Patch updated on 17 May 2006 with this changelog:

================================================================================
--- gtk/gtkfontsel.c
+++ gtk/gtkfontsel.c
@@ -563,11 +563,24 @@
 gtk_font_selection_finalize (GObject *object)
 {
   GtkFontSelection *fontsel;
+  guint selection_timeout;
   
   g_return_if_fail (GTK_IS_FONT_SELECTION (object));
   
   fontsel = GTK_FONT_SELECTION (object);
 
+  selection_timeout = GPOINTER_TO_UINT (g_object_get_data (G_OBJECT (fontsel), "font-selection-timeout"));
+  if (selection_timeout)
+    g_source_remove (selection_timeout);
+
+  selection_timeout = GPOINTER_TO_UINT (g_object_get_data (G_OBJECT (fontsel), "style-selection-timeout"));
+  if (selection_timeout)
+    g_source_remove (selection_timeout);
+
+  selection_timeout = GPOINTER_TO_UINT (g_object_get_data (G_OBJECT (fontsel), "size-selection-timeout"));
+  if (selection_timeout)
+    g_source_remove (selection_timeout);
+
   if (fontsel->font)
     gdk_font_unref (fontsel->font);
   
@@ -646,10 +659,10 @@
 }
 
 /* This is called when a family is selected in the list. */
-static void
-gtk_font_selection_select_font (GtkTreeSelection *selection,
-				gpointer          data)
+static gboolean
+gtk_font_selection_real_select_font (gpointer data)
 {
+  GtkTreeSelection *selection;
   GtkFontSelection *fontsel;
   GtkTreeModel *model;
   GtkTreeIter iter;
@@ -657,7 +670,11 @@
   const gchar *family_name;
 #endif
 
+  if (!g_object_get_data (G_OBJECT (data), "immediate-selection"))
+    GDK_THREADS_ENTER ();
+
   fontsel = GTK_FONT_SELECTION (data);
+  selection = gtk_tree_view_get_selection (GTK_TREE_VIEW (fontsel->family_list));
 
   if (gtk_tree_selection_get_selected (selection, &model, &iter))
     {
@@ -679,6 +696,31 @@
 
       g_object_unref (family);
     }
+
+  g_object_set_data (G_OBJECT (fontsel), "font-selection-timeout", GUINT_TO_POINTER (0));
+
+  if (!g_object_get_data (G_OBJECT (fontsel), "immediate-selection"))
+    GDK_THREADS_LEAVE ();
+
+  /* Remove ourselves */
+  return FALSE;
+}
+
+static void
+gtk_font_selection_select_font (GtkTreeSelection *selection,
+				gpointer          data)
+{
+  GtkFontSelection *fontsel;
+  guint selection_timeout = 0;
+
+  fontsel = GTK_FONT_SELECTION (data);
+  selection_timeout = GPOINTER_TO_UINT (g_object_get_data (G_OBJECT (fontsel), "font-selection-timeout"));
+
+  if (selection_timeout)
+    g_source_remove (selection_timeout);
+
+  selection_timeout = g_timeout_add (200, gtk_font_selection_real_select_font, data);
+  g_object_set_data (G_OBJECT (fontsel), "font-selection-timeout", GUINT_TO_POINTER (selection_timeout));
 }
 
 static int
@@ -881,14 +923,20 @@
 
 
 /* This is called when a style is selected in the list. */
-static void
-gtk_font_selection_select_style (GtkTreeSelection *selection,
-				 gpointer          data)
+static gboolean
+gtk_font_selection_real_select_style (gpointer data)
 {
-  GtkFontSelection *fontsel = GTK_FONT_SELECTION (data);
+  GtkTreeSelection *selection;
+  GtkFontSelection *fontsel;
   GtkTreeModel *model;
   GtkTreeIter iter;
   
+  if (!g_object_get_data (G_OBJECT (data), "immediate-selection"))
+    GDK_THREADS_ENTER ();
+
+  fontsel = GTK_FONT_SELECTION (data);
+  selection = gtk_tree_view_get_selection (GTK_TREE_VIEW (fontsel->face_list));
+
   if (gtk_tree_selection_get_selected (selection, &model, &iter))
     {
       PangoFontFace *face;
@@ -901,6 +949,31 @@
 
   gtk_font_selection_show_available_sizes (fontsel, FALSE);
   gtk_font_selection_select_best_size (fontsel);
+
+  g_object_set_data (G_OBJECT (fontsel), "style-selection-timeout", GUINT_TO_POINTER (0));
+
+  if (!g_object_get_data (G_OBJECT (fontsel), "immediate-selection"))
+    GDK_THREADS_LEAVE ();
+
+  /* Remove ourselves */
+  return FALSE;
+}
+
+static void
+gtk_font_selection_select_style (GtkTreeSelection *selection,
+				 gpointer          data)
+{
+  GtkFontSelection *fontsel;
+  guint selection_timeout = 0;
+
+  fontsel = GTK_FONT_SELECTION (data);
+  selection_timeout = GPOINTER_TO_UINT (g_object_get_data (G_OBJECT (fontsel), "style-selection-timeout"));
+
+  if (selection_timeout)
+    g_source_remove (selection_timeout);
+
+  selection_timeout = g_timeout_add (200, gtk_font_selection_real_select_style, data);
+  g_object_set_data (G_OBJECT (fontsel), "style-selection-timeout", GUINT_TO_POINTER (selection_timeout));
 }
 
 static void
@@ -1033,22 +1106,51 @@
 }
 
 /* This is called when a size is selected in the list. */
-static void
-gtk_font_selection_select_size (GtkTreeSelection *selection,
-				gpointer          data)
+static gboolean
+gtk_font_selection_real_select_size (gpointer data)
 {
+  GtkTreeSelection *selection;
   GtkFontSelection *fontsel;
   GtkTreeModel *model;
   GtkTreeIter iter;
   gint new_size;
   
+  if (!g_object_get_data (G_OBJECT (data), "immediate-selection"))
+    GDK_THREADS_ENTER ();
+
   fontsel = GTK_FONT_SELECTION (data);
-  
+  selection = gtk_tree_view_get_selection (GTK_TREE_VIEW (fontsel->size_list));
+
   if (gtk_tree_selection_get_selected (selection, &model, &iter))
     {
       gtk_tree_model_get (model, &iter, SIZE_COLUMN, &new_size, -1);
       gtk_font_selection_set_size (fontsel, new_size * PANGO_SCALE);
     }
+
+  g_object_set_data (G_OBJECT (fontsel), "size-selection-timeout", GUINT_TO_POINTER (0));
+
+  if (!g_object_get_data (G_OBJECT (fontsel), "immediate-selection"))
+    GDK_THREADS_LEAVE ();
+
+  /* Remove ourselves */
+  return FALSE;
+}
+
+static void
+gtk_font_selection_select_size (GtkTreeSelection *selection,
+				gpointer          data)
+{
+  GtkFontSelection *fontsel;
+  guint selection_timeout = 0;
+
+  fontsel = GTK_FONT_SELECTION (data);
+  selection_timeout = GPOINTER_TO_UINT (g_object_get_data (G_OBJECT (fontsel), "size-selection-timeout"));
+
+  if (selection_timeout)
+    g_source_remove (selection_timeout);
+
+  selection_timeout = g_timeout_add (200, gtk_font_selection_real_select_size, data);
+  g_object_set_data (G_OBJECT (fontsel), "size-selection-timeout", GUINT_TO_POINTER (selection_timeout));
 }
 
 static void