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'])) {
            $build['content']['site_logo']['#uri'] = file_url_transform_relative(file_create_url($logo));
        }
        return $build;
    }

}