datetime: Use GObject property binding for the NTP switch

This makes it possible to remove the code for manually keeping the NTP
switch and the timedated1 DBus proxy properties in sync, and also makes
it easy to share code with the automatic timezone switch.

https://bugzilla.gnome.org/show_bug.cgi?id=707252

panels/datetime/cc-datetime-panel.c

@@ -637,19 +637,6 @@ load_regions_model (GtkListStore *cities)
   tz_db_free (db);
 }
 
-static void
-update_widget_state_for_ntp (CcDateTimePanel *panel,
-                             gboolean         using_ntp)
-{
-  CcDateTimePanelPrivate *priv = panel->priv;
-  gboolean allowed;
-
-  /* need to check polkit before revealing to user */
-  allowed = (! priv->permission || g_permission_get_allowed (priv->permission));
-
-  gtk_widget_set_sensitive (W("datetime-button"), !using_ntp && allowed);
-}
-
 static void
 day_changed (GtkWidget       *widget,
              CcDateTimePanel *panel)
@@ -743,7 +730,6 @@ change_ntp (GObject         *gobject,
             GParamSpec      *pspec,
             CcDateTimePanel *self)
 {
-  update_widget_state_for_ntp (self, gtk_switch_get_active (GTK_SWITCH (gobject)));
   queue_set_ntp (self);
 }
 
@@ -755,13 +741,13 @@ on_permission_changed (GPermission *permission,
   CcDateTimePanelPrivate *priv = CC_DATE_TIME_PANEL (data)->priv;
   gboolean allowed, using_ntp;
 
-  allowed = g_permission_get_allowed (permission);
+  allowed = (priv->permission == NULL || g_permission_get_allowed (priv->permission));
   using_ntp = gtk_switch_get_active (GTK_SWITCH (W("network_time_switch")));
 
   /* All the widgets but the lock button and the 24h setting */
   gtk_widget_set_sensitive (W("auto-datetime-row"), allowed);
+  gtk_widget_set_sensitive (W("datetime-button"), allowed && !using_ntp);
   gtk_widget_set_sensitive (W("timezone-button"), allowed);
-  update_widget_state_for_ntp (data, using_ntp);
 
   /* Hide the subdialogs if we no longer have permissions */
   if (!allowed)
@@ -771,22 +757,6 @@ on_permission_changed (GPermission *permission,
     }
 }
 
-static void
-update_ntp_switch_from_system (CcDateTimePanel *self)
-{
-  CcDateTimePanelPrivate *priv = self->priv;
-  gboolean using_ntp;
-  GtkWidget *switch_widget;
-
-  using_ntp = timedate1_get_ntp (self->priv->dtm);
-
-  switch_widget = W("network_time_switch");
-  g_signal_handlers_block_by_func (switch_widget, change_ntp, self);
-  gtk_switch_set_active (GTK_SWITCH (switch_widget), using_ntp);
-  update_widget_state_for_ntp (self, using_ntp);
-  g_signal_handlers_unblock_by_func (switch_widget, change_ntp, self);
-}
-
 static void
 on_can_ntp_changed (CcDateTimePanel *self)
 {
@@ -809,12 +779,6 @@ on_can_ntp_changed (CcDateTimePanel *self)
                           ntp_available);
 }
 
-static void
-on_ntp_changed (CcDateTimePanel *self)
-{
-  update_ntp_switch_from_system (self);
-}
-
 static void
 on_timezone_changed (CcDateTimePanel *self)
 {
@@ -890,6 +854,36 @@ run_dialog (CcDateTimePanel *self,
   gtk_dialog_run (GTK_DIALOG (dialog));
 }
 
+static gboolean
+switch_to_row_transform_func (GBinding        *binding,
+                              const GValue    *source_value,
+                              GValue          *target_value,
+                              CcDateTimePanel *self)
+{
+  CcDateTimePanelPrivate *priv = self->priv;
+  gboolean active;
+  gboolean allowed;
+
+  active = g_value_get_boolean (source_value);
+  allowed = (priv->permission == NULL || g_permission_get_allowed (priv->permission));
+
+  g_value_set_boolean (target_value, !active && allowed);
+
+  return TRUE;
+}
+
+static void
+bind_switch_to_row (CcDateTimePanel *self,
+                    GtkWidget       *gtkswitch,
+                    GtkWidget       *listrow)
+{
+  g_object_bind_property_full (gtkswitch, "active",
+                               listrow, "sensitive",
+                               G_BINDING_SYNC_CREATE,
+                               (GBindingTransformFunc) switch_to_row_transform_func,
+                               NULL, self, NULL);
+}
+
 static void
 toggle_switch (GtkWidget *sw)
 {
@@ -1229,9 +1223,13 @@ cc_date_time_panel_init (CcDateTimePanel *self)
   setup_datetime_dialog (self);
   setup_main_listview (self);
 
-  /* set up network time button */
+  /* set up network time switch */
-  update_ntp_switch_from_system (self);
+  bind_switch_to_row (self,
-  on_can_ntp_changed (self);
+                      W ("network_time_switch"),
+                      W ("datetime-button"));
+  g_object_bind_property (priv->dtm, "ntp",
+                          W ("network_time_switch"), "active",
+                          G_BINDING_SYNC_CREATE);
   g_signal_connect (W("network_time_switch"), "notify::active",
                     G_CALLBACK (change_ntp), self);
 
@@ -1289,8 +1287,6 @@ cc_date_time_panel_init (CcDateTimePanel *self)
   /* Watch changes of timedated remote service properties */
   g_signal_connect (priv->dtm, "g-properties-changed",
                     G_CALLBACK (on_timedated_properties_changed), self);
-  g_signal_connect_swapped (priv->dtm, "notify::ntp",
-                            G_CALLBACK (on_ntp_changed), self);
   g_signal_connect_swapped (priv->dtm, "notify::can-ntp",
                             G_CALLBACK (on_can_ntp_changed), self);
   g_signal_connect_swapped (priv->dtm, "notify::timezone",