doesn't open after logging in Xorg session "cannot open display"

[fastoslinux]

doesn't open after logging in Xorg session "cannot open display"

[felipeborges]

Thanks for reporting this bug!

I see the same issue also for GNOME Builder. It is interesting that if I boot directly into an X session, it works. But if I logout from a Wayland session and login into a X session, I get the same bug.

I will bring the discussion to my colleagues working in Wayland to see what could have introduced this regression.

[felipeborges]

Apparently, it works if you remove the --socket=fallback-x11 in the permission. Could you verify whether that works for you?

Regardless, it is still a bug. I just want to confirm it is a Flatpak one. :)
Thanks!

[A6GibKm]

@felipeborges, as far as I know GNOME apps work just fine with the sockets wayland and x11-fallback, while many Kde apps require wayland and x11 in order to work on X. In this particular case the app is using both x11-fallback and x11 and it should use only one, maybe it could be related to that.

[debarshiray]

Did this get fixed on GNOME 3.38 hosts?

The cannot open display error makes me suspect that this is related to the way Mutter sets up Xwayland in the user's session. Especially since it manifests itself when switching from a Wayland session to an Xorg one.

X11 servers can listen on two local sockets -- one abstract, and the other a file system socket at `/tmp/.X11-unix. Flatpak applications (or X11 clients) only use the file system socket, because Flatpak containers have a separate network namespace that prevents them from connecting to the abstract socket.

Prior to GNOME 3.38, Mutter used to only listen for X11 clients connecting to the abstract socket. If the first X11 client inside a Wayland session was a Flatpaked one, then Mutter wouldn't launch Xwayland, and the application would fail to start. In GNOME 3.38, Mutter was changed to only listen for connections to the file system socket to address the issue.

I haven't fully thought this through, but it's worth checking if this issue is still relevant.

[felipeborges]

Did this get fixed on GNOME 3.38 hosts?

No, it doesn't seem so. I just tried to reproduce the steps pointed by OP above and I still get the "cannot open display" warning, and the app doesn't launch.

The cannot open display error makes me suspect that this is related to the way Mutter sets up Xwayland in the user's session. Especially since it manifests itself when switching from a Wayland session to an Xorg one.

Sounds like this could be the culprit. I recall @grulja was mentioning a similar issue with KDE applications. I'm not sure tho.