range of 0 to 255 Requires one byte of memory Word Numbers without a fractional part within the range of 0 to 65535 Requires two bytes of memory Real Single A number that can contain a fractional part with 7 8 significant digits Requires 4 bytes of memory Available only when the 8087 80287 option N is on Refer to Real Types in online Help for the range of each real type Double A number that can contain a fractional part with 15 16 significant digits Requires 8 bytes of memory Available only when the 8087 80287 option N is on Extended A number that can contain a fractional part with 19 20 significant digits Requires 10 bytes of memory Available only when the 8087 80287 option N is on Comp A number that can contain a fractional part with 19 20 significant digits that requires 8 bytes of memory Available only when the 8087 80287 option N is on Real A number that can contain a fractional part with 11 12 significant digits Requires 6 bytes of memory Use Real only for compatibility with earlier Borland Pascal releases otherwise use Double or Extended Boolean Boolean Can contain the values of True or False Occupies one byte of memory Char Char An ASCII character String string A sequence of up to 255 ASCII characters Pointer Pointer An untyped pointer that is a pointer that doesn t point to any specific type PChar PChar A pointer to a null terminated string Besides the predefined data types you can define yo
616. the short form To use the short form type the procedure or function reserved word and follow it with the routine s name You can omit any list of parameters and if the routine is a function the return type For example suppose you declare this function in the interface part function CalculateInterest Principal InterestRate Double Double When you write the body of the function in the implementation part you can choose to write the function like this function CalculatelInterest begin Result Principal InterestRate end Note that the parameter and the return type have been omitted If you declare any routines in the implementation part not in the interface part you must use the long form of the procedure or function header Initialization part If you want to initialize any data the unit uses or makes available through the interface part to the application or unit using it you can add an initialization part to the unit Above the final end reserved word at the bottom of the unit add the reserved word initialization Between the initialization and end reserved words you write the code that initializes the data For example initialization Your initialization code goes here end When an application uses a unit the code within the unit s initialization part is called before the any other application code runs If the application uses more than one unit each unit s initialization part is called befo
617. the values of Number and CalcNo are no longer the same when Calculate stops running 192 Delphi User s Guide Figure 5 18 The values of Number and CalcNo after Calculate runs Value of Number Value of CalcNo actual parameter formal parameter Value parameters can be any expression To read about what constitutes an expression see the Expressions topic in online Help Variable parameters Sometimes you want the value of a passed parameter to change as the called procedure or function processes it In these cases you need to use a variable parameter Precede the formal parameter in the called routine with the reserved word var in the parameter list For example procedure Calculate var CalcNo Integer This variable parameter is a reference to the actual parameter which is Number in the example It does not occupy a separate location in memory but instead points to the actual parameter When a variable parameter is passed any changes made to the formal parameter are reflected in the actual parameter because both parameters refer to the same value To see how this works add the word var in front of the CalcNo parameter in the Calculate procedure declaration The Calculate procedure should now look like this procedure Calculate var CalcNo Integer begin Calcosa Ra leno S 404 end Run the application and enter a number in the Edit1 edit box You can see that the Calculate procedure does indeed change the value of th
618. ther picture The skills presented however apply to a number of different kinds of applications In particular tool bars and status bars appear in nearly all commercial applications Using different combinations of panels in your applications you can make many functions easily accessible to users In addition the application uses the standard printer and Clipboard objects with graphics much as the sample application in Chapter 10 does with text Topics presented in this chapter included e Responding to the mouse e Adding a field to a form object e Refining line drawing e Adding a tool bar to a form 356 Delphi User s Guide Adding speed buttons to a tool bar Responding to clicks Drawing with different tools Customizing pens and brushes Adding a status bar Drawing on a bitmap Adding a menu Printing graphics Working with graphics files Using the Clipboard with graphics Chapter 12 Graphics example 357 358 Delphi User s Guide Chapter File manager example This chapter presents all the steps necessary to create a small file manager application Each section in the chapter builds on the previous sections but the individual sections also explain discrete tasks The material assumes you already know how to perform most of the basic Delphi tasks such as placing components on a form and creating a menu Those tasks are described in Chapter 2 and Chapter 3 The complete application appears under the DEMOS D
619. ther recursively The form in this application has one button on it When you click the button the two procedures begin calling one another unit Unitl interface uses WinTypes WinProcs Classes Graphics Forms Controls Apps type TForml class TForm Buttonl TButton procedure ButtonlClick Sender TObject private Private declarations public Public declarations end var Forml TForml Chapter 5 Writing Object Pascal code 189 implementation SR DFM var Alpha Integer procedure Test2 var A Integer forward Test2 is declared as a forward procedure procedure Testl var A Integer begin A A 1 if A gt 0 then Test2 A A call to the Test2 procedure Writeln A end procedure Test2 var A Integer begin A A div 2 if A gt 0 then Testl A A call to the Test1 procedure Writeln A end procedure TForml ButtoniClick Sender TObject begin Alpia sa 155 The Alpha variable receives a starting value Test1 Alpha The first call to the Testl procedure end end The code in the OnClick event handler for the button gives the Alpha variable a value and then calls the Test1 procedure Test1 subtracts one from the value of the Alpha variable and then tests Alpha to determine if it is greater than 0 If it is Test1 calls the Test2 procedure Test2 divides the value of the Alpha variable by 2 and then tests Alpha to determine if it is greater than 0
620. thin the same scope of the executing code so the code cannot directly use the identifier Such an identifer that is not in scope can be accessed if you preface the identifer name with the name of the block and a period Identifiers declared in top level blocks are local to the blocks they are declared in but global in scope to the blocks contained within the block e Writing a procedure or function A procedure or function is made up of a header and a block 212 Delphi User s Guide A procedure or function begins with a header that identifies the procedure and function and lists the parameters the routine uses if any The block contains optional type variable and constant declarations and the statement part the code that implements the logic of the routine Functions must assign a return value in the statement part of the function The value can be assigned to the name of the function or to the Result variable Procedures and functions appear in the implementation part of a unit They can be declared in either the interface or implementation part however depending whether they are to be used only by the current unit or by other units also The parameters of procedures and functions can be value variable or constant parameters A value parameter is a copy of the actual parameter A variable parameter is a reference to the actual parameter A constant parameter never changes in value Defining new data types You can
