ASM6502
; Paint program for Alterchan
; Рисовалка для Альтерчана
;
; Keyboard controls: / Управление по борьбе с клавиатурой:
; Numpad 1 — Numpad 9 — move cursor/brush (numlock ON!)
; / перемещение кисти/курсора (включить numlock);
; Numpad 5 or 5 — paint pixel with current color/return to background
; / рисовать пиксель текущим цветом/вернуть к цвету фона;
; Numpad + — continuous painting mode ON/OFF
; / включить/выключить режим непрерывного рисования;
; Numpad 0 or SPACE - palette (space may stop the sim or do something if some element in browser is focused)
; / палитра (пробел может остановить эмуль или сделать что-то, если что-нибудь выделено в браузере);
; f/F - fill everything flagged as background with current color
; / залить текущим цветом всё, помеченное как фон
; / (если вместо этого открывается палитра, включить английскую раскладку).

*=0
cursor_low: dcb $ef ; $0,$1 - cursor coords
cursor_high: dcb $03 ; = $03ef for screen center
color: dcb $01 ; $2
color_num: dcb $0f ; $3 - palette color index
border_clr: dcb $b ; $4 - palette border color
palette: ; $5 - and palette array[15] itself

*=$80
mode: dcb $0 ; $80 - continuous brush mode, $0/$ff - OFF/ON
bgcolor: dcb $0 ; $81 - current BG color

*=$fe
rand:
*=$ff
keypress:

*=$200
screen:

*=$600
start: ; ---------- CODE BEGINS HERE ----------

; Init
lda #$ef ;<screen
sta $0 ;set cursor position
lda #$03 ;>screen
sta $1

;Copy frame_clr+palette to ZP for quicker access
ldx #16
copy_loop:
lda palette_slow,x
sta $4,x
dex
bpl copy_loop


; Main loop
main:

; Blink cursor and wait for input
ldy #0
lda ($0),y ;get
pha
lda $2 ;current color
ora #$10
sta ($0),y ;put pixel at cursor address

pla
ldx $80 ;mode
bne skip_blink ;skips returning to image color if mode!=0
sta ($0),y ;return image color
skip_blink:

lda $ff ;keypress
beq main
ldx #0
stx $ff ;keypress

; Act on input (key code in A)
cmp #$35 ; NUM5
bne skip_
lda $2 ;get color
ora #$10 ;bit4 ON
cmp ($0),y ;compare to pixel at cursor
bne paint
lda $81 ;get bgcolor
sta ($0),y ;put pixel at cursor address
jmp main
paint: sta ($0),y ;put pixel at cursor address
jmp main
skip_: cmp #$34 ; NUM4
bne skip0 ;can be replaced by "dcb $d0, $03"
jsr input_move_left
jmp main
skip0: cmp #$36 ; NUM6
bne skip1
jsr input_move_right
jmp main
skip1: cmp #$38 ; NUM8
bne skip2
jsr input_move_up
jmp main
skip2: cmp #$32 ; NUM2
bne skip3
jsr input_move_down
jmp main
skip3: cmp #$31 ; NUM1
bne skip4
jsr input_move_down
jsr input_move_left
jmp main
skip4: cmp #$33 ; NUM3
bne skip5
jsr input_move_down
jsr input_move_right
jmp main
skip5: cmp #$37 ; NUM7
bne skip6
jsr input_move_up
jsr input_move_left
jmp main
skip6: cmp #$39 ; NUM9
bne skip7
jsr input_move_up
jsr input_move_right
jmp main
skip7: cmp #$20 ; SPACE
beq show_color_pal
cmp #$30 ; NUM0
beq show_color_pal
skip8: cmp #$66 ; f key
beq fill_BG
cmp #$46 ; F key
beq fill_BG
cmp #$2b ; NUM+
beq brush_mode
jmp main

; Change brush mode
brush_mode:
lda #1
eor $80
sta $80
jmp main

; Fill background routine
fill_BG:
ldy #0
ldx $2 ;color
stx $81 ;store to bgcolor
fill: lda #$f0
and $200,Y
dcb $d0, $04 ; bne +4 instruction
txa
sta $200,Y
lda #$f0
and $300,Y
dcb $d0, $04 ; bne +4 instruction
txa
sta $300,Y
lda #$f0
and $400,Y
dcb $d0, $04 ; bne +4 instruction
txa
sta $400,Y
lda #$f0
and $500,Y
dcb $d0, $04 ; bne +4 instruction
txa
sta $500,Y
iny ;Y++
bne fill
jmp main

; Color palette selector routine
show_color_pal:

