Re: setting export_file_name during export

[Leo Butler <Leo.Butler@umanitoba.ca>]

On Tue, Jan 10 2023, Nick Dokos <ndokos@gmail.com> wrote:

> Leo Butler <Leo.Butler@umanitoba.ca> writes:
>
>>>
>>> So: if you insert 
>>>
>>>   :PROPERTIES:
>>>   :EXPORT_FILE_NAME: lecture-1.pdf
>>>   :END:
>>>
>>
>> Aha! Thank you very much. I had forgotten about using property
>> drawers. It would be a simple matter to create a filter to insert that
>> property drawer under the heading that contains point.
>>
>
> IIUC, you really don't need to insert things dynamically: you can add
> an appropriate property drawer after every top-level heading once and
> for all.

Yes, you are correct. And, in fact, the naïve way to insert the property
dynamically (using ~org-export-before-processing-hook~) does not work:

#+name: does-not-work
#+begin_src emacs-lisp :exports none
  (defun ltb-org-insert-export-file-name (backend)
    (save-excursion
      (goto-char (point-min))
      (while (search-forward-regexp "^[*] Lecture \\([0-9]+\\)" nil t)
	(forward-line 1)
	(let ((num (match-string 1)))
	  (unless (looking-at "^:PROPERTIES:")
	    (let ((pty (format ":PROPERTIES:\n:EXPORT_FILE_NAME: lecture-%s.pdf\n:END:\n" num)))
	      (insert pty)
	      (message (buffer-substring-no-properties (point-min) (point-max)))))))))
  (add-hook 'org-export-before-processing-hook 'ltb-org-insert-export-file-name)
#+end_src

The property drawer is ignored, presumably because org has already
scanned the file and determined the filename. I guess one would need to
reach inside the document structure and alter the filename there, but I
don't have that knowledge.

Suggestions are welcome.

Leo