http://bugs.winehq.org/show_bug.cgi?id=26712
--- Comment #5 from Henri Verbeet hverbeet@gmail.com 2013-04-27 13:56:11 CDT --- It probably adjust the display gamma to implement the fade. If that's the case, I'm not sure if that's really a bug other than perhaps in the sense that gamma adjustment in a virtual desktop affect the entire screen.