TitleResolver.php

<?php

namespace Drupal\Core\Controller;

use Drupal\Core\StringTranslation\StringTranslationTrait;
use Drupal\Core\StringTranslation\TranslationInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpKernel\Controller\ArgumentResolverInterface;
use Symfony\Component\Routing\Route;

/**
 * Provides the default implementation of the title resolver interface.
 */
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, $arguments);
        }
        elseif ($title = $route->getDefault('_title')) {
            $options = [];
            if ($context = $route->getDefault('_title_context')) {
                $options['context'] = $context;
            }
            $args = [];
            if ($raw_parameters = $request->attributes
                ->get('_raw_variables')) {
                foreach ($raw_parameters->all() as $key => $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;
    }

}