https://bugs.winehq.org/show_bug.cgi?id=34560
--- Comment #9 from Vincent Povirk madewokherd@gmail.com --- Well, that change to GdipGetDC turned out to be wrong, reverted in e9d9ef591b490a8b4eb173df34b10a6977f45b6d with a test.
It didn't occur to me that GDI+ might draw to the alpha channel in some cases but not others, until I tried to optimize this and concluded there was no other way to match native's performance.