nixos/display-managers: extract generic display-manager bits

Some settings which where before inside the xserver module, are generic
and also required for SDDM under wayland. To make them easily re-usable
lets extract them.

nixos/modules/module-list.nix

@@ -508,6 +508,7 @@
   ./services/development/nixseparatedebuginfod.nix
   ./services/development/rstudio-server/default.nix
   ./services/development/zammad.nix
+  ./services/display-managers/default.nix
   ./services/display-managers/greetd.nix
   ./services/editors/emacs.nix
   ./services/editors/haste.nix

nixos/modules/services/display-managers/default.nix

@@ -0,0 +1,257 @@
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.services.displayManager;
+
+  installedSessions = pkgs.runCommand "desktops"
+    { # trivial derivation
+      preferLocalBuild = true;
+      allowSubstitutes = false;
+    }
+    ''
+      mkdir -p "$out/share/"{xsessions,wayland-sessions}
+
+      ${lib.concatMapStrings (pkg: ''
+        for n in ${lib.concatStringsSep " " pkg.providedSessions}; do
+          if ! test -f ${pkg}/share/wayland-sessions/$n.desktop -o \
+                    -f ${pkg}/share/xsessions/$n.desktop; then
+            echo "Couldn't find provided session name, $n.desktop, in session package ${pkg.name}:"
+            echo "  ${pkg}"
+            return 1
+          fi
+        done
+
+        if test -d ${pkg}/share/xsessions; then
+          ${pkgs.buildPackages.xorg.lndir}/bin/lndir ${pkg}/share/xsessions $out/share/xsessions
+        fi
+        if test -d ${pkg}/share/wayland-sessions; then
+          ${pkgs.buildPackages.xorg.lndir}/bin/lndir ${pkg}/share/wayland-sessions $out/share/wayland-sessions
+        fi
+      '') cfg.sessionPackages}
+    '';
+
+  dmDefault = config.services.xserver.desktopManager.default;
+  # fallback default for cases when only default wm is set
+  dmFallbackDefault = if dmDefault != null then dmDefault else "none";
+  wmDefault = config.services.xserver.windowManager.default;
+  defaultSessionFromLegacyOptions = dmFallbackDefault + lib.optionalString (wmDefault != null && wmDefault != "none") "+${wmDefault}";
+in
+{
+  options = {
+    services.displayManager = {
+      enable = lib.mkEnableOption "systemd's display-manager service";
+
+      preStart = lib.mkOption {
+        type = lib.types.lines;
+        default = "";
+        example = "rm -f /var/log/my-display-manager.log";
+        description = lib.mdDoc "Script executed before the display manager is started.";
+      };
+
+      execCmd = lib.mkOption {
+        type = lib.types.str;
+        example = lib.literalExpression ''"''${pkgs.lightdm}/bin/lightdm"'';
+        description = lib.mdDoc "Command to start the display manager.";
+      };
+
+      environment = lib.mkOption {
+        type = with lib.types; attrsOf unspecified;
+        default = {};
+        description = lib.mdDoc "Additional environment variables needed by the display manager.";
+      };
+
+      hiddenUsers = lib.mkOption {
+        type = with lib.types; listOf str;
+        default = [ "nobody" ];
+        description = lib.mdDoc ''
+          A list of users which will not be shown in the display manager.
+        '';
+      };
+
+      logToFile = lib.mkOption {
+        type = lib.types.bool;
+        default = false;
+        description = lib.mdDoc ''
+          Whether the display manager redirects the output of the
+          session script to {file}`~/.xsession-errors`.
+        '';
+      };
+
+      logToJournal = lib.mkOption {
+        type = lib.types.bool;
+        default = true;
+        description = lib.mdDoc ''
+          Whether the display manager redirects the output of the
+          session script to the systemd journal.
+        '';
+      };
+
+      # Configuration for automatic login. Common for all DM.
+      autoLogin = lib.mkOption {
+        type = lib.types.submodule ({ config, options, ... }: {
+          options = {
+            enable = lib.mkOption {
+              type = lib.types.bool;
+              default = config.user != null;
+              defaultText = lib.literalExpression "config.${options.user} != null";
+              description = lib.mdDoc ''
+                Automatically log in as {option}`autoLogin.user`.
+              '';
+            };
+
+            user = lib.mkOption {
+              type = with lib.types; nullOr str;
+              default = null;
+              description = lib.mdDoc ''
+                User to be used for the automatic login.
+              '';
+            };
+          };
+        });
+
+        default = {};
+        description = lib.mdDoc ''
+          Auto login configuration attrset.
+        '';
+      };
+
+      defaultSession = lib.mkOption {
+        type = lib.types.nullOr lib.types.str // {
+          description = "session name";
+          check = d:
+            lib.assertMsg (d != null -> (lib.types.str.check d && lib.elem d config.services.displayManager.sessionData.sessionNames)) ''
+                Default graphical session, '${d}', not found.
+                Valid names for 'services.xserver.displayManager.defaultSession' are:
+                  ${lib.concatStringsSep "\n  " cfg.displayManager.sessionData.sessionNames}
+              '';
+        };
+        default =
+          if dmDefault != null || wmDefault != null then
+            defaultSessionFromLegacyOptions
+          else
+            null;
