public function process()
    {
        parent::process();

        if ($this->show_check_all) {
            $this->check_all->process();
        }

        // this is part of the old selection API
        $item_name = $this->getCheckboxRendererId();
        if (isset($_POST[$item_name]) && is_array($_POST[$item_name])) {
            $this->items = $_POST[$item_name];
        }
    }