621. thod of OLEFrameForm procedure TOLEFrameForm FormCreate Sender TObject begin FEmbedClipFmt RegisterClipboardFormat Embedded Object FLinkClipFmt RegisterClipboardFormat Link Source end Note Youcan pass any valid string as a parameter to RegisterClipboardFormat Embedded Object and Link Source are appropriate choices used for this example since that s the purpose of the formats being registered Search for RegisterClipboardFormat in online Help for more information Specifying OLE formats To specify which objects to allow the user to paste you pass an array of object formats in the Fmts parameter of the PasteSpecialDlg method Each format is specified in a BOLEFormat record 418 Delphi User s Guide It is possible to register standard Clipboard formats as well as OLE formats for pasting For example to register text as a paste format specify CF_TEXT for the value of the fmtld field and BOLE_LMED_HGLOBAL for the value of the fmtMedium field of a BOLEFormat record You can use the BOLEMediumCalc function to let Delphi calculate the fmtMedium value depending on which Clipboard format you re specifying Then if the user copies text from another application and pastes it on your application your application can process the pasted text For this example however you will register only two formats one for linked OLE objects and one for embedded OLE objects To specify OLE object formats s
622. thods of the form Displaying a dialog box modelessly To run the About box in a modeless state 1 Create a new blank project with a blank form 2 Add a button to Form1 Chapter 3 Building forms and menus 8 3 Generate the following event handler for Buttont1 procedure TMainForm ButtoniClick Sender TObject begin AboutBox Show This is the line you need to write end 4 Add Unit to the uses clause of the Unit1 source code 9 Add the About box to the project by choosing File New Form and selecting the About Box template from the Browse Gallery 6 Run the application and choose Button1 The About box appears 7 Click on Form1 Notice that focus shifts to Form1 and the About box shifts to the background This is because the About box is acting as a modeless dialog box 8 Use the Control menu to close the About box Displaying a dialog box modally gt Torun the About box as a modal dialog box 1 Change the code in the OnClick event handler for Form1 Button1 to read as follows procedure TMainForm ButtoniClick Sender TObject begin About Box ShowModal end 2 Now run the program choosing Button1 to display the About box 3 Try to click Form1 Notice that you cannot access it until you close the About box 4 Choose the OK button in the About box it now closes Note The choice of modality doesn t affect the appearance of a dialog box Setting form properties for a dialog box By default Delphi form
623. ties at run time Any property you can set at design time can also be set at run time by using code There are also properties that can be accessed only at run time These are known asrun time only properties As you ve seen when you use the Object Inspector to set a component property at design time you follow these steps 1 Select the component 2 Specify the property by selecting it from the Properties page 3 Enter a new value for that property Setting properties at run time involves the same steps in your source code you specify the component the property and the new value in that order However run time property settings override any settings made at design time Using properties to customize forms at run time When you include a form such as a dialog box in several projects you should avoid making design time changes to the form that might conflict with the use of the form in another project Instead write code that changes the form s properties at run time For example the caption of an About box generally includes the name of the program that uses it If you use the same About box in several projects simultaneously you don t want to accidentally use the name from another application Chapter 2 Using components and code 59 The following section discusses how to customize the caption of the About box at run time To do so you ll use the Object Inspector and the Code Editor to generate locate and modify an e
624. time a new window is opened Figure 15 1 The completed OLE container application OLE Example j OLE Object Chapter 15 OLE example 399 The topics discussed in the context of creating this application are Creating the MDI framework Inserting objects Pasting objects Dropping objects Working with objects in files Creating the MDI framework This application will allow the user to create multiple OLE objects each within its own MDI child window This gives the user an easy way to manipulate each object When an OLE object is activated control switches to the OLE server that created the object If the server uses OLE 1 0 the server is activated in a separate window If the server uses OLE 2 0 the server might activate the object within your container application window this is called in place activation Two conditions must be met for an OLE object to activate in place within your OLE container application e The OLE server must support in place activation e The main form of the OLE container application must contain a MainMenu component Note If you don t program your container application for in place activation an OLE object that supports in place activation will be activated in its own window not in place See the documentation for the OLE server for information about whether it supports in place activation This section describes the following steps involved in creating an MDI application framework for i
625. tions Exception Meaning EDivByZero Attempt to divide by zero ERangeError Number or expression out of range EIntOverflow Integer operation overflowed Floating point math exceptions Floating point math exceptions can occur when you perform operations on real type expressions The SysUtils unit defines a generic floating point math exception called EMathError The RTL never raises an EMathError but it provides a base from which all the specific floating point math exceptions descend Chapter 7 Writing robust applications 237 Table 7 3 shows the specific floating point math exceptions each of which descends directly from EMathError Table 7 3 Floating point math exceptions Exception Meaning EInvalidOp Processor encountered an undefined instruction EZeroDivide Attempt to divide by zero EOverflow Floating point operation overflowed EUnderflow Floating point operation underflowed Typecast exceptions Typecast exceptions can occur when you attempt to typecast an object into another type using the as operator The SysUltils unit defines an exception called EInvalidCast that the RTL raises when the requested typecast is illegal Conversion exceptions Conversion exceptions can occur when you convert data from one form to another using functions such as IntToStr StrToInt StrToFloat and so on The SysUtils unit defines an exception called EConvertError that the RTL raises when the function cannot convert the data passed to it
626. to be updated by the server with the RequestData method Client applications can poke data send data to the server with the PokeData method Clients can control the server by running it or sending macros with the ExecuteMacro method Creating DDE server applications To create a DDE server add a DDEServerltem component and optionally a DDEServerConv component to a form You can then copy DDE data to the Clipboard with the CopyToClipboard method and paste the link in the client application What is OLE With OLE you can link or embed OLE objects in a container application An OLE link is defined by its class name of the application that created the object document name of the file containing the object and item the portion of the document containing the OLE object to link Creating OLE container applications To create an OLE container application add an OLEContainer component to a form Then you can use the Insert Object dialog box to specify the ObjClass or ObjDoc properties and the Paste Special dialog box to specify the ObjItem property You can also drag and drop from an OLE server to embed an OLE object at design time OLE data in files You can use the SaveToFile method to save OLE data in a file and the ReadFromFile method to read OLE data from a file Chapter 14 Exchanging data with DDE or OLE 397 e Comparing DDE and OLE DDE exchanges text strings between applications and does not give the user access to t
