triroff, an adaptation of the device-independent troff for formatting tri
Contents
1. Ossana Kernisghan ditroff ditroff Buchman Berry fforld ditroff bditroff 3 0894 3982 89 030003 24 12 00 Received 22 August 1988 1989 by John Wiley amp Sons Ltd Revised 22 November 1989 Z BECKER AND D M BERRY WACO Aol HRA OH 4 eA OCREYE bw SRR gm t xu sa Jn AKA LAR de GN NM IN d 4 Eee iEn ES KR CREE 24 RING CORE EHAR Y RAW YEO OA ee HAKAN LEAD VIG oR OAK IRS 28 Shar nx A Siw Se BU KR Rn oO wea mS Zo Rae dH dB moe mio lt RS au p SE Eo 00 IND m dB 260 KAKRA OWS Offa vite RESCH YK FLORA SO sO PNEU2. Ree 6 Q0 d amp d t 2ggocG u PUOHH Q7Uoo 0 LOO ceca RA re a2 A dd Grae n duo 4 G mooodB8sSd mo ton 0 nd qx d Quas PL OHNHQCHRUHS AMER SO XK e Hoveipe 6 RISK AANA a Day Hons LE e D G4H BOT PS D HR AOR Bo v ss A X LX E DA ai s WR i 5 X H a nr ER E E Ossana and Buchman and E amp up EE d NEUSS p MSEK EMER Soe Sy clE Fy Bu ae E ge Rain RE ER Aye g KE Ey E BEE Re Jg iz Hex i IIS ME abb un e rE PILLE KENE d R Hg 8 MR 5 2H Ds J Cep itroff 1 KERE WC ang eK EHX E edi m cp ONE RE EMS WP BO eX WE E EES RE ERE DX E EE M o m REREPMB E iip KENE Eirg E ss Iq O RERE A i8 BREHM KERE thi me RIES lt gt Rk wh ERR 22 RE SR eR HR El m Bf RRE OCunage d d cr Meu d t dd ToP h OHH EL Re Ms onc ES ZE Te om BE wae Has C HER a lt ex m KEKEE HHEN de tE Kernighan s ditr Berry s ffortid geod motuum OP R UYES o E e o n There has already been much work done in With variants
3. ll n XXu TS additional if invoked from diverted text br AB CD TE additional if invoked from diverted text Jf in reset indentation to previous value ll reset line length to previous value The output obtained is J awp In other words the layout of the page is unchanged by the application of bditroff Thus the page prepared only by ditroff and a device driver can be used as a guide to the ultimate appearance of the page after application of bditroff Finally observe that the algorithm is page preserving That is the page on which a given occurrence of a character appears does not change although the character s loca tion on that page might very well change This fact means that the algorithm needs only to consider one page at a time that the maximum storage required for the program is that to store one page and that the output of the algorithm can be conveniently passed to any device driver which works page by page That is it can assume that once it has built the description of page n and has seen the beginning of the next it may print page n with the assurance that no more information for page n can arrive later A POSTSCRIPT device driver behaves under this assumption as the POSTSCRIPT language is a page description language REQUIREMENTS ON THE INPUT TO bditroff In order for the algorithm described in the previous section to work it must be possible for the program 1 to determine t
4. 18 19 20 21 22 23 24 Abe and D M Berry indx and findphrases A System for Generating Indexes for Ditroff Documents Software Practice and Experience 19 1 1 34 1989 C Buchman D M Berry and J Gonczarowski DITROFF FFORTID An Adaptation of the UNIX DITROFF for Formatting Bi Directional Text ACM Transactions on Office Informa tion Systems 3 4 1985 N Batchelder and T Darrell Psfig DITROFF Preprocessor for POSTSCRIPT Figures Computer and Information Science Department University of Pennsylvania Philadelphia PA 19104 J D Becker Multilingual Word Processing Scientific American 251 1 96 107 1984 J D Becker Arabic Word Processing Communications of the ACM 30 7 600 611 1987 J L Bentley and B W Kernighan GRAP A Language for Typesetting Graphs Tutorial and User Manual Computing Science Technical Report No 114 AT amp T Bell Laboratories Mur ray Hill NJ 07974 December 1984 S Carson and D M Berry Alg Filters for Typesetting Algorithms News Usenet 1985 K P Chow and C T Hung Chinese Workbench An Interactive Environment for Chinese Writers Technical Report TR 87 07 Centre of Computer Studies and Applications Univer sity of Hong Kong June 1987 EgWord Version 2 2 English Reference Manual Ergosoft Corp Tokyo Japan October 1986 FeiMa II Chinese Word Proces
5. ps 11 N and in for desired printing br break Make sure that the appearance of mono spacing is not N destroyed by spreading characters to fill the line na signal beginning of vertical text NN x TS additional NN if invoked from diverted text VS n VV set vertical spacing 55 n VM 12 set space width to be the distance between columns nr VM 5 should be 4 or 5 to get spacewidth 4 or 5 times normal nr VV n s FORMATTING TRI DIRECTIONAL TEXT 19 should be 1 or 1 1 times current ps de E br break signal ending of vertical text NN x TE additional NN if invoked from diverted text ad go back to normal spreading of lines VS reset vertical spacing what it was 55 12 set space width back to normal The BT macro uses the values of the registers VM and VV to adjust the inter word hor izontal space and the inter line vertical space to help make it clearer to the human eye that the text is to be read from top to bottom rather than horizontally It is recommended that VM be set to 4 or 5 and that VV be set to 1 or 1 1 times the current point size To assist the user in in forcing the location of the columns the macros RA BC and EC are defined which force a given number of right adjusted columns force a given number of centered columns and reset normal page margins respectively Their definitions are de RA force right adjusted 1
6. the tri directional formatting system described herein has some weaknesses Some are easily repaired and others are not The problems and possible solutions are presented one by one in this section Orientation of punctuation characters Readers who know a Far East language will have noticed that the punctuation symbols in the examples are oriented incorrectly for top to bottom printing They are oriented correctly for horizontal printing Specifically the stand alone punctuation symbols the period the comma etc are in the lower left hand corner of their bounding boxes and the bracketing punctuation symbols the parentheses the braces etc are oriented in their bounding boxes to wrap around the ends of enclosed horizontal text A stand alone sym bol needs to be in the center of gravity of its bounding box and a bracketing symbol needs to be rotated 90 counter clockwise in its bounding box so that it can wrap around an end of top to bottom text Probably the simplest solution is to add the missing alternative forms to the character sets in unused positions Then the bditroff program can be modified so that when it is working with a region of top to bottom text it simply replaces the codes for the horizon tal versions of these characters by those for the alternative vertical versions of the same characters 22 Z BECKER AND D M BERRY Inclusion of proportional spaced Latin characters in top to bottom text triroff supports
