nixos/sddm: add display manager

nixos/modules/misc/ids.nix

@@ -180,6 +180,7 @@
       panamax = 170;
       marathon = 171;
       exim = 172;
+      sddm = 175;
 
       # When adding a uid, make sure it doesn't match an existing gid. And don't use uids above 399!
 
@@ -322,6 +323,7 @@
       exim = 172;
       fleet = 173;
       input = 174;
+      sddm = 175;
 
       # When adding a gid, make sure it doesn't match an existing
       # uid. Users and groups with the same name should have equal

nixos/modules/module-list.nix

@@ -359,6 +359,7 @@
   ./services/x11/display-managers/gdm.nix
   ./services/x11/display-managers/kdm.nix
   ./services/x11/display-managers/lightdm.nix
+  ./services/x11/display-managers/sddm.nix
   ./services/x11/display-managers/slim.nix
   ./services/x11/hardware/multitouch.nix
   ./services/x11/hardware/synaptics.nix

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

@@ -0,0 +1,108 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  xcfg = config.services.xserver;
+  dmcfg = xcfg.displayManager;
+  cfg = dmcfg.sddm;
+  xEnv = config.systemd.services."display-manager".environment;
+
+  xserverWrapper = pkgs.writeScript "xserver-wrapper" ''
+    #!/bin/sh
+    ${concatMapStrings (n: "export ${n}=\"${getAttr n xEnv}\"\n") (attrNames xEnv)}
+    exec ${dmcfg.xserverBin} ${dmcfg.xserverArgs} "$@"
+  '';
+
+  cfgFile = pkgs.writeText "sddm.conf" ''
+    [General]
+    HaltCommand=${pkgs.systemd}/bin/systemctl poweroff
+    RebootCommand=${pkgs.systemd}/bin/systemctl reboot
+
+    [Theme]
+    Current=${cfg.theme}
+
+    [Users]
+    MaximumUid=${toString config.ids.uids.nixbld}
+
+    [XDisplay]
+    MinimumVT=${toString xcfg.tty}
+    ServerPath=${xserverWrapper}
+    XephyrPath=${pkgs.xorg.xorgserver}/bin/Xephyr
+    SessionCommand=${dmcfg.session.script}
+    SessionDir=${dmcfg.session.desktops}
+    XauthPath=${pkgs.xorg.xauth}/bin/xauth
+  '';
+
+in
+{
+  options = {
+
+    services.xserver.displayManager.sddm = {
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether to enable sddm as the display manager.
+        '';
+      };
+
+      theme = mkOption {
+        type = types.str;
+        default = "maui";
+        description = ''
+          Greeter theme to use.
+        '';
+      };
+    };
+
+  };
+
+  config = mkIf cfg.enable {
+
+    services.xserver.displayManager.slim.enable = false;
+
+    services.xserver.displayManager.job = {
+      logsXsession = true;
+
+      #execCmd = "${pkgs.sddm}/bin/sddm";
+      execCmd = "exec ${pkgs.sddm}/bin/sddm";
+    };
+
+    security.pam.services = {
+      sddm = {
+        allowNullPassword = true;
+        startSession = true;
+      };
+
+      sddm-greeter.text = ''
+        auth     required       pam_succeed_if.so audit quiet_success user = sddm
+        auth     optional       pam_permit.so
+
+        account  required       pam_succeed_if.so audit quiet_success user = sddm
+        account  sufficient     pam_unix.so
+
+        password required       pam_deny.so
+
+        session  required       pam_succeed_if.so audit quiet_success user = sddm
+        session  required       pam_env.so envfile=${config.system.build.pamEnvironment}
+        session  optional       ${pkgs.systemd}/lib/security/pam_systemd.so
+        session  optional       pam_keyinit.so force revoke
+        session  optional       pam_permit.so
+      '';
+    };
+
+    users.extraUsers.sddm = {
+      createHome = true;
+      home = "/var/lib/sddm";
+      group = "sddm";
+      uid = config.ids.uids.sddm;
+    };
+
+    environment.etc."sddm.conf".source = cfgFile;
+
+    users.extraGroups.sddm.gid = config.ids.gids.sddm;
+
+  };
+}