public function onDisplayWorkspace(DisplayToolEvent $event)
    {
        $levelMax = 1;
        $workspace = $event->getWorkspace();
        $authenticatedUser = $this->tokenStorage->getToken()->getUser();
        $user = 'anon.' !== $authenticatedUser ? $authenticatedUser : null;
        $items = $this->progressionManager->fetchItems($workspace, $user, $levelMax);

        $content = $this->templating->render(
            'ClarolineCoreBundle:tool:progression.html.twig', [
                'workspace' => $workspace,
                'context' => [
                    'type' => 'workspace',
                    'data' => $this->serializer->serialize($workspace),
                ],
                'items' => $items,
                'levelMax' => null,    // how deep to process children recursively
            ]
        );

        $event->setContent($content);
        $event->stopPropagation();
    }