anchor.diff:      );
     }
   
  +  void _handleWheelEvent(
  +      html.Event e, void Function(Iterable<ui.PointerData>) sink) {
  +    assert(e is html.WheelEvent);
  +    final html.WheelEvent event = e as html.WheelEvent;
  +    if (_debugLogPointerEvents) {
  +      print(event.type);
  +    }
  +    if (event.getModifierState('Control') &&
  +        operatingSystem != OperatingSystem.macOs &&
  +        operatingSystem != OperatingSystem.iOs) {
  +      // Ignore Control+wheel events since the default handler
  +      // will change browser zoom level instead of scrolling.
  +      // The exception is MacOs where Control+wheel will still scroll and zoom
  +      // is not implemented.
  +      return;
  +    }
  +    _callback(_convertWheelEventToPointerData(event));
  +    // Prevent default so mouse wheel event doesn't get converted to
  +    // a scroll event that semantic nodes would process.
  +    //
  +    event.preventDefault();
  +  }
  +
     /// For browsers that report delta line instead of pixels such as FireFox
     /// compute line height using the default font size.
     ///
  
positive.code:     }, acceptOutsideGlasspane: true);
  
      _addWheelEventListener((html.Event event) {
        assert(event is html.WheelEvent);
        if (_debugLogPointerEvents) {
          print(event.type);
        }
        _callback(_convertWheelEventToPointerData(event as html.WheelEvent));
        // Prevent default so mouse wheel event doesn't get converted to
        // a scroll event that semantic nodes would process.
        event.preventDefault();
      });
    }
  
  
negative.code:     });
  
      _addWheelEventListener((html.Event event) {
        _handleWheelEvent(event, _callback);
      });
    }
  
  