Re: [patch] ox-latex.el: Add `LATEX_PRE_HEADER' keyword

[Max Nikulin <manikulin@gmail.com>]

On 28/09/2023 22:36, AW wrote:
> 
> The idea to have a LATEX_PRE_HEADER to insert `\DocumentMetadata{}` is exactly
> what you need right now, if you export from orgmode to current LaTeX. With
> `\DocumentMetadata{}` you can add most of the necessary xmp data -- and I
> write most, because I'm using it on a daily basis, but haven't checked if
> really everything is included yet.

The question is if Juan Manuel can use \DocumentMetadata instead of the 
pdfx package in his workflow.

However there is a common part of \DocumentMetadata and .xmpdata usage. 
Currently Org mode allows to specify a very limited subset of metadata 
through keywords

#+language: en
#+author: Me
#+title: Statement

The advantage is that the same data are used by all export backends: 
LaTeX, HTML, etc. Specifying \DocumentMetadata literally without 
substitutions from Org keywords may cause diverged values. That is why I 
proposed to consider some kind of templates.

Another issue is extended metadata. I would consider an approach similar 
to header arguments for source code blocks:

#+property: header-args :eval never-export
for all languages
#+property: header-args:elisp :exports both :eval yes
overrides for emacs-lisp

Perhaps it is not reasonable to require to specify all metadata through 
Org keywords and it may be more convenient to combine raw LaTeX code and 
fragments generated by Org

#+name: preamble
#+begin_src latex :exports none :noweb yes
\DocumentMetadata{
   pdfstandard = a-2b
   <<ox-latex-template-document-metadata-entries>>
}
<<ox-latex-template-documentclass>>
<<ox-latex-template-usepackage>>
#+end_src

Access to keywords values during evaluation of source code blocks have 
to be implemented however.