sway: Simplify screen sharing

[primeos]

This should make it easier to get started.
The xdg-desktop-portal backend for wlroots is required and one needs to
"make sure WAYLAND_DISPLAY and XDG_CURRENT_DESKTOP are imported into
D-Bus." 0

Motivation for this change

I've tested this with Chromium (chromium --enable-features=UseOzonePlatform --ozone-platform=wayland --disable-gpu-memory-buffer-video-frames) and it worked (with and without XWayland enabled).

Users need at least the following to make screen sharing work (that shouldn't be part of the Sway module):

xdg.portal.enable = true;
services.pipewire.enable = true;

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[ahdyt]

I wonder this or newest pull req of portal make my screen sharing broke again, especially on obs-wayland overlay and firefox via home-manager?

[primeos]

This shouldn't break screen sharing, please open a new issue with more information.

[siraben]

This breaks screen sharing if the user already has extraPortals = with pkgs; [ xdg-desktop-portal-wlr ]; set.

[primeos]

@siraben why does screen sharing break if xdg-desktop-portal-wlr is twice in extraPortals?

[siraben]

Home Manager also starts a service for xdg-desktop-portal, since this is now added by default, both home-manager and nixos-rebuild fail to build the config. @ahdyt did you experience this as well?

[primeos]

The NixOS module for Sway doesn't start a service for xdg-desktop-portal by default (this option only has an effect with xdg.portal.enable).

both home-manager and nixos-rebuild fail to build the config.

Not sure what's happening here. AFAIK HM should be completely isolated from the NixOS config.
This probably requires further analysis and should also be a dedicated GH issue if it's really something that requires a change in Nixpkgs instead of the HM repo (might make sense to discuss it there first?).

[siraben]

I happened to have xdg.portal.enable = true (but extraPortals was blank). I installed xdg-desktop-portal via Home Manager already so was able to observe the change when upgrading the system config.

[siraben]

As discussed on Matrix, this is the error that appears for HM

  UNIT                           LOAD      ACTIVE SUB    DESCRIPTION                            
● wlsunset.service               not-found failed failed wlsunset.service                       
● xdg-desktop-portal-wlr.service loaded    failed failed Portal service (wlroots implementation)

and for nixos-rebuild

ln: failed to create symbolic link '/nix/store/lj3zw0xfqh4h51vwjrfkv1kvhij3hipk-user-units/xdg-desktop-portal-wlr.service': File exists

Both issues are resolved when xdg.portal.enable = true is removed.

[siraben]

@siraben why does screen sharing break if xdg-desktop-portal-wlr is twice in extraPortals?

Not sure why but I can replicate it with

  xdg = {
    portal = {
      enable = true;
      extraPortals = with pkgs; [
        xdg-desktop-portal-wlr
        xdg-desktop-portal-gtk # optionally remove
      ];
      gtkUsePortal = true;
    };
  };

[primeos]

Both issues are resolved when xdg.portal.enable = true is removed.

Isn't that the actual issue then (enabling this in both the NixOS and Home Manager configurations)?

ln: failed to create symbolic link '/nix/store/lj3zw0xfqh4h51vwjrfkv1kvhij3hipk-user-units/xdg-desktop-portal-wlr.service': File exists

That also isn't ideal but I don't think this warrants changing the Sway module (not sure if there's a meta issue for this case is only an example/instance of the underlying problem).