https://bugs.winehq.org/show_bug.cgi?id=11521
--- Comment #16 from Dmitry Timoshkov dmitry@baikal.ru --- Everything in this application (menu and buttons) use WM_DRAWITEM for custom drawing of the controls. The buttons use "TBitBtn" class. It would make the investigation a bit easier if there would be a simple application with just one button of that style. Also, what is that misterious "z-order problem" mentioned in the bug description?