[Bug 6006] incorrect paint of invisible buttons

[Wine Bugs]

http://bugs.winehq.org/show_bug.cgi?id=6006

------- Additional Comments From [e-mail]  2007-03-02 21:51 -------
Created an attachment (id=4773)
 --> (http://bugs.winehq.org/attachment.cgi?id=4773&action=view)
paint-reproduction.c

Attaching some code that reproduces the rest of this problem.

Interestingly, the WM_PAINT handler does a paint of some child windows, and
calls ValidateRect to prevent extra WM_PAINT events from being generated
afterwards.

Under wine, the result is a window with garbage pixels on it.  Under Windows,
there are no garbage pixels.