More screenload hacking: a faster replrop

[Jef Poskanzer]

After I added the -t for tiling flag to screenload, I was not happy with
the speed.  Just from watching a small bitmap get tiled over the full
screen, it looks like pr_replrop is doing a simple linear replication.
Now, any graphics hacker knows that since edge handling is expensive in
bit blitting, a large blit goes faster than N smaller blits with the same
area.  So I whipped up a quick binary replication wrapper routine, and did
some timings.  For tiling a small bitmap over the full screen, on a 3/50,
my replrop goes four times faster than Sun's.

The routine is appended.  This should be 100% compatible with pr_replrop.
If anyone finds any cases where this isn't so, please let me know.  Also,
I would be interested in hearing whether similar speedups are seen on
other configurations, such as color frame buffers.
---
Jef

             Jef Poskanzer   jef at rtsg.ee.lbl.gov   ...well!pokey

jef_pr_replrop(dpr, dx, dy, dw, dh, op, spr, sx, sy)
Pixrect *dpr, *spr;
int dx, dy, dw, dh, op, sx, sy;
{
	register int w, h, status;

	if ( spr == (Pixrect *) 0 ) {
		return pr_replrop(dpr, dx, dy, dw, dh, op, spr, sx, sy);
	}

	w = spr->pr_size.x;
	h = spr->pr_size.y;
	if (status = pr_replrop(dpr, dx, dy, w, h, op, spr, sx, sy))
		return status;

	op &= ~ PIX_DONTCLIP;

	while ( w < dw || h < dh ) {
		if ( w < dw )
			if (status = pr_rop(dpr, dx + w, dy, w, h, op, dpr, dx, dy))
				return status;
		if ( h < dh )
			if (status = pr_rop(dpr, dx, dy + h, w, h, op, dpr, dx, dy))
				return status;
		if ( w < dw && h < dh )
			if (status = pr_rop(dpr, dx + w, dy + h, w, h, op, dpr, dx, dy))
				return status;
		w *= 2;
		h *= 2;
	}
}