dos33fsprogs/games/sb/gr_putsprite_mask.s
2023-03-13 23:55:12 -04:00

87 lines
1.1 KiB
ArmAsm

;====================
; gr_put_sprite_mask
;====================
; Sprite to display in INL/INH
; MASK (for transparency) on MASKL/MASH
; Location is XPOS,YPOS
; Note, only works if YPOS is multiple of two
; trashes A,X,Y
gr_put_sprite_mask:
ldy #0
lda (INL),Y ; xsize
clc
adc XPOS
sta gps_xmax_smc+1 ; store xmas (self-modify)
iny ; 2
lda (INL),Y ; ysize
asl ; mul by 2
clc
adc YPOS
sta gps_ymax_smc+1
iny
tya
tax
lda INL
sta gps_src_smc+1
lda INH
sta gps_src_smc+2
lda MASKL
sta gps_mask_smc+1
lda MASKH
sta gps_mask_smc+2
gr_put_sprite_loop:
ldy YPOS
lda gr_offsets,Y
sta OUTL
lda gr_offsets+1,Y
clc
adc DRAW_PAGE
sta OUTH
ldy XPOS
gr_put_sprite_row:
cpy #40
bcs gr_put_sprite_dont_draw ; don't draw if out of bounds
; put the pixel
; based on monitor plot code
lda (OUTL),Y
gps_src_smc:
eor $f000,X ; load sprite data
gps_mask_smc:
and $f000,X
eor (OUTL),Y
sta (OUTL),Y
gr_put_sprite_dont_draw:
iny
inx
gps_xmax_smc:
cpy #40
bne gr_put_sprite_row
inc YPOS
inc YPOS
lda YPOS
gps_ymax_smc:
cmp #40
bne gr_put_sprite_loop
gr_put_sprite_done:
rts ; return ; 6