drupal/core/modules/entity/entity.module

<?php

/**
 * @file
 * Manage the entity system.
 *
 * The module is mostly an anchor point for configuration items owned by the
 * entity system.
 */

use Drupal\Core\Config\Entity\ConfigStorageController;

/**
 * Implements hook_permission().
 */
function entity_permission() {
  return array(
    'administer display modes' => array(
      'title' => t('Add, edit, and delete custom display modes.'),
    ),
  );
}

/**
 * Implements hook_menu().
 */
function entity_menu() {
  $items = array();

  $items['admin/structure/display-modes'] = array(
    'title' => 'Display modes',
    'description' => 'Configure what displays are available for your content and forms.',
    'page callback' => 'system_admin_menu_block_page',
    'access arguments' => array('administer display modes'),
    'file' => 'system.admin.inc',
    'file path' => drupal_get_path('module', 'system'),
  );

  // View modes.
  $items['admin/structure/display-modes/view'] = array(
    'title' => 'View modes',
    'description' => 'Manage custom view modes.',
    'route_name' => 'entity_view_mode.list',
  );
  $items['admin/structure/display-modes/view/list'] = array(
    'title' => 'List',
    'type' => MENU_DEFAULT_LOCAL_TASK,
  );
  $items['admin/structure/display-modes/view/add'] = array(
    'title' => 'Add view mode',
    'route_name' => 'entity_view_mode.add',
    'type' => MENU_SIBLING_LOCAL_TASK,
  );
  $items['admin/structure/display-modes/view/add/%'] = array(
    'route_name' => 'entity_view_mode.add_type',
  );
  $items['admin/structure/display-modes/view/manage/%'] = array(
    'title' => 'Edit view mode',
    'route_name' => 'entity_view_mode.edit',
  );
  $items['admin/structure/display-modes/view/manage/%/delete'] = array(
    'route_name' => 'entity_view_mode.delete',
  );

  // Form modes.
  $items['admin/structure/display-modes/form'] = array(
    'title' => 'Form modes',
    'description' => 'Manage custom form modes.',
    'route_name' => 'entity_form_mode.list',
  );
  $items['admin/structure/display-modes/form/list'] = array(
    'title' => 'List',
    'type' => MENU_DEFAULT_LOCAL_TASK,
  );
  $items['admin/structure/display-modes/form/add'] = array(
    'title' => 'Add form mode',
    'route_name' => 'entity_form_mode.add',
    'type' => MENU_SIBLING_LOCAL_TASK,
  );
  $items['admin/structure/display-modes/form/add/%'] = array(
    'route_name' => 'entity_form_mode.add_type',
  );
  $items['admin/structure/display-modes/form/manage/%'] = array(
    'title' => 'Edit form mode',
    'route_name' => 'entity_form_mode.edit',
  );
  $items['admin/structure/display-modes/form/manage/%/delete'] = array(
    'route_name' => 'entity_form_mode.delete',
  );

  return $items;
}

/**
 * Implements hook_local_actions().
 */
function entity_local_actions() {
  return array(
    array(
      'route_name' => 'entity_view_mode.add',
      'title' => t('Add view mode'),
      'appears_on' => array(
        'entity_view_mode.list',
      ),
    ),
  );
}

/**
 * Implements hook_entity_bundle_rename().
 */
function entity_entity_bundle_rename($entity_type, $bundle_old, $bundle_new) {
  // Rename entity displays.
  $entity_info = entity_get_info('entity_display');
  if ($bundle_old !== $bundle_new) {
    $ids = config_get_storage_names_with_prefix('entity.display.' . $entity_type . '.' . $bundle_old);
    foreach ($ids as $id) {
      $id = ConfigStorageController::getIDFromConfigName($id, $entity_info['config_prefix']);
      $display = entity_load('entity_display', $id);
      $new_id = $entity_type . '.' . $bundle_new . '.' . $display->mode;
      $display->id = $new_id;
      $display->bundle = $bundle_new;
      $display->save();
    }
  }

  // Rename entity form displays.
  $entity_info = entity_get_info('entity_form_display');
  if ($bundle_old !== $bundle_new) {
    $ids = config_get_storage_names_with_prefix('entity.form_display.' . $entity_type . '.' . $bundle_old);
    foreach ($ids as $id) {
      $id = ConfigStorageController::getIDFromConfigName($id, $entity_info['config_prefix']);
      $form_display = entity_load('entity_form_display', $id);
      $new_id = $entity_type . '.' . $bundle_new . '.' . $form_display->mode;
      $form_display->id = $new_id;
      $form_display->bundle = $bundle_new;
      $form_display->save();
    }
  }
}

/**
 * Implements hook_entity_bundle_delete().
 */
function entity_entity_bundle_delete($entity_type, $bundle) {
  // Remove entity displays of the deleted bundle.
  $entity_info = entity_get_info('entity_display');
  $ids = config_get_storage_names_with_prefix('entity.display.' . $entity_type . '.' . $bundle);
  foreach ($ids as &$id) {
    $id = ConfigStorageController::getIDFromConfigName($id, $entity_info['config_prefix']);
  }
  entity_delete_multiple('entity_display', $ids);

  // Remove entity form displays of the deleted bundle.
  $entity_info = entity_get_info('entity_form_display');
  $ids = config_get_storage_names_with_prefix('entity.form_display.' . $entity_type . '.' . $bundle);
  foreach ($ids as &$id) {
    $id = ConfigStorageController::getIDFromConfigName($id, $entity_info['config_prefix']);
  }
  entity_delete_multiple('entity_form_display', $ids);
}