Expose response amazingly slow

[sshachar at t2.technion.ac.il]

Oh one more issue, 

I am running a piece of GUI SW written with wxWidgets, and experiencing very
slow refresh rates when one window obscures another and is then moved away.
This phenomenon may be especially emphasized in the above case but is apparent
even when moving a smiple xterm window over the latest Debian desktop. 

I thought what I'd see is that when one window is drawn on top of another, the
contents of the back window would be saved aside (backing store?) but skimming
the list archives it seems the composite manager magically takes care of this
case (without caching offscreen?!).

Assuming it's not an issue with the GUI SW but rather something in my driver/X
configuration, what could it be?

10x again, s