+        defaultText = lib.literalMD ''
+          Taken from display manager settings or window manager settings, if either is set.
+        '';
+        example = "gnome";
+        description = lib.mdDoc ''
+          Graphical session to pre-select in the session chooser (only effective for GDM, LightDM and SDDM).
+
+          On GDM, LightDM and SDDM, it will also be used as a session for auto-login.
+        '';
+      };
+
+      sessionData = lib.mkOption {
+        description = lib.mdDoc "Data exported for display managers’ convenience";
+        internal = true;
+        default = {};
+      };
+
+      sessionPackages = lib.mkOption {
+        type = lib.types.listOf (lib.types.package // {
+          description = "package with provided sessions";
+          check = p: lib.assertMsg
+            (lib.types.package.check p && p ? providedSessions
+            && p.providedSessions != [] && lib.all lib.isString p.providedSessions)
+            ''
+              Package, '${p.name}', did not specify any session names, as strings, in
+              'passthru.providedSessions'. This is required when used as a session package.
+
+              The session names can be looked up in:
+                ${p}/share/xsessions
+                ${p}/share/wayland-sessions
+           '';
+        });
+        default = [];
+        description = lib.mdDoc ''
+          A list of packages containing x11 or wayland session files to be passed to the display manager.
+        '';
+      };
+    };
+  };
+
+  imports = [
+    (lib.mkRenamedOptionModule [ "services" "xserver" "displayManager" "autoLogin" ] [ "services" "displayManager" "autoLogin" ])
+    (lib.mkRenamedOptionModule [ "services" "xserver" "displayManager" "defaultSession" ] [ "services" "displayManager" "defaultSession" ])
+    (lib.mkRenamedOptionModule [ "services" "xserver" "displayManager" "job" "environment" ] [ "services" "displayManager" "environment" ])
+    (lib.mkRenamedOptionModule [ "services" "xserver" "displayManager" "job" "execCmd" ] [ "services" "displayManager" "execCmd" ])
+    (lib.mkRenamedOptionModule [ "services" "xserver" "displayManager" "job" "logToFile" ] [ "services" "displayManager" "logToFile" ])
+    (lib.mkRenamedOptionModule [ "services" "xserver" "displayManager" "job" "logToJournal" ] [ "services" "displayManager" "logToJournal" ])
+    (lib.mkRenamedOptionModule [ "services" "xserver" "displayManager" "job" "preStart" ] [ "services" "displayManager" "preStart" ])
+  ];
+
+  config = lib.mkIf cfg.enable {
+    assertions = [
+      { assertion = cfg.autoLogin.enable -> cfg.autoLogin.user != null;
+        message = ''
+          services.displayManager.autoLogin.enable requires services.displayManager.autoLogin.user to be set
+        '';
+      }
+    ];
+
+    warnings =
+      lib.mkIf (dmDefault != null || wmDefault != null) [
+        ''
+          The following options are deprecated:
+            ${lib.concatStringsSep "\n  " (map ({c, t}: t) (lib.filter ({c, t}: c != null) [
+            { c = dmDefault; t = "- services.xserver.desktopManager.default"; }
+            { c = wmDefault; t = "- services.xserver.windowManager.default"; }
+            ]))}
+          Please use
+            services.displayManager.defaultSession = "${defaultSessionFromLegacyOptions}";
+          instead.
+        ''
+      ];
+
+    # Make xsessions and wayland sessions available in XDG_DATA_DIRS
+    # as some programs have behavior that depends on them being present
+    environment.sessionVariables.XDG_DATA_DIRS = lib.mkIf (cfg.sessionPackages != [ ]) [
+      "${cfg.sessionData.desktops}/share"
+    ];
+
+    services.displayManager.sessionData = {
+      desktops = installedSessions;
+      sessionNames = lib.concatMap (p: p.providedSessions) config.services.displayManager.sessionPackages;
+      # We do not want to force users to set defaultSession when they have only single DE.
+      autologinSession =
+        if cfg.defaultSession != null then
+          cfg.defaultSession
+        else if cfg.sessionData.sessionNames != [] then
+          lib.head cfg.sessionData.sessionNames
+        else
+          null;
+    };
+
+    # so that the service won't be enabled when only startx is used
+    systemd.services.display-manager.enable =
+      let dmConf = config.services.xserver.displayManager;
+          noDmUsed = !(dmConf.gdm.enable
+                    || dmConf.sddm.enable
+                    || dmConf.xpra.enable
+                    || dmConf.lightdm.enable);
+      in lib.mkIf noDmUsed (lib.mkDefault false);
+
+    systemd.services.display-manager = {
+      description = "Display Manager";
+      after = [ "acpid.service" "systemd-logind.service" "systemd-user-sessions.service" ];
+      restartIfChanged = false;
+
+      environment = lib.optionalAttrs config.hardware.opengl.setLdLibraryPath {
+        LD_LIBRARY_PATH = lib.makeLibraryPath [ pkgs.addOpenGLRunpath.driverLink ];
+      } // cfg.environment;
+
+      preStart = cfg.preStart;
+      script = lib.mkIf (config.systemd.services.display-manager.enable == true) cfg.execCmd;
+
+      # Stop restarting if the display manager stops (crashes) 2 times
+      # in one minute. Starting X typically takes 3-4s.
+      startLimitIntervalSec = 30;
+      startLimitBurst = 3;
+      serviceConfig = {
+        Restart = "always";
+        RestartSec = "200ms";
+        SyslogIdentifier = "display-manager";
+      };
+    };
+  };
+}

