This event occurs when a Javascript touch start event occurs on the chart.
Use JsChartViewer.attachHandler with the event id "TouchStartChart" to attach a handler to this event.
The JsChartViewer.getChartMouseX, JsChartViewer.getChartMouseY, JsChartViewer.getPlotAreaMouseX and JsChartViewer.getPlotAreaMouseY can be used to obtain the mouse or touch coordinates relative to the chart.