private static Object getOption( Component owner, Component contents, String clientKey, String uiKey ) {
		for( Component c : new Component[] { owner, contents } ) {
			if( c instanceof JComponent ) {
				Object value = ((JComponent)c).getClientProperty( clientKey );
				if( value != null )
					return value;
			}
		}

		return UIManager.get( uiKey );
	}
Get option from:
<ol>
<li>client property {@code clientKey} of {@code owner}
<li>client property {@code clientKey} of {@code contents}
<li>UI property {@code uiKey}
</ol>
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatPopupFactory.java