627. to display the Gallery Options dialog box 2 Choose the Form Templates page tab 3 Select the Form Template you want as the default main form 4 With the template you want selected choose Default Main Form The folder with form icon appears in the box for the selected default form 5 Choose OK to register the new default setting Adding templates to the Gallery You can save your own projects and forms as templates and add them to those already available in the Gallery This is helpful in situations where you want to enforce a standard framework for programming projects throughout an organization For example suppose you develop custom billing applications You might have a generic billing application project that contains the forms and functionality common to all billing systems Your business centers around adding and modifying features in this application to meet specific client requirements In such a case you might want to save the project containing your Generic Billing application as a Project Template and optionally specify it as the default new project on your Delphi development system Likewise you ll probably have a particular form within this project that you want to appear as the default main or new form Before adding a project or form to the Gallery you should develop it as fully as possible and practical to minimize the amount of additional work needed when you open the template E To add a project to the Gallery 1 If
628. tring lists 272 scope 174 177 183 component names 55 data types 186 defined 177 exception handlers 241 form names 55 objects 222 226 redeclaring identifiers 181 screen coordinates current drawing position 324 origin 314 screens flickering 250 scroll bars 39 240 290 scroll boxes 39 348 as containers 47 ScrollBar component 39 ScrollBox component 39 47 scrolling bitmap images 348 SDI applications 96 searching for text in string lists 270 271 276 secondary tables databases 40 Select All command Edit 46 Select Bitmap dialog box 94 Select Menu command Menu Designer 105 106 Select Menu dialog box 106 SelectAll method 291 selecting components 38 46 48 in containers 46 file types 297 IDE windows 140 menu items 109 292 tabs 363 text 291 SelLength method 291 SelStart method 291 SelStart property 300 SelText property 291 semicolon end of statements 151 165 if statements 165 Sender parameter 64 65 See also event handlers example 343 344 objects and 227 separator bars menus 102 sequential values assigning to constants 335 server applications See DDE applications OLE applications ServerConv property 388 servers 40 services defined 382 See also DDE conversations set types 203 204 Set Watch command Code Editor window 259 SetFocus method 88 92 SetLink method 385 sets 203 constructing 204 setting colors 42 setting environment preferences 28 32 setting property values 16 43 55 design time 53
629. try the following steps 1 Choose File New Form and add a blank form 2 Adda button component to Form2 3 Select the button component and choose Edit Copy 4 Choose Edit Paste You ll notice that both buttons maintain their default caption that is Button However when you inspect the Name property you ll see that Delphi recognized Chapter 2 Using components and code 55 there was already a Button1 in Form2 and consequently changed the Name property for the second Button1 to Button2 Figure 2 11 Form2 with two Button component captions You ll be using Form2 later in this example to open the dialog box at run time gt Change the name for Form2 to MainForm Using property editors The Object Inspector provides several ways to edit properties at design time So far this chapter has described two such ways directly typing in values or choosing from a list of pre existing values For detailed information about other types of property editors see the online Help topic Using Property Editors The following section illustrates one of the Delphi dialog box editors Dialog box editors With certain properties double clicking in the Value column opens a dialog box that you use to set the property Likewise with some components double clicking the component in the form opens such a dialog box Properties you edit through a dialog box are often indicated in the Object Inspector by an ellipsis in the Value col
630. ts a block If you declare a variable within procedure D only the code within procedure D can access that variable as that variable is local in scope to procedure D If you declare a variable in unit B that is not in any procedure all procedures D E and F can use the variable because all these procedures are within the scope of unit B The variable is now global in scope to the procedures but local in scope to unit B In general declare identifiers that are as local in scope as possible This gives the data in your application increased protection from being modified when you do not intend it to be Only when you need to share data between different blocks should you consider using a more global scope Chapter 5 Writing Object Pascal code 177 Accessing declarations that are not within scope You can refer to declarations in blocks that are not within the scope of the current block For example if you create an event handler that calculates an interest payment in one unit it is possible for another unit to access that event handler m To access a declaration that is not within scope preface the declaration name with the name of the block in which it is declared and a period For example to call the CalculateInterest procedure that is declared in Unit1 from Unit2 make the call like this Unitl ComputeInterest Principal InterestRate Double You would also need to add Unit1 to the uses clause of Unit2 For more information a
631. ts respond when the user presses Enter The default button takes the OnClick event when another non button component in the form has focus For an example of this see Setting focus at run time on page 92 E To specify a button as the Default button set its Default property to True E To change focus at run time call the button s SetFocus method For more information see Setting the focus in a dialog box on page 92 Closing a dialog box when the user chooses a button You can specify that a modal dialog box close automatically when the user chooses any button whose ModalResult property has a non zero value By setting ModalResult to match a button s caption you can also determine which button the user chose For example if you have a Cancel button set its ModalResult property to mrCancel if your form contains an OK button set its ModalResult to mrOK Both buttons will close the form when chosen because ModalResult returns a non zero value to the ShowModal function However because ModalResult returns mrCancel in one case and mrOK in the other your code can determine which button was pressed and branch accordingly gt To automatically close the dialog box when the user chooses a Cancel button or presses Esc set the Cancel button s ModalResult property to mrCancel m To automatically close the dialog box when the user presses Enter when an OK button has focus set the button s ModalResult property to mrOK The f
632. ts to open the Install Components dialog box 2 Inthe Installed Units list box select the unit you want to remove 3 Choose Remove to remove the unit from the list box 4 Choose OK to close the Install Components dialog box Delphi rebuilds the library and the deleted components no longer appear in the palette Chapter 2 Using components and code 69 Adding VBX controls You can add VBX controls to the Delphi component library so long as they conform to Microsoft Visual Basic 1 0 specifications To do so you specify the VBX file that contains the control you want to add Delphi then automatically creates a wrapper unit a PAS file for the control to make it into a recognizable object type and adds it to the list of installed units You can specify a name for the control and which palette page you d like it to appear on E To adda VBX control to the component library 1 Open the Install Components dialog box 2 Choose VBX to open the Install VBX File dialog box 3 Navigate until you locate the VBX file you want to add then choose OK The Install VBX dialog box appears with the name of the specified VBX file displayed in a read only edit box 4 Use the options in this dialog box to specify e The directory path where the VBX file is located use the Browse button if you re not sure of the full directory path for the file e The page on the palette where you want the VBX control to be installed e Anew name for the c