nixos/modules/services/x11/display-managers/default.nix

@@ -14,7 +14,6 @@ with lib;
 let
 
   cfg = config.services.xserver;
-  opt = options.services.xserver;
   xorg = pkgs.xorg;
 
   fontconfig = config.fonts.fontconfig;
@@ -130,41 +129,6 @@ let
           exit 1
       fi
     '';
-
-  installedSessions = pkgs.runCommand "desktops"
-    { # trivial derivation
-      preferLocalBuild = true;
-      allowSubstitutes = false;
-    }
-    ''
-      mkdir -p "$out/share/"{xsessions,wayland-sessions}
-
-      ${concatMapStrings (pkg: ''
-        for n in ${concatStringsSep " " pkg.providedSessions}; do
-          if ! test -f ${pkg}/share/wayland-sessions/$n.desktop -o \
-                    -f ${pkg}/share/xsessions/$n.desktop; then
-            echo "Couldn't find provided session name, $n.desktop, in session package ${pkg.name}:"
-            echo "  ${pkg}"
-            return 1
-          fi
-        done
-
-        if test -d ${pkg}/share/xsessions; then
-          ${pkgs.buildPackages.xorg.lndir}/bin/lndir ${pkg}/share/xsessions $out/share/xsessions
-        fi
-        if test -d ${pkg}/share/wayland-sessions; then
-          ${pkgs.buildPackages.xorg.lndir}/bin/lndir ${pkg}/share/wayland-sessions $out/share/wayland-sessions
-        fi
-      '') cfg.displayManager.sessionPackages}
-    '';
-
-  dmDefault = cfg.desktopManager.default;
-  # fallback default for cases when only default wm is set
-  dmFallbackDefault = if dmDefault != null then dmDefault else "none";
-  wmDefault = cfg.windowManager.default;
-
-  defaultSessionFromLegacyOptions = dmFallbackDefault + optionalString (wmDefault != null && wmDefault != "none") "+${wmDefault}";
-
 in
 
