[luatex] lua equivalent of vbox...ht

[Patrick Gundlach]

Another related question:

> what would be the lua equivalent of
>
> \setbox0\vbox{hello world}
> \the\ht0
>
> ? That is, what would I write inside \directlua{ ... } to get the same
> effect?

Is it even possible to write this in Lua? I need to invoke the line  
breaking algorithm at some time, how do I do this in Lua?

Patrick