1 files changed, 283 insertions, 0 deletions
diff --git a/nixos/modules/services/x11/display-managers/default.nix b/nixos/modules/services/x11/display-managers/default.nix
new file mode 100644
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+++ b/nixos/modules/services/x11/display-managers/default.nix
@@ -0,0 +1,283 @@
+# This module declares the options to define a *display manager*, the
+# program responsible for handling X logins (such as xdm, kdm, gdb, or
+# SLiM).  The display manager allows the user to select a *session
+# type*.  When the user logs in, the display manager starts the
+# *session script* ("xsession" below) to launch the selected session
+# type.  The session type defines two things: the *desktop manager*
+# (e.g., KDE, Gnome or a plain xterm), and optionally the *window
+# manager* (e.g. kwin or twm).
+
+{ config, pkgs, ... }:
+
+with pkgs.lib;
+
+let
+
+  cfg = config.services.xserver;
+  xorg = pkgs.xorg;
+
+  vaapiDrivers = pkgs.buildEnv {
+    name = "vaapi-drivers";
+    paths = cfg.vaapiDrivers;
+    # We only want /lib/dri, but with a single input path, we need "/" for it to work
+    pathsToLink = [ "/" ];
+  };
+
+  # file provided by services.xserver.displayManager.session.script
+  xsession = wm: dm: pkgs.writeScript "xsession"
+    ''
+      #! /bin/sh
+
+      . /etc/profile
+      cd "$HOME"
+
+      # The first argument of this script is the session type.
+      sessionType="$1"
+      if [ "$sessionType" = default ]; then sessionType=""; fi
+
+      ${optionalString (!cfg.displayManager.job.logsXsession) ''
+        exec > ~/.xsession-errors 2>&1
+      ''}
+
+      ${optionalString cfg.displayManager.desktopManagerHandlesLidAndPower ''
+        # Stop systemd from handling the power button and lid switch,
+        # since presumably the desktop environment will handle these.
+        if [ -z "$_INHIBITION_LOCK_TAKEN" ]; then
+          export _INHIBITION_LOCK_TAKEN=1
+          exec ${config.systemd.package}/bin/systemd-inhibit --what=handle-lid-switch:handle-power-key "$0" "$sessionType"
+        fi
+
+      ''}
+
+      ${optionalString cfg.startOpenSSHAgent ''
+        if test -z "$SSH_AUTH_SOCK"; then
+            # Restart this script as a child of the SSH agent.  (It is
+            # also possible to start the agent as a child that prints
+            # the required environment variabled on stdout, but in
+            # that mode ssh-agent is not terminated when we log out.)
+            export SSH_ASKPASS=${pkgs.x11_ssh_askpass}/libexec/x11-ssh-askpass
+            exec ${pkgs.openssh}/bin/ssh-agent "$0" "$sessionType"
+        fi
+      ''}
+
+      ${optionalString cfg.startGnuPGAgent ''
+        if test -z "$SSH_AUTH_SOCK"; then
+            # Restart this script as a child of the GnuPG agent.
+            exec "${pkgs.gnupg}/bin/gpg-agent"                         \
+              --enable-ssh-support --daemon                             \
+              --pinentry-program "${pkgs.pinentry}/bin/pinentry-gtk-2"  \
+              --write-env-file "$HOME/.gpg-agent-info"                  \
+              "$0" "$sessionType"
+        fi
+      ''}
+
+      # Handle being called by kdm.
+      if test "''${1:0:1}" = /; then eval exec "$1"; fi
+
+      # Start PulseAudio if enabled.
+      ${optionalString (config.hardware.pulseaudio.enable) ''
+        ${optionalString (!config.hardware.pulseaudio.systemWide)
+          "${pkgs.pulseaudio}/bin/pulseaudio --start"
+        }
+
+        # Publish access credentials in the root window.
+        ${pkgs.pulseaudio}/bin/pactl load-module module-x11-publish "display=$DISPLAY"
+
+        # Keep track of devices.  Mostly useful for Phonon/KDE.
+        ${pkgs.pulseaudio}/bin/pactl load-module module-device-manager "do_routing=1"
+      ''}
+
+      # Load X defaults.
+      if test -e ~/.Xdefaults; then
+          ${xorg.xrdb}/bin/xrdb -merge ~/.Xdefaults
+      fi
+
+      export LIBVA_DRIVERS_PATH=${vaapiDrivers}/lib/dri
+
+      # Speed up application start by 50-150ms according to
+      # http://kdemonkey.blogspot.nl/2008/04/magic-trick.html
+      rm -rf $HOME/.compose-cache
+      mkdir $HOME/.compose-cache
+
+      ${cfg.displayManager.sessionCommands}
+
+      # Allow the user to setup a custom session type.