 {
@@ -215,35 +179,6 @@ in
         '';
       };
 
-      hiddenUsers = mkOption {
-        type = types.listOf types.str;
-        default = [ "nobody" ];
-        description = lib.mdDoc ''
-          A list of users which will not be shown in the display manager.
-        '';
-      };
-
-      sessionPackages = mkOption {
-        type = with types; listOf (package // {
-          description = "package with provided sessions";
-          check = p: assertMsg
-            (package.check p && p ? providedSessions
-            && p.providedSessions != [] && all isString p.providedSessions)
-            ''
-              Package, '${p.name}', did not specify any session names, as strings, in
-              'passthru.providedSessions'. This is required when used as a session package.
-
-              The session names can be looked up in:
-                ${p}/share/xsessions
-                ${p}/share/wayland-sessions
-           '';
-        });
-        default = [];
-        description = lib.mdDoc ''
-          A list of packages containing x11 or wayland session files to be passed to the display manager.
-        '';
-      };
-
       session = mkOption {
         default = [];
         type = types.listOf types.attrs;
@@ -274,51 +209,6 @@ in
         '';
       };
 
-      sessionData = mkOption {
-        description = lib.mdDoc "Data exported for display managers’ convenience";
-        internal = true;
-        default = {};
-        apply = val: {
-          wrapper = xsessionWrapper;
-          desktops = installedSessions;
-          sessionNames = concatMap (p: p.providedSessions) cfg.displayManager.sessionPackages;
-          # We do not want to force users to set defaultSession when they have only single DE.
-          autologinSession =
-            if cfg.displayManager.defaultSession != null then
-              cfg.displayManager.defaultSession
-            else if cfg.displayManager.sessionData.sessionNames != [] then
-              head cfg.displayManager.sessionData.sessionNames
-            else
-              null;
-        };
-      };
-
-      defaultSession = mkOption {
-        type = with types; nullOr str // {
-          description = "session name";
-          check = d:
-            assertMsg (d != null -> (str.check d && elem d cfg.displayManager.sessionData.sessionNames)) ''
-                Default graphical session, '${d}', not found.
-                Valid names for 'services.xserver.displayManager.defaultSession' are:
-                  ${concatStringsSep "\n  " cfg.displayManager.sessionData.sessionNames}
-              '';
-        };
-        default =
-          if dmDefault != null || wmDefault != null then
-            defaultSessionFromLegacyOptions
-          else
-            null;
-        defaultText = literalMD ''
-          Taken from display manager settings or window manager settings, if either is set.
-        '';
-        example = "gnome";
-        description = lib.mdDoc ''
-          Graphical session to pre-select in the session chooser (only effective for GDM, LightDM and SDDM).
-
-          On GDM, LightDM and SDDM, it will also be used as a session for auto-login.
-        '';
-      };
-
       importedVariables = mkOption {
         type = types.listOf (types.strMatching "[a-zA-Z_][a-zA-Z0-9_]*");
         visible = false;
@@ -327,106 +217,19 @@ in
         '';
       };
 
