FilterCaption.php

<?php

namespace Drupal\filter\Plugin\Filter;

use Drupal\Component\Utility\Html;
use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Drupal\Core\StringTranslation\TranslatableMarkup;
use Drupal\filter\Attribute\Filter;
use Drupal\filter\FilterPluginManager;
use Drupal\filter\FilterProcessResult;
use Drupal\filter\Plugin\FilterBase;
use Drupal\filter\Plugin\FilterInterface;
use Drupal\filter\Render\FilteredMarkup;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Provides a filter to caption elements.
 *
 * When used in combination with the filter_align filter, this must run last.
 */
class FilterCaption extends FilterBase implements ContainerFactoryPluginInterface {
    
    /**
     * Filter manager.
     *
     * @var \Drupal\filter\FilterPluginManager
     */
    protected $filterManager;
    
    /**
     * Constructs a new FilterCaption.
     *
     * @param array $configuration
     *   Configuration.
     * @param string $plugin_id
     *   Plugin ID.
     * @param mixed $plugin_definition
     *   Definition.
     * @param \Drupal\filter\FilterPluginManager $filter_manager
     *   Filter plugin manager.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, ?FilterPluginManager $filter_manager = NULL) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->filterManager = $filter_manager ?: \Drupal::service('plugin.manager.filter');
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('plugin.manager.filter'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function process($text, $langcode) {
        $result = new FilterProcessResult($text);
        if (stristr($text, 'data-caption') !== FALSE) {
            $dom = Html::load($text);
            $xpath = new \DOMXPath($dom);
            $html_filter = $this->filterManager
                ->createInstance('filter_html', [
                'settings' => [
                    'allowed_html' => '<a href hreflang target rel> <em> <strong> <cite> <code> <br>',
                    'filter_html_help' => FALSE,
                    'filter_html_nofollow' => FALSE,
                ],
            ]);
            foreach ($xpath->query('//*[@data-caption]') as $node) {
                // Read the data-caption attribute's value, then delete it.
                $caption = Html::escape($node->getAttribute('data-caption'));
                $node->removeAttribute('data-caption');
                // Sanitize caption: decode HTML encoding, limit allowed HTML tags; only
                // allow inline tags that are allowed by default, plus <br>.
                $caption = Html::decodeEntities($caption);
                $raw_caption = $caption;
                $filtered_caption = $html_filter->process($caption, $langcode);
                $result->addCacheableDependency($filtered_caption);
                $caption = FilteredMarkup::create($filtered_caption->getProcessedText());
                // The caption must be non-empty - however the Media Embed CKEditor
                // plugin uses a single space to represent a newly added caption. The
                // HTML filter will transform this into an empty string and prevent the
                // content editor from adding a new caption. To allow for this we treat
                // a raw caption value of ' ' as valid and adding the wrapping figure
                // element.
                // @see core/modules/media/js/plugins/drupalmedia/plugin.js
                if (mb_strlen($caption) === 0 && $raw_caption !== ' ') {
                    continue;
                }
                // Given the updated node and caption: re-render it with a caption, but
                // bubble up the value of the class attribute of the captioned element,
                // this allows it to collaborate with e.g. the filter_align filter.
                $tag = $node->tagName;
                $classes = $node->getAttribute('class');
                $node->removeAttribute('class');
                $node = $node->parentNode->tagName === 'a' ? $node->parentNode : $node;
                $filter_caption = [
                    '#theme' => 'filter_caption',
                    // We pass the unsanitized string because this is a text format
                    // filter, and after filtering, we always assume the output is safe.
                    // @see \Drupal\filter\Element\ProcessedText::preRenderText()
'#node' => FilteredMarkup::create($node->C14N()),
                    '#tag' => $tag,
                    '#caption' => $caption,
                    '#classes' => $classes,
                ];
                $altered_html = \Drupal::service('renderer')->render($filter_caption);
                // Load the altered HTML into a new DOMDocument and retrieve the element.
                $updated_nodes = Html::load($altered_html)->getElementsByTagName('body')
                    ->item(0)->childNodes;
                foreach ($updated_nodes as $updated_node) {
                    // Import the updated node from the new DOMDocument into the original
                    // one, importing also the child nodes of the updated node.
                    $updated_node = $dom->importNode($updated_node, TRUE);
                    $node->parentNode
                        ->insertBefore($updated_node, $node);
                }
                // Finally, remove the original data-caption node.
                $node->parentNode
                    ->removeChild($node);
            }
            $result->setProcessedText(Html::serialize($dom))
                ->addAttachments([
                'library' => [
                    'filter/caption',
                ],
            ]);
        }
        return $result;
    }
    
    /**
     * {@inheritdoc}
     */
    public function tips($long = FALSE) {
        if ($long) {
            return $this->t('
        <p>You can caption images, videos, blockquotes, and so on. Examples:</p>
        <ul>
            <li><code>&lt;img src="" data-caption="This is a caption" /&gt;</code></li>
            <li><code>&lt;video src="" data-caption="The Drupal Dance" /&gt;</code></li>
            <li><code>&lt;blockquote data-caption="Dries Buytaert"&gt;Drupal is awesome!&lt;/blockquote&gt;</code></li>
            <li><code>&lt;code data-caption="Hello world in JavaScript."&gt;alert("Hello world!");&lt;/code&gt;</code></li>
        </ul>');
        }
        else {
            return $this->t('You can caption images (<code>data-caption="Text"</code>), but also videos, blockquotes, and so on.');
        }
    }

}