gcal-window: datetime settings shortcut

Shortcut is added so that time-related system settings can be easily
accessed. See #1023

The code is largely just a copy-paste of the code that opens the
"Online Accounts…" menu.

Fixes #1023

src/gui/gcal-window.c

@@ -425,6 +425,16 @@ on_window_new_event_cb (GSimpleAction *action,
   gtk_widget_set_visible (GTK_WIDGET (self->event_editor), TRUE);
 }
 
+static void
+on_window_open_date_time_settings_cb (GSimpleAction *action,
+                                      GVariant      *param,
+                                      gpointer       user_data)
+{
+  GApplication *application = g_application_get_default ();
+
+  gcal_utils_launch_date_time_settings_panel (g_application_get_dbus_connection (application), NULL, NULL);
+}
+
 static void
 on_window_open_online_accounts_cb (GSimpleAction *action,
                                    GVariant      *param,
@@ -1095,6 +1105,7 @@ gcal_window_init (GcalWindow *self)
     {"change-view", on_view_action_activated, "i" },
     {"next-date", on_window_next_date_activated_cb },
     {"new-event", on_window_new_event_cb },
+    {"open-date-time-settings", on_window_open_date_time_settings_cb },
     {"open-online-accounts", on_window_open_online_accounts_cb },
     {"previous-date", on_window_previous_date_activated_cb },
     {"show-calendars", on_show_calendars_action_activated },

src/gui/gcal-window.ui

@@ -302,6 +302,10 @@
   
   <menu id='menu'>
     <section>
+      <item>
+        <attribute name="label" translatable="yes">_Date &amp; Time Settings…</attribute>
+        <attribute name="action">win.open-date-time-settings</attribute>
+      </item>
       <item>
         <attribute name="label" translatable="yes">_Online Accounts…</attribute>
         <attribute name="action">win.open-online-accounts</attribute>

src/utils/gcal-utils.c

@@ -1123,6 +1123,58 @@ create_dbus_proxy (GDBusConnection *connection,
                                 NULL);
 }
 
+void
+gcal_utils_launch_date_time_settings_panel (GDBusConnection *connection,
+                                            const gchar     *action,
+                                            const gchar     *arg)
+{
+  g_autoptr (GDBusProxy) proxy = NULL;
+  GVariantBuilder builder;
+  GVariant *params[3];
+  GVariant *array[1];
+
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("av"));
+
+  if (!action && !arg)
+    {
+      g_variant_builder_add (&builder, "v", g_variant_new_string (""));
+    }
+  else
+    {
+      if (action)
+        g_variant_builder_add (&builder, "v", g_variant_new_string (action));
+
+      if (arg)
+        g_variant_builder_add (&builder, "v", g_variant_new_string (arg));
+    }
+
+  array[0] = g_variant_new ("v", g_variant_new ("(sav)", "datetime", &builder));
+
+  params[0] = g_variant_new_string ("launch-panel");
+  params[1] = g_variant_new_array (G_VARIANT_TYPE ("v"), array, 1);
+  params[2] = g_variant_new_array (G_VARIANT_TYPE ("{sv}"), NULL, 0);
+
+  proxy = create_dbus_proxy (connection, "org.gnome.Settings", "/org/gnome/Settings");
+
+  /* Fallback for old GNOME versions */
+  if (!proxy)
+    proxy = create_dbus_proxy (connection, "org.gnome.ControlCenter", "/org/gnome/ControlCenter");
+
+  if (!proxy)
+    {
+      g_warning ("Couldn't open Date & Time panel");
+      return;
+    }
+
+  g_dbus_proxy_call_sync (proxy,
+                          "Activate",
+                          g_variant_new_tuple (params, 3),
+                          G_DBUS_CALL_FLAGS_NONE,
+                          -1,
+                          NULL,
+                          NULL);
+}
+
 void
 gcal_utils_launch_online_accounts_panel (GDBusConnection *connection,
                                          const gchar     *action,

src/utils/gcal-utils.h

@@ -120,6 +120,10 @@ GList*               filter_children_by_uid_and_modtype          (GtkWidget
                                                                   GcalRecurrenceModType  mod,
                                                                   const gchar           *uid);
 
+void                 gcal_utils_launch_date_time_settings_panel  (GDBusConnection     *connection,
+                                                                  const gchar         *action,
+                                                                  const gchar         *arg);
+
 void                 gcal_utils_launch_online_accounts_panel     (GDBusConnection     *connection,
                                                                   const gchar         *action,
                                                                   const gchar         *arg);