panel.addMouseHandler(selectionHandler);
panel.addMouseHandler(new MouseClickSelectionHandler());
panel.removeMouseHandler(panel.getZoomHandler());
// add a selection manager with intersection selection
DatasetExtensionManager dExManager = new DatasetExtensionManager();
dExManager.registerDatasetExtension(datasetExtension);
EntitySelectionManager selectionManager = new EntitySelectionManager(
panel, new Dataset[] { xydataset }, dExManager);
selectionManager.setIntersectionSelection(true);
panel.setSelectionManager(selectionManager);