dos33fsprogs/games/lemm/hgr_vlin.s
2022-03-14 22:57:33 -04:00

78 lines
1.1 KiB
ArmAsm

;=================================
; Simple Vertical LINE
;=================================
; line from (x,a) to (x,a+y)
; todo: use Carry to say if X>255
hgr_vlin:
; don't handle run of 0
cpy #0
beq done_hgr_vlin
; get initial ROW into (GBASL)
sta current_row_smc+1 ; save current A
; sty vlin_row_count
lda div7_table,X ; X is X1
sta x1_save_smc+1
txa ; save X ; X is still X1
pha
ldx HGR_COLOR
lda hgr_colortbl,X
sta HGR_BITS
and #$1 ; only shift if in odd column?
beq vlin_no_shift_colors
jsr shift_colors
vlin_no_shift_colors:
pla
tax ; restore X is X1
lda mod7_table,X
tax
lda vlin_masks,X ; get mask
sta vlin_mask_smc+1
tya
tax ; put line count into X
hgr_vlin_loop:
current_row_smc:
ldy #$dd ; get row info for Y1 into GBASL/GBASH
lda hposn_high,Y
sta GBASH
lda hposn_low,Y
sta GBASL
x1_save_smc:
ldy #$dd ; X1/7
lda (GBASL),Y
eor HGR_BITS
vlin_mask_smc:
and #$dd
eor (GBASL),Y
sta (GBASL),Y
inc current_row_smc+1
; dec vlin_row_count
dex
bne hgr_vlin_loop
done_hgr_vlin:
rts
;vlin_row_count: .byte $00
vlin_masks:
.byte $81,$82,$84,$88,$90,$A0,$C0