magnifier: Only connect to ::draw when needed

This making us take the slow path in ::draw handling, so we
want to avoid it if we can.

https://bugzilla.gnome.org/show_bug.cgi?id=765238

1 files changed, 26 insertions, 4 deletions

diff --git a/gtk/gtkmagnifier.c b/gtk/gtkmagnifier.c
index 29905fb584..5d937673d1 100644
--- a/gtk/gtkmagnifier.c
+++ b/gtk/gtkmagnifier.c
@@ -226,9 +226,12 @@ connect_draw_handler (GtkMagnifier *magnifier)
 
   priv = _gtk_magnifier_get_instance_private (magnifier);
 
-  if (priv->inspected)
-    priv->draw_handler = g_signal_connect (priv->inspected, "draw",
-                                           G_CALLBACK (draw_handler), magnifier);
+  if (!priv->draw_handler)
+    {
+      if (priv->inspected)
+        priv->draw_handler = g_signal_connect (priv->inspected, "draw",
+                                               G_CALLBACK (draw_handler), magnifier);
+    }
 }
 
 static void
@@ -255,6 +258,22 @@ _gtk_magnifier_destroy (GtkWidget *widget)
 }
 
 static void
+gtk_magnifier_map (GtkWidget *widget)
+{
+  connect_draw_handler (GTK_MAGNIFIER (widget));
+
+  GTK_WIDGET_CLASS (_gtk_magnifier_parent_class)->map (widget);
+}
+
+static void
+gtk_magnifier_unmap (GtkWidget *widget)
+{
+  GTK_WIDGET_CLASS (_gtk_magnifier_parent_class)->unmap (widget);
+
+  disconnect_draw_handler (GTK_MAGNIFIER (widget));
+}
+
+static void
 _gtk_magnifier_class_init (GtkMagnifierClass *klass)
 {
   GObjectClass *object_class = G_OBJECT_CLASS (klass);
@@ -267,6 +286,8 @@ _gtk_magnifier_class_init (GtkMagnifierClass *klass)
   widget_class->draw = _gtk_magnifier_draw;
   widget_class->get_preferred_width = gtk_magnifier_get_preferred_width;
   widget_class->get_preferred_height = gtk_magnifier_get_preferred_height;
+  widget_class->map = gtk_magnifier_map;
+  widget_class->unmap = gtk_magnifier_unmap;
 
   g_object_class_install_property (object_class,
                                    PROP_INSPECTED,
@@ -353,7 +374,8 @@ _gtk_magnifier_set_inspected (GtkMagnifier *magnifier,
     g_object_add_weak_pointer (G_OBJECT (priv->inspected),
                                (gpointer *) &priv->inspected);
 
-  connect_draw_handler (magnifier);
+  if (gtk_widget_get_mapped (GTK_WIDGET (magnifier)))
+    connect_draw_handler (magnifier);
   connect_resize_handler (magnifier);
 
   g_object_notify (G_OBJECT (magnifier), "inspected");