> Can you see if the coordinates of the exposed region, as reported to
> Emacs, correspond to what is in fact exposed?

Finally I captured a state that although an expose event was sent to
Emacs (correctly), Emacs did not redraw.  In the attached screenshot,
the left-side two windows are Emacs and speedbar frames.  The
top-right terminal shows the output of xev monitoring the events of
the main Emacs window.  This state was captured while shifting out of
the virtual desktop containing Emacs then shifting in.  Emacs did a
partial redraw only.

Yuan