public override void Dispose()
{
Trace.Call();
// HACK: this shouldn't be needed but GTK# keeps GC handles
// these callbacks for some reason and thus leaks :(
// release ListStore.SetSortFunc() callback
// gtk_list_store_finalize() -> _gtk_tree_data_list_header_free() -> destroy(user_data);
_TopicTextView.Dispose();
_PersonListStore.Dispose();
// release TreeViewColumn.SetCellDataFunc() callback
// gtk_tree_view_column_finalize -> GtkTreeViewColumnCellInfo -> info->destroy(info->func_data)
_IdentityNameColumn.Dispose();
base.Dispose();
}