anchor.diff:    String _labelX ;
     String _labelY ;
     String hint ;
  +  int _hintHeight ;
     
     String get labelX => _labelX != null ? _labelX : valueX.toString() ;
     String get labelY => _labelY != null ? _labelY : valueY.toString() ;
  
positive.code:         
          _currentHintElements[e] = prevHint = _createHint(e,distance) ;
          //Distance hint in px
          distance += 24 ;
        }
        hintsMap[e] = prevHint ;
      }
  
negative.code:       this._labelX = label;           
    }
       
    XChartsData( this.valueX , this.valueY , [this._labelX , this._labelY , this.hint, this._hintHeight]) ;
    
    XChartsData clone() {
      var clone = new XChartsData( this.valueX , this.valueY, this._labelX , this._labelY , this.hint , this._hintHeight ) ;
      clone.width = this.width ;
      clone.height = this.height ;
      
      return clone ;
    }
    
    static const int DEFAULT_HINT_HEIGHT = 24 ;
    static const int MIN_HINT_HEIGHT = 2 ;
    
    int get hintHeight => _hintHeight == null ? DEFAULT_HINT_HEIGHT : _hintHeight ;
    
    set hintHeight(int height) => _hintHeight = height >= MIN_HINT_HEIGHT ? height : MIN_HINT_HEIGHT ;
    
    int width ;
    int height ;
  