[gtkmm] Correct base type check in Container_Class::remove_callback()

[Daniel Elstner <daniel src gnome org>]

commit 4474ebb25f0309bb88e890b118db78beed5261d5
Author: Daniel Elstner <danielk openismus com>
Date:   Wed Jul 8 21:43:40 2009 +0200

    Correct base type check in Container_Class::remove_callback()
    
    * gtk/src/container.ccg (Gtk::Container_Class::remove_callback):
    In order to test for the abstract GtkContainer parent class, actually
    compare against the parent type instead of making invalid assumptions
    about the derived type.  By means of the alternative Glib::ObjectBase
    constructor, it is possible to create a custom GObject type different
    from the standard one.

 ChangeLog             |   11 +++++++++++
 gtk/src/container.ccg |   23 ++++++++---------------
 2 files changed, 19 insertions(+), 15 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 87bbd59..d066597 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2009-07-08  Daniel Elstner  <danielk openismus com>
+
+	Correct base type check in Container_Class::remove_callback()
+
+	* gtk/src/container.ccg (Gtk::Container_Class::remove_callback):
+	In order to test for the abstract GtkContainer parent class, actually
+	compare against the parent type instead of making invalid assumptions
+	about the derived type.  By means of the alternative Glib::ObjectBase
+	constructor, it is possible to create a custom GObject type different
+	from the standard one.
+
 2008-03-08  Murray Cumming  <murrayc murrayc com>
 
 	* gtk/src/container.ccg: remove_callback(): When just calling the C
diff --git a/gtk/src/container.ccg b/gtk/src/container.ccg
index 3684856..5bcd683 100644
--- a/gtk/src/container.ccg
+++ b/gtk/src/container.ccg
@@ -162,21 +162,14 @@ void Container_Class::remove_callback(GtkContainer* self, GtkWidget* p0)
   }
   else
   {
-    //Call the original underlying C function:
-
-    //But don't do this if the GType is just the base GtkContainer 
-    //(the case when deriving from Gtk::Container)
-    //because GtkContainer::remove() then shows a warning that it was not implemented,
-    //and that warning is not useful to us in that case.
-    if(G_OBJECT_TYPE(self) == Gtk::Container::get_type())
-      return;
-
-    //Call the original underlying C function:
-    BaseClassType *const base = static_cast<BaseClassType*>(
-        g_type_class_peek_parent(G_OBJECT_GET_CLASS(self)) // Get the parent class of the object class (The original underlying C class).
-    );
-
-    if(base && base->remove)
+    BaseClassType *const base =
+      static_cast<BaseClassType*>(g_type_class_peek_parent(G_OBJECT_GET_CLASS(self)));
+
+    // Do not try to call the default implementation of the virtual function
+    // GtkContainerClass::remove(), because it unhelpfully informs us that
+    // it isn't implemented.  This leaves us with no generic means to check
+    // whether it is implemented.
+    if(base && G_TYPE_FROM_CLASS(base) != GTK_TYPE_CONTAINER && base->remove)
       (*base->remove)(self, p0);
   }
 }