7. and registers if any of them conflict with those of the base macro set used as indeed happened when these were used with the macro package sup plied by the editors of this journal for preparing the camera ready copy Moreover these macros assume that their invocations are not inside diverted text If they are invoked in diverted text the transparent output commands beginning with x must be changed to begin with NNNN x i e an extra pair of V s must be added to delay the output until the surrounding text is printed In order to allow proper control of horizontal spacing in a horizontal printing of the Far East language fonts the following special characters have been provided 1 The interword space has been set at 125 em so that the proper horizontal inter character spacing can be obtained just by making each Far East language character a word 2 The blank character f al al in the upper left hand corner of the charac ter matrix has the same 1 em width that all other characters have 3 The character which is normally 1 6 of an em space has been set to have the width of a full character so it can be used to force a full character width without forcing a font switch to font al the font of the blank character and without forcing emission of a character i e ditroff treats use of as a move ment 4 V character which is normally 1 12 of an em space has been set to have half the width of the character It
8. ffortid has been applied is irrelevant to bditroff because it leaves horizontal lines intact The description of the algorithm in the next subsection appeals to these invariants to demonstrate that the algorithm does work THE bditroff ALGORITHM AND ITS USE The following discussion assumes the following input in which lower case letters represent characters of a variable width font to be printed from left to right and in which upper case letters represent characters of a constant width font to be printed top to bottom Note that the algorithm can be used to print any text from top to bottom so long as the text is composed of characters that have the same constant width either naturally or via the cs command Consider the input site R s9ada is a trademark of the u s dept of defense ms dos is a trademark of microsoft inc s 10 br Nx TS ABCDEF GHIJKL MNOPQR STUV WXYZ Pees TE ft R s9ffortid is a trademark of berry computer scientists ltd unix is a trademark of at amp t bell laboratories s 10 Note the br commands before and after what is considered top to bottom text Note also the transparent outputs V x TS and x TE signalling the start and end of what is to be printed from top to bottom Assuming a line length that allows 5 constant width characters and intervening blanks per line and ignoring page breaks that might occur in the midst of the example the output of ditroff follows shown sch
9. met The basic structure proposed works because of certain observable invariants in tri directional text An algorithm that exploits these invariants is given The algorithm allows a tri directional formatter to be built on the existing full function ditroff system It is explained how the algorithm and the underlying ditroff system can be exploited by the layout designer to achieve most desired effects Some of these effects are illustrated by examples However not all desired effects are achievable the weaknesses of the present system are identified and solutions are proposed for them Implementation of these solutions are left to future work EXISTING SOFTWARE There are a variety of systems for formatting Japanese or Chinese printed from left to right mixed with other left to right languages e g English These include Kameyama and Hasebe s jtroff 17 11 Nagashima and Kawabata s early adaptation of TEXTM 19 for Japanese 22 Saito s JTEX 24 and Berry s and Chow s adaptations of ditroff 12 8 These can also print Japanese and Chinese from top to bottom simply by printing from left to right in landscape mode with a font consisting of the characters rotated 90 coun terclockwise All of these systems use the standard 94x94 matrix arrangement of the 8 Z BECKER AND D M BERRY Japanese or Chinese characters as the case may be The first four of these formatters have modified the base program troff or TEX so that two byte ch
10. section on weaknesses i e with variable width Latin language text printed sideways so that its left to right flow matches the top to bottom flow of the containing Far East language text Due to the limitations mentioned in that section these abstracts could not be typeset as part of the docu ment that ends with the end of this paragraph Instead they had to be typeset as a single other docu ment and pasted in 26 Z BECKER AND D M BERRY Figure 2 Japanese Abstract Figure 3 Chinese Abstract
11. the file is stored as it appears changing either of these lengths means mas sive manual editing If one could recover the original entry order of the characters from the text the original entry algorithms could be applied to the stream of characters relative to the new line and page lengths However with raw printable characters in which punc tuation is not distinguished by language complete recovery is impossible because of punctuational ambiguities Thus a system in which the text is stored in the original input order with the original language information is more general This same problem occurs with many but not all WYSIWYG systems because many of them store the characters in the visual order FORMATTING TRI DIRECTIONAL TEXT 9 DESIRABLE PROPERTIES OF A TRI DIRECTIONAL FORMATTING SYSTEM There appear to be a number of desirable properties that should be satisfied by a tri directional formatting system that make it more general more functional easy to use and easy to program In order to allow maximum formatting flexibility with easily changed sizing charac teristics it is necessary to store the characters of the document in the order entered with backspacing corrections normalized out and to let the formatting algorithm be applied at the time of printing This suggests a batch formatting system but it does not preclude a WYSIWYG system so long as the formatting algorithm is fast enough to be applied on the fly with li
12. too is treated by as a movement with no character emission 5 The amp character is still the zero width character 6 Finally the XX character has been provided in the S font as printing nothing but having a width equal to that of the blank and all other characters It is a true character so ditroff emits a character It is on the first special font so it can be used regardless of the current font without having to request a new font EXAMPLES This section shows a sample of input and of printing it both from left to right and from top to bottom Unlike in 12 there is no need for cutting and pasting to get both of the outputs on the same page The text is a famous Chinese poem composed around 700 A D by the most renowned poet in China Li Bai The input is N eON ae N c1N bO N ccN cO N b7N ee N b8N 7 N alN a4 N b5N b N cON a7 N c3N c N beN e5 f cl N alN a3 Dr f da aa f c6 ac N cbN be N ccN cO N b7N ee N alN a4 N cAN e3 N c6N ac N bbN d7 N b8N ce N b6N bf N alN a3 FORMATTING TRI DIRECTIONAL TEXT 21 Its output in left to right mode is ik AA HOC Bee Its output in top to bottom mode is zB X it Hb o This printing was done using the BT ET RA and EC macros defined above WEAKNESSES The enthusiasm of the authors notwithstanding
