Fullscreen mode is not bound to desktop in Ubuntu

Proton version: Proton Experimental (2023-01-01)
OS: Ubuntu + Regolith-desktop
Game where it occured: Pharao & Cleopatra

This problem seems to be a general problem and not compatibility problem of the game.

Regolith is basically i3-window-manager on Ubuntu. What I see, is, that if I switch to another desktop, the desktop, where the game was, disappears. Hence, from system perspective there is no window any more. From then on I see black flickering, but between the flickering I see, that proton tries to create a new window tile on the current desktop. This means, that the fullscreen tries to go fullscreen not on the desktop, the game has started on, but on the desktop, the user is viewing currently.

Instead of that, the application must be assigned to a certain desktop, no matter, if full screen mode or not. Full screen mode must be paused (exited), if the window is inactive, and resumed, if the window is active again (this might cause problems on games though, that spawn independent windows). At least the attempt to restore fullscreen (which presumably this is) must be paused.

The problem might be located in the underlying wine, but I don't know.

No source files or tests are identified. Start by reproducing the fullscreen behavior on Ubuntu with Regolith/i3 while switching desktops, then trace whether Proton or its underlying Wine handling controls window placement and fullscreen restoration. Done means the fullscreen window remains associated with its originating desktop and restoration pauses while it is inactive.