Chromium apps wrapped with buildFHSEnvBubblewrap don't work on X11 when XAUTHORITY is stored in /run

[steinuil]

Describe the bug

I tried to run the Heroic Games Launcher (which is an Electron application and is wrapped using buildFHSEnvBubblewrap in NixOS), but it returns an error:

Authorization required, but no authorization protocol specified

[74969:0405/130128.036942:ERROR:ozone_platform_x11.cc(240)] Missing X server or $DISPLAY
[74969:0405/130128.036952:ERROR:env.cc(255)] The platform failed to initialize.  Exiting

Which I suspect is related to Xauth, because the $DISPLAY env var is definitely set in my terminal.

I think this is what causes it:

I enabled user-authority-in-system-dir in LightDM to try and clean up my $HOME directory. This option makes LightDM start the X11 server with the .Xauthority file in /run/lightdm/<username>/xauthority rather than $HOME/.Xauthority, which is also reflected in the XAUTHORITY env variable.

I suspect that the bubblewrap env does not expose /run/lightdm, so Electron doesn't find the .Xauthority file and doesn't even try to connect to the X11 display. I kind of confirmed this by copying /run/lightdm/<username>/xauthority to ~/.Xauthority and started heroic with XAUTHORITY=~/.Xauthority heroic, which worked.

I see that there's already a fix for SDDM which places XAUTHORITY in /tmp. Would it be possible to also fix the situation where XAUTHORITY is in /run?

https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/build-fhsenv-bubblewrap/default.nix#L209

Steps To Reproduce

Steps to reproduce the behavior:

1. Enable user-authority-in-system-dir in lightdm config:

   {
     services.xserver.displayManager.lightdm.extraConfig = ''
       [LightDM]
       user-authority-in-system-dir=true
     '';
   }

2. Start an X11 session through LightDM
3. Run heroic

Expected behavior

Heroic Games Launcher connects to the X11 server using the Xauthority file in /run/lightdm/<username>/xauthority.

Notify maintainers

Metadata

 - system: `"x86_64-linux"`
 - host os: `Linux 6.6.22, NixOS, 24.05 (Uakari), 24.05.20240321.20f77aa`
 - multi-user?: `no`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.18.2`
 - nixpkgs: `not found`

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