https://bugs.winehq.org/show_bug.cgi?id=52515
--- Comment #3 from Zhiyi Zhang zzhang@codeweavers.com --- To clarify, SWP_NOCOPYBITS is added to the button WM_WINDOWPOSCHANGED messages so buttons can be successfully repainted on Windows. On Wine, this bit is missing so the old window content is used and no WM_PAINT messages are generated.