13. would be set to mean right to left when the result of saying TB is found and would be set to mean left to right when the result of saying x TM is found The result of saying x TE can be used to end the top to bottom region for either CONCLUSIONS As can be seen from this paper triroff works mostly as desired That is the three pro grams ditroff ffortid and bditroff combine to produce an effective tri directional for matter that accepts any input accepted by ditroff including that produced by any of ditroff s preprocessors works with any set of ditroff macros and generates output indis tinguishable from ditroff s This output is then acceptable to any ditroff device driver The use of this software to typeset this paper is a demonstration of this claim The main strength of the triroff approach is its modularity This modularity allows each new direction of printing to be attacked as a separate problem uncluttered by con cerns with other directions and other formatting problems This modularity allows the use of an unmodified ditroff which in turn allows the use of all of ditroff s preprocessors and macro packages There are a number of minor problems both in appearance and in function However their solutions are straightforward because of this modularity For example changing the orientation of the punctuation symbols and moving them in the bounding box involves no change to any of the prog
14. AL TEXT 11 per row in addition to whatever else is available for the device Because the standard ditroff program is used all existing preprocessors and macro packages still work The system generates output in exactly the same format as is generated by the existing stan dard ditroff Thus all existing postprocessors still work and the formatted output can be printed on any existing device for which both a device driver and all the required fonts are available The ability to format right to left and top to bottom text in addition to left to right text is created by the addition of two programs between the basic ditroff pro gram and the device drivers These two programs each accept as input the output of ditr off and produce output in the same form as ditroff output Thus these two programs can accept as input each other s output as well and can send their outputs to the same post processors to which ditroff can send its output Because the input to the underlying ditroff is in time order ditroff s output reflects formatting decisions made as if all the text were written from left to right The first of the additional programs is ffortid which on a line by line basis reorgan izes the line of text so that each contiguous sub line of text in left to right fonts is printed from left to right and each contiguous sub line of text in right to left fonts is mirrored about its own center in its current position so that it is printed from right
15. ELECTRONIC PUBLISHING VOL 2 3 3 26 DECEMBER 1989 triroff an adaptation of the device independent troff for formatting tri directional text ZEEV BECKER pn RT M AND DANIEL BERRY 73 9x77 7 X JV NY FH Computer Science Department Technion JL Haifa 32000 w 1t Israel fti Al SUMMARY This paper describes a system for formatting documents consisting of text written in languages printed in three different directions left to right right to left and top to bottom For example this paper is such a document because it contains text written in English Hebrew Japanese and Chinese The system assumes that the input is in the order in which the text is read aloud and it produces output in which each language is printed in its own correct direction but for which a human cognizant of the reading conventions will reproduce the input order The system consists of three major pieces of software Ossana and Kernighan s ditroff for formatting text consisting of only left to right or unidirectional text Buchman and Berry s ffortid for rearranging right to left language text buried in ditroff out put to be printed from right to left and a new program bditroff for arranging that top to bottom text buried in ditroff output is printed from top to bottom Below are translations of this English language abstract except for this paragraph into Hebrew Japanese and Chinese The lat
16. RIPT fonts then the added characters can in fact be POSTSCRIPT programs that build and show the numerals using digits from one of the available Latin fonts Since the length of these numerals cannot be too much longer than the width of a normal Far East language char acter the number of these is limited Given the fonts used in this paper it appears that the maximum length of such numerals is two digits thus only 99 numeral characters would have to be added to the Far East font 2 Use the above mentioned facility such as available in devps that can rotate any text any angle to build a macro that rotates its argument about its center and fools ditroff into believing that the size of the argument is the same as that FORMATTING TRI DIRECTIONAL TEXT 23 of the normal Far East font character As one of the referees pointed out in the Xinjinang Uighur region of the PRC there is another language spoken which is not written in any of the directions covered so far in this paper The language is Mongolian and it is written from top to bottom on lines that flow from left to right Even if a font were available for the language the current version of the software cannot handle its printing direction However it would not be difficult to make printing in the Mongolian direction another direction supported by the bditroff pro gram It would mean making the direction in which the reconstructed columns flow determined by a variable The variable