633. ttons 88 89 Cancel property 88 Canvas property printers 305 canvases 313 319 369 manipulating pixels 314 315 capitalization in code 150 Caption property 16 388 invalid entries 101 Name property vs 17 panels 347 captions 16 17 87 200 See also labels cascading child windows 287 case conversions 272 case reserved word 166 case sensitivity of code 150 case statements 166 167 337 else reserved word and 167 CDialogs unit 206 CD ROM drives See media players Cells property 171 centering speed buttons 332 ChangeDefault property 307 ChangeFileExt method 302 changes tracking 300 changing See also editing breakpoints 257 258 component names 218 219 directories 41 376 file attributes 371 372 filenames 353 373 375 fonts 304 forms 26 in text files 94 shared 77 Gallery options 122 main forms 60 112 property values 54 55 56 229 design time 16 27 run time 151 tab order 90 tab sets 363 364 text 300 values while debugging 261 262 263 Char data type 156 character arrays 200 203 character strings See string lists strings Chart component 42 charts 42 318 check boxes 38 data aware 40 check marks menu items 289 CheckBox component 38 child forms See child windows child windows 97 280 287 404 See also MDI applications accessing 287 288 adding 281 401 404 at run time 285 closing 309 310 OLE objects in 401 chords 318 circular references 77 286 classes 72 120 241 debugging 262 Clear method
634. type Unlike records objects also contain code procedures and functions that act on the data contained in the object s fields These procedures and functions are called methods Also unlike records objects can contain properties The properties of Delphi objects have default values You can change these values at design time to modify an object to suit the needs of your project without writing code If you want a property value to change at run time you need to write only a very small amount of code Examining a Delphi object When you choose to create a new project Delphi displays a new form for you to customize In the Code Editor Delphi declares a new object type for the form and produces the code that creates the new form object A later section discusses why a new object type is declared for each new form For now examine the following example to see what the code in the Code Editor looks like unit Uniti interface uses WinTypes WinProcs Classes Graphics Forms Controls Apps type TForml class TForm The type declaration of the form begins here private Private declarations public Public declarations end The type declaration of the form ends here var Forml TForml implementation Beginning of implementation part SR DFM end End of of implemntation part and unit The new object type is TForm1 and it is derived from type TForm which is also an object A later section presents mo
635. u From that point on Delphi treats the template as a separate open project You can modify it adding new forms and units or use it unmodified adding only your event handler code In either case your changes affect only the open project The original Project Template is unaffected and can be used again m To start anew project from a Project Template 1 Choose File New Project to display the Browse Gallery dialog box 2 Select the Project Template you want and choose OK 122 Delphi User s Guide Note 3 Inthe Select Directory dialog box specify a directory for the new project s constituent files A copy of the Project Template opens in the specified directory If the Browse Gallery dialog does not appear in step 2 the Gallery is not enabled in the environment The Project Template option in the Gallery is disabled by default in a new Delphi installation Customizing project options Note While the preceding section discusses how to create new projects using the default values of a new Delphi installation your ability to control project options doesn t end there Delphi offers you the option of customizing the integrated development environment IDE itself The appearance and behavior of the IDE when you start Delphi or begin a new project are governed by the settings of several types of options e Environment settings affect all Delphi projects e Gallery settings determine the default new form and new project e Pr
636. u add a shortcut it appears next to the menu item caption Delphi does not check for duplicate shortcut keys or accelerators so you need to track values you have entered in your application menus Creating nested sub menus Many application menus contain drop down lists that appear next to a menu item to provide additional related commands Such lists are indicated by an arrow to the right of the menu item Delphi supports as many levels of such nested or submenus as you want to build into your menu Organizing your menu structure this way can save vertical screen space However for optimal design purposes you probably want to use no more than two or three menu levels in your interface design For pop up menus you might want to use only one such nested level if any Figure 3 15 Nested menu structures Menu item on ERIE l File Edit Format i the menu bar Menu item in i Italic a menu list Underline Nested menu item To create a nested menu 1 Select the menu item under which you want to create a nested menu 2 Press Cirl to create the first placeholder or choose Create Submenu from the SpeedMenu 3 Type a name for the nested menu item or drag an existing menu item into this placeholder 4 Press Enter or J to create the next placeholder 9 Repeat steps 3 and 4 for each item you want to create in the nested menu 6 Press Esc to return to the previous menu level Creating nested menus by demoting ex
637. u ll just draw lines Later you ll use other drawing tools to draw shapes There are four important topics to understand about mouse events e What s in a mouse event e Responding to a mouse down action e Responding to a mouse up action e Responding to a mouse move What s in a mouse event There are three mouse events defined in Delphi OnMouseDown OnMouseMove and OnMouseUp When a Delphi application detects a mouse action it calls whatever event handler you ve defined for the corresponding event passing five parameters You use the 322 Delphi User s Guide Note information in those parameters to customize your responses to the events The five parameters are as follows Table 12 1 Mouse event parameters Parameter Meaning Sender The object that detected the mouse action Button Indicates which mouse button was involved mbLeft mbMiddle or mbRight Shift Indicates the state of the Alt Ctrl and Shift keys at the time of the mouse action X Y The coordinates where the event occurred Most of the time the most important information in a mouse event handler is the coordinates but sometimes you also need to check Button to determine which mouse button caused the event Delphi uses the same criteria as Microsoft Windows in determining which mouse button has been pressed Thus if you have switched the default primary and secondary mouse buttons so that the right mouse button is now the primary button cl
638. u want Later in the example when you activate an OLE object the menus merged from the OLE server application will be inserted to the right of the File menu because their index values are greater than 0 Next you will program the sample application to create and show a new OLEObjectForm window To be able to create OLE object forms the unit where OLEObjectForm is declared must be referenced by the OLEFrame unit Add the OLEObj unit name to the uses clause of the interface section of the OLEFrame unit interface uses OLEOb Refer to unit OLEOBj PAS Chapter 15 OLE example 403 type gt Write the following CreateChild method in the implementation part of the OLEFrame unit This method will be called by the File New OnClick event handler so you won t use the Object Inspector to generate it function TOLEFrameForm CreateChild TOLEObjectForm begin CreateChild TOLEObjectForm Create Self Create the OLEObjectForm window end You need to declare CreateChild in order to call it at run time Add the following line to the private part of the TOLEFrameForm type declaration in the interface part of the OLEFrame unit interface type TOLEFrameForm class TForm private function CreateChild TOLEObjectForm Add this line to declare CreateChild function public Public declarations end Next you will attach the CreateChild method to the OnClick event of the File New menu item gt Write t
