layout_discovery.module

<?php


/**
 * @file
 */
use Drupal\Core\Render\Element;
use Drupal\Core\Template\Attribute;

/**
 * Prepares variables for layout templates.
 *
 * @param array &$variables
 *   An associative array containing:
 *   - content: An associative array containing the properties of the element.
 *     Properties used: #settings, #layout, #in_preview.
 */
function template_preprocess_layout(&$variables) : void {
    $variables['settings'] = $variables['content']['#settings'] ?? [];
    $variables['layout'] = $variables['content']['#layout'] ?? [];
    $variables['in_preview'] = $variables['content']['#in_preview'] ?? FALSE;
    // Create an attributes variable for each region.
    foreach (Element::children($variables['content']) as $name) {
        if (!isset($variables['content'][$name]['#attributes'])) {
            $variables['content'][$name]['#attributes'] = [];
        }
        $variables['region_attributes'][$name] = new Attribute($variables['content'][$name]['#attributes']);
    }
}