https://bugs.winehq.org/show_bug.cgi?id=39952
--- Comment #2 from Nikolay Sivov bunglehead@gmail.com --- I see what you mean, application completely takes over painting duty, so original procedure is never called for WM_PAINT and we have no chance to update this internal state. Patch is likely to be correct, but I'd like to do some tests first and clean up related things.