code: function(evt, x, y) {
  
          var view = this.getDelegatedView();
          if (!view || !view.can('elementMove')) return;
  
          this.eventData(evt, {
              action: 'move',
              delegatedView: view
          });
  
          view.eventData(evt, {
              x: x,
              y: y,
              restrictedArea: this.paper.getRestrictedArea(view)
          });
      }
docs: Drag Start Handlers