17. aracter codes are acceptable as input The two byte codes are generally distinguished from ASCII charac ters by having the eighth bit turned on in each of the two bytes The latter two formatters avoid having to modify the base program ditroff by considering each row of the matrix to be a separate font and addressing the cdth character of the abth row as f abN cd This by the way is the scheme adopted by the system presented herein as it too is based on ditroff Among the products for Japanese and Chinese wordprocessing on the Macintosh are EgWord 9 and FeiMa 10 Both EgWord a Japanese word processor and FeiMa a Chinese word processor seem not to be able to deal with bi directional text All of their examples are strictly left to right However since they run on a Macintosh computer with its standard user interface there is nothing to stop the user from rearranging some text to be written from top to bottom and cutting this text out and pasting it into another document whose text is printed from left to right In addition at least FeiMa gives the user a choice of printing direction when requesting the printing of a document however this direction applies to the whole document One paper from the Xinjinang Uighur autonomous region 28 describes UKKMC DOS a version of MS DOS which is capable of accepting input in English Uighur Kazak Kirgiz Mongolian and Chinese The text of each language is displayed on the screen printed
18. columns set the page offset to the current line length minus the new line length defined below nr XX NWAn lu NNS1 NNw NN a1NN al u nr XX NN 1 1 NNW NN a1NN u in n XXu N set line length to N 1 times the width of a standard N character plus N 1 minus 1 times the width of the N inter word space ene XX 1 w f a1NN al u nr XX 1 1 w E al u ll n XXu de EC end columns or centering in reset left margin to previous value 11 reset right margin to previous value de centering 1 columns set the page offset to half of the current line length minus the new line length defined below nr XX n 1lu 1 w a1NN al u nr XX NN 1 1 NNw NN a1NN u 2u in n XXu if invoked in diverted text use po set line length to 1 times the width of a standard N character plus N 1 minus 1 times the width of the inter word space nr XX 1 w f a1NN al u nr XX 1 1 w NN 1 u ll n XXu 20 Z BECKER AND D M BERRY In order that RA and CE work properly with respect to the spacewidth established for the top to bottom text in the BT macro it is necessary that the RA or CE come after the BT Obviously these and other macro definitions given in this section must be modified to use different names for macros
19. ction being identified by the current font The system uses the standard essentially unchanged underlying ditroff formatting program to make all the formatting decisions Fonts for the standard character sets from Korea Japan and the People s Republic of China are arranged as a 94x94 matrix For the purpose of ditroff formatting of Far East language text the martix is treated as 94 fonts each containing 94 characters all exactly the same size Thus the only changes to the ditroff program as distributed by AT amp T are the changes of the constant defining the number of fonts mounted to a number large enough to accommodate the 94 row fonts plus whatever else is mounted on the local printing devices and of the constant defining the size of the character set to something large enough to accommodate the 94 characters To make sure that requiring line breaks before and after each block of top to bottom text is reasonable we went to the neighborhood bookstore and bought a Japanese magazine with both left to right and top to bottom printing of Japanese In all cases of switch of direction there was an accompanying line break That is there was no case of beginning top to bottom printing on the same horizontal line that contains the preceding left to right text and there was no case of beginning left to right printing on the same horizontal line serving as the bottom line of the rectangle of the preceding top to bottom text FORMATTING TRI DIRECTION
20. ell Laboratories June 21 1978 M E Lesk TBL A Program to Format Tables Bell Laboratories Murray Hill NJ 07974 1978 and OA BR 20 TeX2 YS CANON 1986 7 17H J F Ossana NROFF TROFF User s Manual Bell Laboratories Murray Hill NJ 07974 October 11 1976 Y Saito Report on JTEX a Japanese TEX TUGboat 2 1987 FORMATTING TRI DIRECTIONAL TEXT 25 25 26 27 28 29 30 Trickey DRAG A Graph Drawing System in Electronic Publishing 88 ed J Andr and H van Vliet Cambridge University Press Cambridge UK 1988 The UNIX Programmer s Manual Technical Report Bell Telephone Laboratories Murray Hill NJ 07974 June 1981 International UNIX Supplement to UNIX World 1989 Z Wu W Islam J Jin S Janbolatov and J Song A Multi Language Characters Operating System on IBM PC XT Microcomputer in Proceedings of Second International Conference on Computers and Applications Beijing PRC June 1987 T Wolfman flo A Language for Typesetting Flowcharts M Sc Thesis Technion Haifa Israel 1989 C J Van Wyk IDEAL User s Manual Computing Science Technical Report No 103 Bell Laboratories December 17 1981 APPENDIX This appendix contains the Japanese and Chinese abstracts printed in the additional form mentioned in the
21. ematically i e after passing it through the device driver ada is a trade mark of the u s dept of defense ms 14 Z BECKER AND D M BERRY dos is a trade mark of microsoft inc A B C D E FGH IJ K LMNO P O IR 285 E U VMWXY 2 ffortid is a trademark of berry com puter scien tists ltd unix is a trademark of at amp t bell laboratories The rectangular region to be reorganized by bditroff is the 5x6 region containing the typewriter font characters This region s last four characters are blanks of exactly the same size as the letters Suppose that all of the text fits on one page Then bditroff reads the characters in the region in a left to right top to bottom sweep as A B C blank blank blank blank It then lays them out in a top to bottom right to left sweep in the same order to fill the same region After this reorganization the text is schematically ada is a trade mark of the u s dept of defense ms dos is a trade mark of microsoft inc Y Z dH Hn A B C D F ffortid is a trademark of berry com puter scien tists ltd unix is a trademark of at amp t bell laboratories The reader should note that the algorithm is being applied by the formatting software on these examples If however the page break were to come relative to the original ditroff output after the third line of the constant width text i e between the and
22. he exact position of each character on the page and 2 independently determine the line and page boundaries in the input EA major source of problems with tbl is that it can violate this single pass page construction property If a table with more lines than can fit on the current page also has vertical lines which are normally drawn after finishing the last row of the table these lines get drawn on the second page from the projection of the start of the table onto this page to the end of the table on this page 18 Z BECKER AND D M BERRY The ditroff output consists of a preamble describing the device followed by a sequence of page descriptions each beginning with a page command of the form pn sig nalling the beginning of page number n The description of a page consists logically of a sequence of position character pairs each describing exactly where on the page to print a character The actual form of the position information is as occasional absolute coordi nates with intervening horizontal and vertical movements Thus a program reading this output must keep a position state and follow the relative movements in order to calculate the exact position of each character Embedded among these position character pairs and actually independent of them are end of line markers of the form nb a the impor tant thing here is the n the and the a give the amount of space before and after the line in the device s units These ma
