The reason is that the calculation of the viewport coordinates does not consider that the window geometry is relative to the root window, not to the workspace. The attached patch should fix this issue. cheers, Flo
This bug still appears to be present in master (4.0.-git-fffbc69). I'm finding it to be a real barrier to using xfce4 effectively with compiz. I can't seem to find the patch below from Florian to run myself either, has it been applied?
No idea what is going on here, but note that compiz is not a target window manager for Xfce.