639. ue if the file named in its first parameter has the specified attribute set and False otherwise Setting the directory outline s Directory property to the new directory changes to that directory Because you handle the directory outline s change event by updating the file list box double clicking a directory in the file list box now has the effect of changing directories Dragging and dropping Dragging and dropping of items on a form can be a handy way to enable users to manipulate objects in a form You can let users drag entire components or let them drag items out of components such as list boxes into other components There are four essential elements to drag and drop operations 1 Starting a drag operation 2 Accepting dragged items 3 Dropping items 4 Ending a drag operation Starting a drag operation Every control has a property called DragMode that controls how the component responds when a user begins dragging the component at run time If DragMode is dmAutomatic dragging begins automatically when the user presses a mouse button with the cursor on the control A more common usage is to set DragMode to dmManual which is the default and start the dragging by handling mouse down events E To start dragging a control manually call the control s BeginDrag method 376 Delphi User s Guide BeginDrag takes a Boolean parameter called Immediate If you pass True dragging begins immediately much as if DragMode were dmAuto
640. ue of the name for the text file that each child window can contain The Filename variable is used in the Open method and several other methods of EditForm for example those you write to save files and create backup files Previously you added the UpdateMenus procedure to the private part of the TEditForm declaration in the MDIEdit unit s type declaration Now you ll add the Filename field to that same part In the private part of the MDIEdit unit s type declaration add the following line Filename string As with all such field declarations this line must precede any method declarations in the private part Thus the Filename declaration should immediately follow the reserved word private in the MDIEdit unit s type declaration Chapter 10 Text editor example 299 When EditForm is instantiated for example through the FrameForm NewChild procedure Filename acts as a form level variable of EditForm Therefore to access it from FrameForm you d need to qualify it EditForm Filename Compiling the application at this point still generates an error message because theOpen method of EditForm does not yet exist The following section discusses the writing and declaration of this method Loading the file The EditForm Open method uses the LoadFromFile method discussed in Chapter 9 In this case the file being loaded corresponds to the value passed from the FrameForm OpenChild method which was the file the user selected from the
641. uide gt gt Caution Write the following event handlers for the EditForm and FrameForm File Open click events respectively procedure TEditForm OpeniClick Sender TObject begin FrameForm OpenChild Sender end procedure TFrameForm OpenChild Sender TObject var EditForm TEditForm begin if OpenFileDialog Execute then begin EditForm TEditForm Create Self EditForm Open OpenFileDialog Filename Calls the Open method of EditForm EditForm Visible True end end The event handler code for the File Open click executes the Open File dialog box If the user then selects a file to open the Execute function returns a value of True and the remaining code runs The value of the file name specified by the user in the Open File dialog box is then passed as a parameter to the Open method The Open method exists in EditForm which is why you need to qualify the method call If you try to compile the application now Delphi generates an error message because the OpenChild event handler calls the Open method of EditForm which you haven t written yet In the following section you ll write the Open method that loads the file the user selected in the Open File dialog box First you need to declare a new field in the MDIEdit unit Declaring a form level variable The text editor application source code uses a form level variable called Filename that you ll declare in the MDIEdit unit Filename stores the val
642. uire the same kind of response to errors you can group them into a block and define error responses that apply to the whole block Blocks with specific responses to exceptions are called protected blocks because they can guard against errors that might otherwise either terminate the application or damage Chapter 7 Writing robust applications 231 data A protected block starts with the reserved word try and ends with the reserved word end Between these reserved words you put the statements you want to protect and define the kind of responses you want to make for that block m To protect blocks of code you need to understand e Responding to exceptions e Exceptions and the flow of execution e Nesting exception responses Responding to exceptions When an error condition occurs the application raises an exception meaning it creates an exception object Once an exception is raised your application can execute cleanup code handle the exception or both Executing cleanup code The simplest way to respond to an exception is to guarantee that some cleanup code is executed This kind of response doesn t correct the condition that caused the error but lets you ensure that your application doesn t leave its environment in an unstable state You typically use this kind of response to ensure that the application frees allocated resources regardless of whether errors occur For a detailed explanation see Protecting resource allocations
643. umn beside that property The Image component provides an example of a dialog box property editor When you double click an Image component in a form the Picture Editor dialog box appears You use the dialog box to specify the image you want displayed in the component Loading an image You can use the Image component to load a picture into your form at design time E To load a picture into a form 1 Add an Image component to your form 2 Inthe form double click the Image component 56 Delphi User s Guide The Picture Editor dialog box appears Figure 2 12 Picture Editor dialog box T 3 Choose the Load button 4 In the Load Picture dialog box select the bitmap BMP icon ICO or Windows Metafile WMEF you want to display and then choose OK The Picture Editor dialog box reappears with your image displayed Figure 2 13 Image displayed in Picture Editor dialog box 5 Choose OK to accept the image you ve selected and exit the Picture Editor dialog box Or repeat steps 3 through 5 to choose another picture Your image appears in the form at design time Load an image file from the Delphi Image Library into the Image component in the About box For more information about the Image Library search online Help under Image Library Figure 2 14 About box with image Product Name Version Copyright Comments Chapter 2 Using components and code _ 57 Sizing an image The picture you
