RendererRegistry.php

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<?php
namespace TYPO3\CMS\Core\Resource\Rendering;

/*
 * This file is part of the TYPO3 CMS project.
 *
 * It is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License, either version 2
 * of the License, or any later version.
 *
 * For the full copyright and license information, please read the
 * LICENSE.txt file that was distributed with this source code.
 *
 * The TYPO3 project - inspiring people to share!
 */

use TYPO3\CMS\Core\Resource\FileInterface;
use TYPO3\CMS\Core\Utility\GeneralUtility;

class RendererRegistry implements \TYPO3\CMS\Core\SingletonInterface
{
    protected $classNames = array();

    protected $instances = null;

    public static function getInstance()
    {
        return GeneralUtility::makeInstance(\TYPO3\CMS\Core\Resource\Rendering\RendererRegistry::class);
    }

    public function registerRendererClass($className)
    {
        if (!class_exists($className)) {
            throw new \InvalidArgumentException('The class "' . $className . '" you are trying to register is not available', 1411840171);
        } elseif (!in_array(\TYPO3\CMS\Core\Resource\Rendering\FileRendererInterface::class, class_implements($className), true)) {
            throw new \InvalidArgumentException('The renderer needs to implement the FileRendererInterface', 1411840172);
        } else {
            $this->classNames[] = $className;
        }
    }

    public function getRendererInstances()
    {
        if ($this->instances === null) {
            $this->instances = array();

            // As the result is in reverse order we need to reverse
            // the array before processing to keep the items with same
            // priority in the same order as they were added to the registry.
            $classNames = array_reverse($this->classNames);
            foreach ($classNames as $className) {
                $object = $this->createRendererInstance($className);
                $this->instances[] = $object;
            }

            if (count($this->instances) > 1) {
                usort($this->instances, array($this, 'compareRendererPriority'));
            }
        }
        return $this->instances;
    }

    protected function createRendererInstance($className)
    {
        return GeneralUtility::makeInstance($className);
    }

    protected function compareRendererPriority(FileRendererInterface $rendererA, FileRendererInterface $rendererB)
    {
        return $rendererB->getPriority() - $rendererA->getPriority();
    }

    public function getRenderer(FileInterface $file)
    {
        $matchingFileRenderer = null;

        foreach ($this->getRendererInstances() as $fileRenderer) {
            if ($fileRenderer->canRender($file)) {
                $matchingFileRenderer = $fileRenderer;
                break;
            }
        }
        return $matchingFileRenderer;
    }
}