_controlNodeDrag(event) {
    this.body.emitter.emit("disablePhysics");
    const pointer = this.body.functions.getPointer(event.center);
    const pos = this.canvas.DOMtoCanvas(pointer);
    if (this.selectedControlNode !== undefined) {
      this.selectedControlNode.x = pos.x;
      this.selectedControlNode.y = pos.y;
    } else {
      this.interactionHandler.onDrag(event);
    }
    this.body.emitter.emit("_redraw");
  }
dragging the control nodes or the canvas
@param {Event}  event   The event
@private