Special Feature: ColorForth Commentary COLOR.ASM: Utilities NOTICE: This is a work in progress. Parts of my commentary are still very rough. However, I have it up on the web because even in this rough form it may be useful to ColorForth enthusiasts. Expect the contents of these files to change frequently. General-purpose routines boot: ;Force a hardware reset. ;[Refs: forth2] mov al, 0feh ; reset out 64h, al jmp $ erase: ;( b n -- ) Erase n blocks, starting with block b. ;[Refs: forth2] mov ecx, eax shl ecx, 8 drop push edi mov edi, eax shl edi, 2+8 xor eax, eax rep stosd pop edi drop ret copy: ;( n -- ) Copy current block to block n, and make that ; block the current block. ;[Refs: forth2] cmp eax, 12 jc abort1 mov edi, eax shl edi, 2+8 push esi mov esi, blk shl esi, 2+8 mov ecx, 256 rep movsd pop esi mov blk, eax drop ret debug: ;(?)Print four numbers -- ;[Refs: forth2] mov xy, 3*10000h+(vc-2)*ih+3 dup_ mov eax, god push [eax] call dot dup_ pop eax call dot dup_ mov eax, main call dot dup_ mov eax, esi jmp dot Screen variables Note the relationships among the variables and equates: The screen width (hp) is 1024 pixels; the screen height (vp) is 768 pixels. An "icon" is actually a glyph from the ColorForth font — a bitmapped image of a character. An icon image is actually 16 pixels wide by 24 pixels high, but ColorForth puts six pixels of blank space between icons when "emitting" them to the screen, so iw (icon width) is 16+6, and ih is 24+6. The number of characters you can fit on a line on the screen (hc) is thus 46, and the number of lines you can fit on the screen (vc) is 25. The left margin (lm) is 3 pixels from the left edge of the screen. The right margin (rm) — the X position beyond which characters must not be emitted — is the character width times the number of characters per line, or 1012. The code to calculate an address in video memory implies that the video card reserves 64KB (0x10000 bytes) per scanline — even though a 16-bit color mode requires only two bytes per pixel, the resolution requires 1024 pixels per scanline, and therefore you don't really need more than 2KB to store a scanline in main memory. This is probably another case of Chuck Moore tightly fitting his code to his own hardware — his video card maps its onboard RAM (displ) to main-memory address 0xF0000000 and starts scanlines at addresses 0xF0010000, 0xF0020000, etc. iw equ 16+6 ;[Refs: space, emit2, text1, hc, rm, keyboard, ring, type0] ih equ 24+6 ;[Refs: debug, vc, down, cr, keyboard] hc equ hp/iw ; 46 ;[Refs: rm, keyboard, text1] vc equ vp/ih ; 25 ;[Refs: debug] align 4 xy ;[Refs: clip, space, emit2, line, debug, xy_, down, blank, top, qcr, cr, at, ; pat, keyboard, ring, rw, type0] dd 3*10000h+3 lm ;[Refs: text1, top, cr, lms, keyboard, rw] dd 3 rm ;[Refs: text1, qcr, rms, keyboard, ring] dd hc*iw ; 1012 xycr ;[Refs: top] dd 0 fov ;[Refs: fov_] dd 10*(2*vp+vp/2) Getting variable addresses nc_: ;"nc" ;[Refs: forth2] dup_ mov eax, (offset nc-offset start)/4 ret xy_: ;"xy" ;[Refs: forth2] dup_ mov eax, (offset xy-offset start)/4 ret fov_: ;"fov" ;[Refs: forth2] dup_ mov eax, (offset fov-offset start)/4 ret sps: ;"sp" ;[Refs: forth2] dup_ mov eax, (offset spaces-offset start)/4 ret last_: ;"last" ;[Refs: forth2] dup_ mov eax, (offset last-offset start)/4 ret Check the index for other entries. |
