** Revision Header * Header built automatically - do not edit! *************
*
*	(C) Copyright 1991 by Olaf `Olsen' Barthel, all rights reserved
*
*	Name .....: Plot.asm
*	Created ..: Monday 26-Aug-91 11:20
*	Revision .: 1
*
*	Date            Author          Comment
*	=========       ========        ====================
*	26-Aug-91	Olsen		Created this file!
*
****************************************************************************

	include	"graphics/gfx.i"

	csect	text,0,0,1,2

	xdef	_Plot
	xdef	_Test

;	VOID __asm Plot(register __a0 struct BitMap *,register __d0 WORD X,register __d1 WORD Y,register __d2 WORD Colour);
;
;		Fast pixel drawing routine, somewhat equivalent to
;	graphics.library/WritePixel.
;
;	Register usage is as follows:
;
;		d1	= Byte offset into bitplane
;		d2	= Pixel colour
;		d3	= Number of bitplanes
;		d4	= Line modulo/pixel number
;		a0	= Pointer to array of bitplanes
;		a1	= Pointer to bitplane

_Plot:	movem.l	d3/d4,-(sp)		; Save registerrs

	moveq	#0,d4			; Clear d3 & d4
	move.l	d4,d3

	move.w	bm_BytesPerRow(a0),d4	; Get line modulo
	move.b	bm_Depth(a0),d3		; Get bitmap depth
	lea.l	bm_Planes(a0),a0	; Get array of planes

	mulu.l	d4,d1			; Multiply Y-position by modulo
	move.l	d0,d4			; Save X-position
	lsr	#3,d0			; Get byte offset of X-position 
	add	d0,d1			; Add byte offsets
	not	d4			; Get bit number
	subq	#1,d3			; One plane less (for dbra)

loop	move.l	(a0)+,a1		; Get next plane
	lsr.b	#1,d2			; Clear or set the pixel?
	bcc	clear
	bset	d4,0(a1,d1)		; Set pixel
	dbra	d3,loop			; Loop until all planes are done

exit	movem.l	(sp)+,d3/d4		; Restore registers
	rts

clear	bclr	d4,0(a1,d1)		; Clear pixel
	dbra	d3,loop			; Loop until all planes are done
	bra	exit

;	BYTE __asm Test(register __a0 struct BitMap *,register __d0 WORD X,register __d1 WORD Y);
;
;		Fast pixel reading routine, somewhat equivalent to
;	graphics.library/ReadPixel, returns 1 if there is a pixel in
;	the given position in bitmap, else 0.
;
;	Register usage is as follows:
;
;		d1	= Byte offset into bitplane
;		d3	= Number of bitplanes
;		d4	= Line modulo/pixel number
;		a0	= Pointer to array of bitplanes
;		a1	= Pointer to bitplane

_Test:	movem.l	d3/d4,-(sp)		; Save registerrs

	moveq	#0,d4			; Clear d3 & d4
	move.l	d4,d3

	move.w	bm_BytesPerRow(a0),d4	; Get line modulo
	move.b	bm_Depth(a0),d3		; Get bitmap depth
	lea.l	bm_Planes(a0),a0	; Get array of planes

	mulu.l	d4,d1			; Multiply Y-position by modulo
	move.l	d0,d4			; Save X-position
	lsr	#3,d0			; Get byte offset of X-position
	add	d0,d1			; Add byte offsets
	not	d4			; Get bit number
	sub.w	#1,d3			; One plane less (for dbra)
	moveq	#0,d0			; So we have valid return code

tloop	move.l	(a0)+,a1		; Get next plane
	btst	d4,0(a1,d1)		; Is a pixel in this position?
	bne.s	go			; Yes, there is
	dbra	d3,tloop		; Test next plane

	movem.l	(sp)+,d3/d4		; Restore registers
	rts

go	moveq	#1,d0			; Got a pixel

	movem.l	(sp)+,d3/d4		; Restore registers
	rts

	end