nixos/sddm: allow running on wayland without xserver enabled

[SuperSandro2000]

Description of changes

I've only ever tested this with #286522, so we are going to wait until that is merged.

Next step would be to move things not related to xserver out of the xserver setting and to something more generic.

Some history irrelevant history to to this: I am thinking about decoupling wayland from xserver since at least September last year motivated by @tanneberger

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[alois31]

I wonder if the GNOME folks have some useful information on what parts of services.xserver.enable = true are needed for a pure Wayland session, given that GDM/GNOME already lacks the assertion and should support running on Wayland without the X server too.

[alois31]

For some reason, SDDM now does not start automatically on boot on my machine. Nvm, this is the defaultUnit issue and I misread the module.

[SuperSandro2000]

Discetting the relevant parts out of xserver is as PR description out of scope of this PR and will done later to keep the scope manageable.

[SuperSandro2000]

I wonder if the GNOME folks have some useful information on what parts of services.xserver.enable = true are needed for a pure Wayland session, given that GDM/GNOME already lacks the assertion

That shouldn't be that hard, we basically need the following but in another PR:

hardware.opengl.enable = mkDefault true;
environment.systemPackages = with pkgs; [ nixos-icons xdg-utils ];
xdg = {
  autostart.enable = true;
  icons.enable = true;
  menus.enable = true;
  mime.enable = true;
};
# The default max inotify watches is 8192.
# most apps require a good number of inotify watches,
# the value below is used by default on several other distros.
boot.kernel.sysctl."fs.inotify.max_user_instances" = mkDefault 524288;  boot.kernel.sysctl."fs.inotify.max_user_watches" = mkDefault 524288;
systemd.defaultUnit = "graphical.target";
fonts.enableDefaultPackages = mkDefault true;

should support running on Wayland without the X server too.

I leave that up to the gnome people. If I didn't do a mistake, there should be no change in functionality and all other display manager need to opt into the new things in explicitly.

[alois31]

That shouldn't be that hard, we basically need the following but in another PR:

hardware.opengl.enable = mkDefault true;
environment.systemPackages = with pkgs; [ nixos-icons xdg-utils ];
xdg = {
  autostart.enable = true;
  icons.enable = true;
  menus.enable = true;
  mime.enable = true;
};
# The default max inotify watches is 8192.
# most apps require a good number of inotify watches,
# the value below is used by default on several other distros.
boot.kernel.sysctl."fs.inotify.max_user_instances" = mkDefault 524288;  boot.kernel.sysctl."fs.inotify.max_user_watches" = mkDefault 524288;
systemd.defaultUnit = "graphical.target";
fonts.enableDefaultPackages = mkDefault true;

Yes, that's what I meant above in one of the comments that's now folded. These are basically required to restore a working system when actually using the functionality of this PR. (The XDG stuff is already enabled by default though.)

I leave that up to the gnome people. If I didn't do a mistake, there should be no change in functionality and all other display manager need to opt into the new things in explicitly.

Oh, I didn't mean that you should change something for GNOME, but that GNOME may already have some things that have been overlooked here because they seem to support running without the X server already.

[SuperSandro2000]

Anyone has an idea why eval-lib-tests fails? It looks really random to me.

[Shawn8901]

as r-ryantm prs also have that issue it seems also quite unrelated to me.

[SuperSandro2000]

Okay, since ofborg was green before the retrigger and this seems to be a general issue, I think we can ignore this right now.

[SuperSandro2000]

Here goes nothing

Don't hit me if this goes wrong and please be so kind and send fixes 🙈

[philiptaron]

476b8c2 broke my config with a message that services.xserver.displayManager.sessionPackages does not exist.

Found this PR and updated to remove xserver.

[gallexme]

breaks for me
i only use

              xserver = {
                # Enable the X11 windowing system.
                enable = true;
                # Enable the GNOME Desktop Environment.
                # services.xserver.displayManager.lightdm = {enable = true;
                # greeter.enable = false;

                # };

                displayManager = {
                  gdm = {
                    enable = true;
                    autoSuspend = false;
                  };
                };
                desktopManager.gnome.enable = true;

                # services.xserver.displayManager.autoLogin.user = "moot";
                # Configure keymap in X11

                layout = "us";
                xkbVariant = "";
              };

  services = {
    xserver = {
      # boot.initrd.kernelModules = ["amdgpu"];
      videoDrivers = ["amdgpu"];
      # videoDrivers = [
      #   "modesetting"
      # ];
      xrandrHeads = [
        "DP-2"
        {
          output = "DP-1";
          primary = true;
        }
      ];
      exportConfiguration = true;
    };
  };

• hyprland

 sudo nixos-rebuild boot --flake .    --show-trace   --max-jobs 2 --keep-going --cores 20  --option eval-cache false
warning: Git tree '/home/moot/dev/depot_space' is dirty
warning: input 'flake-utils' has an override for a non-existent input 'nixpkgs'
warning: input 'mk-shell-bin' has an override for a non-existent input 'nixpkgs'
error:
       … while calling the 'seq' builtin

         at /nix/store/skrr54jsvr8qdsfd1jghmylvbqkcajlp-source/lib/modules.nix:322:18:

          321|         options = checked options;
          322|         config = checked (removeAttrs config [ "_module" ]);
             |                  ^
          323|         _module = checked (config._module);

       … while calling the 'throw' builtin

         at /nix/store/skrr54jsvr8qdsfd1jghmylvbqkcajlp-source/lib/modules.nix:298:18:

          297|                     ''
          298|             else throw baseMsg
             |                  ^
          299|         else null;

       error: The option `services.xserver.displayManager.sessionPackages' does not exist. Definition values:
       - In `/nix/store/skrr54jsvr8qdsfd1jghmylvbqkcajlp-source/flake.nix':
           {
             _type = "if";
             condition = false;
             content = [
               <derivation qtile-wayland-session>
           ...

      repl is also broken any advice? 

[alois31]

I guess another mkRenamedOptionModule should be added for that setting.

[SuperSandro2000]

Please take a look at #303186

[samueldr]

This PR causes a regression for the assert message:

       error: attribute 'displayManager' missing

       at /nix/store/2arfgnb82dbh6s3h9fv05rxpr4f6z930-source/nixos/modules/services/display-managers/default.nix:125:49:

          124|                 Valid names for 'services.displayManager.defaultSession' are:
          125|                   ${lib.concatStringsSep "\n  " cfg.displayManager.sessionData.sessionNames}
             |                                                 ^
          126|               '';

See line 4:

  cfg = config.services.displayManager;

[SuperSandro2000]

#309095

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/enable-plasma-6/40541/24

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/enable-plasma-6/40541/30