[Lonewolf10]

I now have an optimized line routine, but it is slightly buggy. It would be hard to describe, so I have attached 2 pictures - "drawline" is working normally, and "drawline2_bug" is drawn using the optimized routine (below). Any ideas what is causing this? (other than my dodgy code )

drawline2:				;INPUT: d0=x1, d1=y1, d2=x2, d3=y2
					;	d4=width, a0=aptr	

.deltax_and_sx
	moveq	#1,d6			;sx = 1
	move.w	d2,d4			;d4 = x2
	sub.w	d0,d4			;delta_x = x2 - x1
	bgt.b	.deltay_and_sy
	neg.w	d4			;-delta_x  -> delta_x
	moveq	#-1,d6			;sx = -1
.deltay_and_sy
	moveq	#1,d7			;sy = 1
	move.w	d3,d5			;d5 = y2
	sub.w	d1,d5			;delta_y = y2 - y1
	bgt.b	.get_ERR
	neg.w	d5			;-delta_y  -> delta_y
	moveq	#-1,d7			;sy = -1
.get_ERR
	move.w	d4,a1			;a1 = delta_x
	sub.w	d5,a1			;a1 = delta_x - delta_y
					;a1=ERR
.mainloop
	movem.l	d0-d2/a1,-(sp)
	jsr	plot			;plot a pixel
	movem.l	(sp)+,d0-d2/a1
	cmp.w	d2,d0			;does x1 equal x2?
	beq	.exit1
.no_exit
	move.w	a1,a2			;\ a2 = ERR * 2
	add.w	a1,a2			;/
	neg.w	d5			;delta_y  ->  -delta_y
	cmp.w	d5,a2			;E2 > -delta_Y ?
	bgt.b	.dec_ERR
.dec_ERR_return
	cmp.w	d4,a2
	blt.b	.add_ERR		;E2 < delta_x ?
	bra.s	.mainloop

.dec_ERR
	neg.w	d5			;-delta_y  ->  delta_y
	sub.w	d5,a1			;ERR=ERR-delta_Y
	add.w	d6,d0			;X1=X1+shift_X
	bra.s	.dec_ERR_return

.add_ERR
	add.w	d4,a1			;ERR=ERR+delta_X
	add.w	d7,d1			;Y1=Y1+SY
	bra	.mainloop
.exit1
	cmp.w	d1,d3			;exit if y1 equals y2
	bne	.no_exit
.exit
	rts

Regards,
Lonewolf10