@Override
		public void focusLost( FocusEvent e ) {
			// necessary to update focus border
			if( scrollpane.getBorder() instanceof FlatBorder )
				HiDPIUtils.repaint( scrollpane );
		}
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