anchor.diff:  import 'package:flutter/foundation.dart';
   import 'package:flutter/gestures.dart';
   import 'package:flutter/rendering.dart';
  +import 'package:flutter/services.dart';
   
   /// Low level LineChart Widget.
   class LineChartLeaf extends LeafRenderObjectWidget {
  
positive.code:   @override
    void handleEvent(PointerEvent event, covariant BoxHitTestEntry entry) {
      assert(debugHandleEvent(event, entry));
      if (_touchCallback == null) {
        return;
      }
  
negative.code: 
      _touchCallback?.call(response);
    }
  
    @override
    void attach(PipelineOwner owner) {
      super.attach(owner);
      _validForMouseTracker = true;
    }
  
    @override
    void detach() {
      _validForMouseTracker = false;
      super.detach();
    }
  }
  