Re: [AUCTeX] Listing and not listing regions inverted if `\begin{lstlisting}' not followed by what is expected

[Tassilo Horn]

Denis Bitouzé <address@hidden> writes:

Hi Denis,

> OK but, if `latexcode' is not declared as a verbatim environment, only
> `lstlisting' is considered as such in:
>
>   ┌────
>   │ \begin{latexcode}
>   │ \begin{lstlisting}+\only<2->{+[+\emph{options}+]+}+
>   │ +\emph{listing}+
>   │ \end{lstlisting}
>   │ \end{latexcode}
>   └────
>
> and what is strange is that, because of the non expected `+' in:
>
>   ┌────
>   │ \begin{lstlisting}+\only<2->{+[+\emph{options}+]+}+
>   └────
>
> the beginning of this environment is missed (okay) /but/ that's the
> following `\end{lstlisting}' which is considered as the /beginning/ of
> this environment.
>
> Wouldn't it be possible for `\end{...}' to never be considered as the
> /beginning/ of `...' environment?

No, actually syntactic font-lock has no notion of beginning or end.
Basically, what AUCTeX' font-latex does is telling emacs that the
contents of verbatim environments are a kind of string which should be
highlighted using the verbatim face.  For that purpose, it has to tell
emacs where the "quotes" (delimiters) of that string are.  For that,
there's the "generic string fence" syntax class (|).  As an example, in

--8<---------------cut here---------------start------------->8---
\begin{lstlisting}
foo bar
\end{lstlisting}
--8<---------------cut here---------------end--------------->8---

the newline character after \begin{lstlisting} and the \ of
\end{lstlisting} have that |-syntax.  When the emacs encounters a char
with that syntax, it *toggles* string highlighting.

But that's just the simple case.  Many verbatim environments support
arguments which must start on the same line as the \begin{env} but which
may span many lines, e.g.,

--8<---------------cut here---------------start------------->8---
\begin{lstlisting}[o1=x,
                   o2=y]
foo bar
\end{lstlisting}

\begin{minted}[o1=x,
               o2=y]{language}
foo bar
\end{minted}
--8<---------------cut here---------------end--------------->8---

Of course, in these cases, the arguments shouldn't be fontified in the
verbatim face.  Therefore, the corresponding regular expression matches
\begin{<verbenv>} followed by optional and mandatory arguments, and the
char after the arguments gets the |-syntax.  But since it only skips
over arguments which are either enclosed in [] or {}, your example line

  \begin{lstlisting}+\only<2->{+[+\emph{options}+]+}+

is not recognized as something toggeling verbatim.  I think, that's
actually correct because

--8<---------------cut here---------------start------------->8---
\begin{lstlisting}foobar
\end{lstlisting}
--8<---------------cut here---------------end--------------->8---

is invalid, i.e., prints nothing.

So long story short: I think we can get either argument highlighting
right or we can get nested verbatim environments right but not both.
And since your use-case, i.e., documenting how to use verbatim
environments, is the only one which requires nested verbatim
environments, I think the current implementation which fontifies
arguments correctly, is more useful for the majority of users.

> Meanwhile, is it possible to stop a listing region highlight with some
> (magic) comments?

Yes, but not so easily.  You have to remove "lstlisting" from the
verbatim environments and then re-initiate font-locking.  You can do so
by writing a custom listings style and placing that in style/listings.el
(that path is relative to your master file; don't replace the existing
listings.el that ships with AUCTeX).

--8<---------------cut here---------------start------------->8---
(TeX-add-style-hook
 "listings"
 (lambda ()
   (setq LaTeX-verbatim-environments-local
         (remove "lstlisting" LaTeX-verbatim-environments-local))
   (font-latex-set-syntactic-keywords)
   (setq font-lock-set-defaults nil)
   (font-lock-set-defaults)))
--8<---------------cut here---------------end--------------->8---

However, you need the current Git master for that to work.  Until the
last commit, AUCTeX would have called your custom style hook before the
style hook that ships with AUCTeX.  Now I do that in reversed order, so
a local (or private) listings.el style runs after the global listings.el
style and may undo what the former did like we do.

Bye,
Tassilo