class EntityDisplayModeListBuilder

class EntityDisplayModeListBuilder extends ConfigEntityListBuilder {
    
    /**
     * All entity types.
     *
     * @var \Drupal\Core\Entity\EntityTypeInterface[]
     */
    protected $entityTypes;
    
    /**
     * Constructs a new EntityDisplayModeListBuilder object.
     *
     * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
     *   The entity type definition.
     * @param \Drupal\Core\Entity\EntityStorageInterface $storage
     *   The entity storage class.
     * @param \Drupal\Core\Entity\EntityTypeInterface[] $entity_types
     *   List of all entity types.
     */
    public function __construct(EntityTypeInterface $entity_type, EntityStorageInterface $storage, array $entity_types) {
        parent::__construct($entity_type, $storage);
        // Override the default limit (50) in order to display all view modes.
        $this->limit = FALSE;
        $this->entityTypes = $entity_types;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
        $entity_type_manager = $container->get('entity_type.manager');
        return new static($entity_type, $entity_type_manager->getStorage($entity_type->id()), $entity_type_manager->getDefinitions());
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildHeader() {
        $header['label'] = $this->t('Name');
        $header['description'] = $this->t('Description');
        return $header + parent::buildHeader();
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildRow(EntityInterface $entity) {
        $row['label'] = $entity->label();
        $row['description'] = $entity->getDescription();
        return $row + parent::buildRow($entity);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getOperations(EntityInterface $entity) {
        // Make the edit form render in a dialog, like the add form.
        // The edit form also contains an option to delete the view mode, which
        // also spawns a dialog. Rather than have nested dialogs, we allow the
        // existing dialog to be replaced, so users will be shown the list again
        // if they cancel deleting the view mode.
        $operations = parent::getOperations($entity);
        if (isset($operations['edit'])) {
            $operations['edit'] = NestedArray::mergeDeepArray([
                [
                    'attributes' => [
                        'class' => [
                            'button',
                            'use-ajax',
                        ],
                        'data-dialog-type' => 'modal',
                        'data-dialog-options' => Json::encode([
                            'width' => '880',
                        ]),
                    ],
                ],
                $operations['edit'],
            ]);
        }
        return $operations;
    }
    
    /**
     * {@inheritdoc}
     */
    public function load() {
        $entities = [];
        foreach (parent::load() as $entity) {
            $entities[$entity->getTargetType()][] = $entity;
        }
        return $entities;
    }
    
    /**
     * {@inheritdoc}
     */
    public function render() {
        $build = [];
        foreach ($this->load() as $entity_type => $entities) {
            if (!isset($this->entityTypes[$entity_type])) {
                continue;
            }
            // Filter entities.
            if (!$this->isValidEntity($entity_type)) {
                continue;
            }
            $table = [
                '#prefix' => '<h2>' . $this->entityTypes[$entity_type]
                    ->getLabel() . '</h2>',
                '#type' => 'table',
                '#header' => $this->buildHeader(),
                '#rows' => [],
                '#attributes' => [
                    'class' => [
                        'display-mode-table',
                    ],
                ],
            ];
            foreach ($entities as $entity) {
                if ($row = $this->buildRow($entity)) {
                    $table['#rows'][$entity->id()] = $row;
                }
            }
            // Move content at the top.
            if ($entity_type == 'node') {
                $table['#weight'] = -10;
            }
            $short_type = str_replace([
                'entity_',
                '_mode',
            ], '', $this->entityTypeId);
            $table['#rows']['_add_new'][] = [
                'data' => [
                    '#type' => 'link',
                    '#url' => Url::fromRoute($short_type == 'view' ? 'entity.entity_view_mode.add_form' : 'entity.entity_form_mode.add_form', [
                        'entity_type_id' => $entity_type,
                    ]),
                    '#title' => $this->t('Add %label for @entity-type', [
                        '@entity-type' => $this->entityTypes[$entity_type]
                            ->getLabel(),
                        '%label' => $this->entityType
                            ->getSingularLabel(),
                    ]),
                    '#button_type' => 'primary',
                    '#attributes' => [
                        'class' => [
                            'button',
                            'use-ajax',
                            'button--small',
                        ],
                        'data-dialog-type' => 'modal',
                        'data-dialog-options' => Json::encode([
                            'width' => '880',
                        ]),
                    ],
                    '#attached' => [
                        'library' => [
                            'core/drupal.dialog.ajax',
                            'field_ui/drupal.field_ui_table',
                        ],
                    ],
                ],
                'colspan' => count($table['#header']),
            ];
            $build[$entity_type] = $table;
        }
        return $build;
    }
    
    /**
     * Filters entities based on their view builder handlers.
     *
     * @param $entity_type
     *   The entity type of the entity that needs to be validated.
     *
     * @return bool
     *   TRUE if the entity has the correct view builder handler, FALSE if the
     *   entity doesn't have the correct view builder handler.
     */
    protected function isValidEntity($entity_type) {
        return $this->entityTypes[$entity_type]
            ->get('field_ui_base_route') && $this->entityTypes[$entity_type]
            ->hasViewBuilderClass();
    }

}