XLIB	plotpixel

	LIB pixeladdress
	XREF	COORDS

; ******************************************************************
;
; Plot pixel at (x,y) coordinate.
;
; Design & programming by Gunther Strube, Copyright (C) InterLogic 1995
;
; The (0,0) origin is placed at the bottom left corner.
;
; in:  hl	= (x,y) coordinate of pixel (h,l)
;
; registers changed	after return:
;  ..bc..../ixiy same
;  af..dehl/.... different
;
.plotpixel		ld	a,l
				cp	64
				ret	nc				; y0	out of range

				push	bc
				ld	(COORDS),hl
				ld	a,l
				xor	@00111111			; (0,0) is hardware	(0,63)
				ld	l,a

				call	pixeladdress
				ld	b,a
				ld	a,1
				jr	z, or_pixel		; pixel is at bit 0...
.plot_position		rlca
				djnz	plot_position
.or_pixel			ex	de,hl
				or	(hl)
				ld	(hl),a
				pop	bc
				ret