[Bug 1841] wrong region drawn

[Wine Bugs]

http://bugs.winehq.org/show_bug.cgi?id=1841

------- Additional Comments From [e-mail]  2005-05-10 09:16 -------
I am attaching a screen shot showing the "bug" reproduced on a win2000 SP2 machine.

This happens in a fraction of the cases. Look at the output of the message spy
in the same picture. Lines 1-18 are the messages generated during a successfull
update, lines 21-38 when it fails.(the wm_null messages are my addition, sent in
the programs wm_paint handler).
Under Wine the messages are almost identical as in the second case, resulting in
an background erase after the painting which causes the illusion that the area
is not updated.