public void onMouseDown(MouseDownEvent event) {
		if (event.getNativeButton() != NativeEvent.BUTTON_RIGHT) {
			dragging = true;
			center = getScreenPosition(event);

			LineString radiusLine = mapWidget.getMapModel().getGeometryFactory().createLineString(
					new Coordinate[] { center, center });
			mapWidget.getVectorContext().drawGroup(mapWidget.getGroup(RenderGroup.SCREEN), circleGroup);
			mapWidget.getVectorContext().drawCircle(circleGroup, "outer", center, 1.0f, circleStyle);
			mapWidget.getVectorContext().drawCircle(circleGroup, "center", center, 2.0f, circleStyle);
			mapWidget.getVectorContext().drawLine(circleGroup, "radius", radiusLine, circleStyle);
		}
	}
public void onMouseDown ( MouseDownEvent event ) { if ( event . getNativeButton ( ) != NativeEvent . BUTTON_RIGHT ) { dragging = true ; center = getScreenPosition ( event ) ; LineString radiusLine = mapWidget . getMapModel ( ) . getGeometryFactory ( ) . createLineString ( new Coordinate [ ] { center , center } ) ; mapWidget . getVectorContext ( ) . drawGroup ( mapWidget . getGroup ( RenderGroup . SCREEN ) , circleGroup ) ; mapWidget . getVectorContext ( ) . drawCircle ( circleGroup , "outer" , center , 1.0f , circleStyle ) ; mapWidget . getVectorContext ( ) . drawCircle ( circleGroup , "center" , center , 2.0f , circleStyle ) ; mapWidget . getVectorContext ( ) . drawLine ( circleGroup , "radius" , radiusLine , circleStyle ) ; } }
Register center point for the circle, and start dragging and rendering.

@param event
event