class EntityViewController

class EntityViewController implements ContainerInjectionInterface, TrustedCallbackInterface {
    use DeprecatedServicePropertyTrait;
    
    /**
     * {@inheritdoc}
     */
    protected $deprecatedProperties = [
        'entityManager' => 'entity.manager',
    ];
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * The renderer service.
     *
     * @var \Drupal\Core\Render\RendererInterface
     */
    protected $renderer;
    
    /**
     * Creates an EntityViewController object.
     *
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     * @param \Drupal\Core\Render\RendererInterface $renderer
     *   The renderer service.
     */
    public function __construct(EntityTypeManagerInterface $entity_type_manager, RendererInterface $renderer) {
        $this->entityTypeManager = $entity_type_manager;
        $this->renderer = $renderer;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('entity_type.manager'), $container->get('renderer'));
    }
    
    /**
     * Pre-render callback to build the page title.
     *
     * @param array $page
     *   A page render array.
     *
     * @return array
     *   The changed page render array.
     */
    public function buildTitle(array $page) {
        $entity_type = $page['#entity_type'];
        $entity = $page['#' . $entity_type];
        // If the entity's label is rendered using a field formatter, set the
        // rendered title field formatter as the page title instead of the default
        // plain text title. This allows attributes set on the field to propagate
        // correctly (e.g. RDFa, in-place editing).
        if ($entity instanceof FieldableEntityInterface) {
            $label_field = $entity->getEntityType()
                ->getKey('label');
            if (isset($page[$label_field])) {
                $page['#title'] = $this->renderer
                    ->render($page[$label_field]);
            }
        }
        return $page;
    }
    
    /**
     * Provides a page to render a single entity.
     *
     * @param \Drupal\Core\Entity\EntityInterface $_entity
     *   The Entity to be rendered. Note this variable is named $_entity rather
     *   than $entity to prevent collisions with other named placeholders in the
     *   route.
     * @param string $view_mode
     *   (optional) The view mode that should be used to display the entity.
     *   Defaults to 'full'.
     *
     * @return array
     *   A render array as expected by
     *   \Drupal\Core\Render\RendererInterface::render().
     */
    public function view(EntityInterface $_entity, $view_mode = 'full') {
        $page = $this->entityTypeManager
            ->getViewBuilder($_entity->getEntityTypeId())
            ->view($_entity, $view_mode);
        $page['#pre_render'][] = [
            $this,
            'buildTitle',
        ];
        $page['#entity_type'] = $_entity->getEntityTypeId();
        $page['#' . $page['#entity_type']] = $_entity;
        return $page;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function trustedCallbacks() {
        return [
            'buildTitle',
        ];
    }
    
    /**
     * Provides a page to render a single entity revision.
     *
     * @param \Drupal\Core\Entity\EntityInterface $_entity_revision
     *   The Entity to be rendered. Note this variable is named $_entity_revision
     *   rather than $entity to prevent collisions with other named placeholders
     *   in the route.
     * @param string $view_mode
     *   (optional) The view mode that should be used to display the entity.
     *   Defaults to 'full'.
     *
     * @return array
     *   A render array.
     */
    public function viewRevision(EntityInterface $_entity_revision, $view_mode = 'full') {
        return $this->view($_entity_revision, $view_mode);
    }

}