*************¢¢ FANCY FONT DISPLAY ROUTINES¢ ---------------------------¢¢ For so long now people have been ¢after text display routines for ¢graphic modes 7 & 15. These routines ¢have been provided, but they always ¢use a block copy technique which uses ¢a standard 8 by 8 bit character set.¢¢ My routines throw away these ¢principles and allow the programmer ¢to define the individual characters ¢in terms of their image, width, ¢height and drop.¢¢Example: The word 'Tie' might be ¢displayed as follows¢¢+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¢|X|X|X|X|X|X| |X| | | | | | | |¢+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¢| | |X| | | | | | | | | | | | |¢+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¢| | |X| | | | |X| | |X|X|X| | |¢+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¢| | |X| | | | |X| |X| | | |X| |¢+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¢| | |X| | | | |X| |X|X|X|X|X| |¢+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¢| | |X| | | | |X| |X| | | | | |¢+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¢| | |X| | | | |X| | |X|X|X|X| |¢+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¢¢The accompanying data¢to go along with the¢image for the 'e' would¢be as follows:¢¢Height = 5¢Width = 6¢Drop = 2¢¢Note that the gap should¢be included in the width¢¢ This produces output which is ¢more pleasing to look at. It's ¢difficult to do justice to this with ¢words, so run the program ¢"D:EGFFDR.BAS" to see what is ¢possible.¢¢HOW TO USE THE ROUTINES FROM BASIC¢----------------------------------¢¢ For ease of use, the routines are ¢loaded upon booting the disk, the ¢program being in an AUTORUN.SYS file. ¢(Note: on the news-disk the program ¢has been called FFDR.COM. It should ¢be copied to a fresh disk and renamed ¢AUTORUN.SYS). The code is loaded ¢above DOS, then it protects itself ¢from SYSTEM RESET by altering MEMLO ¢and DOSINI addresses. The routines ¢and example font (Taken from the ST ¢game 'Paradroid 90' which inspired ¢these routines) take up ^7.5K but ¢this still leaves you with ^30K ¢available for your BASIC program.¢¢ There are 4 routines that you can ¢use. In order to do this it is best ¢that you set up the following ¢variables within your program.¢¢e.g. 10 MESSAGE=7459:REM Address¢ of Display routine vector.¢ 20 SETXY=MESSAGE+3¢ 30 COLOUR=SETXY+3¢ 40 DRWLET=COLOUR+3¢¢ Definitions for each of these ¢routines now follow:¢¢SETXY¢-----¢¢Format : A=USR(SETXY,xpos,ypos)¢Limits : xpos between 0 and 159¢ ypos between 0 and 191¢ (for graphics mode 15)¢ ypos between 0 and 95¢ (for graphics mode 7)¢¢Desc. : this moves the current¢ printing position to the¢ coordinates (xpos,ypos).¢ Important note - a SETXY¢ must be executed before¢ any printing is done (i.e.¢ a MESSAGE or DRWLET).¢¢COLOUR¢------¢¢Format : A=USR(COLOUR,col)¢Limits : col between 0 and 3¢ (Although MC routine will¢ force any value of col to¢ be between 0 <-> 3 )¢¢Desc. : Sets the output colour as¢ follows -¢¢ 0 = COLOR4 (location 712)¢ (Background)¢ 1 = COLOR0 (location 708)¢ 2 = COLOR1 (location 709)¢ 3 = COLOR2 (location 710)¢¢DRWLET¢------¢¢Format : A=USR(DRWLET,ASC("A"))¢ A=USR(DRWLET,char)¢Limits : char between 0 and 127¢¢Desc. : Outputs the character at¢ the current screen¢ position (which is¢ updated accordingly).¢ Spaces are always drawn¢ in COLOR4, leaving the¢ background intact.¢¢MESSAGE¢-------¢¢Format : A=USR(MESSAGE,ADR(M$))¢ A=USR(MESSAGE,ADR("An¢ Example!"))