anchor.diff:  }
   
   class ColumnChart extends ChartWithAxes {
  +  
  +  final EventStream<Object> _onItemClick = new EventStream<Object>();
  +  Stream<Object> get onItemClick => _onItemClick.stream;
     
     Element $elmt;
     
  
positive.code:             hover.datum = datum;
            }
          });
        }
        
        $elmt.onMouseLeave.listen((_) {
  
negative.code: part of D3Dart;
  
  /**
   * EventStream provides a sync broadcast event
   */
  class EventStream<T> {
    StreamController<T> _controller = new StreamController<T>(sync: true);
    Stream<T> stream;
  
    EventStream() {
      stream = _controller.stream.asBroadcastStream();
    }
  
    signal([T value = null]) {
      _controller.add(value);
    }
  }
  
  
  abstract class ChartWithAxes {
    num width;
  