Set the NOCAREREFESH flag.  Even SMART_REFRESH windows may generate
refresh events if there is a sizing gadget.  If you don't have specific
code to handle this, you must set the NOCAREREFRESH flag.  If you do have
refresh code, be sure to use the Begin/EndRefresh() calls.  Failure to
do one or the other will leave Intuition in an intermediate state, and
slow down operation for all windows on the screen.