ModalRenderer.php

<?php

namespace Drupal\Core\Render\MainContent;

use Drupal\Core\Ajax\AjaxResponse;
use Drupal\Core\Ajax\OpenModalDialogCommand;
use Drupal\Core\Routing\RouteMatchInterface;
use Symfony\Component\HttpFoundation\Request;

/**
 * Default main content renderer for modal dialog requests.
 */
class ModalRenderer extends DialogRenderer {
    
    /**
     * {@inheritdoc}
     */
    public function renderResponse(array $main_content, Request $request, RouteMatchInterface $route_match) {
        $response = new AjaxResponse();
        // First render the main content, because it might provide a title.
        $content = $this->renderer
            ->renderRoot($main_content);
        // Attach the library necessary for using the OpenModalDialogCommand and set
        // the attachments for this Ajax response.
        $main_content['#attached']['library'][] = 'core/drupal.dialog.ajax';
        $response->setAttachments($main_content['#attached']);
        // If the main content doesn't provide a title, use the title resolver.
        $title = isset($main_content['#title']) ? $main_content['#title'] : $this->titleResolver
            ->getTitle($request, $route_match->getRouteObject());
        // Determine the title: use the title provided by the main content if any,
        // otherwise get it from the routing information.
        $options = $request->request
            ->get('dialogOptions', []);
        $response->addCommand(new OpenModalDialogCommand($title, $content, $options));
        return $response;
    }

}