r8/examples/draw.asm at main · tsoding/r8 · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
FPS_CONFIG    = $FFFD
CANVAS        = $1000
CANVAS_WIDTH  = 64
CANVAS_HEIGHT = 64
KEYBOARD      = $2000
MOUSE_BTN     = $2080
MOUSE_X       = $2081
MOUSE_Y       = $2082
LINE          = $00

    org $8000

init:
    lda #<update
    sta $FFFE
    lda #>update
    sta $FFFE+1

    lda #30
    sta FPS_CONFIG

    rts


update:
    ldx MOUSE_BTN
    beq .not_pressed

    jsr line_reset
    ldy MOUSE_Y
.loop:
    dey
    bmi .out
    jsr line_next
    jmp .loop
.out

    ldy MOUSE_X
    lda #$00
    cpx #$01
    bne .skip_set_white
    lda #$FF
.skip_set_white:
    sta (LINE),Y
.not_pressed:
    rts

line_next:
    clc
    lda #64
    adc LINE
    sta LINE
    lda #00
    adc LINE+1
    sta LINE+1
    rts


line_reset:
    lda #<CANVAS
    sta LINE
    lda #>CANVAS
    sta LINE+1
    rts