class BlockPluginUI

1. 8.x drupal/core/modules/block/lib/Drupal/block/Plugin/Derivative/BlockPluginUI.php \Drupal\block\Plugin\Derivative\BlockPluginUI
2. 8.x drupal/core/modules/block/lib/Drupal/block/Plugin/PluginUI/BlockPluginUI.php \Drupal\block\Plugin\PluginUI\BlockPluginUI

class BlockPluginUI implements DerivativeInterface {

  /**
   * List of derivative definitions.
   *
   * @var array
   */
  protected $derivatives = array();

  /**
   * Implements \Drupal\Component\Plugin\Derivative\DerivativeInterface::getDerivativeDefinition().
   *
   * @todo Add documentation to this method.
   */
  public function getDerivativeDefinition($derivative_id, array $base_plugin_definition) {
    if (!empty($this->derivatives) && !empty($this->derivatives[$derivative_id])) {
      return $this->derivatives[$derivative_id];
    }
    $this
      ->getDerivativeDefinitions($base_plugin_definition);
    return $this->derivatives[$derivative_id];
  }

  /**
   * Implements \Drupal\Component\Plugin\Derivative\DerivativeInterface::getDerivativeDefinitions().
   */
  public function getDerivativeDefinitions(array $base_plugin_definition) {

    // Provide a derivative of the plugin UI for each theme.
    foreach (list_themes() as $key => $theme) {
      $this->derivatives[$key] = $base_plugin_definition;
    }
    return $this->derivatives;
  }

}