ThemeLocalTask.php

<?php

namespace Drupal\system\Plugin\Derivative;

use Drupal\Component\Plugin\Derivative\DeriverBase;
use Drupal\Core\Extension\ThemeHandlerInterface;
use Drupal\Core\Plugin\Discovery\ContainerDeriverInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Provides dynamic tabs based on active themes.
 */
class ThemeLocalTask extends DeriverBase implements ContainerDeriverInterface {
    
    /**
     * The theme handler.
     *
     * @var \Drupal\Core\Extension\ThemeHandlerInterface
     */
    protected $themeHandler;
    
    /**
     * Constructs a new ThemeLocalTask instance.
     *
     * @param \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler
     *   The theme handler.
     */
    public function __construct(ThemeHandlerInterface $theme_handler) {
        $this->themeHandler = $theme_handler;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, $base_plugin_id) {
        return new static($container->get('theme_handler'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDerivativeDefinitions($base_plugin_definition) {
        foreach ($this->themeHandler
            ->listInfo() as $theme_name => $theme) {
            if ($this->themeHandler
                ->hasUi($theme_name)) {
                $this->derivatives[$theme_name] = $base_plugin_definition;
                $this->derivatives[$theme_name]['title'] = $theme->info['name'];
                $this->derivatives[$theme_name]['route_parameters'] = [
                    'theme' => $theme_name,
                ];
            }
        }
        return $this->derivatives;
    }

}