644. unit followed by the unit s name an identifier The next item in a unit is the reserved word interface which indicates the beginning of the interface part of the unit the part visible to other units or applications that use this unit A unit can use the declarations in other units by specifying those units in a uses clause The uses clause can appear in two places 206 Delphi User s Guide e It can appear immediately after the reserved word interface Any code in the current unit can use the declarations declared in theinterface parts of the units specified in the uses clause For example suppose you are writing code in unit A and you want to call a procedure declared in the interface part of unit B Once you add the name of unit B to the uses clause in the interface part of unit A any code in unit A can call the procedure declared in unit B Also any unit that uses the current unit can also use any of the units listed in the current unit s uses clause For example if unit C is in the uses clause in the interface part of unit B and unit B is in the uses clause in the interface part of unit A unit A can use any declarations in the interface parts of both C and B even if unit C is not in the uses clause of unit A If unit B is in the uses clause in the interface part of unit A unit A cannot be in the uses clause in the interface part of unit B This creates a circular unit reference and when you attempt to compile Delph
645. unter determines how many times a for statement runs You need to declare a variable for each for loop you use in your code The variable can be any integer Boolean Char enumerated or subrange type The simplest way to understand a for statement is to look at an example The code shown here would print the numbers 1 to 5 each on a separate line X is the control variable var X Integer for X 1 to 5 do Writeln X The for statement defines an initial value 1 and a final value 5 for variable X When the for statement begins running X is assigned the initial value and the Writeln procedure runs displaying the current value of X The value of X is then incremented by 1 Because the value of X now 2 is not greater than the final value 5 the Writeln procedure runs again this time displaying the value of X as 2 This process continues 170 Delphi User s Guide until the value of X becomes greater than the final value 5 and the execution of thefor statement ends A counting example This is a variation of the same for loop just discussed It uses a string grid control and a button the user clicks to start the counting process To create the form 1 Place a string grid control and a button on the form 2 Use the Object Inspector to e Change the value of the button s Name property to CountButton e Change the caption of the button to Count e Change the ColCount property for the string grid to 6 e Change the Ro
646. ur own data types For many Delphi applications the predefined data types are sufficient This chapter however has already discussed the use of a user defined data type The Color property is of type 156 Delphi User s Guide TColor which isn t a predefined data type in Object Pascal but a type defined by the creators of the Delphi run time library To learn more about predefined types see the Type Declarations topic in online Help To read about defining your own data types see the section Defining new data types on page 195 Type and assignment compatibility Table 5 1 Object Pascal predefined data types lists five different data types that make up the integer category and five data types that make up the real category Within each category all types are compatible with each other You can assign a value of one type to a variable or property of a different type but within the same category as long as the value falls within the range of possible values for the target variable or property For example you can assign a variable of type Integer with the value 7 to a variable of type Shortint because a Shortint type can contain any value from 127 to 128 If the value of the Integer variable is 300 however you can t assign it to a Shortint variable because 300 is outside the Shortint range If you try and have range checking turned on choose Options Project and select Range Checking on the Compiler Options page you
647. value Edit1 Text IntToStr Sum Using functions that return a Boolean value to branch code Some functions return a Boolean value which is either True or False Your code can use such a function to branch to various tasks and routines based upon the value returned Here is an example Add a color dialog box and a button to a form Using the Object Inspector change the name of the button to ChangeColor Your form should look something like this Figure 5 3 A form for an example that uses the Execute function Form1 gt Create this event handler for the OnClick event procedure TForm1 ChangeColorClick Sender TObject begin if ColorDialog1 Execute then if user clicks OK button Forml Color ColorDialogl Color else Forml Color clRed end gt Run the application and click the button The event handler uses the Execute method a function that returns a Boolean value You can either select a color in the dialog box and choose OK or choose Cancel to exit the dialog box without selecting a color If you choose OK the ColorDialog1 Execute method 162 Delphi User s Guide returns True if you choose Cancel the method returns False If ColorDialog1 Execute returns True the form is colored with your color selection Form1 Color is assigned the value you selected which is ColorDialog1 Color if it returns False the form is colored red The compiler would interpret the code the same way if you wrote
648. ve else if Sender Copyl then Caption Copy else if Sender Renamel then Caption Rename else Exit CurrentDir Caption DirectoryOutline Directory FromFileName Text FileList FileName ToFileName Text if ShowModal lt gt mrCancel and ToFileName Text lt gt then ConfirmChange Caption FromFileName Text ToFileName Text end end The application now displays the file change dialog box with the correct caption and performs the correct operation Executing an application Many times an application needs to execute another application either to perform a specific task or just to have that application run concurrently The Windows API provides a function ShellExecute that executes an application but it requires a number of parameters superfluous to Delphi applications The FMXUtils unit provides a more useful alternative called ExecuteFile ExecuteFile operates in two different ways If passed the name of an executable file ExecuteFile runs that application If passed the name of a document with an associated application ExecuteFile runs the application automatically opening that document at startup Executing a file from a file list box ExecuteFile takes three string parameters and a fourth parameter that indicates how it should display the window containing the executed application The three strings represent the name of the file any command line parameters to pass to the application and t
649. ve a string in the list call the Move method passing two parameters the current index of the item and the index where you want to move the item to For example to move the third string in a list to the fifth position you would callMove 2 4 Deleting a string from a list To delete a string from a string list you call the string list s Delete method passing the index of the string you want to delete If you don t know the index of the string you want to delete use the IndexOf method to locate it To delete all the strings in a string list use the Clear method This example uses IndexOf to determine the location of a string in a list and deletes that string if present with ListBoxl Items do begin if IndexOf bureaucracy gt 1 then Delete IndexOf bureaucracy end Chapter 9 Working with string lists 271 Copying a complete string list E Tocopy a list of strings from one string list to another just assign the source list to the destination list Even if the lists are associated with different kinds of components or no components at all Delphi handles the copying of the list for you Copying the strings from one list to another overwrites the strings that were originally in the destination list If you want to add a list of strings to the end of another list you call the AddStrings method passing as a parameter the list of strings you want to add This example copies the items from a combo box into an outli
