https://bugs.winehq.org/show_bug.cgi?id=56149
--- Comment #12 from Gabriel Ivăncescu gabrielopcode@gmail.com --- Ok, this is not about double-setting it to fullscreen at all. According to an old bug I found when searching: https://bugs.openjdk.org/browse/JDK-6500686
This happens if _MOTIF_WM_HINTS is set without MWM_FUNC_RESIZE | MWM_FUNC_MOVE, and then setting it to fullscreen, and it affects several WMs already (not just Kwin, compiz too for instance). I confirmed it's the cause of the issue.
It worked before because X11DRV_SetDesktopWindow was setting it to fullscreen *before* the hint. Any fullscreen attempt after the hint removes resize makes it fail.
We already set MWM_FUNC_MOVE on desktop windows, what do you think about also setting MWM_FUNC_RESIZE only for fullscreen desktop windows?