23. he line will have exactly the same length 4 Within any contiguous rectangle of top to bottom Far East language text 2 The origin of the name bditroff is that to get ditroff written from top to bottom in the unenhanced ditroff one says b ditroff this utterance appears to the shell as bditroff For the length to be totally independent of the order it is required that any kerning algorithm have the current font s direction as a parameter in order to know which pairs of letters must be kerned If the algorithm is table driven then the kerning distance of the pair X Y must be adjusted to look good when Y is printed to the left of X 12 Z BECKER AND D M BERRY ditroff input format ditroff ditroff output format ffortid Z output format OO ditroff output format Figure 1 Data flow of triroff FORMATTING TRI DIRECTIONAL TEXT 13 within a page any permutation of the text within the rectangle will exactly fill the rectangle For the purpose of this statement trailing blanks are considered to be characters This invariant works because the widths and the heights of all Far East language characters are the same Observe that application of ffortid to the output of ditroff should not affect the holding of the invariants ffortid merely permutes the characters of horizontal lines these lines remain horizontal In fact whether or not
24. ices rang ing from line printers dot matrix printers laser printers through to photo typesetters 2 all the various software which allows preview on a high resolution screen of how a document will appear when printed on some printing device and 3 Indx 1 for preparing a back of document index Finally the macro packages include mm man ms me and mX which are described in the various versions of the UNIX Programmer s Manual 26 The primary advantage of the ditroff system over other more monolithic systems is precisely that it is not monol ithic and is composed of many programs which may be combined for application to a document to get their combined functionality It is relatively easy to add new programs with new functionality as evidenced by the ever growing collection of pre and postpro cessors cited above Thus it is relatively easy to experiment with new functionality in the context of a full function system These formatting programs were developed in a primarily English speaking environ ment However in principle these programs can be used in conjunction with any language written from left to right with lines flowing top to bottom for which fonts are mounted on the printing device The goal of the authors and their colleagues has been to adapt the ditroff collection to the multi lingual setting A ditroff postprocessor ffortid 2 has been developed to make the collection useable as a bi directional formatting sy
25. in its own proper direction as it is being entered The system is a WYSIWYG system in which the screen appearance reflects exactly what is in the file The text in the file is broken into pages Each page is treated as a two dimensional array of characters When a page is seen on the screen the array is displayed directly on the screen with each row of the array being displayed on a separate row of the screen Entry of a Latin character causes cursor movement one position to the right both on the screen and in the array entry of a Uighur Kazak or Kirgiz character causes cursor movement one position to the left and entry of a Chinese or Mongolian character causes cursor movement one position downward In the editor one moves around this array to directly address each character in its own position Working with this system is rather straightforward precisely because the visual image is a very accurate model of the internal structure One is formatting the text as it is entered with the software taking care of most of the global formatting details such as keeping to the line length and to the page length It is easy to address each character for direct manipulation of the character However certain formatting operations are difficult with this system most notably changing the page sizing characteristics e g the line length and the page length Because the formatting is done during entry based on the current setting of line and page lengths and
26. inclusion of Latin language text among top to bottom text but only in an unrotated advancing downward form using the constant width Latin characters found in row three of the JIS the GB 2312 and the KS C 5601 character sets It is also common these days to rotate the Latin language text so that its natural right to left flow matches the top to bottom flow of the surrounding Far East language text That is the Latin text is printed in a variable width font sideways with its base line coinciding with the line run ning down the left edge of the vertical column containing the text This printing is achieved by having a Far East language font with its letters rotated 90 counter clockwise and printing this Far East font together with the available Latin fonts from left to right If such a page is then rotated 90 counter clockwise it appears to the reader that the Far East language characters are printed right side up top to bottom and the Latin letters are printed sideways Probably this style arose simply because it is so easy to implement with modern printing devices Figures 2 and 3 found in the appendix show the Japanese and Chinese abstracts of the paper printed in that style The reason these figures are in the appendix is to preserve the truth of the claim made at the beginning of the paper that the entire paper is printed as a single document with the software describe herein The appendix figures cannot be printed in the same run of ditr
27. m top to bottom with the columns laid out from right to left one gets as output something like 10 Z BECKER AND D M BERRY English nay To minimize both programming effort and user learning effort it is useful that the for matting software be an upward compatible extension of an existing system For max imum functionality it is useful that the underlying existing system be a stabilized system capable of dealing with pictures tables graphs equations indices tables of contents bibliographical citations program code formatting indexing etc One example of such a system is the UNIX documentor s workbench DWB or ditroff collection Another is the collection In this respect it is best of all if the underlying system s software can be used unchanged Then only the new capabilities need to be programmed Full functionality is obtained with no additional programming effort Finally the user community can rely on extant behavior being reproduced even down to the bugs that have become features BASIC STRUCTURE OF SYSTEM This paper describes a system for tri directional formatting based on the UNIX DWB or ditroff collection The system assumes input 1 in time order and with line breaks before and after each contiguous stream of constant width characters in Far East language fonts all characters are the same width to be printed from top to bottom and 3 with the current language and dire
