Contents
Contents
1. 39 tvpographic feel to a Narrow font from another familv Examples of SETWIDTH_NAME are Normal Condensed Narrow and Double Wide ADD STVLE NAME is a string that identifies additional typographic style information not captured by other fields Examples of ADD_STYLE_NAME are Serif Sans Serif Informal and Decorated Serif characters have a smaller line that finishes off a large stroke where Sans Serif characters do not have these finishing strokes PIXEL SIZE is an unsigned integer string giving the body size of the font at a particular POINT SIZE and RESOLUTION V PIXEL SIZE can be approximated by the following equation PIXEL SIZE ROUND RESOLUTION_Y POINT_SIZE DeciPointsPerInch where the value of DeciPointsPerInch is 722 7q POINT SIZE is an unsigned integer string giving the bodv size of the font in device independent units POINT SIZE is not necessarilv equivalent to the height of the font bounding box POINT SIZE is expressed in decipoints 72 27 points equal one inch RESOLUTION X field is an unsigned integer string giving the hori zontal resolution in dots per inch dpi for which the font was designed RESOLUTION_LY field is an unsigned integer string giving the vertical resolution in dots per inch dpi for which the font was designed FONT_ASCENT is the extent of the character above the baseline FONT_DESCENT is the extent of the character below the baseline SPACING is an encoded stri2. 6 8 Compiling a font file and installing a new font 6 9 Example 0 0 02 00 000008 7 Appendix B Font Utilities 7 1 Displaying fonts utilities 000000 7 2 Font conversion utilities 0 08 4 8 Appendix C Program Listing 35 37 37 38 38 38 41 43 43 43 44 45 45 47 49 Chapter 1 Overview 1 1 Introduction Recent years have seen an uprising in the use of networking multitasking environments Most of these environments make use of the Unix operating system which allows more than one task to be executed simultaneously As more powerful computers became available this power was used to provide better user interfaces supportive of the user easier to learn and use X Windows is a graphical user interface which uses windows pull down or pop up menus and a pointing device With X Windows multiple applications can run simultaneously in windows X Windows provides the means for creating device independent applications and facilities for generating mul tifont text and two dimensional graphics FontCreator uses the X Windows environment to enable users to create easily their own fonts for use with their applications or for experimenting Throughout this dissertation we concentrate on showing how to use FontCreator effectively to create fonts 1 1 1 Report Structure The first chapter is an introduction to the FontCreator project The second chapter is an overview of X Windows with spe
3. 6700 FEOO F800 3E00 7F00 6300 6300 7F00 3E00 0000 0000 0000 0000 0000 0000 ENDCHAR STARTCHAR 9 ENCODING 57 SWIDTH 360 0 DWIDTH 8 0 BBX 9 22 0 6 BITMAP 0000 0000 0000 0000 0000 1E00 3F00 3300 3300 22 3F00 1E00 0600 0C00 1800 3000 3000 0000 0000 0000 0000 0000 0000 ENDCHAR ENDFONT 23 24 Chapter 4 Font Creator 4 1 The need for FontCreator The most common operation in a windowing svstem is drawing text Almost every application program big or small relies on text in one way or another Although X Windows support a lot of different fonts there can be many reasons to justify the need of creating new fonts First of all although X Windows support a lot of different fonts as already mentioned not all X servers support all fonts This is the usually the case with foreign alphabets FontCreator closes this gap by giving users the means to create their fonts But FontCreator also gives ground for experimenting One of the possible experiments could be to investigate the user s response when presented with text printed in their own handwritting For this experiment a sample of users would first create fonts resembling their handwritting and then use these fonts with text operations such as editing The experiment could then focus on evaluating whether the users worked more efficiently when they were using fonts similar to their handwritting rather than the standard X fonts Font
4. 1992 35 36 Chapter 6 Appendix A User Manual 6 1 Introduction Welcome to FontCreator FontCreator will enable you to create your own fonts for X Windows environment Although some knowledge about fonts is desirable we believe that FontCreator can be easily used by novice users Our intention was to make the more complicated steps of creating a font transparent to the user This is the reason why a file with default font prop erties is provided along with the program Of course you may select to edit this file to change the predefined font properties We do not recommend editing this file unless you are certain of the changes you are making other wise undesired effects may occur We also recommend that you should read this manual carefully before operating FontCreator You should also be aware that certain font names are registered trademarks and that for most of the font files copyright exists Apart from FontCreator itself the follow ing files should be present to ensure that FontCreator operates properly defaults txt messages txt load hlp new hlp edit hlp and general hip If one or more of the above files is missing FontCreator will issue a message informing the user of the missing file We hope that you will enjoy using FontCreator For any questions or suggestions you can contact G Lepouras University of Strathclyde E Mail glepoura cs strath ac uk Notice Permission to use and distribute this program
5. 3 4 1 File format Each font file is encoded in ASCII printable characters plus carriage return and linefeed The general form of a font file is the following e The word STARTFONT with the version number in this case 2 1 indicate the format version used e The word COMMENT with comments about the font These may extend to more than one lines all lines starting with the word COMMENT These lines may be ignored by any program reading the file 19 The word FONT followed py either the X Logical Font Description font name or some private font name The word SIZE followed by the point size the x and the y reso lution described earlier The word FONTBOUNDINGBOX followed bv the width height x and v displacement of the character The word STARTPROPERTIES with the number p of properties that follow Then follow p lines of properties starting with the propertv name and an integer or a string contained in double quotes Properties like FONT_ASCENT FONT_DESCENT and DEFAULT CHAR should be provided If these properties are not defined a compiler may reject the font e The property section is ended with the word ENDPROPERTIES e The word CHARS followed by the number of character segments contained in the font file Each character segment starts with the word STARTCHAR followed by the name of the encoded character up to 14 characters long Next comes the word ENCODING followed by a positive in teger which is th
6. AT amp T and Sun Microsystems while Motif was created by Open Software Foundation Both include many things specifications for a graphical interface style guides for providing application consistency toolkits and window managers Open Look provides olwm and Motif provides mwm window manager Motif toolkit is based on Xt Intrinsics while Open Look XView toolkit is based on X Library Although many people would think that programs using one or the other toolkit would be incompatible with each other this is not the case Motif programs can easily be run on an Open Look system and vice versa Of course without mwm Motif programs will not have the look and feel they do but they still be able to run Programs based on X Library will run with both window managers as well as with twm 10 Chapter 3 Fonts in X Windows 3 1 About fonts A font is a graphical description of a set of characters In general there are two font representations used by X outline and bitmap Outline fonts are fonts whose characters are described as outlines Bitmap fonts are fonts which characters are described as two dimensional arrays of bits BDF 2 or Bitmap Distribution Format is the standard font interchange format for X Consortium It consists of ASCII text understandable by both human and computers SNF or Server Natural Font is the standard format used by X servers for release 4 of X11 SNF files have an snf extension From release 5 of X11 anew format