+      if test -x ~/.xsession; then
+          exec ~/.xsession
+      else
+          if test "$sessionType" = "custom"; then
+              sessionType="" # fall-thru if there is no ~/.xsession
+          fi
+      fi
+
+      # The session type is "<desktop-manager> + <window-manager>", so
+      # extract those.
+      windowManager="''${sessionType##* + }"
+      : ''${windowManager:=${cfg.windowManager.default}}
+      desktopManager="''${sessionType% + *}"
+      : ''${desktopManager:=${cfg.desktopManager.default}}
+
+      # Start the window manager.
+      case $windowManager in
+        ${concatMapStrings (s: ''
+          (${s.name})
+            ${s.start}
+            ;;
+        '') wm}
+        (*) echo "$0: Window manager '$windowManager' not found.";;
+      esac
+
+      # Start the desktop manager.
+      case $desktopManager in
+        ${concatMapStrings (s: ''
+          (${s.name})
+            ${s.start}
+            ;;
+        '') dm}
+        (*) echo "$0: Desktop manager '$desktopManager' not found.";;
+      esac
+
+      test -n "$waitPID" && wait "$waitPID"
+      exit 0
+    '';
+
+  mkDesktops = names: pkgs.runCommand "desktops" {}
+    ''
+      mkdir -p $out
+      ${concatMapStrings (n: ''
+        cat - > "$out/${n}.desktop" << EODESKTOP
+        [Desktop Entry]
+        Version=1.0
+        Type=XSession
+        TryExec=${cfg.displayManager.session.script}
+        Exec=${cfg.displayManager.session.script} '${n}'
+        Name=${n}
+        Comment=
+        EODESKTOP
+      '') names}
+    '';
+
+in
+
+{
+
+  options = {
+
+    services.xserver.displayManager = {
+
+      xauthBin = mkOption {
+        default = "${xorg.xauth}/bin/xauth";
+        description = "Path to the <command>xauth</command> program used by display managers.";
+      };
+
+      xserverBin = mkOption {
+        default = "${xorg.xorgserver}/bin/X";
+        description = "Path to the X server used by display managers.";
+      };
+
+      xserverArgs = mkOption {
+        default = [];
+        example = [ "-ac" "-logverbose" "-nolisten tcp" ];
+        description = "List of arguments for the X server.";
+        apply = toString;
+      };
+
+      sessionCommands = mkOption {
+        default = "";
+        example =
+          ''
+            xmessage "Hello World!" &
+          '';
+        type = types.string;
+        description = "Shell commands executed just before the window or desktop manager is started.";
+      };
+
+      desktopManagerHandlesLidAndPower = mkOption {
+        default = true;
+        description = ''
+          Whether the display manager should prevent systemd from handling
+          lid and power events. This is normally handled by the desktop
+          environment's power manager. Turn this off when using a minimal
+          X11 setup without a full power manager.
+        '';
+      };
+
+      session = mkOption {
+        default = [];
+        example = [
+          {
+            manage = "desktop";
+            name = "xterm";
+            start = "
+              ${pkgs.xterm}/bin/xterm -ls &
+              waitPID=$!
+            ";
+          }
+        ];
+        description = ''
+          List of sessions supported with the command used to start each
+          session.  Each session script can set the
+          <varname>waitPID</varname> shell variable to make this script
+          wait until the end of the user session.  Each script is used
+          to define either a windows manager or a desktop manager.  These
+          can be differentiated by setting the attribute
+          <varname>manage</varname> either to <literal>"window"</literal>
+          or <literal>"desktop"</literal>.
+
+          The list of desktop manager and window manager should appear
+          inside the display manager with the desktop manager name
+          followed by the window manager name.
+        '';
+        apply = list: rec {
+          wm = filter (s: s.manage == "window") list;
+          dm = filter (s: s.manage == "desktop") list;
+          names = flip concatMap dm
+            (d: map (w: d.name + optionalString (w.name != "none") (" + " + w.name))
+              (filter (w: d.name != "none" || w.name != "none") wm));
+          desktops = mkDesktops names;
+          script = xsession wm dm;
+        };
+      };
+
+      job = mkOption {
+        default = {};
+        type = types.uniq types.optionSet;
+        description = "This option defines how to start the display manager.";
+
+        options = {
+
+          preStart = mkOption {
+            default = "";
+            example = "rm -f /var/log/my-display-manager.log";
+            description = "Script executed before the display manager is started.";
+          };
+
+          execCmd = mkOption {
+            example = "${pkgs.slim}/bin/slim";
+            description = "Command to start the display manager.";
+          };
+
+          environment = mkOption {
+            default = {};
+            example = { SLIM_CFGFILE = /etc/slim.conf; };
+            description = "Additional environment variables needed by the display manager.";
+          };
+
+          logsXsession = mkOption {
+            default = false;
+            description = ''
+              Whether the display manager redirects the
+              output of the session script to
+              <filename>~/.xsession-errors</filename>.
+            '';
+          };
+
+        };
+
+      };
+
+    };
+
+  };
+
+}