function split_text($offset)
    {
        if ($offset == 0) {
            return null;
        }

        $split = $this->_frame->get_node()->splitText($offset);

        $deco = $this->copy($split);

        $p = $this->get_parent();
        $p->insert_child_after($deco, $this, false);

        if ($p instanceof Inline) {
            $p->split($deco);
        }

        return $deco;
    }