/** Adds an option
	 * @param array &$options where the option is to be added to
	 * @param Object $obj of $type 
	 * @param string $type of $object 
	 * @param PntStringConverter $cnv initialized to convert id and $obj toLabel and toHtml
	 * @param PntPropertyDescriptor $idProp to derive the id from the object
	 */
	function addOptionFromObject(&$options, $obj, $type, $cnv, $idProp) {
		$id = $cnv->toLabel( $idProp->getValueFor($obj), $idProp->getType() );
		
		$label = $cnv->toLabel($obj, $type);
		$options[$id] = $cnv->toHtml($label, false, 2);
		$this->optionsMaxLength = max($this->optionsMaxLength, strLen($label));
		return $id == $this->getSelectedId();
	}