Latex export: Differing behavior for symbols in headlines

Latex export: Differing behavior for symbols in headlines

[Richard Lawrence]

Dear Orgsters,

I am seeing differing behavior for how special symbols that appear in a
headline are exported to LaTeX, depending on whether I export an entire
Org document or just the current subtree.

I have, for example, a file that looks like this:

* Headline 1
** Headline 2, concerning $\alpha$ and $\beta$

If I export the whole document, the $'s around \alpha and \beta are
properly interpreted as math-mode delimiters, and Headline 2 becomes a
section title that looks exactly as I would expect.

If I export just Headline 2, however, the $'s are escaped, and show up
as literal '$' characters in the title of the exported document.

(I can't remove the $'s, because I am actually using some custom LaTeX
commands, not special symbols like \alpha and \beta that Org would
recognize as needing to be put in math mode.)

So, two questions:

1) Is this difference between whole-document vs. current-subtree export
the expected behavior?

2) If so, what's the right way to work around it?  If not, where should
I look to try and fix it?

(I am running the latest development version of Org.)

Thanks!

Best,
Richard

Re: Latex export: Differing behavior for symbols in headlines

[Nick Dokos]

Richard Lawrence <richard.lawrence@berkeley.edu> wrote:

> Dear Orgsters,
> 
> I am seeing differing behavior for how special symbols that appear in a
> headline are exported to LaTeX, depending on whether I export an entire
> Org document or just the current subtree.
> 
> I have, for example, a file that looks like this:
> 
> * Headline 1
> ** Headline 2, concerning $\alpha$ and $\beta$
> 
> If I export the whole document, the $'s around \alpha and \beta are
> properly interpreted as math-mode delimiters, and Headline 2 becomes a
> section title that looks exactly as I would expect.
> 
> If I export just Headline 2, however, the $'s are escaped, and show up
> as literal '$' characters in the title of the exported document.
> 
> (I can't remove the $'s, because I am actually using some custom LaTeX
> commands, not special symbols like \alpha and \beta that Org would
> recognize as needing to be put in math mode.)
> 
> So, two questions:
> 
> 1) Is this difference between whole-document vs. current-subtree export
> the expected behavior?
> 
Looks like a bug to me. I can reproduce it too.

> 2) If so, what's the right way to work around it?  If not, where should
> I look to try and fix it?
> 

I tried using \( and \) as the inline math delimiters but that did not
work either: I got $ signs *inserted* and then latex complains about that:

foo.org:
--8<---------------cut here---------------start------------->8---
* Headline 1
** Headline 2, concerning \(\alpha\) and \(\beta\)
--8<---------------cut here---------------end--------------->8---

foo.tex (elided):
--8<---------------cut here---------------start------------->8---
...
\title{Headline 2, concerning \($\alpha$\) and \($\beta$\)}
...
--8<---------------cut here---------------end--------------->8---

Nick

Bug: Re: Latex export: Differing behavior for symbols in headlines

[Richard Lawrence]

Nick Dokos <nicholas.dokos@hp.com> writes:

>> 1) Is this difference between whole-document vs. current-subtree export
>> the expected behavior?
>> 
> Looks like a bug to me. I can reproduce it too.

Was my original email enough to constitute a bug report?  

>> 2) If so, what's the right way to work around it?  If not, where should
>> I look to try and fix it?
>> 

I'm still wondering about the latter question here.  This is important
enough to me that I am willing to take a stab at fixing it, but my Elisp
experience is basically limited to init file customizations.  Can anyone
who knows the ins and outs of the LaTeX export code give me a few
pointers about where to start?

Thanks,
Richard

Re: Bug: Re: Latex export: Differing behavior for symbols in headlines

[Richard Lawrence]

Richard Lawrence <richard.lawrence@berkeley.edu> responds to himself:

>>> 2) If so, what's the right way to work around it?  If not, where should
>>> I look to try and fix it?
>>> 
>
> I'm still wondering about the latter question here.  This is important
> enough to me that I am willing to take a stab at fixing it, but my Elisp
> experience is basically limited to init file customizations.  Can anyone
> who knows the ins and outs of the LaTeX export code give me a few
> pointers about where to start?

OK, I've been reading the code in org-latex.el for a while now, and I
have at least come to understand why $'s in a headline are escaped when
the export is restricted to a subtree.

The explanation is this: within org-export-as-latex, the headline is
bound to `title', and passed to org-export-latex-make-header, which in
turn passes the value into org-export-latex-content, thusly:

;; org-latex.el, line 1283

     (format
      "\n\n\\title{%s}\n"
      ;; convert the title
      (org-export-latex-content
       title '(lists tables fixed-width keywords)))

org-export-latex-content works by performing a series of mutations on a
temporary buffer.  One of these mutations,
org-export-latex-special-chars, replaces "$" with "\$".  So that's
where the replacement is happening when the headline of a subtree is
used as the title for a LaTeX export.

(Actually, this begs the question: how should one export an Org file to
LaTeX if part of the title should be in math mode?  Is escaping $'s in
the document title really the best behavior?  My guess would be that
people need math mode in their document titles far more often than they
need a literal "$".)

Here's what I don't understand yet: when the entire Org file is
exported, rather than just a subtree, the headlines (which eventually
become the section titles in the output) are apparently *not* processed
this way, because then the $'s in such headlines pass through unescaped.
I'm not sure if this is because they never pass through
org-export-latex-content, or because $'s have had the org-protected
property set by the time they *do* pass through it.

Guidance would be much appreciated!

Best,
Richard

Re: Bug: Re: Latex export: Differing behavior for symbols in headlines

[Giovanni Ridolfi]

Richard Lawrence <richard.lawrence@berkeley.edu> writes:

Hi, Richard,

> Nick Dokos <nicholas.dokos@hp.com> writes:
>
>>> 1) Is this difference between whole-document vs. current-subtree export
>>> the expected behavior?
>>> 
>> Looks like a bug to me. I can reproduce it too.
>
> Was my original email enough to constitute a bug report?  

Well, a week ago Carsten wrote[1]:

"Org-mode will never be a perfect TeX scanner, and this is really hard.
 Help yourself and Org by using \( and \) as math delimiters [...] "

How about:

* Headline 1
** Headline 2, concerning \(\alpha\) and \(\beta\)

that will be exported as:

\title{Headline 2, concerning \($\alpha$\) and \($\beta$\)}

cheers,
Giovanni

[1] http://lists.gnu.org/archive/html/emacs-orgmode/2010-10/msg00981.html