private static void registerSystemScaleFactor( JFrame frame, String keyStrokeStr, String scaleFactor ) {
		KeyStroke keyStroke = KeyStroke.getKeyStroke( keyStrokeStr );
		if( keyStroke == null )
			throw new IllegalArgumentException( "Invalid key stroke '" + keyStrokeStr + "'" );

		((JComponent)frame.getContentPane()).registerKeyboardAction(
			e -> applySystemScaleFactor( frame, scaleFactor ),
			keyStroke,
			JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT );
	}
register Alt+Shift+F1, F2, ... F12 keys to change system scale factor
flatlaf-demo/src/main/java/com/formdev/flatlaf/demo/DemoPrefs.java