@Override
		public void componentRemoved( ContainerEvent e ) {
			e.getChild().removeFocusListener( this );
		}
ContainerListener is added to JViewport to keep focus listener on view up-to-date.
FocusListener is added to view for repainting when view gets focused.
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatScrollPaneUI.java