GUI?
[Last modified: Nov 97]

Answer: For each change you make, the widget decides if it needs to redraw.
If so, Xt calls XtClearArea to generate an expose event.  You main loop
dispatches the resulting expose event to your widget, causing a redisplay.
Note that the redisplay may be delayed somewhat if you do not immediately
return to the event loop after calling XtSetValues.  You can often work around
this by calling XmUpdateDisplay().

Note also that you should try to make all your changes in one large
XtSetValues changing several values at once.  If you call XtSetValues
individually for each change you need to make, you could generate several
expose events and redraw several times.