Painting a huge Xlib surface (I think > 256 pixels in width and/or height) onto
another Xlib surface fails. This does not happen if it's an image surface.
The output looks garbled.
(I'm using X 7.0.0, render is enabled)
Hijacking this bug as I managed to trigger a crash within xlib whilst investigating - woohoo! The test case is commit c23dbc4c616aed05dfe71901ce7ac0cadcbfb13d.
As expected it was a subtle bug in the test case (destroying the source surface triggered an XCloseDisplay whilst I was still using surfaces on that connection). Resolving that bug, the test case runs flawlessly - so closing the bug.