mirror of
https://github.com/cc65/cc65.git
synced 2024-11-01 11:04:34 +00:00
165 lines
2.1 KiB
ArmAsm
165 lines
2.1 KiB
ArmAsm
;
|
|
; Christian Groessler, June 2000
|
|
;
|
|
; void __fastcall__ scroll (signed char numlines);
|
|
; numlines > 0 scrolls up
|
|
; numlines < 0 scrolls down
|
|
;
|
|
|
|
.include "atari.inc"
|
|
.importzp tmp1,tmp4,ptr1,ptr2
|
|
.import mul40,_clrscr
|
|
.export _scroll
|
|
|
|
.proc _scroll
|
|
|
|
cmp #0
|
|
beq jmpfin
|
|
; cmp #$80
|
|
; bcc up
|
|
bpl up
|
|
|
|
;scroll down
|
|
eor #$ff
|
|
clc
|
|
adc #1 ; make positive
|
|
sta tmp1
|
|
|
|
cmp #24 ; scroll >= the whole screen?
|
|
bcc down_ok
|
|
jmp _clrscr
|
|
|
|
down_ok:lda SAVMSC
|
|
clc
|
|
adc #<(40*23)
|
|
sta ptr1
|
|
sta ptr2
|
|
lda SAVMSC+1
|
|
adc #>(40*23)
|
|
sta ptr1+1 ; point to last line on screen
|
|
sta ptr2+1
|
|
|
|
lda tmp1
|
|
jsr mul40
|
|
sta tmp4
|
|
lda ptr2
|
|
sec
|
|
sbc tmp4
|
|
sta ptr2
|
|
stx tmp4
|
|
lda ptr2+1
|
|
sbc tmp4
|
|
sta ptr2+1
|
|
|
|
lda #24 ; # of lines on screen
|
|
sec
|
|
sbc tmp1 ; # of lines to move
|
|
tax
|
|
|
|
;very simple, could be improved
|
|
|
|
scrold: ldy #39 ; # of chars on a line - 1
|
|
copy_d: lda (ptr2),y
|
|
sta (ptr1),y
|
|
dey
|
|
bpl copy_d
|
|
lda ptr1
|
|
sec
|
|
sbc #40
|
|
sta ptr1
|
|
bcs u1
|
|
dec ptr1+1
|
|
u1: lda ptr2
|
|
sec
|
|
sbc #40
|
|
sta ptr2
|
|
bcs u2
|
|
dec ptr2+1
|
|
u2: dex
|
|
bne scrold
|
|
|
|
; fill new scrolled in lines with space
|
|
|
|
ldx tmp1 ; # of new lines
|
|
fild: lda #0
|
|
ldy #39
|
|
fill_d: sta (ptr1),y
|
|
dey
|
|
bpl fill_d
|
|
dex
|
|
jmpfin: beq finish
|
|
lda ptr1
|
|
sec
|
|
sbc #40
|
|
sta ptr1
|
|
bcs u3
|
|
dec ptr1+1
|
|
u3: jmp fild
|
|
|
|
;scroll up
|
|
up: sta tmp1 ; # of lines to scroll
|
|
cmp #24 ; scroll >= the whole screen?
|
|
bcc up_ok
|
|
jmp _clrscr
|
|
|
|
;multiply by 40 (xsize)
|
|
up_ok: jsr mul40
|
|
clc
|
|
adc SAVMSC ; add start of screen mem
|
|
sta ptr2
|
|
txa
|
|
adc SAVMSC+1
|
|
sta ptr2+1
|
|
lda SAVMSC+1
|
|
sta ptr1+1
|
|
lda SAVMSC
|
|
sta ptr1
|
|
lda #24 ; # of lines on screen
|
|
sec
|
|
sbc tmp1 ; # of lines to move
|
|
tax
|
|
|
|
;very simple, could be improved
|
|
|
|
scroll: ldy #39 ; # of chars on a line - 1
|
|
copy_l: lda (ptr2),y
|
|
sta (ptr1),y
|
|
dey
|
|
bpl copy_l
|
|
lda #40
|
|
clc
|
|
adc ptr1
|
|
sta ptr1
|
|
bcc l1
|
|
inc ptr1+1
|
|
l1: lda #40
|
|
clc
|
|
adc ptr2
|
|
sta ptr2
|
|
bcc l2
|
|
inc ptr2+1
|
|
l2: dex
|
|
bne scroll
|
|
|
|
; fill new scrolled in lines with space
|
|
|
|
ldx tmp1 ; # of new lines
|
|
fill: lda #0
|
|
ldy #39
|
|
fill_l: sta (ptr1),y
|
|
dey
|
|
bpl fill_l
|
|
dex
|
|
beq finish
|
|
lda #40
|
|
clc
|
|
adc ptr1
|
|
sta ptr1
|
|
bcc l3
|
|
inc ptr1+1
|
|
l3: jmp fill
|
|
|
|
finish: rts
|
|
|
|
.endproc
|