code: public void onGeometryEditStart(GeometryEditStartEvent event) {
  		// Also look at the map for changes in the MapView:
  		mapViewRegistration = mapWidget.getMapModel().getMapView().addMapViewChangedHandler(this);
  
  		// Render the geometry on the map:
  		groups.clear();
  		draw(event.getGeometry());
  	}
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