GSCats/fontEngine.s
2023-07-16 14:17:02 -07:00

113 lines
2.0 KiB
ArmAsm

.include "equates.s"
.include "macros.s"
.org $0000
FIRST_CHAR = 32
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; renderString (Far entry point)
;
; Draws a Pascal string
;
; PARAML0 = Pointer to string
; X = Font index
; Y = VRAM position of lower right corner of string at which to draw
;
; Trashes SCRATCHL,PARAML1,X, Y, A
;
renderString:
NATIVE
SAVE_DBR
sty SCRATCHL ; Cache VRAM position
txa ; Cache font character table
asl
tay
lda fontJumpTable,y
sta renderCharBounce+1
lda fontCharWidthTable,y
sta PARAML1
plb ; Temporarily revert to caller's DBR to access their pointer
BITS8
lda (PARAML0)
tax
BITS16
phb
renderStringLoop:
; Fetch and render next character in string
txy
lda #0
plb ; Temporarily revert to caller's DBR to access their pointer
BITS8A
lda (PARAML0),y
BITS16
phb
ldy SCRATCHL
jsr renderChar
dex
beq renderStringDone
; Calculate VRAM pointer for position of next character
lda SCRATCHL
sec
sbc PARAML1
sta SCRATCHL
bra renderStringLoop
renderStringDone:
RESTORE_DBR
rtl
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; renderChar
;
; Draws a single character
;
; A = ASCII code to draw
; Y = VRAM position of lower right corner at which to draw
;
renderChar:
SAVE_AXY
sec ; Bounce off glyph-rendering jump table
sbc #FIRST_CHAR
asl
tax
FASTGRAPHICS
renderCharBounce: ; Self modifying code. Don't panic
jmp (font16characterJumpTable,x)
renderCharJumpReturn: ; Compiled glyphs jump back here. Can't rts because stack is turboborked
SLOWGRAPHICS
RESTORE_AXY
rts
fontJumpTable:
.addr font8characterJumpTable
.addr font16characterJumpTable
fontCharWidthTable: ; In bytes
.word 4
.word 8
.include "font8x8.s"
.include "font16x16.s"
; Suppress some linker warnings - Must be the last thing in the file
; This is because Quinn doesn't really know how to use ca65 properly
.SEGMENT "ZPSAVE"
.SEGMENT "EXEHDR"
.SEGMENT "STARTUP"
.SEGMENT "INIT"
.SEGMENT "LOWCODE"