Popsu-coloque/web/core/lib/Drupal/Core/Render/Plugin/DisplayVariant/SimplePageVariant.php

<?php

namespace Drupal\Core\Render\Plugin\DisplayVariant;

use Drupal\Core\Display\PageVariantInterface;
use Drupal\Core\Display\VariantBase;

/**
 * Provides a page display variant that simply renders the main content.
 *
 * @PageDisplayVariant(
 *   id = "simple_page",
 *   admin_label = @Translation("Simple page")
 * )
 */
class SimplePageVariant extends VariantBase implements PageVariantInterface {

  /**
   * The render array representing the main content.
   *
   * @var array
   */
  protected $mainContent;

  /**
   * The page title: a string (plain title) or a render array (formatted title).
   *
   * @var string|array
   */
  protected $title = '';

  /**
   * {@inheritdoc}
   */
  public function setMainContent(array $main_content) {
    $this->mainContent = $main_content;
    return $this;
  }

  /**
   * {@inheritdoc}
   */
  public function setTitle($title) {
    $this->title = $title;
    return $this;
  }

  /**
   * {@inheritdoc}
   */
  public function build() {
    $build = [
      'content' => [
        'messages' => [
          '#type' => 'status_messages',
          '#weight' => -1000,
          '#include_fallback' => TRUE,
        ],
        'page_title' => [
          '#type' => 'page_title',
          '#title' => $this->title,
          '#weight' => -900,
        ],
        'main_content' => ['#weight' => -800] + $this->mainContent,
      ],
    ];
    return $build;
  }

}