28. may be the bottom of a page In any case the region cannot be larger than one page Any such region is a rectangle bounded by the beginning the end the left margin of the page and the right margin of the page rN The rearrangement algorithm makes a column of text as long as necessary to fill the region All the extra blanks end up in the left most columns If the user does not desire this sort of filling then it is straightforward for the user to adjust the page offset line length page length line spacing etc to obtain the desired physical appearance The authors examined Japanese magazines and found that the spacing between successive characters in a column is about 1 times the character size but that the space between columns is about 1 2 times the character size To achieve this appearance with the 16 Z BECKER AND D M BERRY algorithm it suffices for ditroff to be told that the vertical spacing is 1 1 times the current point size as opposed to the more usual 1 2 times and that the spacewidth is 1 2 ems as opposed to the more usual approximately 333 ems for variable width fonts or 1 em for fixed width fonts Of course it is necessary to reset these upon leaving a region of top to bottom text Observe that with this algorithm text of length n residing within one line in ditroff e g ABCD will end up being in what appears to be a right to left order e g DCBA as the algorithm fills a 1xn region t
29. nes written in the right to left direction These same newspapers and magazines have advertisements using Latin language text written in the left to right direction Thus in one document text is written in three directions left to right right to left and top to bottom In the Xinjinang Uighur autonomous region of the People s Republic of China inha bitants speak the languages Uighur Kazak and Kirgiz 28 which are written in the right to left direction as are their linguistic cousins Arabic Farsi and Urdu When com bined with the general use of Chinese and Latin languages in the country the need arises in the region for tri directional formatting For example at universities in the region a technical paper might very well be written in a local language use English for technical FORMATTING TRI DIRECTIONAL TEXT 7 words have formulae and be required to have a Chinese abstract Finally any business contract for high technology work done jointly by companies from a Far East country and a Mid East country could require tri directional formatting There is an additional language used in the Xinjinang Uighur region whose correct traditional printing direction was learned only after the software was written and the referees comments on the first draft of this paper had been received Mongolian is the language and in its traditional writing direction the characters flow from top to bottom on a line and the lines flow from left
30. of the UNIX operating system spreading throughout the world 27 there is a concern to adapt the various UNIX facilities to be useable in a variety of languages multi lingual formatting For example Becker describes one such what you see is what KEY WORDS Document Preparation Multi lingual Multi directional Troff Typesetting and in mixed language environments 13 BACKGROUND FORMATTING TRI DIRECTIONAL TEXT 5 you get WYSISYG formatting system 4 This paper describes new software whose general goal is to help adapt the facilities of the UNIX device independent troff known as ditroff 23 16 to the multi lingual environment The ditroff system is composed of a basic formatter called ditroff 16 23 plus a number of preprocessors postprocessors and macro packages Among the preprocessors are refer for handling bibliographical citations 20 ideal for drawing pictures 30 pic for drawing pictures 15 grap for plotting graphs 6 drag for drawing directed graphs 25 flo for drawing flowcharts 29 psfig for including figures drawn in POSTSCRIPTTM 3 alg and its derivatives for formatting included program code 7 tbl for laying out tables 21 and eqn for laying out mathematical formulae 14 OO AON de Among the postprocessors are 1 all the various device drivers for translating ditroff output into the instructions needed to print the formatted documents on the various printing dev
31. off that prints the rest of the paper even with a rotated Latin font because the Latin font does not meet the constant width requirement for using bditroff It is typeset as a separate document using the trick of the rotated Far East language font In order to be able to print the appendix in the same run of ditroff that prints the paper it is necessary to have a ditroff device driver that can change from portrait to landscape mode and vice versa at any arbitrary point in the document The particular device driver used to print this paper psdit from Adobe s TRANSCRIPT package does not have this capability There exists a device driver namely Pipeline Associate s devpsTM that has facilities for rotating arbitrary text at any angle Thus it should be pos sible to put the needed capability into any device driver In top to bottom Far East language text a short multi digit numeral in a Latin text font is occasionally printed as a unit unrotated with its base line perpendicular to the vertical axis of the column that contains it This works nicely when the numeral is short enough so that it does not stick out to far from the width of the column This cannot be done in the current version of the software However there are a number of ways that this feature can be implemented as easy extension of the current software 1 to the Far East language font all possible short multi digit numerals as single characters If the fonts are POSTSC