; Save pic to stack
ldx #17
save_loop:
lda $507,x
pha
lda $527,x
pha
lda $547,x
pha
lda $567,x
pha
lda $587,x
pha
lda $5a7,x
pha
dex
bpl save_loop

; Draw borderlines
ldx #17
lda $4 ;border_clr to A
border_loop:
sta $507,x
sta $5a7,x
dex
bpl border_loop

; Draw center borderlines
tax ;border_clr to X
ldx #0
clc
border_loop2:
sta $527,x
sta $538,x
pha
txa
adc #$20 ;next line
tax
pla
cpx #$80
bne border_loop2

; Draw palette
ldx #7
pal_loop:
txa
asl ; A=A*2
tay
lda $5,x ;palette address
sta $528,y
sta $548,y
iny
sta $528,y
sta $548,y
lda $d,x ;palette address + 8 for 2nd row
sta $568,y
sta $588,y
dey
sta $568,y
sta $588,y
dex
bpl pal_loop

; Flash color and wait for input
palette_input_loop:
; Blink current color
lda $3 ;color_num
tax
clc
asl ;A=color_num*2
cmp #16
bmi less_than_16
clc ;+$30 for the 2nd palette row
adc #$30 ;(for ex., $8*2+$30=$40, $528->$568 which is correct)
less_than_16:
tay
cpx #$c
beq darkblink
cpx #$d
beq darkblink
cpx #$f
beq darkblink
cpx #$5
beq darkblink
lda #1 ;white color for blink
bne brightblink
darkblink:
lda #$c ;or gray
brightblink:
sta $528,y
sta $548,y
iny
sta $528,y
sta $548,y

txa
ldx #150 ;cycle 150 times
wait1: dex
bne wait1
tax

lda $5,x ;load color from palette address
sta $528,y
sta $548,y
dey
sta $528,y
sta $548,y

ldx #0 ;cycle 255 times
wait2: dex
bne wait2

lda $ff ;keypress
beq palette_input_loop ;jumps up if no key pressed
ldx #0
stx $ff ;keypress

; Act on input (key code in A)
cmp #$34 ; NUM4
bne skip10
lda $3 ;color_num
clc
adc #$ff ;-1
and #$0f
sta $3
skip10: cmp #$36 ; NUM6
bne skip11
lda $3 ;color_num
clc
adc #1
and #$0f
sta $3
skip11: cmp #$38 ; NUM8
beq num8_2
cmp #$32 ; NUM2
bne skip12
num8_2: lda $3 ;color_num
clc
adc #8
and #$0f
sta $3
skip12: cmp #$31 ; NUM1
beq num1_7
cmp #$37 ; NUM7
bne skip13
num1_7: lda $3 ;color_num
clc
adc #$ff ;-1
and #$0f
sta $3
bpl num8_2 ;always branch (= jmp)
skip13: cmp #$33 ; NUM3
beq num3_9
cmp #$39 ; NUM9
bne skip14
num3_9: lda $3 ;color_num
clc
adc #1
and #$0f
sta $3
bpl num8_2 ;always branch (= jmp)
skip14: cmp #$20 ; SPACE
beq exit_palette
cmp #$30 ; NUM0
beq exit_palette
cmp #$35 ; NUM5
beq exit_palette
jmp palette_input_loop
exit_palette:
; Load pic from stack
ldx #0
load_loop:
pla
sta $5a7,x
pla
sta $587,x
pla
sta $567,x
pla
sta $547,x
pla
sta $527,x
pla
sta $507,x
inx
cpx #18
bne load_loop

ldx $3 ;get color_num
lda $5,x ;palette[color_num]
sta $2 ;to color
jmp main

; Main input handlers (subroutines)
input_move_left:
lda $0
and #$1f
beq edge_l
dec $0
edge_l:
rts ;return

input_move_right:
inc $0
lda #$1f
bit $0 ;Z={A&$0)
beq edge_r
rts ;return
edge_r:
dec $0
rts ;return

input_move_up:
lda $0
tay
sec
sbc #$20
sta $0
bcc borrow_u
rts ;return
borrow_u:
ldx $1
dex
cpx #01
beq edge_u
stx $1
rts ;return
edge_u:
sty $0
rts ;return

input_move_down:
lda $0
tax
clc
adc #$20
sta $0
lda #0
adc $1
cmp #$6
beq edge_d
sta $1
rts ;return
edge_d:
stx $0
rts ;return

; ---------- END ----------

palette_slow:
dcb $b ; border color
dcb $0, $2, $4, $6, $5, $7, $b, $f ; palette[15]
dcb $9, $8, $a, $e, $d, $3, $c, $1

;offscreen_buffer: ;not done yet
;dcb 0