-      job = {
-
-        preStart = mkOption {
-          type = types.lines;
-          default = "";
-          example = "rm -f /var/log/my-display-manager.log";
-          description = lib.mdDoc "Script executed before the display manager is started.";
-        };
-
-        execCmd = mkOption {
-          type = types.str;
-          example = literalExpression ''"''${pkgs.lightdm}/bin/lightdm"'';
-          description = lib.mdDoc "Command to start the display manager.";
-        };
-
-        environment = mkOption {
-          type = types.attrsOf types.unspecified;
-          default = {};
-          description = lib.mdDoc "Additional environment variables needed by the display manager.";
-        };
-
-        logToFile = mkOption {
-          type = types.bool;
-          default = false;
-          description = lib.mdDoc ''
-            Whether the display manager redirects the output of the
-            session script to {file}`~/.xsession-errors`.
-          '';
-        };
-
-        logToJournal = mkOption {
-          type = types.bool;
-          default = true;
-          description = lib.mdDoc ''
-            Whether the display manager redirects the output of the
-            session script to the systemd journal.
-          '';
-        };
-
-      };
-
-      # Configuration for automatic login. Common for all DM.
-      autoLogin = mkOption {
-        type = types.submodule ({ config, options, ... }: {
-          options = {
-            enable = mkOption {
-              type = types.bool;
-              default = config.user != null;
-              defaultText = literalExpression "config.${options.user} != null";
-              description = lib.mdDoc ''
-                Automatically log in as {option}`autoLogin.user`.
-              '';
-            };
-
-            user = mkOption {
-              type = types.nullOr types.str;
-              default = null;
-              description = lib.mdDoc ''
-                User to be used for the automatic login.
-              '';
-            };
-          };
-        });
-
-        default = {};
-        description = lib.mdDoc ''
-          Auto login configuration attrset.
-        '';
-      };
-
     };
 
   };
 
   config = {
     assertions = [
-      { assertion = cfg.displayManager.autoLogin.enable -> cfg.displayManager.autoLogin.user != null;
-        message = ''
-          services.xserver.displayManager.autoLogin.enable requires services.xserver.displayManager.autoLogin.user to be set
-        '';
-      }
       {
         assertion = cfg.desktopManager.default != null || cfg.windowManager.default != null -> cfg.displayManager.defaultSession == defaultSessionFromLegacyOptions;
         message = "You cannot use both services.xserver.displayManager.defaultSession option and legacy options (services.xserver.desktopManager.default and services.xserver.windowManager.default).";
       }
     ];
 
-    warnings =
+    services.displayManager.sessionData.wrapper = xsessionWrapper;
-      mkIf (dmDefault != null || wmDefault != null) [
-        ''
-          The following options are deprecated:
-            ${concatStringsSep "\n  " (map ({c, t}: t) (filter ({c, t}: c != null) [
-            { c = dmDefault; t = "- services.xserver.desktopManager.default"; }
-            { c = wmDefault; t = "- services.xserver.windowManager.default"; }
-            ]))}
-          Please use
-            services.xserver.displayManager.defaultSession = "${defaultSessionFromLegacyOptions}";
-          instead.
-        ''
-      ];
 
     services.xserver.displayManager.xserverBin = "${xorg.xorgserver.out}/bin/X";
 
@@ -449,7 +252,7 @@ in
 
     # Create desktop files and scripts for starting sessions for WMs/DMs
     # that do not have upstream session files (those defined using services.{display,desktop,window}Manager.session options).
-    services.xserver.displayManager.sessionPackages =
+    services.displayManager.sessionPackages =
       let
         dms = filter (s: s.manage == "desktop") cfg.displayManager.session;
         wms = filter (s: s.manage == "window") cfg.displayManager.session;
@@ -511,20 +314,14 @@ in
             )
             (cartesianProductOfSets { dm = dms; wm = wms; })
           );
-
-    # Make xsessions and wayland sessions available in XDG_DATA_DIRS
-    # as some programs have behavior that depends on them being present
-    environment.sessionVariables.XDG_DATA_DIRS = lib.mkIf (cfg.displayManager.sessionPackages != [ ]) [
-      "${cfg.displayManager.sessionData.desktops}/share"
-    ];
   };
 