32. op to bottom with the columns of length one being filled in from the right to the left If it is desired to obtain an nx1 space with all the text down one column one must trick the formatter a bit ditroff can be forced to format the text in a line length equal to the width of one character Then the text gets printed correctly top down without application of bditroff and applying bditroff reorganizes the rectangle of width one character into itself Thus one can have the B C D printed downward in a right justified column by giving the input set the page indentation to the current line length minus the new line length defined below nr XX Mn lu Nw NfCA u in n XXu set line length to the indentation plus the width of a standard character nr XX w fCA u 11 n XXu Nx TS additional if invoked from diverted text Ir AB CD Hons Nx TE NV additional if invoked from diverted text br in reset indentation to previous value ll N reset line length to previous value Doing so yields the output uu ow One can obtain a centered column by giving the input FORMATTING TRI DIRECTIONAL TEXT 17 set the indentation to half of the current line length minus the new line length defined below nr XX n lu w CA u 2u in n XXu set line length to indentation plus the width of a standard character nr XX w fCA u
33. op to bottom direction is called the Far East languages There are a number of writing directions dealt with in this paper they are identified as follows The direction of writing in which the characters flow from left to right on a line and the lines flow from top to bottom is called the left to right direction 2 The direction of writing in which the characters flow from right to left on a line and the lines flow from top to bottom is called the right to left direction 3 The direction of writing in which the characters flow from top to bottom on a line and the vertical lines flow from right to left is called the top to bottom direction 4 Together the left to right and right to left directions are called the horizontal directions while the top to bottom direction is a vertical direction THE NEED FOR BI AND TRI DIRECTIONAL FORMATTING Throughout the Far East documents are written containing a mixture of text in Far East and Latin languages The Latin language text may include mathematical formulae It is often desired to print the Far East language text in the traditional top to bottom direction While it is possible to print the Latin language text letter by letter in the same direction it is preferable to print the Latin language text in its traditional left to right direction Moreover in Hong Kong and Japan newspapers and magazines have their main line Far East language written in the top to bottom direction and their headli
34. rams composing triroff it requires only the use of a different Far East language font containing the reoriented and repositioned punctuation symbols as added characters The solution to these problems are left for future work Of course the ultimate judge of the quality of the software is the user Accordingly the bditroff software described herein is available from the second author for a nominal fee and under a non disclosure agreement ACKNOWLEDGEMENTS The Japanese and Chinese translations of the abstract were provided by Taiichi Yuasa iX X and Kam Pui Chow respectively Low Hwee Boon X provided samples of Hong Kong and Singaporean magazines and newspapers The authors thank one particular enthusiastic but critical anonymous referee whose hard questions resulted in a greatly improved paper devps is a trademark of Pipeline Associates Inc DWB is a trademark of AT amp T Bell Laboratories ffortid is a trademark of Berry Computer Scientists Linotronic is a trademark of Linotronic Inc Macintosh is a trademark of Apple Computers Inc MS 24 Z BECKER AND D M BERRY DOS is a trademark of Microsoft Inc POSTSRIPT is a trademark of Adobe Computer Systems TEX is a trademark of the American Mathematical Society TRANSCRIPT is a trademark of Adobe Computer Systems UNIX is a trademark of AT amp T Bell Labora tories REFERENCES 1 2 OUR 11 12 13 14 15 16 17
35. rkers are necessary and cannot be calculated from the movements There is no guarantee that all large movements to the left with small move ments downward are ends of lines One finds such movements in equations graphs pic tures tables etc Because there are no end of line markers in TEX s DVI output format the system structure adopted in this paper cannot be applied to make a tri directional version of TEX Instead one must make modifications to TEX either to have it do the reorganization or to have it emit end of line markers 18 In either case one cannot use the standard distri buted TEX and one faces the problem of maintaining more than one version of the pro gram ACTUAL PROGRAM In the input one must signal the beginning of the text to be printed vertically by use of the transparent output V x TS and signal its ending by use of V x TE If the text to be printed vertically appears in a diversion the signals must be preceded by one level of diversion In addition if the signals occur in macro definitions each must be doubled These signals must be preceded by breaking commands such as br To assist the user in dealing with the top to bottom text macros BT and ET are defined which do these activities and which also adjust the line and word spacing to produce nicely spaced columns Their definitions are de BT begin top to bottom processing N The user is presumed to have properly set the
36. sor English Reference Manual Version 3 0 Wu Corp Avon Connecticut August 1986 and A tat in pp 1 10 1985 C H Ip D M Berry K P Chow CWPR a Chinese Japanese Word Processing System for Use with UNIX Device Independent TROFF in Proceedings of Second International Conference on Computers and Applications Beijing PRC June 1987 R Kasbarian The Language of Choice International UNIX 41 46 1989 B W Kernighan and L L Cherry Typesetting Mathematics User s Guide Second Edition Bell Laboratories Murray Hill NJ 07974 1978 B W Kernighan PIC A Graphics Language for Typesetting User Manual Computing Science Technical Report No 85 Bell Laboratories March 1982 B W Kernighan A Typesetter independent TROFF Computing Science Technical Report No 97 Bell Laboratories March 1982 SWS A and UU EC UR Gr MARY A A JTROFFO B8 in 31 60 D E Knuth and P MacKay Mixing Right to left Texts with Left to right Texts TUGboat 8 1 1987 D E Knuth The TEXbook Addison Wesley Reading MA 1984 Lesk Some Applications of Inverted Indexes on the UNIX System Computing Science Technical Report No 69 B
37. stem in conjunction with Arabic Farsi and Hebrew fonts In addition the ability to handle very large character sets such as those used in Japan Korea and the People s Republic of China requiring two bytes for encoding characters has been added 12 Interestingly the three character sets from these countries the JIS KS C 5601 and GB 2312 standards are all arranged as 94x94 matrices Given that all characters in all of these character sets are exactly the 6 Z BECKER AND D M BERRY same square size the width tables and the processing for these character sets are nearly identical For the purpose of identifying groups of languages with similar formatting problems the following group names are used in this paper 1 group of languages including English whose members are printed with alphabets of size less than 256 in the left to right direction is called the Latin languages even though it includes many languages such as Greek and Rus sian not written with the Latin alphabet 2 group of languages including Arabic Farsi and Hebrew whose members are printed with alphabets of size less than 256 in the right to left direction is called the Middle East languages even though it includes languages such as Urdu whose locale is not really in the Middle East 3 The group of languages including Chinese Japanese and Korean whose members are printed with alphabets of size greater than 256 traditionally in the t
