LayoutInfoController.php

<?php

namespace Drupal\devel\Controller;

use Drupal\Core\Controller\ControllerBase;
use Drupal\Core\Layout\LayoutPluginManagerInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Returns response for Layout Info route.
 */
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;
    }

}