Creating a window with no pixmap and no bg color when using a compositor returns a pixmap with random data. Without a compositor, creating a window w/out a back pixmap nor a bg color gives a windows inheriting underlying content (ie whatever was under the window at the time of creation). When running a compositor with Xorg 7.0, it works the same. But when running a compositor with Xorg 7.1, the window shows with random data, not unlike an uninitialized pixmap... This is a problem because many apps, like gtk+, create its top level windows w/out bg pixmap or pixel and it shows when running a compositor. I'll attach a test program that exhibit the problem with relevant screenshots.
Created attachment 7288 [details] Test case
Created attachment 7289 [details] A window with no background without any compositor running This shows the "regular" expected behavior w/out any compositor running
Created attachment 7290 [details] A window with no background with a compositor in Xorg 7.0 The window has no content with a compositor in Xorg 7.0, this is the expected behavior.
Created attachment 7291 [details] A window with no background with a compositor running in Xorg 7.1 Now, in Xorg 7.1, when a compositor is running, the window shows random data. The problem shows equally when using XCompositeNameWindowPixmap () or when accessing the drawable id directly. It seems that the buffer pixmap is not properly initialized in Xorg 7.1.
The test case works fine here with current git (and the xfwm4 compositor :). Did you build the X server yourself? Some distros use a patch with this effect for performance reasons.
I'm using Ubuntu Edgy on an AMD64.
Yeap, ok, I've filled a bug in Launchpad for Ubuntu then.
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