38. ter two are each printed twice once in a modern left to right style and once in a more traditional top to bottom style The software described in this paper was used to format and typeset this paper Yspn Draw pan pm Pawa uv mins 12 minii maw Dyan ODOM NITY n n INN own mas may moii INIA DO D 5n NAW TWIN Jno us TNA RANT 055 noynom OWN 23 NoaTw 55 120 v55 AP DD v Rp1 NW 12 1702 Tini NAAT Ossana Pv ditroff igypyy open naama noma oopn nw nA ox meopna nao ym anon r0 Berry Buchman 70 ffortid 7nx 122 1X par Prawa p Tay Kernighan nun nyana vo2on 770 bditroff non miam praw pan oDTYY 72 ditroff v 0995 ADA DRAW ma num noynmen 35 ditroffn v 0999 non JU AER 3 1
39. the P the output would be schematically ada is a trade mark of the FORMATTING TRI DIRECTIONAL TEXT 15 u s dept of defense ms dos is a trade mark of microsoft inc MJG N O ON HT n1 pr U QU NK Xxx GHU P Q R ffortid is a trademark of berry com puter scien tists ltd unix is a trademark of at amp t bell laboratories Here the horizontal rule represents the page boundary If one is using a ditroff macro package in which page headers and footers are gen erated even just page numbering then additional measures must be taken lest the header and footer be included in the regions that are to be rearranged into top to bottom printing The macro that is invoked at the page bottom trap must issue the same commands that are used to end a top to bottom region before it emits any of the regular page footer text Moreover it must arrange that the very next invocation of the page header macro issue the same commands that are used to begin a top to bottom region after it has emitted any of the regular page header text This arranging is done by setting a register to a value which is interrogated by the page header macro Consider any region in which bditroff has been asked to rearrange the text to be printed from top to bottom The beginning of the region may have been requested expli citly by the user or it may be the top of a page The end of the region may have been requested explicitly by the user or it
40. to left To this program top to bottom text is treated as left to right text The second of the additional programs is bditroff On a page by page basis bditroff reorganizes the text on a page so that each contiguous nxm rectangle scanned left to right top to bottom of text in top to bottom fonts is permuted to become an rectangle scanned top to bottom right to left Because the scanning directions of the two rectangles are perpendicular to each other and the characters are all the same size the nxm and the mxn rectangles actually occupy the same area on the paper Thus the structure of the system is as given in Figure 1 INVARIANTS THAT ALLOW THIS SYSTEM TO WORK The simple modular structure described in the previous section works because of a number of invariants that apply both to the text and its printing 1 given horizontal line on the page consists either of left to right and right to left text or of top to bottom text This is the case because of the line breaks that are required at each point of changing from horizontal to vertical text or vice versa 2 While reading within each contiguous rectangle of horizontal text on a page one does not move from a line to the next until one is finished reading all the text on line Within line one may in fact bounce around reading in alternat ing directions however no text is read more than once 3 Within any such horizontal line any permutation of the characters in t
41. to right How this direction can be handled is dis cussed later in the section on weaknesses implementing this solution is left for future work Note that if the tri directional formatting problem is solved then any bi directional sub problem e g left to right and right to left left to right and top to bottom and right to left and top to bottom is also solved THIS PAPER This paper describes a pair of programs that enhance the ditroff collection to be tri directional One of these ffortid which provides the right to left formatting capability was described in detail in an earlier paper 2 The second of these bditroff which pro vides the top to bottom formatting capability is the focus of this paper The sequential piped composition of ditroff with these two programs is called triroff By enhancing an existing full function formatting system it is intended to be able to use the existing system s preprocessors and macros with no change Indeed this very paper was typeset camera ready for this journal on a Linotronic 300 at 1250 dpi with the help of refer pic eqn ditroff ffortid bditroff and variants of the ms and MX macro packages that were developed for this journal The plan for the rest of the paper is as follows Existing software is surveyed in order to be able to determine desirable properties of a tri directional formatting system Then it is possible to identify a basic structure that allows these properties to be
42. ttle observable delay to the user This order of input is called time order it is the order in which the text is thought of as it is being written It is the order in which the properly formatted text is read out loud by a human reader cognizant of the multi directional text reading conventions It is also the order in which the letters would appear on paper if all languages were written in the same say left to right direction This time order is the input order that is assumed by a variety of multi lingual systems specifically those implemented by Joseph Becker 4 5 by Pierre MacKay and Donald Knuth 18 and by Cary Buchman Daniel Berry and Jakob Gonczarowksi 2 The groups doing these projects seem to have arrived independently at the conclusion that time order is best That is each group had written at least a draft of its paper and code before any of the others papers had appeared Thus from the input shown in stylized form ft R Roman English in 5i V effective 11 4 51 line length 4 inches zT PR predominantly right to left ft HB Hebrew yarn br PL predominantly left to right ft KT Katakana br BT begin top to bottom ft HR Hiragana SD ft CH Chinese br ET end top to bottom assuming that English and Katakana are printed from left to right Hebrew is printed from right to left and Hiragana and Chinese are printed fro
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