class LayoutInfoController

class LayoutInfoController extends ControllerBase {
  
  /**
   * The Layout Plugin Manager.
   *
   * @var Drupal\Core\Layout\LayoutPluginManagerInterface
   */
  protected $layoutPluginManager;
  
  /**
   * LayoutInfoController constructor.
   *
   * @param \Drupal\Core\Layout\LayoutPluginManagerInterface $pluginManagerLayout
   *   The layout manager.
   */
  public function __construct(LayoutPluginManagerInterface $pluginManagerLayout) {
    $this->layoutPluginManager = $pluginManagerLayout;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('plugin.manager.core.layout'));
  }
  
  /**
   * Builds the Layout Info page.
   *
   * @return array
   *   Array of page elements to render.
   */
  public function layoutInfoPage() {
    $headers = [
      $this->t('Icon'),
      $this->t('Label'),
      $this->t('Description'),
      $this->t('Category'),
      $this->t('Regions'),
      $this->t('Provider'),
    ];
    $rows = [];
    foreach ($this->layoutPluginManager
      ->getDefinitions() as $layout) {
      $rows[] = [
        'icon' => [
          'data' => $layout->getIcon(),
        ],
        'label' => $layout->getLabel(),
        'description' => $layout->getDescription(),
        'category' => $layout->getCategory(),
        'regions' => implode(', ', $layout->getRegionLabels()),
        'provider' => $layout->getProvider(),
      ];
    }
    $output['layouts'] = [
      '#type' => 'table',
      '#header' => $headers,
      '#rows' => $rows,
      '#empty' => $this->t('No layouts available.'),
      '#attributes' => [
        'class' => [
          'devel-layout-list',
        ],
      ],
    ];
    return $output;
  }

}