views/month: Move out of the view when pressing tab

This makes it so the user can easily skip the entire month view
by pressing tab within the month view. This means, events can only
be accessed with arrow keys in the month view.

src/gui/views/gcal-month-view.c

@@ -1368,6 +1368,19 @@ gtk_buildable_interface_init (GtkBuildableIface *iface)
  * GtkWidget overrides
  */
 
+static gboolean
+gcal_month_view_focus (GtkWidget        *widget,
+                       GtkDirectionType  direction)
+{
+  if (gtk_widget_get_focus_child (widget) &&
+      (direction == GTK_DIR_TAB_FORWARD || direction == GTK_DIR_TAB_BACKWARD))
+    {
+      return FALSE;
+    }
+
+  return GTK_WIDGET_CLASS (gcal_month_view_parent_class)->focus (widget, direction);
+}
+
 static void
 gcal_month_view_measure (GtkWidget      *widget,
                          GtkOrientation  orientation,
@@ -1625,6 +1638,7 @@ gcal_month_view_class_init (GcalMonthViewClass *klass)
   object_class->get_property = gcal_month_view_get_property;
   object_class->set_property = gcal_month_view_set_property;
 
+  widget_class->focus = gcal_month_view_focus;
   widget_class->measure = gcal_month_view_measure;
   widget_class->size_allocate = gcal_month_view_size_allocate;
   widget_class->snapshot = gcal_month_view_snapshot;