7. These observations make the rationale for creating a toolkit obvious The framework of a toolkit is an object oriented one A toolkit contains reusable configurable user interface components such as pushbuttons scroll bars pop up menus called widgets Widgets operate independently of the application For example a pushbutton knows how to draw itself how to highlight itself when it is clicked on with the mouse and how to respond to a mouse click by calling an application function The object oriented approach of building a toolkit means that the application programmer is completely insulated from the code inside the widgets All he has access to are functions to create manipulate and destroy widgets This way the internal implementation of a widget can change without re quiring changes to the application itself A further benefit is that an object oriented approach forces the programmer to think about the application in a more abstract fashion which leads to better design and fewer bugs In an object oriented approach of creating a toolkit certain base classes of widgets are defined whose behaviour can be inherited and augmented or modified by their subclasses In FontCreator toolkit the base widget is the ToolWindow 2 6 Motif and Open Look Motif and Open Look are sets of guidelines specifying how a user interface should look how an application appears on the screen and feel how the user interacts with it Open Look was created by
8. When the mouse pointer enters the edit window it changes from being an arrow to a pencil implying that this is drawing area By clicking the left mouse button on grid s square the square changes color from white to black and vice versa By pressing the right mouse button a dialogue box will ask you whether you wants to quit editing Clicking on Cancel pushbutton returns you back to editing mode while clicking on Ok pushbutton pops up another dialogue box asking whether to save edited character or not You may select to save the character being edited in the font file by clicking on 7OK pushbutton or exit editing without saving by clicking on Cancel 42 6 6 Quitting FontCreator When you click on Quit pushbutton the program first checks the state of the program If there is some other operation on the program will ask you whether to abort it or not If no other operation is on the program will ask you to affirm your choice If you insist on your choice the FontCreator will save the font file being edited and then exit 6 7 Geting help To get on line help click with the mouse pointer the Help pushbutton Depending on the operation you are on the relevant help text will appear However if the help file is missing the message lt help file hlp gt is missing will be displayed in the help window where lt helpfile hlp gt is the name of the help file 6 8 Compiling a font file and installi
9. extension and possiblv substituting a new directorv part 48 Chapter 8 Appendix C Program Listing 49
10. for any purpose and with out fee is granted as long as the copyright notice appears This program is provided as is without expressed or implied warranty 37 6 2 Getting started FontCreator is designed to run under X Windows version 11 release 4 or later If you try to execute FontCreator directly from the Unix prompt the message Cannot connect to X server will appear You can use any of the existing window managers such as twm or olwm However we suggest that you use X Windows window manager twm Twm provides special decorations for pop up windows and responds from our experience more readily to the program s requests We have found that sometimes this is not the case with olwm Open Look window manager which sometimes does not respond accordingly especially when conflicts arise between client programs Make also sure that at least defaults txt the default font properties file is present Once you run X Windows give the FontCreator command at the console followed by lt Return gt What you first see is the FonCreator main window You can use the mouse pointer to resize or move the main or any other window of FontCreator The first step you have to take before drawing any character bitmap is to load or create a font file 6 3 Loading a font file Load push button is used to load a font file The file to be loaded should conform to the Bitmap Distribution Format ver 2 1 To load the file click on lo
11. in x and y of character is a vector indicating the position of the next character s origin relative to the origin of this character Scalable widths are in units of 1 1000th of the size of the character If the size of the character is p points the width information must be scaled by p 1000 to get the width of the character in printer s points The scalable width s x value can be computed from the following equation x 1000 charsize 72 resolution charwidth where charsize is the character s size resolution is the device resolution in pixels per inch and the charwidth is the character s width The result is a real number giving the ideal print width in device pixels The actual device width must be an integral number of device pixels The scalable width s y value should always be zero for a standard X font Width in x and y of character in device pixels is also a vector indicating the position of the next character s origin relative to the origin of this character The device width s y value should always be zero for a standard X font 3 3 X Logical Font Description 3 3 1 Requirements and goals The X Logical Font Description p 53 meets the sort and long term goal to have a font description that 12 e Provides unique descriptive font names that support simple pattern matching e Supports multiple font vendors arbitrary character sets and encod ings e Is independent of X server and operati
12. screen One way is to find pointer s location and to display the window as close as possible The other way is to pop up the window anywhere on the screen and move the mouse pointer into the window often called warping the mouse It was thought that the first way of implement ing a pop up window was better since warping the mouse is unexpected and tends to confuse the user Two functions control the display of the dialogue box Every time the dialogue is popped down it is not destroyed as creating a window takes a relatively long time PopDownDialog simply unmaps the dialog which can then be used again with another prompt and different pur pose but with the same look and feel In certain cases it is necessary to pin the dialogue box For this reason PinDialog function is provided which pins the dialogue at a certain position UnpinDialog function undoes the result of PinDialog Get DialogData returns a string of characters containing user s input and SetDialogCallback and Set DialogCancelCallback functions can be used to associate callback functions with OK and Cancel PushButtons of the dialogue box SetDialogPrompt and SetDialogData can be used to set the dialogue prompt and to initialise the data in the Text Entry field respectively There is no need to provide redraw function since in case of expose events all dialogue components have their own redraw functions to handle expose events 4 4 How FontCreator works FontCreato
13. style This name must be human understandable It is up to the type supplier to secure the proper legal title and not to infringe other s copyrights or trade marks Examples of FAMILY_NAME are Helvetica Times Times Roman Bitstream Amerigo WEIGHT_NAME identifies the font s typographic weight that is the blackness of the font according to FOUNDRY s judgement The in terpretation of this field can be problematic since it is subjective It is possible that a font which is identified as Bold from a font family to have almost the same blackness of a SemiBold font from another font family e SLANT is an encoded string identifying the way in which the character is designed The following are possible codes R for Roman that is upright design T for Italic that is italic design slanted clockwise from the vertical O for Oblique obliqued upright design slanted clockwise from the vertical RE for Reverse Italic italic design slanted counterclockwise from the vertical RO for Reverse Oblique obliqued design slanted counterclock wise from the vertical SETWIDTH_NAME is human understandable string identifying the nominal width per horizontal unit of the font according to the FOUNDRY s judgement As with WEIGHT_NAME since its definition is subjec tive the interpretation can be problematic What can be charac terised as Normal for a family font may be almost equivalent in
