# [luatex] Accessing pgf nodes from inside Lua(La)Tex

Paul Isambert zappathustra at free.fr
Tue Jun 19 08:45:18 CEST 2012

"Keith J. Schultz" <schultzk at uni-trier.de> a écrit:
>
> Hi All,
>
> I am writing a package with pgf/TikZ from making Nassi-Schneider diagramms.
> I have the code working under XeLaTeX and wanted to refracture it to LuaTeX.
> I have to admit that I am not very TeXian.
>
> My question is if I have the name of a pgf node how do I get at its coordinates from
> within LuaTeX.
>
> Or, is there a way to call pgf from directly inside LuaTeX.
>
> What I am looking for is to have a LuaTeX call to get the coordinates.
> The following code that I have is:
>
> 	\pgfextracty{\YCoordinate}{\pgfpointanchor{\LastNode}{south}}
>
> 	where \LastNode is the Name of the pgf node and \YCoordinate is a dimension.
>
> So my do I access pgf structures from in LuaTeX?
>
> Any help or pointers would be appreciated.

I don't think PGF has any Lua interface, but I might be wrong here.

>
> It would help me, also, if someone could tell me how to access something I have defined
> with \edef in LuaTeX
>
> eg.
>
> in the TeX file
> \edef{\aValue}{tttt}
>
> in a loaded .lua file
>
> function get_my_value(NameValue)
> 	local a = <some in Lua to access the edef>(NameValue)
>
> 	return a
> end

You can't do that, really. You may devise a complex system of
\directlua/tex.print calls, but I have some doubts it'll work.

Instead, you can use token lists:

\edef\aValue{tttt}
\mytok\expandafter{\aValue}

and in Lua:

function get_my_value (name)
local a = tex.toks.mytok
return a
end

Otherwise, if you really need a TeX macro (not a token list), you can
try:

\directlua{ mymacros = {} }
\def\gobble#1{}
\def\Def#1#2{%
\edef#1{#2}%
\directlua{%
mymacros["\expandafter\gobble\string#1"] =
"\luaescapestring{#2}" }%
}

then

\Def\aValue{tttt}

defines \aValue as before and makes its replacement text available in