%class is an abstract class that provides a default implementation of the
ViewPortListener interface with empty methods. This class allows ViewPortListener objects to be created conveniently, as only the methods for the events of interest need to be overridden.
| Method | Inherited | Description |
| viewPortChanged | (Self) | The system will call this method when the viewport is changed through mouse actions, or when ChartViewer.updateViewPort is called. |
| selectionChanged | (Self) | The system will call this method when the user is selecting a region on the chart using "drag to select" mouse actions. |
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