--- /dev/null
+<?php
+
+namespace Drupal\Core\Render\MainContent;
+
+use Drupal\Core\Ajax\AjaxResponse;
+use Drupal\Core\Controller\TitleResolverInterface;
+use Drupal\Core\Render\RendererInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Ajax\OpenOffCanvasDialogCommand;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Default main content renderer for off-canvas dialog requests.
+ *
+ * @internal
+ */
+class OffCanvasRenderer extends DialogRenderer {
+
+ /**
+ * The renderer.
+ *
+ * @var \Drupal\Core\Render\RendererInterface
+ */
+ protected $renderer;
+
+ /**
+ * Constructs a new OffCanvasRenderer.
+ *
+ * @param \Drupal\Core\Controller\TitleResolverInterface $title_resolver
+ * The title resolver.
+ * @param \Drupal\Core\Render\RendererInterface $renderer
+ * The renderer.
+ */
+ public function __construct(TitleResolverInterface $title_resolver, RendererInterface $renderer) {
+ parent::__construct($title_resolver);
+ $this->renderer = $renderer;
+ }
+
+ /**
+ * {@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 OpenOffCanvasDialogCommand and
+ // set the attachments for this Ajax response.
+ $main_content['#attached']['library'][] = 'core/drupal.dialog.off_canvas';
+ $response->setAttachments($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', []);
+ $response->addCommand(new OpenOffCanvasDialogCommand($title, $content, $options));
+ return $response;
+ }
+
+}