14. the display screens Each root window is partially or completely covered by child windows All windows except for root windows have parents Child windows may in turn be parents of other windows This way an application can create an arbitrarily deep tree of window on each screen X provides graphics and text operations for windows A child window can be larger than its parent That is part or all of the child window can extend beyond the boundaries of the parent but all output to a window is clipped by its parent If several children of a window have overlapping locations one of the children is considered to be on top of others X does not guarantee to preserve the contents of windows When part or all of a window is hidden and then brought back on to the screen its contents may be lost The server then sends the client program an Expose event to notify that part or all of the window needs to be repainted The number of Expose events can be cut down by having the application to ask X server to provide backing store on windows This way the X server preserves any obscured areas However not all X servers provide backing store and even those that do do not guarantee to provide backing store for all windows all the time Creating and displaying windows is a complex task Details such as the display the parent window the location on the screen the width and the height the border width and color and the background color have to be defined On
15. the edit window shows where the baseline is At the bottom of the edit window a small message window reminds the user of the character being edited When the mouse pointer enters the edit window it changes from being an arrow to a pencil implying that this is drawing area By clicking the left mouse button on erid s square the square changes color from white to black and vice versa By pressing the right mouse button a dialogue box asks the user whether he wants to quit editing Clicking on Cancel pushbutton returns the user back to editing mode while clicking on Ok pushbutton pops up another dialogue box asking whether to save the edited character or not During the editing procedure the user is assisted by useful messages printed in the main message window helping him accomplish the character s editing The fourth push button is the 7 Quit button Pressing the mouse button while the mouse pointer is on it displays a message in the message window explaining quit s use Clicking on the Quit pushbutton pops up a dialogue box asking the user to confirm his decision to exit FontCreator Again clicking on Cancel aborts the exit procedure and returns the program back to its previous state If the user insists the program will save the font file edited if any and exit The fifth pushbutton is the Help button Its 29 operation is self evident Clicking on Help pushbutton makes the help window appear a
16. with the rationale of exploring the design decisions that toolkit builders face This toolkit will be described later For the moment we will focus on the guidelines upon which the interface design was based First of all it was decided that the interface should comply with the Motif style specifications The Motif interface was modelled after the Microsoft s Common User Access specifications which define the interface for Microsoft Windows The key point of the specification is that consistency should be maintained across all applications Similar user interface elements should look and act similarly regardless of the application that contains them When the user interface is standardised the user gets more quickly to the point where he is working with the application rather than just mastering its mechanics According to the Motif Style Guide p 6 the main window should have a menu bar across the top and a message window at the bottom This message area is not used for messages that require a response from the user Messages requiring a response cause a transient window called a dialogue box to be displayed Dialogue boxes are pop up windows that contain a text label on the top right beneath it there is optionally a text entry window and at the bottom there are two push buttons named Ok and Cancel The main point when designing the FontCreator interface was to keep it as simple as possible Having this point in mind the menu bar wa
17. word space value to be used with this font NORM_SPACE NORM SPACE is an unsigned integer value that gives the recommended normal word space value to be used with this font MAX SPACE MAX SPACE is an unsigned integer value that gives the recommended max imum word space value to be used with this font END_SPACE END_SPACE is an unsigned integer value that gives the recommended spac ing at the end of sentences to be used with this font AVG_CAPITAL_WIDTH AVG CAPITAL WIDTH is an integer value that gives the mean width of all capital letters in the font letters A through Z for Latin fonts 17 AVG LOWERCASE WIDTH AVG LOWERCASE WIDTH is an integer value that gives the mean width of all lowercase letters in the font letters a through z for Latin fonts SUBSCRIPT X SUBSCRIPT_X is an integer value that gives the recommended horizontal offset in pixels from the position point to the X origin of subscript text SUBSCRIPT V SUBSCRIPT_Y is an integer value that gives the recommended vertical offset in pixels from the position point to the Y origin of subscript text SUBSCRIPT SIZE SUBSCRIPT_SIZE is an unsigned integer value that gives the recommended body of subscripts to be used with this font it is usually smaller than the size of the current font UNDERLINE POSITION UNDERLINE POSITION is an integer value that gives the recommended vertical offset in pixels from the baseline to the top of the underline UNDERLIN
18. Contents 1 Overview 1 1 Introduction 00 00 1 1 1 Report Structure LL 0 20 a 2 X Window System 2 1 The history of X LL 0000 2 2 Overview of X LL 2 3 Windows in X L 2 4 Window managers LL 2 5 Toolkits 2 0 0 0 0 0 02 ee ee ee ee 2 6 Motif and Open Look See 3 Fonts in X Windows 3 1 About fonts 2 2 2 0 0 020202 22 ee 3 2 Character s properties ooa a 3 3 X Logical Font Description oaoa a 3 3 1 Requirements and goals LL 00000 3 3 2 FontName description 5 a 3 3 3 Examples 00000 3 3 4 Font properties 000000 3 4 Bitmap Distribution Format Version 2 1 3 4 1 File format 00000 3 4 2 File format example L 00000000 4 FontCreator 4 1 The need for FontCreator 0000 4 2 Graphical User Interfaces onoo a 42 1 Interface design 000000 w w O OON DD or AN 4 2 2 Interface implementation 4 3 FontCreator toolkit L 4 3 1 ToolWindow structure 4 3 2 Text Label widget 00 4 3 3 PushButton widget 00 4 3 4 Text Entry widget 00 4 3 5 Dialogue window 4 4 How FontCreator works 024 5 References 6 Appendix A User Manual 6 1 Introduction 6 2 Getting started 2 2 e 6 3 Loading a font file oaaae 6 4 Creating a new font file oaoa 6 5 Drawing a new character oaoa 6 6 Quitting FontCreator 6 6 7 Geting heljp 2 2 0 2 0 0 0 00
19. Creator seeks to enable users to create easily their own font files for use with their applications 4 2 Graphical User Interfaces Graphical User Interfaces GUIs p 64 are user interfaces which rely on graphics in order to communicate with the user WIMP interfaces derived from Windows Icons Menus and Pointing is a type of graphical user inter face which use windows pull down or pop up menus and pointing devices 25 WIMPs have a lot of advantages over traditional user interfaces Thev are supportive of the user making users feel in control of the computer thev are easy to learn and use and they provide full screen interaction WIMPs are characterised by multiple windows allowing different information to be displayed simultaneously iconic information representation command se lection via menus and the use of a pointing device such as a mouse or a trackball to select choices from a menu or indicate objects on the screen Until recently there were different user interface management systems pro duced by different vendors which were incompatible with each other The Motif interface toolkit however has been a move to standardisation on the X Window interface 4 2 1 Interface design While designing the FontCreator interface there was an argument whether it should be based upon available toolkits like Open Look or Motif toolkit or anew toolkit should be built especially for the program needs The latter approach was chosen
20. E THICKNESS UNDERLINE_THICKNESS is an unsigned integer value that gives the un derline thickness in pixels ITALIC_ANGLE ITALIC_ANGLE is an integer value that gives the nominal posture angle of the typeface design in 1 64 degrees measured from the character origin counterclockwise from the three o clock position CAP_HEIGHT CAP_HEIGHT is an unsigned integer that gives the nominal height of the capital letters contained in the font Where applicable it is defined to be the height of the Latin uppercase letter X 18 X HEIGHT X HEIGHT is an unsigned integer that gives the nominal height above the baseline of the lowercase characters contained in the font Where applicable it is defined to be the height of the Latin lowercase letter x COPYRIGHT COPYRIGHT is a human understandable string containing the copyright information of the legal owner of the digital font data NOTICE NOTICE is a human understandable string that gives the copyright or the trademark information of the legal owner of the font DEFAULT_CHAR DEFAULT_CHAR is an unsigned integer value that gives the ASCII code of the default character to be used by the X server when an attempt is made to display an undefined or non existent character in the font 3 4 Bitmap Distribution Format Version 2 1 The Bitmap Distribution Format Version 2 1 p 50 is an X Consortium standard for font interchange understandable by both humans and comput ers
