https://bugs.winehq.org/show_bug.cgi?id=53910
--- Comment #1 from Rafał Mużyło galtgendo@o2.pl --- Also, some windows (but this looks app-specific) turn invisible from that test.
By 'invisible' I mean exactly that - mouse cursor changes upon entering the window area, but the window itself isn't drawn on the screen.
xwininfo reports: 'Map State: IsViewable'.