Apple II Technical Notes _____________________________________________________________________________ Developer Technical Support Pascal #15: Apple II Pascal SHORTGRAPHICS Module Revised by: Cheryl Ewy & Dan Strnad November 1988 Written by: Cheryl Ewy December 1983 This Technical Note describes the Apple II Pascal SHORTGRAPHICS routine, which is available as part of the 48K Run-Time System. _____________________________________________________________________________ Introduction Many applications, especially those designed to use the 48K Run-Time System, run out of memory quickly if they use the TURTLEGRAPHICS unit provided with the standard SYSTEM.LIBRARY. This document describes a library unit called SHORTGRAPHICS which removes the relative polar coordinate features of TURTLEGRAPHICS to save memory. General Comments If your application uses (or can be modified to use) only those TURTLEGRAPHICS procedures which refer to absolute screen coordinates, you can use the SHORTGRAPHICS unit. The SHORTGRAPHICS unit has the same segment numbers assigned to it, as does TURTLEGRAPHICS, thus you may not use both in the same program. Deletions The following routines are not available in the SHORTGRAPHICS unit: PROCEDURE TURN(ANGLE: INTEGER); PROCEDURE TURNTO(ANGLE: INTEGER); PROCEDURE MOVE(DIST: INTEGER); FUNCTION TURTLEANG: INTEGER; Additions The following definitions have been added to the INTERFACE section of SHORTGRAPHICS: TYPE FONT=PACKED ARRAY[0..127,0..7] OF 0..255; VAR FONTPTR:^FONT; The variable FONTPTR is a pointer to the memory area used by the WCHAR and WSTRING procedures to display text on the graphics screen. Thus, if you have a character set named KATAKANA.FONT, you could load it into memory and use it as follows: VAR SPECIALFONT:^FONT; (* where the new font goes *) SAVEFONT:^FONT; (* to save pointer to standard font area *) PROCEDURE LOADFONT; VAR F:FILE; NIO:INTEGER; BEGIN NEW(SPECIALFONT); RESET(F,'KATAKANA.FONT'); NIO:=BLOCKREAD(F,SPECIALFONT^,2,0); CLOSE(F) END; PROCEDURE USESPECIAL; BEGIN SAVEFONT:=FONTPTR; (* save standard font pointer *) FONTPTR:=SPECIALFONT; (* and point to special font *) END; PROCEDURE USENORMAL; BEGIN FONTPTR:=SAVEFONT (* restore pointer to normal font *) END; Memory Considerations When the system is booted, the heap pointer is normally below the start of high-resolution page one. The TURTLEGRAPHICS unit automatically sets the heap pointer above high-resolution page one. This protects the high-resolution page from being overwritten by your program, but it also prevents you from using the space between the original top of the heap and the start of high- resolution page one for your own variables. SHORTGRAPHICS does not protect the high-resolution page, thus you may use this extra space for yourself. The following code will check to see if you have n bytes available between the top of the heap and high-resolution page one. If the room is not available, the heap pointer will be jumped to the top of the high-resolution page. PROCEDURE MAKEROOM(N:INTEGER); CONST BOTTOM=8192; TOP=16384; VAR CHEAT:RECORD CASE BOOLEAN TRUE:(IPART:INTEGER); FALSE:(PPART:^INTEGER); END; BEGIN MARK(CHEAT.PPART); IF (CHEAT.IPART+N)>=BOTTOM THEN BEGIN CHEAT.IPART:=TOP; RELEASE(CHEAT.PPART) END END; Thus, if you wanted to allocate a special font (which requires 1,024 bytes) below the high-resolution page, you could use this code: MAKEROOM(1024); NEW(SPECIALFONT); If there are at least 1,024 bytes beneath the high-resolution page, the new font will be allocated there. If there is not enough space there, the new font will be allocated above the high-resolution page. All of these heap allocations should be done as the very first actions of your program. When you finish allocating your variables, you should invoke the following procedure to make sure the heap pointer is above high-resolution page one (thus protecting it). PROCEDURE PROTECT; CONST TOP=16384; VAR CHEAT:RECORD CASE BOOLEAN OF TRUE:(IPART:INTEGER); FALSE:(PPART:^INTEGER); END; BEGIN MARK(CHEAT.PPART); IF CHEAT.IPART