********************************************************************************
* ByteSCApe: draw the SCA logo in 256 bytes. Coded by Saturnus the Invincible. *
* The Mega-Mighty Swiss Cracking Association - reaching out to you! 2024-03-08 *
********************************************************************************

                include "graphics/graphics_lib.i"
                include "graphics/rastport.i"
                include "intuition/screens.i"

wrch		equ	$e0			; d1:char
writespaces	equ	$d4			; d2:amount
intuitionbase	equ	$170			; globvec offset
eb_gfxbase	equ	$9c			; execbase offset

_main:		moveq	#32,d0			; bcpl stack frame size
		moveq	#78,d2			; 78 spaces
		movea.l	writespaces(a2),a4	; get routine from globvec
		jsr	(a5)			; call bcpl

		lea	text(pc),a0
.charloop:	move.b	(a0)+,d1
		beq.b	.text_done
		movea.l	wrch(a2),a4
		move.l	a0,d5			; wrch() preserves d5 but not a0
		jsr	(a5)
		moveq	#' ',d1
		movea.l	wrch(a2),a4
		jsr	(a5)
		movea.l	d5,a0
		bra.b	.charloop
.text_done:
		movea.l	intuitionbase(a2),a6
		movea.l	ib_ActiveScreen(a6),a1
		lea	sc_RastPort(a1),a1
		movea.l	4.w,a6
		movea.l	eb_gfxbase(a6),a6	; shortcut to graphics.library

		moveq	#1,d0			; white
		jsr	_LVOSetAPen(a6)		; preserves a1, nice!

		lea	sca_logo(pc),a4
		movem.w	(a4)+,d3-d7/a3		; #lines,x,y,length,dx,dy
.stem_loop:	bsr.b	draw_line
		addi.w	#140,d4			; x
		dbf	d3,.stem_loop

.draw_loop:	move.w	(a4)+,d0		; dx
		beq.b	draw_done
		add.w	d0,d4			; d4: x
		move.b	(a4)+,d0		; dy
		ext.w	d0
		add.w	d0,d5			; d5: y
		moveq	#0,d6
		move.b	(a4)+,d6		; d6: length (unsigned)
		move.b	(a4)+,d7		; d7: dx (signed)
		ext.w	d7
		move.b	(a4)+,d0		; dy (signed)
		ext.w	d0
		movea.w	d0,a3			; a3: dy
		bsr.b	draw_line
		bra.b	.draw_loop
		rts				; waste two bytes (we're gonna save them later)

		; The secret BrazenHum algorithm: d4:x, d5:y, d6:length, d7:dx, a3:dy
draw_line:	movem.l	d3-d6,-(sp)
.loop:		move.w	d4,d0
		move.w	d5,d1
		moveq	#3,d2			; width of ellipse
		moveq	#2,d3			; height
		jsr	_LVODrawEllipse(a6)	; preserves a1, nice!
		add.w	d7,d4
		add.w	a3,d5
		dbf	d6,.loop
		movem.l	(sp)+,d3-d6
draw_done:	moveq	#0,d0			; CLI return code (TnX Depeche for saving 2 bytes!)
		rts

sca_logo:	dc.w	3,110,72,50,-1,2	; four stems

		; array of [word dx0 byte dy0,length,dx,dy]
		dc.w	-137			; horizontal top line
		dc.b	2,143,-3,0
		dc.w	593			; horizontal bottom line
		dc.b	95,143,-3,0
		dc.w	-249			; S top
		dc.b	-66,24,-3,0
		dc.w	-91			; S bottom
		dc.b	33,24,-3,0
		dc.w	224			; C
		dc.b	-18,24,-3,0
		dc.w	112			; A horizontal
		dc.b	-18,24,-3,0
		dc.w	-53			; A vertical
		dc.b	33,18,-1,2
		dc.w	0			; end marker

text:		dc.b	"The Mega-Mighty",10,0	; 0 follows anyway, not necessary but we got the space

		end