21. Latin alphabet No 1 15O8859 2 Latin alphabet No 2 15O8859 3 Latin alphabet No 3 15O8859 4 Latin alphabet No 4 15O8859 5 Latin Cyrillic alphabet 1SO8859 6 Latin Arabic alphabet 1SO8859 7 Latin Greek alphabet 1SO8859 8 Latin Hebrew alphabet 15O8859 9 Latin alphabet No 5 JISX0201 1976 0 8 bit Alphanumeric Katakana Code GB2312 1980 0 GL encoding China PRC Hanzi JISX0208 1983 0 GL encoding Japanese Graphic Character Set KSC5601 1987 0 GL encoding Korean Graphic Character Set 3 3 3 Examples The following are examples of font names 75 dpi fonts Bitstream Charter Medium R Normal 12 120 75 75 P 68 1508859 1 Bitstream Charter Bold I Normal 12 120 75 75 P 75 ISO8859 1 Adobe Courier Medium R Normal 8 80 75 75 M 50 ISO8859 1 Adobe Courier Medium R Normal 10 100 75 75 P 124 1508859 1 16 Adobe Times Medium R Normal 24 240 75 75 P 124 ISO8859 1 100 dpi fonts Adobe Times Bold R Normal 14 100 100 100 P 76 ISO8859 1 Adobe Times Bold I Normal 14 100 100 100 P 77 ISO8859 1 Adobe Times Medium I Normal 14 100 100 100 P 73 ISO8859 1 Adobe Times Medium R Normal 14 100 100 100 P 74 ISO8859 1 3 3 4 Font properties All font properties p 67 are optional but a font file will generally include the font name fields already discussed and some more useful information We will describe some of the font properties not already described MIN_SPACE MIN SPACE is an unsigned integer value that gives the recommended min imum
22. ad push button to initiate the loading process then enter the full file name in the special text input area of the pop up window and click on OK if you want to abort the operation just click on Cancel If the load operation is successful File loaded is displayed in the message window otherwise if the file does not exist File not found will be displayed If another font file was being edited while the load procedure was initiated it will be automatically saved and the message File saved will appear in the message window 6 4 Creating a new font file Click on New pushbutton to initiate the procedure of creating a new font file The first thing you will be asked is to enter the new font file name The program itself will provide the identifier bdf at the end of every font file you create The program will then ask you if you want to edit the default font properties file You can answer yes or no depending on whether you want 38 to edit the file If you answer yes a full screen editor will appear containing the defaults file We give a brief explanation of the font properties included in the file e FOUNDRY is an X registered name the name or identifier of the supplier of the font data or the identifier of the organisation that last modified the font shape or metric information FAMILY_NAME is a string that identifies the family of typeface de signs that are all variations of one basic typographic
23. an unsigned integer value that gives the recommended minimum word space value to be used with this font e DEFAULT CHAR is an unsigned integer value that gives the ASCH code of the default character to be used bv the X server when an attempt to displav an undefined or non existent character in the font Once vou finish editing the defaults file save it and then exit the editor Fontcreator scans the defaults file to determine the new font file name If a font file with the same name alreadv exists vou will be asked whether to overwrite the existing font file or abort the creation of the new file 6 5 Drawing a new character The first step in order to draw a new character is to click the Edit pushbut ton By clicking on Edit pushbutton a series of pop up windows appear prompting vou to enter the character to be edited the character width 41 height x and v displacement Character s width is the number of pixels between the leftmost and the rightmost parts of the character Character s height is the number of pixels between the uppermost and downmost parts of the character Character s x displacement is the horizontal distance of the lower left corner from the origin of the character Character s y dis placement is the vertical distance of the lower left corner from the origin of the character Both x and v displacement can be positive or negative For example character p extents below the baseline therefore the baseline is
24. ce the window is created the application has to sent hints to the window manager about the window The window manager may accept or deny any hinted request Most window managers will try to deliver what the application wants but there is no guarantee If the application fights the window manager the window manager wins The X server apart from sending expose events may send keyboard pointer window crossing client communication events and so on Programs should be able to handle or ignore events of all types 2 4 Window managers As already mentioned X protocol provides mechanisms with which a variety of user interfaces can be build Using these mechanisms a single client called a window manager can provide the user interface which is independent of all the other clients A window manager can enforce a strict window layout policy as well as automatically provide the following e Title bars borders and other window decorations for each application e Uniform icons for applications e A uniform means of moving and resizing windows e A uniform interface for switching the keyboard between applications X itself comes from MIT with twm p 3 the Tab or Tom s window manager 2 5 Toolkits When building X Window applications one soon discovers that when cre ating multiple windows large sections of code are being duplicated Also soon one discovers that creating subwindows allows for tasks to be encap sulated into windows
25. cial mention on windows window managers and toolkits The third chapter explains the character properties and goes on to define the X Logical Font Description and the Bitmap Distribution Format which is used in X Windows The chapter ends with an example of a font file The next chapter establishes the need for the FontCreator and describes the way FontCreator was designed and implemented the FontCreator toolkit and how FontCreator works We have provided three appendices The first is a user s manual for FontCreator and the second outlines the utilities provided with X Window to manipulate fonts The last appendix lists the FontCreator code Chapter 2 X Window Svstem 2 1 The history of X X was born in 1984 at Massachusetts Institute of Technology MIT X was the result of MIT Project Athena a project sponsored by Digital and IBM with a goal of providing a graphical networking environment that was hardware independent X design was based on the following principles p 5 e Do not add new functionalitv unless an implementor can not complete a real application without it e It is as important to decide what a system is not as to decide what it is Do not serve all the world s needs rather make the svstem extensible so that additional needs can be met in an upwardly compatible fashion e The only thing worse than generalising from one example is generalis ing from no examples at all e If a problem is not completely un
26. d whether to overwrite the file or abort the procedure If the New procedure is successful the message File created is displayed in the message window otherwise the message No file created appears The edit procedure starts with the program asking for the character to be edited If the user inputs a non printable character the program will issue a warning message and wait for valid input If the character already exists the user may select to overwrite the previous character or abort the edit operation Next the program will ask consecutively for character s width height x and y displacement All input is checked for validity The program will complain if the input is not integer or an invalid integer for example if the user enters a negative character width and wait for valid input to be entered When the user has input all required values he can draw the character glyph The program keeps an two dimensional array holding the bitmap of the character as zero white and one black values Each time the user draws a pixel of the character the program updates the array as well as the edit window and the actual display window This latter window displays the character as it will actually appear on the screen in its real size The edit window displays the character magnified so as to make it easy for the user to draw When the user finishes the draw procedure the program asks whether to save the character or not If the user sel
