private function flattenTree(
        &$options,
        SwatTreeFlydownNode $node,
        $level = 0,
        $path = array()
    ) {
        $tree_option = clone $node->getOption();

        $pad = str_repeat('&nbsp;', $level * 3);
        $path[] = $tree_option->value;

        $tree_option->title = $pad . $tree_option->title;
        $tree_option->value = $path;

        $options[] = $tree_option;

        foreach ($node->getChildren() as $child_node) {
            $this->flattenTree($options, $child_node, $level + 1, $path);
        }
    }