4cade/src/ui.font.lc2.a

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;license:MIT
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;(c) 2018-2020 by 4am
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;
; hi-res font drawing routines
;
; /!\ These live in LC RAM 2 and rely on the font data which is also in LC RAM 2. /!\
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; Code in LC RAM 1 (which is most program code) should call the functions in ui.font
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; which handle bank switching for you.
;
DrawPageInternal
; A/Y contains address of character buffer
; X contains 0-indexed left margin (HTAB)
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; carry bit clear -> draw on page 1
; carry bit set -> draw on page 2
; drawing starts at VTAB 0
; each line starts at column X which was passed in (0-indexed)
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; clobbers PTR
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; clobbers $FF
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; clobbers A/X/Y
; preserves all flags, by a quirk of implementation
php
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stx $FF
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ldx #0
stx VTAB
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+ST16 PTR
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@drawLine
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lda $FF
sta HTAB
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ldy #0
@parseLine
lda (PTR), y
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beq @donePage
cmp #$0A
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beq @doneParsingLine
iny
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bne @parseLine
@doneParsingLine
sty SAVE
tya
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beq @skip
ldx SAVE
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+LD16 PTR
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plp
php
jsr DrawBufferInternal
@skip inc SAVE ; skip carriage return
lda SAVE ; advance PTR to start of next line
clc
adc PTR
sta PTR
bcc +
inc PTR+1
+ inc VTAB ; this will print 255 lines if you give it
bne @drawLine ; 255 lines, so don't do that
@donePage
plp
rts
Draw40CharsInternal
; A/Y contains address of character buffer
; carry bit clear -> draw on page 1
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;v carry bit set -> draw on page 2
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; $25 contains textpage line (0..23) (this is the standard VTAB address)
; drawing starts at HTAB 0
; increments VTAB
; sets HTAB to 0 on exit
; clobbers A/X/Y
jsr +
ldx #40
jsr DrawBufferInternal
inc VTAB
+ ldx #0
stx HTAB
rts
DrawCenteredStringInternal
; A/Y contains address of length-prefixed string
; carry bit clear -> draw on page 1
; carry bit set -> draw on page 2
; $25 contains textpage line (0..23) (this is the standard VTAB address)
; clobbers A/X/Y
; clobbers PTR/PTR+1
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+ST16 PTR
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ldy #0
php
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lda #40
sec
sbc (PTR),y
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lsr
sta HTAB
plp
beq +
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DrawStringInternal
; A/Y contains address of length-prefixed string
; carry bit clear -> draw on page 1
; carry bit set -> draw on page 2
; $24 contains starting column (0..39) (this is the standard HTAB address)
; $25 contains textpage line (0..23) (this is the standard VTAB address)
; clobbers A/X/Y
; clobbers PTR/PTR+1
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+ST16 PTR
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ldy #0
+ lda (PTR),y
tax
inc PTR
bne +
inc PTR+1
+
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+LD16 PTR
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; /!\ execution falls through here to DrawBufferInternal
DrawBufferInternal
; A/Y contains address of character buffer
; X contains buffer length (1..40)
; carry bit clear -> draw on page 1
; carry bit set -> draw on page 2
; characters MUST have high bit off (0x00..0x7F)
; special characters (0x00..0x1F) will be drawn
; $24 contains starting column (0..39) (this is the standard HTAB address)
; $25 contains textpage line (0..23) (this is the standard VTAB address)
; all characters are drawn on the same line
; HTAB is incremented for each character
; VTAB is NOT incremented
; clobbers A/X/Y
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+ST16 DBISrc+1
php
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dex
lda VTAB
asl
asl
asl
; routine to calculate memory address within HGR page
; and self-modify addresses within draw loop that follows
; (routine clobbers A and Y but preserves X)
asl
tay
and #$F0
bpl @calc1
ora #$05
@calc1 bcc @calc2
ora #$0A
@calc2 asl
asl
sta @hgrlo+1
tya
and #$0E
adc #$10
asl @hgrlo+1
rol
plp
bcc +
eor #$60
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clc
+
sta DBIRow0+2
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adc #$04
sta DBIRow1+2
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adc #$04
sta DBIRow2+2
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adc #$04
sta DBIRow3+2
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adc #$04
sta DBIRow4+2
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adc #$04
sta DBIRow5+2
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adc #$04
sta DBIRow6+2
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adc #$04
sta DBIRow7+2
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@hgrlo lda #$FD
clc
adc HTAB
sta DBIRow0+1
sta DBIRow1+1
sta DBIRow2+1
sta DBIRow3+1
sta DBIRow4+1
sta DBIRow5+1
sta DBIRow6+1
sta DBIRow7+1
DBILoop
DBISrc ldy $FDFD,x
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lda FontDataRow0,y
DBIRow0 sta $FDFD,x
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lda FontDataRow1,y
DBIRow1 sta $FDFD,x
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lda FontDataRow2,y
DBIRow2 sta $FDFD,x
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lda FontDataRow3,y
DBIRow3 sta $FDFD,x
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lda FontDataRow4,y
DBIRow4 sta $FDFD,x
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lda FontDataRow5,y
DBIRow5 sta $FDFD,x
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lda FontDataRow6,y
DBIRow6 sta $FDFD,x
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lda FontDataRow7,y
DBIRow7 sta $FDFD,x
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inc HTAB
dex
bpl DBILoop
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rts