[boost] [parameter] Extendable named parameter keywords

Hi, I'm creating a GUI library (still in pre-alpha) using the named parameter library for the create function. It has a interface like this: wnd_lock<frame_window> w = create<frame_window>( _driver = gtk , _pos = std::make_pair(20, 20), _size = std::make_pair(600, 400) ); Until here everything is alright. But, for some controls, we must have extended keywords: wnd_lock<text_box> text = create<text_box>( _parent = w, _pos = std::make_pair(0, 0) , text_box::_multi_line = true ); Is it achievable? Thanks in advance, -- Felipe Magno de Almeida