lightdm-gtk-greater: add configuration options for clock format and indicators

nixos/doc/manual/release-notes/rl-1803.xml

@@ -189,6 +189,51 @@ following incompatible changes:</para>
       corrupted blocks.
     </para>
   </listitem>
+  <listitem>
+    <para>
+      <literal>displayManager.lightdm.greeters.gtk.clock-format.</literal>
+      has been added, the clock format string (as expected by
+      strftime, e.g. <literal>%H:%M</literal>) to use with the lightdm
+      gtk greeter panel.
+    </para>
+    <para>
+      If set to null the default clock format is used.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+      <literal>displayManager.lightdm.greeters.gtk.indicators</literal>
+      has been added, a list of allowed indicator modules to use with
+      the lightdm gtk greeter panel.
+    </para>
+    <para>
+      Built-in indicators include <literal>~a11y</literal>,
+      <literal>~language</literal>, <literal>~session</literal>,
+      <literal>~power</literal>, <literal>~clock</literal>,
+      <literal>~host</literal>, <literal>~spacer</literal>. Unity
+      indicators can be represented by short name
+      (e.g. <literal>sound</literal>, <literal>power</literal>),
+      service file name, or absolute path.
+    </para>
+    <para>
+      If set to <literal>null</literal> the default indicators are
+      used.
+    </para>
+    <para>
+      In order to have the previous default configuration add
+<programlisting>
+  services.xserver.displayManager.lightdm.greeters.gtk.indicators = [
+    "~host" "~spacer"
+    "~clock" "~spacer"
+    "~session"
+    "~language"
+    "~a11y"
+    "~power"
+  ];
+</programlisting>
+      to your <literal>configuration.nix</literal>.
+    </para>
+  </listitem>
 </itemizedlist>
 
 </section>

nixos/modules/services/x11/display-managers/lightdm-greeters/gtk.nix

@@ -45,6 +45,8 @@ let
     theme-name = ${cfg.theme.name}
     icon-theme-name = ${cfg.iconTheme.name}
     background = ${ldmcfg.background}
+    ${optionalString (cfg.clock-format != null) "clock-format = ${cfg.clock-format}"}
+    ${optionalString (cfg.indicators != null) "indicators = ${concatStringsSep ";" cfg.indicators}"}
     ${cfg.extraConfig}
     '';
 
@@ -104,6 +106,35 @@ in
 
       };
 
+      clock-format = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        example = "%F";
+        description = ''
+          Clock format string (as expected by strftime, e.g. "%H:%M")
+          to use with the lightdm gtk greeter panel.
+
+          If set to null the default clock format is used.
+        '';
+      };
+
+      indicators = mkOption {
+        type = types.nullOr (types.listOf types.str);
+        default = null;
+        example = [ "~host" "~spacer" "~clock" "~spacer" "~session" "~language" "~a11y" "~power" ];
+        description = ''
+          List of allowed indicator modules to use for the lightdm gtk
+          greeter panel.
+
+          Built-in indicators include "~a11y", "~language", "~session",
+          "~power", "~clock", "~host", "~spacer". Unity indicators can be
+          represented by short name (e.g. "sound", "power"), service file name,
+          or absolute path.
+
+          If set to null the default indicators are used.
+        '';
+      };
+
       extraConfig = mkOption {
         type = types.lines;
         default = "";