week-view: improve scroll timeout logic

Instead of keeping an active timeout source spamming the
console, just connect to the right signal and wait for the
week view to be visible again.

src/views/gcal-week-view.c

@@ -69,6 +69,8 @@ struct _GcalWeekView
   gint            clicked_cell;
 };
 
+static void           schedule_position_scroll                  (GcalWeekView      *self);
+
 static void           gcal_view_interface_init                  (GcalViewInterface *iface);
 
 static void           gcal_data_model_subscriber_interface_init (ECalDataModelSubscriberInterface *iface);
@@ -101,6 +103,19 @@ on_event_activated (GcalWeekView *self,
   g_signal_emit (self, signals[EVENT_ACTIVATED], 0, widget);
 }
 
+static void
+stack_visible_child_changed_cb (GtkStack     *stack,
+                                GParamSpec   *pspec,
+                                GcalWeekView *self)
+{
+  if (gtk_stack_get_visible_child (stack) != (GtkWidget*) self)
+    return;
+
+  schedule_position_scroll (self);
+
+  g_signal_handlers_disconnect_by_func (stack, stack_visible_child_changed_cb, self);
+}
+
 /* Auxiliary methods */
 static gboolean
 update_grid_scroll_position (GcalWeekView *self)
@@ -117,7 +132,18 @@ update_grid_scroll_position (GcalWeekView *self)
   if (!gtk_widget_get_realized (self->scrolled_window) ||
       !gtk_widget_get_mapped (self->scrolled_window))
     {
-      GCAL_RETURN (G_SOURCE_CONTINUE);
+      GtkWidget *stack;
+
+      stack = gtk_widget_get_ancestor (GTK_WIDGET (self), GTK_TYPE_STACK);
+
+      g_signal_connect (stack,
+                        "notify::visible-child",
+                        G_CALLBACK (stack_visible_child_changed_cb),
+                        self);
+
+      self->scroll_grid_timeout_id = 0;
+
+      GCAL_RETURN (G_SOURCE_REMOVE);
     }
 
   now = g_date_time_new_now_local ();