650. ve already created the Window menu for the text editor application Enabling the Tile Cascade and Arrange Icons commands requires just a few lines of code Similarly providing a list of open documents as part of the Window menu requires only that you set a property Both of these procedures are described in the next section Coding the Window menu commands To handle the clicks for the Tile Cascade and Arrange Icons menus commands generate the following OnClick event handlers assigning each handler to the appropriate command For each event handler you need write only one line of code a method call and Delphi does the rest for you procedure TFrameForm TilelClick Sender TObject begin Tile this is the only code you write end procedure TFrameForm CascadelClick Sender TObject begin Cascade this is the only code you write end Chapter 10 Text editor example 287 procedure TFrameForm ArrangelIconslClick Sender TObject begin Arrangelcons this is the only code you write end Including a list of open documents in a menu You can add a list of open documents to any menu item that appears on a menu bar in the MDI form However there can be only one such list per menu bar The list of open documents appears underneath the last item in the menu To include a list of open documents as part of a menu set the frame form s WindowMenu property to the name not the caption of the menu under which you want the l
651. ve no menu bar therefore no OnClick event is available prior to users opening the menu The OnClick event handler for menu items on a menu bar is often used to change the state of underlying menu items dependent on program conditions before the menu is opened Handling menu item events There is only one event for menu items as opposed to menu components The OnClick event Code that you associate with a menu item s OnClick event is executed whenever the user chooses the menu item in the running application either by clicking the menu command or by using its accelerator or shortcut keys E To generate an event handler for any menu item 1 From the Menu Designer window double click the menu item 2 Inside the begin end block type the code you want to execute when the user clicks this menu command Chapter 3 Building forms and menus 109 You can also easily generate event handlers for menu items displayed in a form This procedure does not apply to pop up menu items as they are not displayed in the form at design time m To generate an event handler for a menu item displayed in the form simply click the menu item not the menu component For example if your form contains a File menu with an Open menu item below it you can click the Open menu item to generate or open the associated event handler This procedure applies only to menu items in a list not those on a menu bar Clicking a menu item on a menu bar opens that menu d
652. vent by double clicking in the Value column next to the selected event Delphi generates the initial code in the Code Editor placing your cursor inside the begin end block 2 Inside the begin end block type the method call For the sample application write the following two event handlers 1 Select AddBtn generate an OnClick event handler and type the statement shown inside the begin end block procedure TForml AddBtnClick Sender TObject begin Listboxl Items Add Edit1l Text add this line of code end The code you typed calls the Add method of the list box in response to a click on the AddBtn The parameter being passed is the Text property of Edit1 This specifies that when the user clicks AddBin any text in Edit1 is added to the items in the list box Now generate the OnClick event handler for ClearBtn and type the statement shown inside the following begin end block procedure TForml ClearBtnClick Sender TObject begin ListBoxl Items Clear add this line of code end This code calls the Clear method of the list box in response to the ClearBin click As you might guess the Clear method clears the text from the list box All that s left is to run your program Try this program out 1 From the Run menu choose Run Delphi compiles your code and runs your program 2 Add text to the edit box and then choose the Add button or press Alt A The text you typed in the edit box appears in t
653. vent handler Working with code Note In Delphi almost all the code you write are executed indirectly or directly in response to an event As noted such code is called an event handler Event handlers are actually specialized procedures In Delphi you usually use the Object Inspector to generate event handlers Of course you can write source code in the Code Editor without using the Object Inspector For example you might write a general purpose routine that s not associated directly with a component event but that is called by an event handler You can also write event handlers manually but any time you can use the Object Inspector you should The Object Inspector not only generates the event handler name for you but if you change that name later by using the Object Inspector Delphi changes it everywhere that it occurs in your source code This is not the case for event handlers you write without using the Object Inspector This section discusses ways to use the Object Inspector and the Code Editor to generate and navigate your source code It describes this in the context of testing and using the About box at run time The following topics are explained e Generating the default event handler e Working with the Code Editor e Locating an existing event handler e Associating an event with an existing event handler Generating the default event handler In Chapter 1 you saw how to use the Object Inspector to generate an eve
654. vent handler has a Sender parameter of type TObject For example note the Sender parameter in this empty Button1Click handler procedure TForml ButtoniClick Sender TObject begin end If you look back at Figure 6 3 A simplified hierarchy diagram on page 221 you ll recall that TObject is at the top of the Delphi Visual Component Library That means that all Delphi objects are descendants of TObject Because Sender is of type TObject any object can be assigned to Sender Although you don t see the code that makes the assignment the component or control to which the event happened is assigned to Sender This means the value of Sender is always the control or component that responds to the event that occurred How is this information useful You can test Sender to find the type of component or control that called the event handler using the reserved wordis For example if Sender is TEdit then DoSomething else DoSomethingElse The drag and drop demonstration project shipped as part of the Delphi package has a project file named DRAGDROP DPR If you load the project and look at the DROPFONT PAS unit code you ll find that the Memo1DragOver method checks the type of an object variable In this case the parameter is Source rather than Sender procedure TForml MemolDragOver Sender Source TObject X Y Integer State TDragState var Accept Boolean begin Accept Source is TLabel end The Source parameter is als
655. w 11 12 renaming components 44 running projects to specific locations 251 saving project files 138 setting breakpoints 254 setting watches 259 switching to forms 62 viewing pages 62 63 colon function declarations 161 variable declarations 155 Color common dialog box 41 color grids 42 344 Color property brushes 316 345 pens 315 343 ColorDialog component 41 ColorGrid component 42 colors 42 brushes 316 pens 315 343 pixels 314 315 ColWidths property 368 combo boxes 39 41 data aware 40 items See string lists owner draw controls 365 369 measure item events 368 variant styles 365 ComboBox component 39 command buttons See buttons speed buttons command line options See compiling options comments in code 150 common dialog boxes 85 206 228 295 304 See also specific adding 41 Help buttons 296 listed 41 options 296 Comp data type 156 comparing values 158 164 compatibility of types 157 Compile command Compile 142 Compile menu 141 compiler directives 120 conditional compilation 143 range checking 199 Compiler Options dialog box 249 Compiler page Project Options 128 compiler generated files 117 compiling options 32 128 129 command line arguments 250 compiling projects 141 144 returning status 143 specific parts 143 starting compiler 142 COMPLIB DCL 42 component classes 72 component exceptions 242 Component Expert 71 72 Component Expert dialog box 71 component libraries 42 71 adding components 69 7
