anchor.diff:     * soon as there is a drag movement. When a drag is started an [onDrag] event 
      * will also be fired.
      */
  -  Stream<DragEvent> get onDragStart => _dragDetector.onDragStart;
  +  Stream<DraggableEvent> get onDragStart => _draggable.onDragStart;
     
     /**
      * Fired periodically throughout the drag operation. 
      */
  -  Stream<DragEvent> get onDrag => _dragDetector.onDrag;
  +  Stream<DraggableEvent> get onDrag => _draggable.onDrag;
     
     /**
      * Fired when the user ends the dragging. 
  
positive.code:   /**
     * Handles drag.
     */
    void _handleDrag(DragEvent dragEvent) {
      int deltaX = _calcDragDelta(dragEvent.startCoords.x, dragEvent.coords.x);
      
      _log.finest('Drag: deltaX=$deltaX');
  
  
negative.code:         double autoHeightRatio: null, 
          this.distanceThreshold: 20,
          this.durationThreshold: 250,
          String handle: null, 
          String cancel: 'input,textarea,button,select,option',
          String draggingClassSwiper: 'swiper-dragging',
  