   imports = [
     (mkRemovedOptionModule [ "services" "xserver" "displayManager" "desktopManagerHandlesLidAndPower" ]
      "The option is no longer necessary because all display managers have already delegated lid management to systemd.")
-    (mkRenamedOptionModule [ "services" "xserver" "displayManager" "job" "logsXsession" ] [ "services" "xserver" "displayManager" "job" "logToFile" ])
+    (mkRenamedOptionModule [ "services" "xserver" "displayManager" "job" "logsXsession" ] [ "services" "displayManager" "logToFile" ])
-    (mkRenamedOptionModule [ "services" "xserver" "displayManager" "logToJournal" ] [ "services" "xserver" "displayManager" "job" "logToJournal" ])
+    (mkRenamedOptionModule [ "services" "xserver" "displayManager" "logToJournal" ] [ "services" "displayManager" "logToJournal" ])
-    (mkRenamedOptionModule [ "services" "xserver" "displayManager" "extraSessionFilesPackages" ] [ "services" "xserver" "displayManager" "sessionPackages" ])
+    (mkRenamedOptionModule [ "services" "xserver" "displayManager" "extraSessionFilesPackages" ] [ "services" "displayManager" "sessionPackages" ])
   ];
 
 }

nixos/modules/services/x11/display-managers/sddm.nix

@@ -129,17 +129,17 @@ in
 {
   imports = [
     (mkRemovedOptionModule
-      [ "services" "xserver" "displayManager" "sddm" "themes" ]
+      [ "services" "displayManager" "sddm" "themes" ]
-      "Set the option `services.xserver.displayManager.sddm.package' instead.")
+      "Set the option `services.displayManager.sddm.package' instead.")
     (mkRenamedOptionModule
-      [ "services" "xserver" "displayManager" "sddm" "autoLogin" "enable" ]
+      [ "services" "displayManager" "sddm" "autoLogin" "enable" ]
-      [ "services" "xserver" "displayManager" "autoLogin" "enable" ])
+      [ "services" "displayManager" "autoLogin" "enable" ])
     (mkRenamedOptionModule
-      [ "services" "xserver" "displayManager" "sddm" "autoLogin" "user" ]
+      [ "services" "displayManager" "sddm" "autoLogin" "user" ]
-      [ "services" "xserver" "displayManager" "autoLogin" "user" ])
+      [ "services" "displayManager" "autoLogin" "user" ])
     (mkRemovedOptionModule
-      [ "services" "xserver" "displayManager" "sddm" "extraConfig" ]
+      [ "services" "displayManager" "sddm" "extraConfig" ]
-      "Set the option `services.xserver.displayManager.sddm.settings' instead.")
+      "Set the option `services.displayManager.sddm.settings' instead.")
   ];
 
   options = {
@@ -281,6 +281,8 @@ in
       }
     ];
 
+    services.displayManager.execCmd = "exec /run/current-system/sw/bin/sddm";
+
     security.pam.services = {
       sddm.text = ''
         auth      substack      login

nixos/modules/services/x11/xserver.nix

@@ -639,6 +639,7 @@ in
   ###### implementation
 
   config = mkIf cfg.enable {
+    services.displayManager.enable = true;
 
     services.xserver.displayManager.lightdm.enable =
       let dmConf = cfg.displayManager;
@@ -650,15 +651,6 @@ in
                     || config.services.greetd.enable);
       in mkIf (default) (mkDefault true);
 
-    # so that the service won't be enabled when only startx is used
-    systemd.services.display-manager.enable  =
-      let dmConf = cfg.displayManager;
-          noDmUsed = !(dmConf.gdm.enable
-                    || dmConf.sddm.enable
-                    || dmConf.xpra.enable
-                    || dmConf.lightdm.enable);
-      in mkIf (noDmUsed) (mkDefault false);
-
     hardware.opengl.enable = mkDefault true;
 
     services.xserver.videoDrivers = mkIf (cfg.videoDriver != null) [ cfg.videoDriver ];