FilterController.php

<?php

namespace Drupal\filter\Controller;

use Drupal\filter\FilterFormatInterface;

/**
 * Controller routines for filter routes.
 */
class FilterController {
    
    /**
     * Displays a page with long filter tips.
     *
     * @param \Drupal\filter\FilterFormatInterface|null $filter_format
     *   (optional) A filter format, or NULL to show tips for all formats.
     *   Defaults to NULL.
     *
     * @return array
     *   A renderable array.
     *
     * @see template_preprocess_filter_tips()
     */
    public function filterTips(?FilterFormatInterface $filter_format = NULL) {
        $tips = $filter_format ? $filter_format->id() : -1;
        $build = [
            '#theme' => 'filter_tips',
            '#long' => TRUE,
            '#tips' => _filter_tips($tips, TRUE),
        ];
        return $build;
    }
    
    /**
     * Gets the label of a filter format.
     *
     * @param \Drupal\filter\FilterFormatInterface $filter_format
     *   The filter format.
     *
     * @return string
     *   The label of the filter format.
     */
    public function getLabel(FilterFormatInterface $filter_format) {
        return $filter_format->label();
    }

}