https://bugs.winehq.org/show_bug.cgi?id=43737
--- Comment #14 from Zebediah Figura z.figura12@gmail.com --- Unfortunately I think the WM_ERASEBKGND message is correct. If I modify test_window_threading() in quartz:filtergraph to make both the parent and child visible, I get WM_ERASEBKGND (and a similar hang if I refuse to process it).