# How can I use a tl variable in TikZ options

Im setting up a command with some options via l3keys. One of the options is tikz-options and it should take a list of TikZ options and pass them to a {tikzpicture}.

\documentclass{article}

\usepackage{tikz,xparse}

\ExplSyntaxOn

\keys_define:nn { mymodule } {
tikz-options .tl_set:N = \l_mymodule_tikz_options_tl,
tikz-options .initial:n = {},
}

\tikzset{
every~my~image/.style = {
fill = blue,
}
}

\NewDocumentCommand{ \myimage }{ o }{
\IfValueT { #1 } {
\keys_set:nn { mymodule } { #1 }
}
\begin{tikzpicture}[every~my~image, \l_mymodule_tikz_options_tl]
\filldraw (0,0) rectangle (2,2);
\end{tikzpicture}
}

\ExplSyntaxOff

\begin{document}
\myimage

\myimage[tikz-options={fill=red,draw=black}]
\end{document}


The above example gives this error

! Package pgfkeys Error: I do not know the key '/tikz/fill=red,draw=black' and
I am going to ignore it. Perhaps you misspelled it.


I guess there’s a problem with expansion, since TikZ considers the whole content of the token list as one option. How can I manually expand it?

• Good question! I suspect something with .code=\pgfkeysalsofrom{...} -- I've done something similar with tcolorbox (which is tikz) and a \l_tmpa_tl. Perhaps, I'll find that! – user31729 Feb 5 '16 at 20:32
• TikZ has pgfkeys. That's a done deal. – percusse Feb 5 '16 at 20:41
• What's the point of using l3keys here? You can just say \begin{tikzpicture}[every-my-image, #1] .... Even aside from the difficulties of combining l3 syntax with TikZ, why would you want to bring in an additional key-value system to no purpose? – cfr Feb 5 '16 at 22:19
• \l_mymodule_tikz_options_tl is not a set of options, but it contains a set of options. No key-value based package does expansion when absorbing options. – egreg Feb 5 '16 at 22:40
• @cfr: Yes in this example #1 would work but tikz-options is only one among other l3 options … – Tobi Feb 6 '16 at 0:01

You're not passing a set of options but something that contains a set of options. The error message is a bit misleading, because the expansion takes place when issuing the error, so it appears you have passed the right options.

No key-value based package performs expansion when absorbing key-value pairs, because it could be disastrous. So the solution is to expand the token list before passing it in the optional argument to \begin{tikzpicture}:

\documentclass{article}

\usepackage{tikz,xparse}

\tikzset{
every my image/.style = {
fill = blue,
}
}

\ExplSyntaxOn

\keys_define:nn { mymodule }
{
tikz-options .tl_set:N = \l_mymodule_tikz_options_tl,
tikz-options .initial:n = {},
}

\NewDocumentCommand{ \myimage }{ O{} }
{
\group_begin:
\keys_set:nn { mymodule } { #1 }
\__tobi_start_tikzpicture:V \l_mymodule_tikz_options_tl
\filldraw (0,0) rectangle (2,2);
\end{tikzpicture}
\group_end:
}
\cs_new_protected:Nn \__tobi_start_tikzpicture:n
{
\begin{tikzpicture}[every~my~image,#1]
}
\cs_generate_variant:Nn \__tobi_start_tikzpicture:n { V }

\ExplSyntaxOff

\begin{document}

\myimage

\myimage[tikz-options={fill=red,draw=black}]

\end{document}


• I knew that it was an expansion problem ;-) but didn’t know how to expand the token list before passing it … thanks for your help! – Tobi Feb 6 '16 at 0:03
• Out of curiosity does L3keys have something similar to <key>/.expanded = <value> handler? – percusse Feb 6 '16 at 6:49
• @percusse One can use .code:n=\tl_set:Nx <tl-var> { #1 } or similar. – egreg Feb 6 '16 at 10:30