private Rectangle boundsInWindow( JComponent c ) {
		return c.isShowing()
			? SwingUtilities.convertRectangle( c.getParent(), c.getBounds(), window )
			: null;
	}
Returns whether windows uses native window border and has custom decorations enabled.
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTitlePane.java