dos33fsprogs/demos/xmas_2023/hgr_sprite_big.s
2023-12-23 23:56:36 -05:00

206 lines
3.3 KiB
ArmAsm

;===========================================
; hgr draw sprite (only at 7-bit boundaries)
;===========================================
; can handle sprites bigger than a 256 byte page
; Note this is optimized for blue/orange sprites
; it treats black0 as transparent
; SPRITE in INL/INH
; Location at SPRITE_X SPRITE_Y
; xsize, ysize in first two bytes
; sprite AT INL/INH
; orange = color5 1 101 0101 1 010 1010
hgr_draw_sprite_big:
lda SPRITE_X
ror
bcs hgr_draw_sprite_big_odd
hgr_draw_sprite_big_even:
ldy #0
lda (INL),Y ; load xsize
clc
adc SPRITE_X
sta big_sprite_width_end_smc+1 ; self modify for end of line
iny ; load ysize
lda (INL),Y
sta big_sprite_ysize_smc+1 ; self modify
; point smc to sprite
lda INL ; 16-bit add
sta big_sprite_smc1+1
lda INH
sta big_sprite_smc1+2
ldx #0 ; X is pointer offset
stx CURRENT_ROW ; actual row
ldx #2
hgr_big_sprite_yloop:
lda CURRENT_ROW ; row
clc
adc SPRITE_Y ; add in cursor_y
; calc GBASL/GBASH
tay ; get output ROW into GBASL/H
lda hposn_low,Y
sta GBASL
lda hposn_high,Y
clc
adc DRAW_PAGE
sta GBASH
ldy SPRITE_X
big_sprite_inner_loop:
big_sprite_smc1:
lda $f000,X ; load sprite data
beq big_sprite_transparent
sta (GBASL),Y ; store to screen
big_sprite_transparent:
inx ; increment sprite offset
; if > 1 page
bne big_sprite_no_page_cross
inc big_sprite_smc1+2
big_sprite_no_page_cross:
iny ; increment output position
big_sprite_width_end_smc:
cpy #6 ; see if reached end of row
bne big_sprite_inner_loop ; if not, loop
inc CURRENT_ROW ; row
lda CURRENT_ROW ; row
big_sprite_ysize_smc:
cmp #31 ; see if at end
bne hgr_big_sprite_yloop ; if not, loop
rts
hgr_draw_sprite_big_odd:
ldy #0
lda (INL),Y ; load xsize
clc
adc SPRITE_X
sta osprite_width_end_smc+1 ; self modify for end of line
iny ; load ysize
lda (INL),Y
sta osprite_ysize_smc+1 ; self modify
; point smc to sprite
lda INL ; 16-bit add
sta osprite_smc1+1
lda INH
sta osprite_smc1+2
ldx #0 ; X is pointer offset
stx CURRENT_ROW ; actual row
ldx #2
ohgr_sprite_yloop:
lda CURRENT_ROW ; row
clc
adc SPRITE_Y ; add in cursor_y
; calc GBASL/GBASH
tay ; get output ROW into GBASL/H
lda hposn_low,Y
sta GBASL
lda hposn_high,Y
clc
adc DRAW_PAGE
sta GBASH
ldy SPRITE_X
clc
php ; store 0 carry on stack
osprite_inner_loop:
osprite_smc1:
lda $f000,X ; load sprite data
bne osprite_not_transparent
; we can't just skip if 0 because we might shift a bit in
; from previous byte
plp
bcs osprite_oops
clc
php
bcc osprite_transparent_done
osprite_not_transparent:
plp ; restore carry from last
osprite_oops:
rol ; rotate in carry
asl ; one more time, bit6 in carry
php ; save on stack
sec ; assume blur/orange
ror ; rotate it back down
sta (GBASL),Y ; store to screen
osprite_transparent_done:
inx ; increment sprite offset
; if > 1 page
bne osprite_no_page_cross
inc osprite_smc1+2
osprite_no_page_cross:
iny ; increment output position
osprite_width_end_smc:
cpy #6 ; see if reached end of row
bne osprite_inner_loop ; if not, loop
plp ; restore stack
inc CURRENT_ROW ; row
lda CURRENT_ROW ; row
osprite_ysize_smc:
cmp #31 ; see if at end
bne ohgr_sprite_yloop ; if not, loop
rts