EntityDisplayModeController.php

<?php

namespace Drupal\field_ui\Controller;

use Drupal\Core\Controller\ControllerBase;
use Drupal\Core\Url;

/**
 * Provides methods for entity display mode routes.
 */
class EntityDisplayModeController extends ControllerBase {
    
    /**
     * Provides a list of eligible entity types for adding view modes.
     *
     * @return array
     *   A list of entity types to add a view mode for.
     */
    public function viewModeTypeSelection() {
        $entity_types = [];
        foreach ($this->entityTypeManager()
            ->getDefinitions() as $entity_type_id => $entity_type) {
            if ($entity_type->get('field_ui_base_route') && $entity_type->hasViewBuilderClass()) {
                $entity_types[$entity_type_id] = [
                    'title' => $entity_type->getLabel(),
                    'url' => Url::fromRoute('entity.entity_view_mode.add_form', [
                        'entity_type_id' => $entity_type_id,
                    ]),
                    'localized_options' => [],
                ];
            }
        }
        return [
            '#theme' => 'admin_block_content',
            '#content' => $entity_types,
        ];
    }
    
    /**
     * Provides a list of eligible entity types for adding form modes.
     *
     * @return array
     *   A list of entity types to add a form mode for.
     */
    public function formModeTypeSelection() {
        $entity_types = [];
        foreach ($this->entityTypeManager()
            ->getDefinitions() as $entity_type_id => $entity_type) {
            if ($entity_type->get('field_ui_base_route') && $entity_type->hasFormClasses()) {
                $entity_types[$entity_type_id] = [
                    'title' => $entity_type->getLabel(),
                    'url' => Url::fromRoute('entity.entity_form_mode.add_form', [
                        'entity_type_id' => $entity_type_id,
                    ]),
                    'localized_options' => [],
                ];
            }
        }
        return [
            '#theme' => 'admin_block_content',
            '#content' => $entity_types,
        ];
    }

}