https://bugs.winehq.org/show_bug.cgi?id=39730
--- Comment #8 from Dmitry Timoshkov dmitry@baikal.ru --- (In reply to Dmitry Timoshkov from comment #1)
One of the ways to fix this could be to make 16-bit FillRect() to create a 32-bit brush and call 32-bit FillRect() with it.
This comment still applies to RegisterClass16().