BlockController.php

<?php

namespace Drupal\block\Controller;

use Drupal\Component\Utility\Html;
use Drupal\block\BlockInterface;
use Drupal\Core\Controller\ControllerBase;
use Drupal\Core\Extension\ThemeHandlerInterface;
use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;

/**
 * Controller routines for admin block routes.
 */
class BlockController extends ControllerBase {

  /**
   * The theme handler.
   *
   * @var \Drupal\Core\Extension\ThemeHandlerInterface
   */
  protected $themeHandler;

  /**
   * Constructs a new BlockController instance.
   *
   * @param \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler
   *   The theme handler.
   */
  public function __construct(ThemeHandlerInterface $theme_handler) {
    $this->themeHandler = $theme_handler;
  }

  /**
   * Calls a method on a block and reloads the listing page.
   *
   * @param \Drupal\block\BlockInterface $block
   *   The block being acted upon.
   * @param string $op
   *   The operation to perform, e.g., 'enable' or 'disable'.
   *
   * @return \Symfony\Component\HttpFoundation\RedirectResponse
   *   A redirect back to the listing page.
   */
  public function performOperation(BlockInterface $block, $op) {
    $block
      ->{$op}()
      ->save();
    $this
      ->messenger()
      ->addStatus($this
      ->t('The block settings have been updated.'));
    return $this
      ->redirect('block.admin_display');
  }

  /**
   * Returns a block theme demo page.
   *
   * @param string $theme
   *   The name of the theme.
   *
   * @return array
   *   A #type 'page' render array containing the block region demo.
   */
  public function demo($theme) {
    if (!$this->themeHandler
      ->hasUi($theme)) {
      throw new NotFoundHttpException();
    }
    $page = [
      '#title' => Html::escape($this->themeHandler
        ->getName($theme)),
      '#type' => 'page',
      '#attached' => [
        'drupalSettings' => [
          // The block demonstration page is not marked as an administrative
          // page by \Drupal::service('router.admin_context')->isAdminRoute()
          // function in order to use the frontend theme. Since JavaScript
          // relies on a proper separation of admin pages, it needs to know this
          // is an actual administrative page.
          'path' => [
            'currentPathIsAdmin' => TRUE,
          ],
        ],
        'library' => [
          'block/drupal.block.admin',
        ],
      ],
    ];

    // Show descriptions in each visible page region, nothing else.
    $visible_regions = $this
      ->getVisibleRegionNames($theme);
    foreach (array_keys($visible_regions) as $region) {
      $page[$region]['block_description'] = [
        '#type' => 'inline_template',
        '#template' => '<div class="block-region demo-block">{{ region_name }}</div>',
        '#context' => [
          'region_name' => $visible_regions[$region],
        ],
      ];
    }
    return $page;
  }

  /**
   * Returns the human-readable list of regions keyed by machine name.
   *
   * @param string $theme
   *   The name of the theme.
   *
   * @return array
   *   An array of human-readable region names keyed by machine name.
   */
  protected function getVisibleRegionNames($theme) {
    return system_region_list($theme, REGIONS_VISIBLE);
  }

}