private static boolean hasCustomDecoration( Window window ) {
		return (window instanceof JFrame && JFrame.isDefaultLookAndFeelDecorated() && ((JFrame)window).isUndecorated()) ||
			(window instanceof JDialog && JDialog.isDefaultLookAndFeelDecorated() && ((JDialog)window).isUndecorated());
	}
Checks whether native library is loaded/available.
<p>
<b>Note</b>: It is required to invoke this method before invoking any other
             method of this class. Otherwise, the native library may not be loaded.
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatNativeLinuxLibrary.java