code: function (e) {
  			var chart = this.chart;
  
  			e = this.normalize(e);
  
  			if (chart.isInsidePlot(e.chartX - chart.plotLeft, e.chartY - chart.plotTop)) {
  				chart.mapZoom(
  					0.5,
  					chart.xAxis[0].toValue(e.chartX),
  					chart.yAxis[0].toValue(e.chartY)
  				);
  			}
  		}
docs: The event handler for the doubleclick event