/app/code/core/Mage/Page/Helper/Layout.php

<?php

/**

 * Magento

 *

 * NOTICE OF LICENSE

 *

 * This source file is subject to the Open Software License (OSL 3.0)

 * that is bundled with this package in the file LICENSE.txt.

 * It is also available through the world-wide-web at this URL:

 * http://opensource.org/licenses/osl-3.0.php

 * If you did not receive a copy of the license and are unable to

 * obtain it through the world-wide-web, please send an email

 * to license@magentocommerce.com so we can send you a copy immediately.

 *

 * DISCLAIMER

 *

 * Do not edit or add to this file if you wish to upgrade Magento to newer

 * versions in the future. If you wish to customize Magento for your

 * needs please refer to http://www.magentocommerce.com for more information.

 *

 * @category    Mage

 * @package     Mage_Page

 * @copyright   Copyright (c) 2012 Magento Inc. (http://www.magentocommerce.com)

 * @license     http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)

 */



/**

 * Page layout helper

 *

 * @category   Mage

 * @package    Mage_Page

 * @author     Magento Core Team <core@magentocommerce.com>

 */

class Mage_Page_Helper_Layout extends Mage_Core_Helper_Abstract

{

    /**

     * Apply page layout handle

     *

     * @param string $pageLayout

     * @return Mage_Page_Helper_Layout

     */

    public function applyHandle($pageLayout)

    {

        $pageLayout = $this->_getConfig()->getPageLayout($pageLayout);



        if (!$pageLayout) {

            return $this;

        }



        $this->getLayout()

            ->getUpdate()

            ->addHandle($pageLayout->getLayoutHandle());



        return $this;

    }



    /**

     * Apply page layout template

     * (for old design packages)

     *

     * @param string $pageLayout

     * @return Mage_Page_Helper_Layout

     */

    public function applyTemplate($pageLayout = null)

    {

        if ($pageLayout === null) {

            $pageLayout = $this->getCurrentPageLayout();

        } else {

            $pageLayout = $this->_getConfig()->getPageLayout($pageLayout);

        }



        if (!$pageLayout) {

            return $this;

        }



        if ($this->getLayout()->getBlock('root') &&

            !$this->getLayout()->getBlock('root')->getIsHandle()) {

                // If not applied handle

                $this->getLayout()

                    ->getBlock('root')

                    ->setTemplate($pageLayout->getTemplate());

        }



        return $this;

    }



    /**

     * Retrieve current applied page layout

     *

     * @return Varien_Object|boolean

     */

    public function getCurrentPageLayout()

    {

        if ($this->getLayout()->getBlock('root') &&

            $this->getLayout()->getBlock('root')->getLayoutCode()) {

            return $this->_getConfig()->getPageLayout($this->getLayout()->getBlock('root')->getLayoutCode());

        }



        // All loaded handles

        $handles = $this->getLayout()->getUpdate()->getHandles();

        // Handles used in page layouts

        $pageLayoutHandles = $this->_getConfig()->getPageLayoutHandles();

        // Applied page layout handles

        $appliedHandles = array_intersect($handles, $pageLayoutHandles);



        if (empty($appliedHandles)) {

            return false;

        }



        $currentHandle = array_pop($appliedHandles);



        $layoutCode = array_search($currentHandle, $pageLayoutHandles, true);



        return $this->_getConfig()->getPageLayout($layoutCode);

    }



    /**

     * Retrieve page config

     *

     * @return Mage_Page_Model_Config

     */

    protected function _getConfig()

    {

        return Mage::getSingleton('page/config');

    }

}