* as usual, all methods here are not threadsafe
*/
public DragAndDrop getDragAndDrop() {
// a space saver, since only a few panels will support drag and drop.
if (dragAndDropImpl == null) {
dragAndDropImpl = new DragAndDropImpl(new DraggableCreator() {
public Draggable createDraggable() {
Draggable drag = new Draggable() {
public List getContainerIds() {
return Panel.this.draggableGetContainerIds();
}