Merge pull request #187507 from nrdxp/gamescope-module

Launch GameScope/Steam session from Display Manager

nixos/modules/module-list.nix

@@ -171,6 +171,7 @@
   ./programs/fuse.nix
   ./programs/fzf.nix
   ./programs/gamemode.nix
+  ./programs/gamescope.nix
   ./programs/geary.nix
   ./programs/git.nix
   ./programs/gnome-disks.nix

nixos/modules/programs/gamescope.nix

@@ -0,0 +1,85 @@
+{ config
+, lib
+, pkgs
+, ...
+}:
+with lib; let
+  cfg = config.programs.gamescope;
+
+  gamescope =
+    let
+      wrapperArgs =
+        optional (cfg.args != [ ])
+          ''--add-flags "${toString cfg.args}"''
+        ++ builtins.attrValues (mapAttrs (var: val: "--set-default ${var} ${val}") cfg.env);
+    in
+    pkgs.runCommand "gamescope" { nativeBuildInputs = [ pkgs.makeBinaryWrapper ]; } ''
+      mkdir -p $out/bin
+      makeWrapper ${cfg.package}/bin/gamescope $out/bin/gamescope --inherit-argv0 \
+        ${toString wrapperArgs}
+    '';
+in
+{
+  options.programs.gamescope = {
+    enable = mkEnableOption (mdDoc "gamescope");
+
+    package = mkOption {
+      type = types.package;
+      default = pkgs.gamescope;
+      defaultText = literalExpression "pkgs.gamescope";
+      description = mdDoc ''
+        The GameScope package to use.
+      '';
+    };
+
+    capSysNice = mkOption {
+      type = types.bool;
+      default = false;
+      description = mdDoc ''
+        Add cap_sys_nice capability to the GameScope
+        binary so that it may renice itself.
+      '';
+    };
+
+    args = mkOption {
+      type = types.listOf types.string;
+      default = [ ];
+      example = [ "--rt" "--prefer-vk-device 8086:9bc4" ];
+      description = mdDoc ''
+        Arguments passed to GameScope on startup.
+      '';
+    };
+
+    env = mkOption {
+      type = types.attrsOf types.string;
+      default = { };
+      example = literalExpression ''
+        # for Prime render offload on Nvidia laptops.
+        # Also requires `hardware.nvidia.prime.offload.enable`.
+        {
+          __NV_PRIME_RENDER_OFFLOAD = "1";
+          __VK_LAYER_NV_optimus = "NVIDIA_only";
+          __GLX_VENDOR_LIBRARY_NAME = "nvidia";
+        }
+      '';
+      description = mdDoc ''
+        Default environment variables available to the GameScope process, overridable at runtime.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    security.wrappers = mkIf cfg.capSysNice {
+      gamescope = {
+        owner = "root";
+        group = "root";
+        source = "${gamescope}/bin/gamescope";
+        capabilities = "cap_sys_nice+pie";
+      };
+    };
+
+    environment.systemPackages = mkIf (!cfg.capSysNice) [ gamescope ];
+  };
+
+  meta.maintainers = with maintainers; [ nrdxp ];
+}

nixos/modules/programs/steam.nix

@@ -4,6 +4,24 @@ with lib;
 
 let
   cfg = config.programs.steam;
+  gamescopeCfg = config.programs.gamescope;
+
+  steam-gamescope = let
+    exports = builtins.attrValues (builtins.mapAttrs (n: v: "export ${n}=${v}") cfg.gamescopeSession.env);
+  in
+    pkgs.writeShellScriptBin "steam-gamescope" ''
+      ${builtins.concatStringsSep "\n" exports}
+      gamescope --steam ${toString cfg.gamescopeSession.args} -- steam -tenfoot -pipewire-dmabuf
+    '';
+
+  gamescopeSessionFile =
+    (pkgs.writeTextDir "share/wayland-sessions/steam.desktop" ''
+      [Desktop Entry]
+      Name=Steam
+      Comment=A digital distribution platform
+      Exec=${steam-gamescope}/bin/steam-gamescope
+      Type=Application
+    '').overrideAttrs (_: { passthru.providedSessions = [ "steam" ]; });
 in {
   options.programs.steam = {
     enable = mkEnableOption (lib.mdDoc "steam");
@@ -32,6 +50,12 @@ in {
             then [ package ] ++ extraPackages
             else [ package32 ] ++ extraPackages32;
         in prevLibs ++ additionalLibs;
+      } // optionalAttrs (cfg.gamescopeSession.enable && gamescopeCfg.capSysNice)
+      {
+        buildFHSEnv = pkgs.buildFHSEnv.override {
+          # use the setuid wrapped bubblewrap
+          bubblewrap = "${config.security.wrapperDir}/..";
+        };
       });
       description = lib.mdDoc ''
         The Steam package to use. Additional libraries are added from the system
@@ -57,6 +81,30 @@ in {
         Open ports in the firewall for Source Dedicated Server.
       '';
     };
+
+    gamescopeSession = mkOption {
+      description = mdDoc "Run a GameScope driven Steam session from your display-manager";
+      type = types.submodule {
+        options = {
+          enable = mkEnableOption (mdDoc "GameScope Session");
+          args = mkOption {
+            type = types.listOf types.string;
+            default = [ ];
+            description = mdDoc ''
+              Arguments to be passed to GameScope for the session.
+            '';
+          };
+
+          env = mkOption {
+            type = types.attrsOf types.string;
+            default = { };
+            description = mdDoc ''
+              Environmental variables to be passed to GameScope for the session.
+            '';
+          };
+        };
+      };
+    };
   };
 
   config = mkIf cfg.enable {
@@ -66,6 +114,19 @@ in {
       driSupport32Bit = true;
     };
 
+    security.wrappers = mkIf (cfg.gamescopeSession.enable && gamescopeCfg.capSysNice) {
+      # needed or steam fails
+      bwrap = {
+        owner = "root";
+        group = "root";
+        source = "${pkgs.bubblewrap}/bin/bwrap";
+        setuid = true;
+      };
+    };
+
+    programs.gamescope.enable = mkDefault cfg.gamescopeSession.enable;
+    services.xserver.displayManager.sessionPackages = mkIf cfg.gamescopeSession.enable [ gamescopeSessionFile ];
+
     # optionally enable 32bit pulseaudio support if pulseaudio is enabled
     hardware.pulseaudio.support32Bit = config.hardware.pulseaudio.enable;