protected Component findHorizontalGlue( JMenuBar menuBar ) {
		if( menuBar == null )
			return null;

		int count = menuBar.getComponentCount();
		for( int i = count - 1; i >= 0; i-- ) {
			Component c = menuBar.getComponent( i );
			if( c instanceof Box.Filler && c.getMaximumSize().width >= Short.MAX_VALUE )
				return c;
		}
		return null;
	}
Returns whether the menubar should be embedded into the title pane.
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTitlePane.java