Hi James, I tried your patch on my machine (ubuntu 9.04 ashamed ATI radeon non-supported) and it's working fine.
ATI is a crap. If you want to make serious 3d/video stuff in GEM on Linux or you change video card, or you go back 8.04. Meanwhile you may want to check this tips for a decent configuration of ATI cards:
http://www.thinkwiki.org/wiki/Additional_options_for_the_radeon_driver https://help.ubuntu.com/community/RadeonDriver
this helped me to not go crazy and throw my video card... but I still can't work properly. hope this helps..
Marco
What's more, with desktop effects enabled gem has a lot of weirdness! The window border disappears, the lower half of the window displays a garbled image, and it corrupts the rest of my desktop! So I disabled desktop effects and am currently now having trouble with multiple gemheads - please see the attached patch. If all 3 gemheads are enabled, the first two seem to switch places very quickly (many times a second) - they should be static and scroll with the key presses. However I've just tested this on my desktop box running karmic with an nvidia card and it seems fine!
If anyone can help with any of these issues, please let me know - it's very frustrating!
thanks,
James