Description of problem: Desktop-effects on dual head ati 9800pro fail using default drivers supplied with FC6. Monitors are Dell 1905FP, one digital and one analog using supplied connections on the ATI 9800pro card. Version-Release number of selected component (if applicable): How reproducible: Type desktop-effects from command line. Steps to Reproduce: 1. 2. 3. Actual results: compiz: No RandR extension The program 'gnome-window-decorator' received an X Window System error. This probably reflects a bug in the program. The error was 'RenderBadPicture (invalid Picture parameter)'. (Details: serial 623 error_code 179 request_code 153 minor_code 8) (Note to programmers: normally, X errors are reported asynchronously; that is, you will receive the error a while after causing it. To debug your program, run it with the --sync command line option to change this behavior. You can then get a meaningful backtrace from your debugger if you break on the gdk_x_error() function.) Expected results: desktop-effects should run. Additional info: see attachment for xorg.conf and errors from Xorg.0.log.
Created attachment 140852 [details] xorg.conf and errors from xorg.0.log
This is not a bug. You cannot use OpenGL based effects with Xinerama based dualhead setups, since Xinerama abstracts out the card. It's almost like you aren't even using an ATI card anymore, you're using an Xinerama card. You can get desktop effects to work in dual head mode, however, by using MergedFB. That will create a single framebufffer for both heads that OpenGL can work with. Read about MergedFB in the radeon man page.