27. derstood it is probably best to pro vide no solution at all e If you can get 90 per cent of the desired effect for 10 per cent of the work use the simpler solution e Isolate complexity as much as possible e Provide mechanisms rather than policy In particular place user in terface policy in the client s hands X Window Svstem was a success Design of version 11 started in May 1986 During autumn 1986 Digital decided to base its entire desktop work station strategv for ULTRIX VMS and MSDOS on X The last version 10 release was made available in December 1986 In January 1987 the first X technical conference was held in MIT In September 1987 the first release of version 11 was made available In September 1991 the latest release release 5 of version 11 came out 2 2 Overview of X X is a network transparent window svstem X permits application programs to run on machines scattered through out the network and to be device independent The latter feature allows applications to be portable that is applications need not be rewritten recompiled or even relinked to work with new displav hardware X provides facilities for generating multifont text and two dimensional graphics in a hierarchy of rectangular windows Windows can overlap each other can be moved resized and restacked dy namicallv Windows are inexpensive resources applications using several hundred subwindows are common For example windows are often used to impl
28. dified the font shape or metric information 13 FAMILV NAME field FAMILY_NAME is a string that identifies the family of typeface designs that are all variations of one basic typographic style This name must be human understandable It is up to the type supplier to secure the proper legal title and not to infringe other s copyrights or trademarks Examples of FAMILY_NAME are Helvetica Times Times Roman Bitstream Amerigo WEIGHT_NAME field WEIGHT_NAME identifies the font s typographic weight that is the black ness of the font according to FOUNDRY s judgement The interpretation of this field can be problematic since it is subjective It is possible that a font which is identified as Bold from a font family to have almost the same blackness of a SemiBold font from another font family SLANT field SLANT is an encoded string identifying the way in which the character is designed The following are possible codes e R for Roman that is upright design e T for Italic that is italic design slanted clockwise from the vertical e 7O for Oblique obliqued upright design slanted clockwise from the vertical e RP for Reverse Italic italic design slanted counterclockwise from the vertical e RO for Reverse Oblique obliqued design slanted counterclockwise from the vertical SETWIDTH_NAME field SETWIDTH_NAME is human understandable string identifying the nom inal width per horizontal u
29. e character code as defined by the encoded character set given by CHARSET_REGISTRY CHARSET_ENCODING font properties For ISO8859 1 this code is the same as the character ASCII value The word SWIDTH followed by the scalable width in x and y of character as defined earlier The word DWIDTH followed by the width in x and y of the character in device units as defined earlier The word BBX followed by the width height x and y dis placement of the lower left corner from the character s origin The word BITMAP Then come h lines of the hex encoded bitmap padded on the right with zeros to the nearest byte multiple of eight The character segment ends with the word ENDCHAR e The file is terminated with the word ENDFONT 20 3 4 2 File format example STARTFONT 2 1 FONT Misc Greek Bold R Normal 24 240 75 75 P 65 ISO8859 1 SIZE 24 75 75 FONTBOUNDINGBOX 9 24 2 6 STARTPROPERTIES 20 FOUNDRY Misc FAMILY Greek WEIGHT_NAME Bold SLANT R SETWIDTH_NAME Normal ADD_STYLE_NAME PIXEL_SIZE 24 PIXEL_POINT 240 RESOLUTION_X 75 RESOLUTION_Y 75 SPACING P AVERAGE_WIDTH 65 CHARSET_REGISTRY ISO8859 CHARSET_ENCODING 1 MIN_SPACE 4 FONT_ASCENT 21 FONT_DESCENT 7 DEFAULT_CHAR 32 COPYRIGHT public domain NOTICE ENDPROPERTIES CHARS 70 STARTCHAR b ENCODING 98 SWIDTH 360 0 DWIDTH 8 0 BBX 9 22 2 6 BITMAP 1C00 3E00 3700 6300 21 6300 6300 6300
30. ects to save the character the program appends the character to chars txt and updates the character list and character number When the user clicks on Quit pushbutton the program first checks the state of the program If there is some other operation on the program will first ask the user whether to abort it or not If no other operation is on the program will ask the user to affirm his choice If the user insists on his choice the program will merge header txt and chars txt files and name the new file after the filename When designing the program it was thought that no special Save button had to be implemented It would rather complicate the interface rather than make it easier for the user Instead a mechanism is provided that merges the two files whenever the user quits or loads or creates a new font file This way the procedure of breaking up and merging the font file is kept transparent to the user The user has only to decide whether a character should be saved in the font file or not The program keeps track of its state by use of special flags thus achieving two things One it knows whether the user tries to 33 load or create a font file while he is editing a character or tries to edit a character while no file has been opened or tries to make an operation which will put data in risk or simplv is unacceptable This wav when such a case occurs the program will involve the user in a dialogue bv means of po
31. ement individual user interface components such as pushbuttons dialog boxes menus etc X applications in terms of the network are the clients that use the network services of the window system A program running on the machine with the display hardware provides these services and so is called X server X server controls and draws all output to the display monitors reads input and forwards it to the appropriate clients for processing X consists of a network protocol an interface library Xlib and client libraries Xt Intrinsics The X protocol and X library avoid specifying push buttons dialogue boxes menus or how an application should respond to user input but provide a set of mechanisms that can implement a variety of user interface policies Toolkits providing menus scrollbars and so on higher level graphics libraries and user interface management systems UIMS can be all implemented on top of the X library The most popular specifications for interfaces are Open Look and Motif 2 3 Windows in X Creating windows is what a windowing system is all about The X Window system supports one or more screens containing overlapping windows or subwindows A screen is a physical monitor and hardware which can be either color or black and white There can be multiple screens for each display or workstation All windows in an X server are arranged in strict hierarchies At the top of each hierarchy is a root window which covers each of
32. f he made an error he could avoid bad consequences and abort the operation The next point that needed consideration was the 27 messages that should appear in the message window The tvpe of messages that should be displaved in the message window becomes clear once the need for providing such a window is thought about Its use is to make apparent the state of the program 2 therefore messages such as Loading a font file or Editing character s bitmap should be printed in it This way useful feedback is provided to the user and the user can act more readilv 4 2 2 Interface implementation FontCreator s main window consists of five pushbuttons placed at the top of the window and labelled as Load New Edit Quit and Help and a message window placed at the bottom of the main window capable of displaying various messages for the user depending on the state of the program and the user s actions In more detail The first push button from the left is Load button By placing the mouse pointer on it and holding down the mouse button the user is informed for the Load pushbutton operation with a message displayed at the message window By clicking the mouse button on Load the load procedure is initiated If a font file was being edited the program will first save the file before continuing the load operation The user is prompted by a pop up window to enter the file name to be loaded At any ti
