[Cairo] Cairo on older X servers, (eg. with Render version 0.2)

[Carl Worth]

On Sep 29, Carl Worth wrote:
 > Oops. That now leaks the pixmap instead. Better would be to move the
 > XFreePixmap call to cairo_surface_destroy. Jamey's virtualization
 > patch includes a fix along those lines.

I've just committed a fix like Jamey's that should eliminate the bad
drawable error on older X servers due to this XFreePixmap call.

If Cairo users with an older server that were seeing the error would
retest and let me know if things are working better now, I would
appreciate that.

However, even if the programs now run, they still should be quite
slow.

But it occurs to me that there's an almost trivially easy way to speed
up Cairo on old servers. If Cairo can assume that nothing external to
Cairo will be drawing to any drawable that has been handed to Cairo,
then a lot of useless image transfer can be eliminated with a couple
of lines of code.

Would this be an acceptable assumption?  Otherwise, is there a cheap
way that Cairo could determine whether the drawable contents it has
cached are stale or not?

-Carl