public function setAttribute($key, $value)
    {
        switch ($key) {
            case 'orientation':
                $this->attributes[$key] = 
                    $value == 'horizontal' ?
                    wxHORIZONTAL :
                    wxVERTICAL
                ;
            default:
                $this->attributes[$key] = $value;
            break;
        }
    }