¢Limits : Last character of string¢ must be inverse.¢¢Desc. : Displays the string on the¢ screen at the current x,y¢ position. The last¢ character of the string¢ must be inverse (in the¢ example the '!' is¢ inverse) in order to¢ denote the end of string¢ within the display¢ routine.¢¢ROUTINES FOR USE BY THE ASSEMBLY ¢PROGRAMMER ¢--------------------------------------¢-----¢¢ Calling protocols are different ¢within assembly language:¢¢ SETXY -> LDX xpos¢ LDY ypos¢ JSR POSITION¢¢ COLOUR -> LDA col¢ JSR SETCOL¢¢ DRWLET -> LDA char¢ JSR ONELET¢¢ MESSAGE -> LDX # >string¢ LDY # <string¢ JSR DOMSG¢ JMP skip¢ msg¢ .BYTE "An Example!"¢(Remember '!' is inverse!)¢ skip¢ ... your code ¢continues here¢¢ Assembler/Editor users must ¢remember to replace all '>' and '<' ¢symbols as follows:¢¢ # >name becomes #name/256¢ # <name becomes #name&255¢¢ If your including these routines ¢in your own program then you can ¢delete all the MEMLO initialisation ¢code (lines 1014 to 1078), otherwise ¢assemble it to an AUTORUN.SYS file ¢using the command:¢¢ ASM#D:FFDR.SRC,,#D:AUTORUN.SYS¢ - Ass/Ed¢¢ ASM#D:FFDR.M65,#-,#D:AUTORUN.SYS¢ - MAC/65¢¢N.B. MAC/65 users should first load ¢the source file using¢¢ ENTER#D:FFDR.SRC¢¢then save it in MAC/65 format using¢¢ SAVE#D:FFDR.M65¢¢The file "D:FFDR.SRC" can then be ¢deleted, saving disk space.¢¢DESIGNING YOUR OWN FONTS¢------------------------¢¢ Designing your own font is just ¢as easy as designing your own 8*8 ¢character sets. Let's go through an ¢example - a lower case 'g'¢¢ |¢+-+-+-+-+-+-+-+-+¢| | | | | | | | | ^ Drop = 2¢+-+-+-+-+-+-+-+-+ |¢| | | | | | | | | v¢+-+-+-+-+-+-+-+-+¢| |X|X|X| | | | | = $3F00 ^¢+-+-+-+-+-+-+-+-+ |¢|X| | | |X| | | | = $C0C0 |¢+-+-+-+-+-+-+-+-+ |¢|X| | | |X| | | | = $C0C0 |¢+-+-+-+-+-+-+-+-+ |¢| |X|X|X|X| | | | = $3FC0 |*¢+-+-+-+-+-+-+-+-+ |¢| | | | |X| | | | = $00C0 |¢+-+-+-+-+-+-+-+-+ |¢|X| | | |X| | | | = $C0C0 |¢+-+-+-+-+-+-+-+-+ |¢| |X|X|X| | | | | = $3F00 v¢+-+-+-+-+-+-+-+-+¢ |¢¢ (*Height=7)¢¢<---------> Width = 6 (Remember¢ to include gap!)¢¢ Remember too that in mode 7 & 15, ¢each pixel is two bits wide, giving ¢four possible colours. So define the ¢character for colour 3, i.e. both ¢bits set per pixel, as the ¢draw_letter routine simply AND'S it ¢with the current colour mask to ¢produce the right colour. This is ¢also why the image is two bytes wide, ¢to allow for characters with widths ¢up to 8 pixels wide.¢ The data image is stored in the ¢source listing as follows:¢¢1000 LG¢1002 .DBYTE ¢$3F00,$C0C0,$C0C0,$3FC0,$00C0,$C0C0,$3¢F00¢¢ All the characters are referenced ¢in the character table (see CHRTAB - ¢line 1574). This is best left alone, ¢and you should use the same labels ¢for your images.¢ All that's left to do is to store ¢the height, width and drop ¢information in the correct positions ¢in the relevant tables. So for our ¢example:¢¢ Height = 7, Width = 6, Drop = 2¢¢ These are stored in position 4 of ¢lines 1656, 1686 and 1716 ¢respectively, corresponding to the LG ¢entry in CHRTAB.¢¢ Hope that's enough for you to be ¢able to do your own thing, if you ¢have any queries, or just want to ¢discuss programming on the 8-bit ¢Atari, then write to:¢¢ Mark Keates,¢ 24 Hayes Mead,¢ Meadowcroft,¢ Holbury,¢ Southampton,¢ Hampshire,¢ S04 1JZ,¢ England.¢¢Enjoy!¢¢(This article was re-formatted and ¢edited by Dean Garraghty.), and¢reprinted by THE OL' HACKERS ATARI¢USERS GROUP, INC., WITH THANKS TO BOTH!¢¢ +-+-+-+-+- END -+-+-+-+-+¢
