class TitleResolver

class TitleResolver implements TitleResolverInterface {
  use StringTranslationTrait;
  
  /**
   * The controller resolver.
   *
   * @var \Drupal\Core\Controller\ControllerResolverInterface
   */
  protected $controllerResolver;
  
  /**
   * The argument resolver.
   *
   * @var \Symfony\Component\HttpKernel\Controller\ArgumentResolverInterface
   */
  protected $argumentResolver;
  
  /**
   * Constructs a TitleResolver instance.
   *
   * @param \Drupal\Core\Controller\ControllerResolverInterface $controller_resolver
   *   The controller resolver.
   * @param \Drupal\Core\StringTranslation\TranslationInterface $string_translation
   *   The translation manager.
   * @param \Symfony\Component\HttpKernel\Controller\ArgumentResolverInterface $argument_resolver
   *   The argument resolver.
   */
  public function __construct(ControllerResolverInterface $controller_resolver, TranslationInterface $string_translation, ArgumentResolverInterface $argument_resolver) {
    $this->controllerResolver = $controller_resolver;
    $this->stringTranslation = $string_translation;
    $this->argumentResolver = $argument_resolver;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getTitle(Request $request, Route $route) {
    $route_title = NULL;
    // A dynamic title takes priority. Route::getDefault() returns NULL if the
    // named default is not set.  By testing the value directly, we also avoid
    // trying to use empty values.
    if ($callback = $route->getDefault('_title_callback')) {
      $callable = $this->controllerResolver
        ->getControllerFromDefinition($callback);
      $arguments = $this->argumentResolver
        ->getArguments($request, $callable);
      $route_title = call_user_func_array($callable, $arguments);
    }
    elseif ($route->hasDefault('_title') && strlen($route->getDefault('_title')) > 0) {
      $title = $route->getDefault('_title');
      $options = [];
      if ($route->hasDefault('_title_context')) {
        $options['context'] = $route->getDefault('_title_context');
      }
      $args = [];
      if ($raw_parameters = $request->attributes
        ->get('_raw_variables')) {
        foreach ($raw_parameters->all() as $key => $value) {
          if (is_scalar($value)) {
            $args['@' . $key] = $value;
            $args['%' . $key] = $value;
          }
        }
      }
      if ($title_arguments = $route->getDefault('_title_arguments')) {
        $args = array_merge($args, (array) $title_arguments);
      }
      // Fall back to a static string from the route.
      $route_title = $this->t($title, $args, $options);
    }
    return $route_title;
  }

}