PreviewFallbackInterface.php

<?php

namespace Drupal\Core\Render;


/**
 * Allows an element to provide a fallback representation of itself for preview.
 */
interface PreviewFallbackInterface {
    
    /**
     * Returns a string to be used as a fallback during preview.
     *
     * This is typically used when an element has no output and must be displayed,
     * for example during configuration.
     *
     * @return string|\Drupal\Core\StringTranslation\TranslatableMarkup
     *   A string representing for this.
     */
    public function getPreviewFallbackString();

}