FilterHtmlEscape.php

<?php

namespace Drupal\filter\Plugin\Filter;

use Drupal\Core\StringTranslation\TranslatableMarkup;
use Drupal\filter\Attribute\Filter;
use Drupal\filter\FilterProcessResult;
use Drupal\filter\Plugin\FilterBase;
use Drupal\filter\Plugin\FilterInterface;

/**
 * Provides a filter to display any HTML as plain text.
 */
class FilterHtmlEscape extends FilterBase {
  
  /**
   * {@inheritdoc}
   */
  public function process($text, $langcode) {
    return new FilterProcessResult(_filter_html_escape($text));
  }
  
  /**
   * {@inheritdoc}
   */
  public function getHTMLRestrictions() {
    // Nothing is allowed.
    return [
      'allowed' => [],
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function tips($long = FALSE) {
    return $this->t('No HTML tags allowed.');
  }

}