+ if (de->old_vbox_widget)
+ g_object_unref (de->old_vbox_widget);
+ de->old_vbox_widget = de->datasheet_vbox_widget;
+ g_object_ref (de->old_vbox_widget);
+ /* FIXME: old_vbox_widget needs to be unreffed in dispose.
+ (currently it seems to provoke an error if I do that.
+ I don't know why. */
+ gtk_container_remove (GTK_CONTAINER (de->vbox), de->datasheet_vbox_widget);