33. ftopef greek bdf gt greek pcf We then copied the PCF file to a font directory and updated the directory information cp greek pcf SHOME fonts mkfontdir SHOME fonts mkfontdir created a file called fonts dir which looked like that 1 greek pcf misc greek bold r normal 24 240 75 75 p 65 iso8859 1 The first line of the file is the number of valid font files found and the second line is the name of the file followed by the XLFD font name We then created an alias file in SHOME fonts named fonts alias which looked like that greek misc greek bold r normal 24 240 75 75 p 65 iso8859 1 Finally we tested the new font by updating the font path and starting a new xterm xset fp HOME fonts xset fp rehash xterm fn greek Instead of starting a new xterm we could have used xfd to display the new font xfd fn greek 44 Chapter 7 Appendix B Font Utilities 7 1 Displaying fonts utilities There are a number of utilities which can be used to help us display and select a font We will give a brief description of the operation and syntax of each utility e SHOWFONT showfont displavs information about the specified font Its svntax is showfont l server servernamej extents_only l I m L M l unit HI l pad l bitmap pad value l start first_char end last_char fn fontname showfont is only available with X11R5 e XFD xfd displays all the characters in a font Its syntax is xfd l opt
34. h the font was designed RESOLUTION_CY field RESOLUTION X field is an unsigned integer string giving the vertical res olution in dots per inch dpi for which the font was designed SPACING field SPACING is an encoded string that gives the escapement class of the font A font can be proportional spaced or fixed width A fixed width allows the same width for all characters In a fixed width font a w will take the same space as al In a proportional spaced font the space each character takes is character dependent The encoding of SPACING is as follows 7P standing for proportional M standing for monospaced and C standing for CharCell 15 CharCell is a monospaced font that follows the standard tvpewriter character cell model that is that all characters can be modelled as boxes of the same width and height AVERAGE WIDTH field AVERAGE WIDTH is an unsigned integer string tvpographic metric value that gives the mean width of all characters in the font For monospaced and charcell font this is the width of all characters in the font CHARSET REGISTRV and CHARSET ENCODING fields CHARSET_REGISTRY and CHARSET ENCODING are registered names identifving the registration authoritv that owns the specified encoding and the coded character set as defined by that registration authority respectively The following CharSet names are registered for use in font names under the X Logical Font Description 15O8859 1
35. has been added which is portable across all hosts and is called Portable Compiled Format or PCF PCF font files have an extension of pcf The placement of the character s bitmap on the screen is controlled by properties such as the ascent the descent the character s width height and spacing We will look in more detail in character s properties 3 2 Character s properties We will define the most basic of the character s metrics e Character s width is the number of pixels between the leftmost and the rightmost parts of the character e Character s height is the number of pixels between the uppermost and downmost parts of the character 11 Character s ascent is the extent of the character above the base line Character s descent is the extent of the character below the base line Character s x displacement is the horizontal distance of the lower left corner from the origin of the character Character s y displacement is the vertical distance of the lower left corner from the origin of the character Both x and v dis placement can be positive or negative For example character p extents below the baseline therefore the baseline is in its font box and y displacement will be negative and equal to the extent of the character below the baseline Apostrophe acter on the other hand has the baseline underneath its font box and the y displacement will be positive char Scalable width
36. in its font box and y displacement will be negative and equal to the extent of the character below the baseline Apostrophe character on the other hand has the baseline underneath its font box and the y displacement will be positive At any time you can quit the edit procedure by clicking on the Cancel pushbutton of any of the pop windows that appear The program performs validity checks on the your input If the input is invalid or out of range then you will be informed and asked to reenter the value For example if the you try to edit a non printable character enter a non inte ger value when an integer was expected or enter a negative width or height the program will complain If the character to be edited already exists be fore continuing the program will ask you whether to overwrite the existing character or abandon the editing operation When you finish entering the required input two windows appear The bigger window is the edit window which has a grid drawn into where you can draw the bitmap of the charac ter A line drawn in the edit window shows the baseline A smaller window at the upper right corner of the first displays the actual character as it is being drawn The grid displayed in the edit window consists of w columns and h rows where w and h are the width and height of the character respec tively already entered At the bottom of the edit window a small message window reminds you of the character being edited
37. ions fn font where options include display dpy X server to contact geometry geom size and location of window start num first character to show box show a box around each character center center each character inside its grid 45 rows number number of rows in grid columns number number of columns in grid XFONTSEL xfontsel is a program that can be used to select easily a font by use of its XLFD name Wildcards can be used and in the case there are more than one fonts matching the description only the first font found is shown xfontsel syntax is xfontsel options fn font where options include display dpy X server to contact geometry geom size and location of window pattern fontspec font name pattern to match against print print selected font name on exit noscaled do not use scaled instances of fonts sample string sample text to use for 1 byte fonts samplel6 string sample text to use for 2 byte fonts XLSFONTS xisfonts lists all fonts available in a X server Its syntax is xisfonts options l fn pattern where options include beginitemize ILU give long info about each font m give character min and max bounds C force columns 1 force single column u keep output unsorted o use OpenFont QueryFont instead of ListFonts w width maximum width for multiple columns n columns number of columns if multi column display displayname X server to contact 46 7 2 F
38. me the user can cancel the operation by clicking on the Cancel pushbutton of the dialogue box If the user chooses to continue and enter a filename the program will try to load the file On success a message File loaded ok will appear on the message window otherwise File not found will be displayed and a warning sound will be heard The second pushbutton is New button By holding down the mouse button while the mouse pointer is on New the user can be informed of the New operation by a message displayed in the message window By clicking on New pushbutton the user initiates the procedure of creating a new font file If a font file was being edited the program will first save the file before continuing the new operation The first pop up window that appears asks for the font family name Next the user is asked whether he wants to edit the default font properties file If the user selects to edit the file a full screen editor will appear with the defaults file already loaded enabling the user to make any alterations required Once the user exits the editor the program will scan the file to determine the new file name If this filename exists the user will be prompted with a pop up dialogue box asking whether the existing file will be overwritten Again during the whole new procedure the user can abort at any time by clicking the Cancel 28 pushbutton of any of the pop up windows appearing The third
39. nd on line help to be displayed in it Clicking on Ok push button of the help window closes the help window 4 3 FontCreator toolkit 4 3 1 ToolWindow structure As already mentioned in FontCreator the base widget is the ToolWindow The ToolWindow structure p 49 contains a pointer to the display on which the window is to be mapped the parent of the window the window itself information about the window s graphics context font width height and name Perhaps the most important element of the structure are three functions namely drawfunc userfunc and eventfunc The drawfunc function redraws the window after an expose event has occurred the eventfunc func tion takes care of all events that take place in the window and userfunc can be associated with a user callback function Not all of these functions need to be defined for every of ToolWindow subclasses except perhaps for the draw func Since the toolkit is built in an object oriented way the user does not access the ToolWindow fields directly To manipulate ToolWindow object a set of functions is provided that allow the user to set or get the values of ToolWindow s fields In the small toolkit used for FontCreator an array of ToolWindow structures was used to hold all ToolWindow structures created For a larger application this would have been inefficient Instead a linked list of ToolWindow would permit the user to create as many ToolWindows as the computer s memory all
