code: function (e) {
  
              var chart = this.chart;
  
              hoverChartIndex = chart.index;
  
              e = this.normalize(e);
              e.returnValue = false; // #2251, #3224
  
              if (chart.mouseIsDown === 'mousedown') {
                  this.drag(e);
              }
  
              // Show the tooltip and run mouse over events (#977)
              if ((this.inClass(e.target, 'highcharts-tracker') ||
                chart.isInsidePlot(e.chartX - chart.plotLeft, e.chartY - chart.plotTop)) && !chart.openMenu) {
                  this.runPointActions(e);
              }
          }
docs: The mousemove, touchmove and touchstart event handler