656. wCount property for the string grid to 6 You might have to resize the form and the string grid so that you can see all six columns Your form should look like this Figure 5 8 A sample form to illustrate a for loop Form Column 0 Create this CountButtonClick event handler procedure TForml CountButtonClick Sender TObject var Col Integer begin for Col 1 to 5 do StringGridl Cells Col 1 IntToStr Col end Run the application and click the Count button This event handler uses the Cells property which is a two dimensional array of strings indexed by a column and row value If you are unfamiliar with arrays you can read about them starting on page 199 Each cell in the string grid is represented in theCells property array To access a particular cell in the grid you specify the cell s column and row value For example the top left cell in the grid is Cells 0 0 meaning that the cell is in column 0 and row 0 the first position in the Cells array is 0 Chapter 5 Writing Object Pascal code 171 The for statement in the CountButtonClick handler displays the numbers 1 through 5 one in each cell in row 1 of the string grid starting with column 1 As the for statement runs the column number increases but the row number remains the same 1 The for statement can also decrement values using the downto reserved word gt Change the CountButtonClick handler to look like this proce
657. wing tool for this application is the line you need to ensure that the line button on the tool bar is pressed when the application starts Set LineButton s Down property to True Creating a group of speed buttons A series of speed buttons often represents a set of mutually exclusive choices In that case you need to associate the buttons into a group so that clicking any button in the group causes the others in the group to pop up To associate any number of speed buttons into a group assign the same number to each speed button s GroupIndex property The easiest way to do that is to select all the buttons you want in the group and with the whole group selected set GroupIndex to a unique value Since the shape drawing tool buttons are mutually exclusive you assign them to a group Select the four shape drawing tools the four leftmost buttons and set their GroupIndex to 1 Now when you run the application you can click any tool s button and all others POP UP Chapter 12 Graphics example 333 Allowing toggle buttons Sometimes you want to be able to click a button in a group that s already pressed and have it pop up leaving no button in the group pressed Such a button is called atoggle Use AllowAllUp to create a grouped button that acts as a toggle click it once it s down click it again it pops up m To make a grouped speed button a toggle set its AllowAllUp property to True Setting AllowAllUp to True for a
658. xception To indicate an error condition in an application you can raise an exception which involves constructing an instance of that type and calling the reserved word raise m To raise an exception call the reserved word raise followed by an instance of an exception object When an exception handler actually handles the exception it finishes by destroying the exception instance so you never need to do that yourself Setting the exception address Raising an exception sets the ErrorAddr variable in the System unit to the address where the application raised the exception You can refer to ErrorAddr in your exception 244 Delphi User s Guide handlers for example to notify the user of where the error occurred You can also specify a value for ErrorAddr when you raise an exception m To specify an error address for an exception add the reserved wordat after the exception instance followed by and address expression such as an identifier For example given the following declaration type EPasswordinvalid class Exception you can raise a password invalid exception at any time by calling raise with an instance of EPasswordInvalid like this if Password lt gt CorrectPassword then raise EPasswordInvalid Create Incorrect password entered summary Exceptions provide a powerful and flexible mechanism for reporting and responding to error conditions in your applications The Delphi run time library and all the st
659. y and Edit Paste commands respectively Chapter 10 Text editor example 291 procedure TEditForm CutToClipboard Sender TObject begin Memol CutToClipboard end procedure TEditForm CopyToClipboard Sender TObject begin Memol CopyToClipboard end procedure TEditForm PasteFromClipboard Sender TObject begin Memol PasteFromClipboard end Deleting text without changing the contents of the Clipboard The Edit menu also includes a Delete command that simply clears any selected text from the memo without copying the text to the Clipboard The event handler for the Edit Delete command calls the ClearSelection method for Memo1 Write the following event handler for the Edit Delete OnClick event procedure TEditForm Delete Sender TObject begin Memol ClearSelection end Save and run the application then try cutting copying and pasting selected text To demonstrate that the text you delete doesn t get copied to the Clipboard delete some text and choose Edit Paste again The text that gets pasted into the memo corresponds to the last text copied or cut to the Clipboard not the text you deleted Dimming menu items Often in an application you want to prevent users from accessing certain menu commands based on current program conditions but you don t want to remove the command from the menu altogether In the text editor application for example if there is no text currently selected in the docu
660. y not allowing the user to activate and edit the spreadsheet from your client application OLE is able to exchange more complex information than DDE such as sounds and documents Control transfers to the OLE server application when you activate an object in your OLE container so the user can access all the functionality of the server application from within your container application The server does all the processing and you don t have to program your container to edit the OLE object This would be good if you wanted to allow your users to modify the profits spreadsheet from within your application 396 Delphi User s Guide The final factor in determining when to use DDE and when to use OLE is the capabilities of the applications involved Some Windows applications don t support DDE Some don t support OLE Other applications can be OLE containers but can t be OLE servers For more information see the documentation for the application with which you want to exchange data summary This chapter presented these topics DDE conversations A DDE client application and DDE server application exchange text data in a DDE conversation A conversation is defined by its service name of the server topic file containing the linked data and item the actual text to link Creating DDE client applications To create a DDE client add a DDEClientConv component and a DDEClientItem component to a form Client applications can request
661. y of the Edit Object menu item from Object1 to OLEObjectMenultem This is simply to make this menu command easier to identify The OLE object menu item can have any valid value for its Name property including Object1 3 In the Object Inspector change the value of the OLE object form s ObjectMenultem property to OLEObjectMenultem Save the project now then run it 1 Choose File New to create a new OLE Object window The application should look like Figure 15 3 Note that the OLEObjectForm menu has merged with the OLEFrameForm menu 2 Choose the various menu commands of the application The Window menu commands should control the appearance of any OLEObjectForm MDI child windows Note that the Edit Object menu item is disabled automatically because OLEContainer does not contain an OLE object yet Chapter 15 OLE example 407 3 Choose File Exit to close the application Figure 15 3 The OLE container application menu OLE Example File Edit Object Window OLE Object OLE tool bars and status bars When an OLE object is activated in place the OLE server might try to replace the container application s tool bar and status bar messages with its own depending on the OLE server application If you intend the container application to contain OLE objects that can be activated in place you should program your application to allow the OLE server to use your container s tool bar and status bar This section describes the

Delphi User's Guide

Contents

Download Pdf Manuals

Related Search

Related Contents