Re: GC graphics_exposures

On Wed, 22 Jan 2003 23:24:52 +0000
Tor Lillqvist <[email protected]> wrote:

>  > Just wondering if there are any plans to implement the graphics_exposures
>  > flag of GCs? Without it, my custom widgets display visual artifacts when
>  > trying to scroll while partly obscured.
> 
> Umm, I'm too lazy to dig out the X11 protocol specs and/or Xlib docs
> right now, refresh my memory, what does graphics_exposures mean?

When you gdk_draw_drawable from the same src/dest (just copy an area of a window),
there might be parts of the src-rectangle that are obscured by another top-level
window. Of course, copying parts of the obscured areas will copy garbage.

With the gc->graphics_exposures flag true, it would generate an expose event
for the parts of the draw_drawable-src-rectangle that were obscured.

Pseudo code:

gdk_win32_draw_drawable(drawable, gc, src, xsrc, ysrc, xdest, ydest, width, height)
{
	_gdk_win32_blit (....);

	if (gc->graphics_exposures)
	{
		obscured_rect = find_obscured_rect (src);
		if (obscured_rect)
		{
			expose_region = intersection (obscured_rect,
						      xsrc, ysrc, width, height);
			generate_expose_event (drawable, expose_region);
		}
	}

}

I'm not sure if "intersection" is the right word there, but we want the area
that's apart of the obscured_rect AND src-rectangle (if any).

Find_obscured_rect() might be a problem. I'm not too famaliar with win32 API, but
is there a call to find this?


-- 
Peter Zelezny.

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