40. ng a new font Once you create your font file exit FontCreator by pressing Quit Then convert the font file from BDF format to PCF format using bdftopef bdftopef filename gt filename pcf Copy the PCF file to a font directory cp filename pef SHOME fonts Since you add a new font file you should update the directory informa tion with mkfontdir mkfontdir searches the directory for valid font files in the following order PCF SNF and BDF mkfontdir SHOME fonts mkfontdir creates in fonts directorv a file named fonts dir fonts dir first line is the number of valid font files found in the directorv and the second line is the font file name followed by the XLFD font name defined in the font file Next create an alias for the font named HOME fonts fonts alias The contents of the alias file will be the alias of the font followed by the XLFD X Logical Font Description font name as defined in fonts dir Now vou can test the new font file Update vour font path using xset xset fp HOME fonts xset fp rehash Finally you can start an xterm with the new font file 43 xterm fn lt aliasname gt 6 9 Example We first created a new font file The font family name was greek therefore the program created the font file with a greek bdf name We then edited some characters of the Greek alphabet and saved them in the file Once we left FontCreator we first converted greek bdf file to PCF format bd
41. ng or file system implementa tions e Supports arbitrarily complex font matching or substitution e Is extensible In more detail It should be possible to have font names that are long enough and descriptive enough to have a reasonable probability of being unique The name itself should be structured to be amenable to simple pattern matching making simple for X clients to limit font queries to a subset of all possible fonts X clients applications that require a particular font should be able to load it without knowledge of the file system The X Logical Font Description must be extensible so that new font properties can be added to conforming fonts without making old files obsolete or incompatible 3 3 2 FontName description Each FontName is composed of two strings a FontNameRegistry prefix which is the registration authority that ows the font and a FontNameSuffix In the X protocol specification the FontName is required to be a string therefore numeric fields are represented in the name as string equivalents The FontName structure is the following FOUNDRY FAMILY_NAME WEIGHT_NAME SLANT SETWIDTH_NAME ADD_STYLE_NAME PIXEL_SIZE POINT_SIZE RESOLUTION_X RESOLUTION_Y SPACING AVERAGE WIDTH CHARSET_REGISTRY CHARSET_ENCODING We will describe each of these fields separately FOUNDRY field FOUNDRY is an X registered name the name or identifier of the supplier of the font data or the identifier of the organisation that last mo
42. ng that gives the escapement class of the font A font can be proportional spaced or fixed width A fixed width allows the same width for all characters In a fixed width font a w will take the same space as a l In a proportional spaced font the space each character takes is character dependent The encoding of SPACING is as follows P standing for proportional M stand ing for monospaced and C standing for CharCell CharCell is a monospaced font that follows the standard typewriter character cell 40 model that is that all characters can be modelled as boxes of the same width and height e AVERAGE WIDTH is an unsigned integer string typographic metric value that gives the mean width of all characters in the font For monospaced and charcell font this is the width of all characters in the font e CHARSET REGISTRV and CHARSET_ENCODING are registered names identifving the registration authoritv that owns the specified encoding and the coded character set as defined bv that registration authority respectively The following CharSet names are registered for use in font names under the X Logical Font Description IS0O8859 1 Latin alphabet No 1 ISO08859 2 Latin alphabet No 2 IS08859 3 Latin alphabet No 3 ISO08859 4 Latin alphabet No 4 ISO8859 5 Latin Cvrillic alphabet 1S08859 6 Latin Arabic alphabet 1SO08859 7 Latin Greek alphabet 1SO08859 8 Latin Hebrew alphabet 15O8859 9 Latin alphabet No 5 e MIN SPACE is
43. nit of the font according to the FOUNDRY s judgement As with WEIGHT_NAME since its definition is subjective the interpretation can be problematic What can be characterised as Nor mal for a family font may be almost equivalent in typographic feel to a Narrow font from another family Examples of SETWIDTH_NAME are Normal Condensed Narrow and Double Wide 14 ADD STVLE NAME field ADD STVLE NAME is a string that identifies additional typographic style information not captured by other fields Examples of ADD STVLE NAME are Serif Sans Serif Informal and Decorated Serif characters have a smaller line that finishes off a large stroke where Sans Serif characters do not have these finishing strokes PIXEL SIZE field PIXEL SIZE is an unsigned integer string giving the body size of the font at a particular POINT SIZE and RESOLUTION_Y PIXEL SIZE can be ap proximated by the following equation PIXEL SIZE ROUND RESOLUTION_Y POINT SIZE DeciPointsPerInch where the value of DeciPointsPerInch is 722 7 POINT SIZE field POINT SIZE is an unsigned integer string giving the body size of the font in device independent units POINT SIZE is not necessarily equivalent to the height of the font bounding box POINT SIZE is expressed in decipoints 72 27 points equal one inch RESOLUTION X field RESOLUTION X field is an unsigned integer string giving the horizontal resolution in dots per inch dpi for whic
44. ont conversion utilities There are a number of utilities that can be used to convert one font format to another We briefly describe their use and svntax BDFTOPCF bdftopcf converts BDF format fonts to PCF format bdftopcf replaced in X11R5 the bdftosnf utilitie which compiled BDF font files to SNF format Its syntax is bdftopef p u m l M L t li l o pef file bdf file where for p is 1 2 4 or 8 and for s is 1 2 or 4 CONVERTFONT convertfont reads the font files and converts them to the specified for mat Its syntax is convertfont abcdnstv files a Write readable text version of file Adobe ASCII b Write a CScript format file the default c STR Set the comment associated with the font d STR Set the output destination directory to STR f N Set the maximum length of the output filename to N char acters default 8 n STR Set the name of the font o STR Set the output file name s STR Set the size of the font 9 Set the size of the font by magic t Tell briefly what is in the font tv Tell in detail what is in the font ta Tell in gory detail what is in the font v Write a vfont file vf Write a vfont file forcing fixed widths x Write BDF 2 1 format file for X11 M Force matrix font encoding use carefully AT Convertfont reads each named font and then writes it out in the specified format The output name is derived from the input name by replacing the
45. owed and manipulate the ToolWindows in a much more efficient way 4 3 2 Text Label widget The simplest of all widgets is the Text Label widget The Text Label widget is used only to display text Since there is no input or user action associated with it there is no need for an event function or user callback function The only events the Text Label has to take care of are expose events For this reason LabelDraw function is implemented LabelDraw redraws the Text Label in case of an expose event 30 4 3 3 PushButton widget The PushButton widget is much more complicated widget A PushButton can be pressed or released and has a user callback function associated with it When a ButtonPress event occurs the 3D bevel of the PushButton is reversed This way the effect of the button being pushed in is created On the arrival of a ButtonRelease event the 3D bevel is restored to its normal state giving the look of the button being pushed out When the PushButton is pushed in the ProvidePushButtonMessage function is executed and if a message exists for that PushButton it will be displayed in the message window This gives the opportunity to the programmer to display a message explaining the use of the PushButton that is what will happen when the PushButton s callback function is executed If the time between the moment the pushbutton is being pressed and released is less than response time a constant which was set to 500 milliseconds for Fon
