http://bugs.winehq.org/show_bug.cgi?id=14067
--- Comment #4 from markk@clara.co.uk 2008-07-10 17:14:20 --- To elaborate on this some more...
Consider virtualisation/emulation programs like VirtualBox, Bochs, VMware etc., which completely emulate the hardware of a PC. The program does not know anything about the guest OS/windowing system. Therefore, it must handle remembering and restoring covered & revealed parts of the display window.
If X doesn't already support doing that automatically (when requested by the X client), it's safe to say there's no chance of X supporting it -- and the support fitering downstream to OS distributions -- in the forseeable future.
A demo version of Age of Mythology is available from
http://www.microsoft.com/Downloads/details.aspx?familyid=9F52C391-683F-46D6-...
Direct URL is
http://download.microsoft.com/download/4/7/8/4785f001-bec0-44c3-8adb-5bb5f8f...
(Warning: 337MB file!)
Hopefully installing that when in virtual desktop mode will demonstrate the problem I'm referring to.