SymbOS MSX multitasking operating system - help needed!

One to get you started. It should still be optimised. For one it used the slow pixel accurate fill and not the byte accurate one if possible. But hey, it's a start.

PNTBOX:
	ld 	(LMMV.C),a
	ld	a,$80
	jr	nc,$+4
	or	3
	ld	(LMMV.CM),a
	push	hl
	ld	hl,(winxbg)
	ex	de,hl
	or	a
	sbc	hl,de	
	ld	de,(winxps)
	jr	c,.off_left
	add	hl,de
	push	bc
	jr	.set_left
.off_left:
	add	hl,bc
	push	hl
	ex	de,hl
.set_left:
	ld	(LMMV.DX),hl
	pop	de
	add	hl,de
	or	a
	ld	bc,(winxps)
	sbc	hl,bc
	ld	bc,(winxln)
	sbc	hl,bc
	jr	c,.set_right
	ex	de,hl
	sbc	hl,de
	ex	de,hl
.set_right:
	ld	(LMMV.NX),de
	
	pop	hl
	ld	de,(winybg)
	or	a
	sbc	hl,de	
	ld	de,(winyps)
	jr	c,.off_top
	add	hl,de
	jr	.set_top
.off_top:
	ex	de,hl
	add	ix,de
.set_top:
	push	ix
	ld	(LMMV.DY),hl
	pop	de
	add	hl,de
	or	a
	ld	bc,(winyps)
	sbc	hl,bc
	ld	bc,(winyln)
	sbc	hl,bc
	jr	c,.set_bottom
	ex	de,hl
	sbc	hl,de
	ex	de,hl
.set_bottom:
	ld	(LMMV.NY),de

	call	WaitForVDP
        ld      a,36	; start at DX
        out     (99h),a
        ld      a,91h
        out     (99h),a

	ld	bc,$0B9B
	ld	hl,LMMV
	otir
	ret

LMMV:
.DX:	dw	0
.DY:	dw	0
.NX:	dw	0
.NY:	dw	0
.C:	db	0
	db	0
.CM:	db	0

WaitForVDP:
        ld      a,2	; select S#2
        out     (99h),a
        ld      a,8Fh
        out     (99h),a
.wait:
	in	a,(99h)
	rra
	jr	c,.wait
        xor 	a	; select S#0
        out     (99h),a
        ld      a,8Fh
        out     (99h),a
	ret

PS I hope it's free of bugs

PSS Yes, yes, the comments were lost somewhere

You may be a bit less impressed after checking this.

The visible screen only exceeds one byte when using interlace. But I have hopes that someone will write the same stuff for v9990 so we can enjoy 640x400. ;)

German comments should be no problem for most Dutchies. Don't know about the visitors from the rest of the world though.

http://www.work.de/nocash/portar.htm#vdpregisters20h2ehmsx2videocommandregisters

Thanx again for the information. Now I have a much better understanding about the possibilities and the usage of the VDP.
Currently I am excited about it, as it looks like a nice 2D accelerator I just hope, that the VDP itself is not too slow. I will make some tests by myself now to get an impression about the possible speed. Maybe I need to rethink something.
As an example now I think it could be optimal to store the complete font 12 or 16times in the VRAM to have a version for any pen(0-3)/paper(0-3) combination. But when plotting proportional text, the VDP has to do a lot of very small pixel copy operations (one for every char). I hope that it will still be fast enough...

Do you mean setting bit3 of the command register 2E to 1? Is the VDP in transparent mode as fast as in normal mode? If yes, that's a good idea, as then I would only need to store it 6 times in memory (3 times with colours 1-3 and background=0; and 3 times with colour 0 and background 1-3).