Module position Custom Param type for Joomla

<?php
/**
 * @version Id: adminpowermenu.php $
 * @package Joomla
 * @subpackage  Content
 * @copyright   Copyright (C)2010-2012 codeboxr.com. All rights reserved.
 * @license GNU/GPL, http://www.gnu.org/licenses/gpl-2.0.html GNU/GPL
 * @Support Forum http://codeboxr.com/product/admin-power-menu-for-joomla
 */


// no direct access
defined( '_JEXEC' ) or die( 'Restricted access' );

if(version_compare(JVERSION,'1.6.0','ge')) {
    jimport('joomla.form.formfield');
    class JFormFieldModposition extends JFormField {
        var $type = 'modposition';
        function getInput(){
            return JElementModposition::fetchElement($this->name, $this->value, $this->element, $this->options['control']);
        }
    }
}

class JElementModposition extends JElement
{
    /**
     * Element name
     *
     * @access  protected
     * @var     string
     */
    var $_name = 'modposition';
        function fetchElement( $name, $value, &$node, $control_name ) {
            if (!defined ('CODEBOXR_MODPOS')) {
                define ('CODEBOXR_MODPOS', 1);
                //
            }

            //let's list the module positions
            //$client   =& JApplicationHelper::getClientInfo(JRequest::getVar('client', '0', '', 'int'));

            $clientid = 0;  // for home page
            $user =& JFactory::getUser();
            $db   =& JFactory::getDBO();
            $query = 'SELECT m.position AS text, m.position AS value'
                            . ' FROM #__modules as m'
                            . ' WHERE m.client_id = '.(int) $clientid
                            . ' GROUP BY m.position'
                            . ' ORDER BY m.position'
                            ;
            //$positions[] = JHTML::_('select.option',  '0', '- '. JText::_( 'Select Position' ) .' -' );
            $db->setQuery( $query );
            //$positions = array();
            $positions =  $db->loadObjectList();
            //var_dump($positions);
            //var_dump($positions);
            //$lists['position']    = JHTML::_('select.genericlist',   $positions, 'filter_position', 'class="inputbox" size="1" onchange="this.form.submit()"', 'value', 'text', "$filter_position" );


            if(version_compare(JVERSION,'1.6.0','ge')) {
                    $fieldName = $name.'[]';
            }
            else {
                    $fieldName = $control_name.'['.$name.'][]';
            }

            //$doc->addScriptDeclaration($js);
            $output= JHTML::_('select.genericlist',  $positions, $fieldName, 'class="inputbox" style="width:90%;" multiple="multiple" size="10"', 'value', 'text', $value );
            return $output;

    }//end function fectchElement

}//end class
?>