https://bugs.winehq.org/show_bug.cgi?id=57474
--- Comment #4 from Rémi Bernon rbernon@codeweavers.com --- Wine virtual desktop setting is completely unrelated, it corresponds to the "Emulate a virtual desktop" setting in winecfg.
The issue here is probably that we now more accurately match the Win32 window position with the X window manager positions, whereas the re-entry guards before allowed them to sometimes get out of sync.
I suspect that FVWM virtual desktop mode works by having different coordinate spaces for each desktop, but Wine is not aware of that and it believes that windows on the non-active desktops are being moved off screen.
Off-screen windows have historically been hidden, perhaps because it is allowed to have visible windows outside of the virtual screen on Windows (although that needs to be confirmed), and probably to avoid triggering WM-specific mechanisms that would try to move them back on screen.
We would need to remove that workaround to fix this, or perhaps to make it optional, so that it can be opted-in in use cases similar to FVWM virtual desktops.