46. p up windows trving to figure out what the user reallv wants to do and make sure that is done properly The other thing achieved is that the user has on line help that corresponds to the operation being done For this reason four help files namely general hlp load hlp new hlp and edit hlp are provided Each time Help pushbutton is clicked the program first checks its state to decide which help file is appropriate to be loaded and then displays the help information in the special help window The program displays all messages to user in its message window These messages include messages informing the user of the state the program is in such as Saving file messages that affirm that action has been taken such as File loaded or warning messages with a beep sound All these messages are stored in messages txt file This way messages can easily be changed if need for such action arises 34 Chapter 5 References 1 R W Scheifler amp J Gettvs X Window System Second Edition Digital Press USA 1990 2 D McNutt amp M O Neal The Administrator Font Formats and Utilities The X Resource Issue 2 Spring 1992 3 I Sommerville Software Engineering Fourth Edition Addison Wes ley Ltd New York 1992 4 D Heller Motif Programming Manual O Reilly amp Associates Inc Sebastopol USA 1991 5 E F Johnson amp K Reichard X Window Applications Programming MIS Press New York
47. pushbutton is the Edit button By placing the mouse pointer on it and holding down the mouse button a message displayed at the message window informs the user of the Edit operation By clicking on Edit pushbutton a series of pop up windows appear prompting the user to enter the character to be edited the character width height x and y displacement At any time the user can quit the edit procedure by clicking on the Cancel pushbutton of any of the pop windows that appear The program performs validity checks on the user s input If the input is invalid or out of range the user is informed and asked to reenter the value For example if the user tries to edit a non printable character enter a non integer value when an integer was expected or enter a negative width or height the program will complain If the character to be edited already exists before continuing the program will ask the user whether to overwrite the existing character or abandon the editing operation When the user finishes entering the required input two windows appear The bigger window is the edit window which has a grid drawn into where the user can draw the bitmap of the character A smaller window at the upper right corner of the first displays the actual character as it is being drawn The grid displayed in the edit window consists of w columns and h rows where w and h are the width and height of the character respectively entered by the user A line drawn in
48. r views each font file as consisting of two separate files a header file that contains the font properties and a characters file that contains all information such as the character s encoding width height and bitmap for all characters Adopting this framework when a font file is loaded it is broken down to header txt and chars txt files header txt contains the font properties and chars txt contains all character segments The number of characters is not contained in neither file Instead this number along with a list of all the characters contained in the file is being kept by the program and updated every time a new character is saved This way the program can easily check if the user is trying to edit a character that already exists and inform the user and ask him about the step to be taken next overwrite the existing character or abort the editing procedure Likewise when a new font file is created the program creates a header file and initialises the value of characters number to zero The user may select to use the default font properties file as is or make changes If the user chooses 32 the latter possibilitv a full screen editor is called within the program and the user can easilv edit the defaults file Once the user quits the editor the program will scan the file to determine the new font file name This will be the font family name with the bdf extension If a file with the same name exists the user is aske
49. s designed to contain only five push buttons Load New Edit Quit and Help The need for having Load and New pushbuttons 26 is obvious The user may want to load an existing font file or create a new one But along with these two buttons shouldn t there be and a Save one After careful consideration the answer to this question was negative The user does not have to save the file The font file loaded or created exists anvwav What the user saves are the characters So if a save question should be asked to the user that should happen once the user has finished drawing a character For this reason it was decided that each time the user finishes drawing a character s bitmap a dialogue box should appear asking him whether to save or not Simplifving the user interface is more easilv said than done This became apparent when designing the dialogue boxes for the Edit procedure If the font is monospaced where all characters can be viewed as boxes of the same width and height the user has to enter only the character to be edited The width height x displacement and y displacement of each character remain the same for all character in the font and can be calculated from the font properties defined in the font file But for a proportional font where the size of character is not constant the user has to enter the width height x displacement and y displacement of the character What makes things worse i
50. s the fact that novice users may find it difficult to understand what exactly is meant by x and y displacement The best solution would have been to design the program so that it could scan the font file to determine whether the font was fixed width or proportional and ask for more information only in the second case Unfortunately due to lack of time this solution could not be implemented although we hope that a next version of the program will adopt it Therefore there were two alternatives either create a program that could only manipulate fixed width fonts and reduce the information needed from the user or create a program that could handle all types of fonts but on the other hand increase the stress upon the user The second alternative was chosen since proportional fonts account for the largest part of fonts being used and could not have been excluded so easily Another point where special attention was paid was the design of dialogues All dialogues had to be uniform and their look and feel should remain the same For this reason the same dialogue box was used through out all the dialogues What changed was the message at the text label Clicking on Ok pushbutton would always signalled that the user accepted the message and if appropriate had entered input and clicking on Cancel pushbutton would signalled that the user wanted to abort the operation Providing a cancel possibility was a way to make the user confident that even i
51. tCreator the callback function will be executed The reason of implementing the PushButton event function this way is that the user can either press the button to see its operation or click it to execute the callback function On expose events PushButtonDraw function redraws the PushButton 4 3 4 Text Entry widget The Text Entry widget is used to get input from the user The programmer can associate a user callback function with it that will be executed when the user presses lt Return gt The TextEntryEvent function handles user s key presses and responds accordingly If the user enters printable characters the function will append them to the ones already entered and if the width of the Text Entry widget is not long enough for all the characters to be displayed it will scroll them to the left If the user presses lt Delete gt or lt BackS pace gt the last entered character will be deleted allowing the user to correct wrong input On expose events the TextEntryDraw function will redraw the Text Entry widget 4 3 5 Dialogue window The dialogue window is a transient pop up window having a Text Label widget at the top for messages to be displayed just beneath a Text Entry widget for user s input and two PushButton widgets at the bottom named OK and Cancel Pressing the lt Return gt key has the same result as Clicking on the OK button There are two ways for a pop up window to be 31 mapped on the
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