anchor.diff:  
       _touchCallback?.call(response);
     }
  +
  +  @override
  +  void attach(PipelineOwner owner) {
  +    super.attach(owner);
  +    _validForMouseTracker = true;
  +  }
  +
  +  @override
  +  void detach() {
  +    _validForMouseTracker = false;
  +    super.detach();
  +  }
   }
  
positive.code:   @override
    void handleEvent(PointerEvent event, covariant BoxHitTestEntry entry) {
      assert(debugHandleEvent(event, entry));
      if (_touchCallback == null) {
        return;
      }
  
negative.code: 
    List<LineBarSpot>? _lastTouchedSpots;
  
    late bool _validForMouseTracker;
  
    @override
    void performLayout() {
      size = computeDryLayout(constraints);
  