http://bugs.winehq.org/show_bug.cgi?id=58488
--- Comment #3 from MarcinZw marcinzw@gmail.com --- I ran into another issue. This time it’s with WinUAE — after hitting "Start". In Sway, it creates "XWayland unmanaged surface" that shows up as a black rectangle in the top-left corner of the screen.
Bisect points to this commit:
commit 62449bcfec546a7d52fd4c556c239a28c107b207 win32u: Update client surfaces when window state changes.
Looks like it might be related. This time it works fine when using "Emulate a virtual desktop".