How to extract text from argument

Question

The following code tries to extract plain text from formatted argument(here is \bfseries) and fails.

\x is used to store the expansion result of \pgfkeysvalueof.

\edef is for fully expansion of \pgfkeysvalueof to get the value of the key which may be used latter.

Why is the second try wrong?

How to extract plain text(ABC without bolded in this example) from the value of a key by \pgfkeys in the second try?

Code:

\documentclass{article}
\usepackage{tikz,etoolbox}%
\begin{document}
%(1)
\pgfkeys{title/.initial,title=ABC}
\edef\x{\pgfkeysvalueof{/title}}\x %This works all right
%(2)
\pgfkeys{title=\bfseries ABC}
\edef\x{\pgfkeysvalueof{/title}}\x %This can not pass compile
\end{document}

Answer 1

I can think of three approaches here. The first two ignore using any keys. Instead, I just use command structures.

This first example illustrates the basic idea. Here this is similar to what your example with the keys.

\documentclass{article}
\newcommand\lyimarkup{\bfseries}
\makeatletter
\newcommand\lyititle{@ifstar{\lyititle@starred}{\lyititle@nostar}}
\newcommand\lyititle@starred[2]{\providecommand#1{}\renewcommand#1{#2}}
\newcommand\lyititle@nostar[2]{\providecommand#1{}\renewcommand#1{{\bfseries#2}}}
\makeatother
\begin{document}
\lyititle\x{Hello World}\x
\lyititle*\x{Hello World}\x
\end{document}

This second example illustrates how you could work with something more dynamic as per what you suggested in the comments.

\documentclass{article}
\usepackage{xcolor}
\newcommand\lyicolor[1]{\color{#1}}
\makeatletter
\newcommand\lyitext{\@ifstar{\lyitext@starred}{\lyitext@nostar}}
\newcommand\lyitext@starred[2]{%%
  \providecommand#1{}%%
  \renewcommand#1{{\renewcommand\lyicolor[1]{}#2}}}
\newcommand\lyitext@nostar[2]{\providecommand#1{}\renewcommand#1{#2}}
\makeatother
\begin{document}
\lyitext\x{ab{\lyicolor{red}cd}ef}\x
\lyitext*\x{ab{\lyicolor{red}cd}ef}\x%% no mark up
\lyitext\x{ab{\lyicolor{red}cd}ef}\x%% mark up restored
\end{document}

I'll leave it for you to work out how to do this with pgfkeys.

---

The examples given above where written as they are because I wanted to stick closely to what the OP was doing in their MWE. Perhaps the OP wants to use \x in different places throughout the document. But, if that's not the case and if the OP only wants the option of rendering unmarked up text, then the answers above are far more clunky than necessary.

I don't want to assume that the OP (or anyone else stumbling across this answer) understands LaTeX enough to write these examples a bit more simply. So, I provide simplified versions here.

The first example can be rewritten as:

\documentclass{article}
\newcommand\lyimarkup{\bfseries}
\makeatletter
\newcommand\lyititle{@ifstar{\lyititle@starred}{\lyititle@nostar}}
\newcommand\lyititle@starred[1]{#1}
\newcommand\lyititle@nostar[1]{\textbf{#1}}
\makeatother
\begin{document}
\lyititle{Hello World}
\lyititle*{Hello World}
\end{document}

The second example can be rewritten as:

\documentclass{article}
\usepackage{xcolor}
\newcommand\lyicolor[1]{\color{#1}}
\makeatletter
\newcommand\lyitext{\@ifstar{\lyitext@starred}{\lyitext@nostar}}
\newcommand\lyitext@starred[1]{%%
  {\renewcommand\lyicolor[1]{}%%
  #1}}
\newcommand\lyitext@nostar[1]{#1}
\makeatother
\begin{document}
\lyitext{ab{\lyicolor{red}cd}ef}
\lyitext*{ab{\lyicolor{red}cd}ef}
\lyitext{ab{\lyicolor{red}cd}ef}
\end{document}

---

If you try to abide by the principle that content and markup should be clearly separated, then this sort of situation is relatively easy to deal with. If you're not used to doing this and you're only thinking about how you want the end product to look, this will take some effort to learn. So, for example, in a math textbook you might bold a word in the text when you first introduce it.

Instead of writing

\textbf{new fangled word}

you could write something like

\vocab{new fangled word}

where you define

\newcommand\vocab[1]{\textbf{#1}}

It takes some thought about how you're structuring the document. But once you start thinking this way, LaTeX's power really shines through.

Answer 2

You can use the \text_purify:n function from expl3. This is not a fool proof way to get everything right, because parsing TeX requires TeX, but at least it'll work in most simple cases like your MWE.

\documentclass{article}
\usepackage{tikz,etoolbox}%
\ExplSyntaxOn
\NewExpandableDocumentCommand \PurifiedPgfkeysvalueof { m }
  { \text_purify:n { \pgfkeysvalueof {#1} } }
\NewDocumentCommand \GetPurifiedPgfkey { m m }
  { \tl_set:Nx #1 { \text_purify:n { \pgfkeysvalueof {#2} } } }
\ExplSyntaxOff
\begin{document}
%(1)
\pgfkeys{title/.initial,title=ABC}
\edef\x{\pgfkeysvalueof{/title}}\x %This works all right
%(2)
\pgfkeys{title=\bfseries ABC}
\GetPurifiedPgfkey\mytitle{/title}\mytitle %This can not pass compile
or without an assignment: \PurifiedPgfkeysvalueof{/title}
\end{document}

Answer 3

If you know what macros are used in the extracted text then you can \let them to \relax temporary in a group:

\pgfkeys{title=\bfseries ABC}
{\let\bfseries=\relax \xdef\x{\pgfkeysvalueof{/title}}}\meaning\x

If you don't know the macros used in the text, you must to use right number of \expandafter in connection with \unexpanded in order to expand the right level of the \pgfkeysvalueof macro:

\def\threeexa{\expandafter\expandafter\expandafter}
\def\pgfkeyprotect#1#2{\unexpanded\expandafter\threeexa\expandafter{#1{#2}}}
\pgfkeys{title=\bfseries ABC}
\edef\x{\pgfkeyprotect\pgfkeysvalueof{/title}}\meaning\x