Chart components also provide a area renderer mechanism that developers can manipulate the cutting area components of the chart.
Only two steps needed to use the area renderer.
Implement the org.zkoss.zul.event.ChartAreaListener interface for manipulating the area components. e.g. Change the tooltiptext of the area.
Set the listener object or listener class name to the chart's areaListener property.
So developers get a chance to change the area component's properties or insert more information into the area component's componentScope property and thus be passed through to the onClick event listener.