Re: org-export-current-backend variable and org-mode 8

[Christophe Rhodes <csr21@cantab.net>]

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Brett Viren <bv@bnl.gov> writes:

> Christophe Rhodes <csr21@cantab.net> writes:
>
>> In org-mode 7, I was able to use the (documented) variable
>> org-export-current-backend to test what the current backend is, allowing
>> me to dynamically produce and include images of different formats
>> depending on whether I was exporting to latex (tikz) or html (png).
>>
>> In org-mode 8, I cannot find this variable, or any documented variable
>> of a similar nature.  What is the recommended way for dispatching at the
>> emacs-lisp level when exporting a document on the export backend?
>
> I don't know if this is exactly what you are asking for but I hit on the
> following a few weeks ago.  It defines an elisp macro inside the org
> file and then calls it later in the header of a code block to switch the
> output file names based on which backend (if any) is in effect.  I hope
> it helps.

Thanks.  Well, it proves at least that I'm not going mad :-(

> If you have a better way to do these kind of output switches, I'd like
> to know.

> #+begin_src emacs-lisp :results silent
>   (defmacro by-backend (&rest body)
>     `(case (if (boundp 'backend) backend nil) ,@body))
> #+end_src

It's funny -- I felt queasy using the bare backend variable in the olden
6.x days, and was very happy when org-export-current-backend showed up.
Now, there's a real reason to be worried about using backend: it's
fairly clearly used as an internal variable, and all it would take would
be for lexical binding to be turned on for ox.el and this would
(probably) stop working.

If we're grubbing around in internals, I might be tempted instead by
something like [untested]

#+begin_src emacs-lisp :exports results :results silent
  (unless (boundp 'org-export-current-backend)
    (defadvice org-export-as (around oecb-around)
      (let ((org-export-current-backend (ad-get-arg 0)))
        ad-do-it)))
#+end_src

so that if (as I hope) org-export-current-backend makes a later
reappearance, my documents can work with both org-mode 7 and 8, and
maybe 9?  I'm hoping that the disappearance of the variable is an
oversight rather than intentional :-/

Cheers,

Christophe

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