This topic is somewhat old.  But I'd like to take up this because the
similar problem also occurs in Carbon Emacs, where drawing text is
much slower than in X11.

>>>>> On Tue, 11 May 2004 23:34:53 +0200, jmarant@nerim.net (Jérôme Marant) said:

>>> I also tried something which is even worse: When I split the main
>>> window (C-x 2) and move the modeline of the top buffer, everything
>>> is flickering: both scrollbars and buffers.  It is pretty ugly.
>> 
>> Turn off scrollbars and see if there is a difference.

> Yes, there is. It is OK without them :(

How about preventing redisplay from pausing in the case that there are
no pending inputs other than the mouse movement?  One can "squeeze" a
sequence of mouse movement events into the latest one, and I think
it's OK to postpone such kind of events until redisplay is completed.

Here's a patch for testing the above idea.  It would be better to make
redisplay pause even in the case mentioned above, if the latest mouse
movement gets too old.

				     YAMAMOTO Mitsuharu
				mituharu@math.s.chiba-u.ac.jp