[luatex] How to pass a box from TeX to lua

[Paul Isambert]

Andreas Matthias <andreas.matthias at gmail.com> a écrit:
> 
> \directlua {%
>   function out(t)
>      x = node.vpack(t)
>      node.write(x)
>    end
> }
> 
> \def\foo{%
>   \directlua {%
>     s = node.new(node.id('glyph'))
>     s.char = 97
>     s.font = 1
>     out(node.hpack(s))
>   }}
> \foo
> 
> 
> This code creates an hbox that is passed to function `out' which
> then packs everything into a vbox. Fine. But now I would like
> to do the first part (creation of the hbox) in TeX and the second
> part (creation of the vbox) in lua. The following code doesn't
> work but it might show what I'm trying to do.
> 
> 
> \def\bar#1{%
>   \directlua {
>     out(#1)
>   }}
> \bar{\hbox{a}}
> 
> 
> How can this be done?

Use a box register, assign your box to it, and retrieve it in Lua:

      \newbox\mybox
      \def\bar#1{%
        \setbox\mybox=#1%
        \directlua {
          out(tex.box.mybox)
        }}

      \bar{\hbox{a}}

If you \mybox doesn't have any other use, or is considered a scratch box
anyway, you don't need grouping.

Best,
Paul