Comment 44 for bug 278112

I debugged that a bit further and the current theory is that when XCompositeUnredirectWindow() on a redirected window is called (that happens with unredirect fullscreen windows) then the xserver will do a internal map/unmap cycle. No events are generated for this, its for internal resource (re)allocation. But it looks like it still has as the side-effect a user-visible "Unobscured", "FulylObscured", "Unobscured".

I see the following options:
a) fix it in the xserver (hard but the best way)
b) fix it in xscreensaver by adding detection if the window cycles between redirected and unredirected (medium hard)
c) re-add the hack in compiz that ignored gnome-screensaver for redirect fullscreen windows (easy, but we get the whie-screen bug back this way)