ColorSystemBrandingBlockAlter.php

<?php

namespace Drupal\color;

use Drupal\Core\Cache\CacheableMetadata;
use Drupal\Core\Render\Element\RenderCallbackInterface;

/**
 * Provides a trusted callback to alter the system branding block.
 *
 * @see color_block_view_system_branding_block_alter()
 */
class ColorSystemBrandingBlockAlter implements RenderCallbackInterface {
  
  /**
   * #pre_render callback: Sets color preset logo.
   */
  public static function preRender($build) {
    $theme_key = \Drupal::theme()->getActiveTheme()
      ->getName();
    $config = \Drupal::config('color.theme.' . $theme_key);
    CacheableMetadata::createFromRenderArray($build)->addCacheableDependency($config)
      ->applyTo($build);
    // Override logo.
    $logo = $config->get('logo');
    if ($logo && $build['content']['site_logo'] && preg_match('!' . $theme_key . '/logo.svg$!', $build['content']['site_logo']['#uri'])) {
      $build['content']['site_logo']['#uri'] = \Drupal::service('file_url_generator')->generateString($logo);
    }
    return $build;
  }

}