CkeditorOffCanvasTestController.php

<?php

namespace Drupal\ckeditor_test;

use Drupal\Core\Url;

/**
 * Provides controller for testing CKEditor in off-canvas dialogs.
 */
class CkeditorOffCanvasTestController {
    
    /**
     * Returns a link that can open a node add form in an off-canvas dialog.
     *
     * @return array
     *   A render array.
     */
    public function testOffCanvas() {
        $build['link'] = [
            '#type' => 'link',
            '#title' => 'Add Node',
            '#url' => Url::fromRoute('node.add', [
                'node_type' => 'page',
            ]),
            '#attributes' => [
                'class' => [
                    'use-ajax',
                ],
                'data-dialog-type' => 'dialog',
                'data-dialog-renderer' => 'off_canvas',
            ],
        ];
        $build['#attached']['library'][] = 'core/drupal.dialog.off_canvas';
        return $build;
    }

}