page_manager-8.x-4.0-beta6/page_manager.module

<?php

/**
 * @file
 * Provides a way to place blocks on a custom page.
 */

use Drupal\page_manager\Entity\LayoutBuilderStorage;
use Drupal\page_manager\Form\LayoutBuilderForm;

/**
 * Implements hook_entity_type_build().
 */
function page_manager_entity_type_build(array &$entity_types) {
  if (_page_manager_is_layout_builder_enabled()) {
    /** @var \Drupal\Core\Entity\EntityTypeInterface[] $entity_types */
    $entity_types['page_variant']
      ->setHandlerClass('storage', LayoutBuilderStorage::class)
      ->setFormClass('layout_builder', LayoutBuilderForm::class);
  }
}

/**
 * Implements hook_display_variant_plugin_alter().
 */
function page_manager_display_variant_plugin_alter(array &$definitions) {
  // Disable the layout builder plugin if layout builder is not enabled.
  if (!_page_manager_is_layout_builder_enabled()) {
    unset($definitions['layout_builder']);
  }
}

/**
 * Helper to check if layout builder is enabled.
 *
 * @return bool
 *   TRUE is layout_builder is enabled, otherwise FALSE.
 */
function _page_manager_is_layout_builder_enabled() {
  return Drupal::moduleHandler()->moduleExists('layout_builder');
}