anchor.diff:      } else {
         prop.clear(thing);
       }
  -  }
  -
  -  static GlobalId addHandler(Thing thing,
  -                             Action1<ThingMouseEventArgs> handler) {
  -    return _clickEvent.addHandler(thing, handler);
  -  }
  -
  -  static bool removeHandler(Thing obj, GlobalId handlerId) {
  -    return _clickEvent.removeHandler(obj, handlerId);
  -  }
  -
  -  static GlobalId addMouseMoveHandler(Thing thing,
  -                                      Action1<ThingMouseEventArgs> handler) {
  -    return _mouseMoveEvent.addHandler(thing, handler);
  -  }
  -
  -  static bool removeMouseMoveHandler(Thing thing, GlobalId handlerId) {
  -    return _mouseMoveEvent.removeHandler(thing, handlerId);
  -  }
  -
  -  static GlobalId addMouseUpHandler(Thing thing,
  -                                      Action1<ThingMouseEventArgs> handler) {
  -    return _mouseUpEvent.addHandler(thing, handler);
  -  }
  -
  -  static bool removeMouseUpHandler(Thing thing, GlobalId handlerId) {
  -    return _mouseUpEvent.removeHandler(thing, handlerId);
  -  }
  -
  -  static GlobalId addMouseDownHandler(Thing thing,
  -                                      Action1<ThingMouseEventArgs> handler) {
  -    return _mouseDownEvent.addHandler(thing, handler);
  -  }
  -
  -  static bool removeMouseDownHandler(Thing thing, GlobalId handlerId) {
  -    return _mouseDownEvent.removeHandler(thing, handlerId);
  -  }
  -
  -  static GlobalId addMouseOutHandler(Stage stage,
  -                                     Action1<ThingMouseEventArgs> handler) {
  -    return _mouseOutEvent.addHandler(stage, handler);
  -  }
  -
  -  static bool removeMouseOutHandler(Stage stage, GlobalId handlerId) {
  -    return _mouseOutEvent.removeHandler(stage, handlerId);
  -  }
  -
  -  static GlobalId addDragHandler(Thing thing,
  -                                     Action1<Vector> handler) {
  -    return _dragEvent.addHandler(thing, handler);
  -  }
  -
  -  static bool removeDragHandler(Thing thing, GlobalId handlerId) {
  -    return _dragEvent.removeHandler(thing, handlerId);
     }
   
     bool get _isDragging => _dragCoordinate != null;
  
positive.code:   static final Property<bool> _isDraggableProperty =
        new Property<bool>("isDraggable", false);
  
    static final AttachedEvent<ThingMouseEventArgs> _clickEvent =
        new AttachedEvent<ThingMouseEventArgs>('clickEvent');
  
  
negative.code:   static final AttachedEvent _mouseOutEvent =
        new AttachedEvent('mouseOut');
  
    static final AttachedEvent<Vector> _dragEvent =
        new AttachedEvent<Vector>('drag');
  
    final Stage _stage;
  
  