[glom] Dnd layout: Avoid a crash.

[Murray Cumming <murrayc src gnome org>]

commit e16defe6a724ffe7e582b144368ffb05755a62ed
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Dec 30 17:07:08 2009 +0100

    Dnd layout: Avoid a crash.
    
    * glom/utility_widgets/flowtable_dnd.cc: on_drag_data_received():
    Use a dynamic_cast<> to avoid memory corruption with the MI class.

 ChangeLog                             |    7 +++++++
 glom/utility_widgets/flowtable_dnd.cc |   18 +++++++++++-------
 2 files changed, 18 insertions(+), 7 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 885e070..20e82e3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2009-12-30  Murray Cumming  <murrayc murrayc com>
+
+	Dnd layout: Avoid a crash.
+
+	* glom/utility_widgets/flowtable_dnd.cc: on_drag_data_received():
+	Use a dynamic_cast<> to avoid memory corruption with the MI class.
+
 2009-12-16  Armin Burgmeier  <armin arbur net>
 
 	* win32/build-installer:
diff --git a/glom/utility_widgets/flowtable_dnd.cc b/glom/utility_widgets/flowtable_dnd.cc
index 354622f..42fd285 100644
--- a/glom/utility_widgets/flowtable_dnd.cc
+++ b/glom/utility_widgets/flowtable_dnd.cc
@@ -195,11 +195,14 @@ void FlowTableDnd::on_drag_data_received(const Glib::RefPtr<Gdk::DragContext>& d
   }
   else
   {
-    //TODO: When is this code path taken?
-    std::cout << "DEBUG: FlowTableDnd::on_drag_data_received(): Unexpected code path." << std::endl;
-    /*
-    gpointer* data = (gpointer*)selection_data.get_data();
-    LayoutWidgetBase* base = (LayoutWidgetBase*)*data;
+    gpointer* pdata = (gpointer*)selection_data.get_data();
+    if(!pdata)
+      return;
+
+    Gtk::Widget* widget = static_cast<Gtk::Widget*>(*pdata); //The type that was set in on_child_drag_data_get().
+
+    //A dynamic cast (from Gtk::Widget) is necessary because of the virtual inheritance: 
+    LayoutWidgetBase* base = dynamic_cast<LayoutWidgetBase*>(widget);
     if(base)
     {
       sharedptr<LayoutItem> item = base->get_layout_item();
@@ -215,11 +218,12 @@ void FlowTableDnd::on_drag_data_received(const Glib::RefPtr<Gdk::DragContext>& d
         else
           m_internal_drag = false;
 
-        on_dnd_add_layout_item(above, item);
+        LayoutWidgetBase* above_casted = dynamic_cast<LayoutWidgetBase*>(above);
+        on_dnd_add_layout_item(above_casted, item);
         base->set_dnd_in_progress(false);
       }
     }
-    */
+
   }
 }