Composite extension and VisibilityNotify events

[Timo Korvola <Timo Korvola iki fi>]

I just tried enabling the Composite extension, and raise-lower-window
stopped working.  Apparently VisibilityNotify events are no longer
generated and Sawfish cannot keep track of window visibility.  Is this
intended behaviour for the Composite extension?  How can one check
whether a window is unobscured then?  One could loop over windows
higher in the stacking order and check each for intersection, but that
feels rather clumsy.

-- 
	Timo Korvola		<URL:http://www.iki.fi/tkorvola>