Drupal 8 CKEditor filter

CKEditor_filter.php

<?php

namespace Drupal\MODULE_NAME\Plugin\Filter;

use Drupal\filter\FilterProcessResult;
use Drupal\filter\Plugin\FilterBase;

/**
 * Provides a filter to limit allowed HTML tags.
 *
 * @Filter(
 *   id = "filter_font_family",
 *   title = @Translation("Font family filter"),
 *   type = Drupal\filter\Plugin\FilterInterface::TYPE_HTML_RESTRICTOR,
 *   settings = {},
 *   weight = -10
 * )
 */
class FontFamilyFilter extends FilterBase {

  /**
   * {@inheritdoc}
   */
  public function process($text, $langcode) {
    return new FilterProcessResult($text);
  }

  
  /**
   * {@inheritdoc}
   */
  public function getHTMLRestrictions() {
    $restrictions = [];
    $restrictions['forbidden_tags'][] = 'font face';

    return $restrictions;
  }
  
}