[gtkmm] Gtk::Builder::get_type_from_name_vfunc(): Call the base class function

[Kjell Ahlstedt <kjellahl src gnome org>]

commit aecd310515b05a39b77635ef7f0c861c8587f7e0
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Tue Jan 20 16:33:44 2015 +0100

    Gtk::Builder::get_type_from_name_vfunc(): Call the base class function
    
    * gtk/src/builder.ccg: get_type_from_name_vfunc_callback(): If there is no
    gtkmm derived type, call GtkBuilder.get_type_from_name() rather than
    g_type_from_name(). Bug #742637.

 gtk/src/builder.ccg |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)
---
diff --git a/gtk/src/builder.ccg b/gtk/src/builder.ccg
index 7846801..1f8dd31 100644
--- a/gtk/src/builder.ccg
+++ b/gtk/src/builder.ccg
@@ -23,7 +23,7 @@
 // Allow GtkBuilder to instantiate a gtkmm derived GType instead of the regular
 // GTK+ GType, so we can, for instance, use our vfuncs and default signal handlers.
 static GType
-get_type_from_name_vfunc_callback(GtkBuilder*, const char* type_name)
+get_type_from_name_vfunc_callback(GtkBuilder* self, const char* type_name)
 {
   if (!type_name)
     return G_TYPE_INVALID;
@@ -34,10 +34,18 @@ get_type_from_name_vfunc_callback(GtkBuilder*, const char* type_name)
 
   GType gtype = g_type_from_name(classname_prefixed.c_str());
 
-  if(gtype == G_TYPE_INVALID) // if it's not a registered typename
+  if (gtype == G_TYPE_INVALID) // If it's not a registered typename
   {
-    // There's no gtkmm derived type, so just use the normal one.
-    gtype = g_type_from_name(type_name);
+    // Get the parent class of the object class (the original underlying C class).
+    Gtk::Builder_Class::BaseClassType* const base =
+      static_cast<Gtk::Builder_Class::BaseClassType*>(
+      g_type_class_peek_parent(G_OBJECT_GET_CLASS(self)));
+
+    // Call the original underlying C function.
+    if (base && base->get_type_from_name)
+      gtype = (*base->get_type_from_name)(self, type_name);
+    else // If that's not possible, just use the normal GType.
+      gtype = g_type_from_name(type_name);
   }
 
   return gtype;