@Override
      public void mouseDragged(MouseEvent event) {
        JTree tree = (JTree)event.getSource();
        Object property = tree.getClientProperty("DnD Source"); // DnDManagerImpl.SOURCE_KEY
        if (property == null) {
          super.mouseDragged(event); // use Swing-based DnD only if custom DnD is not set
        }
      }
@Override
      public void mouseDragged(MouseEvent event)