Missing window decorations on Flatpak + Wayland

[hugomg]

If we package xjump using Flatpak + Wayland, then it has no window decoration. That is, there is no window title or close button. If I understand correctly, the issue is that with Wayland the application is responsible for drawing its own window. In our case, we depend on SDL doing that for us. Recent versions of SDL should be able to do that, but I am not sure if those versions are already present in the Freedesktop flatpak runtime.

The current workaround is to use --socket=x11 but that is unsatisfying because the whole point of xjump-sdl is moving to a future free from the tyranny of X. We should try again when the next release of freedesktop.Platform, using the following permissions in the manifest:

--socket=fallback-x11
--socket=wayland

[hugomg]

22.08 still doesn't do it. I think we should wait until 23.08 and then investigate if it's still broken at that point.