Re: [possible patch] Basic fontspec code for LuaLaTeX and XelaTeX (was "LaTeX export: when is it more useful...")

[Timothy]

Hi Ihor & co.,

> As I recall, Timothy has been working on simplifying preamble
> generation. If we do not put unnecessary packages into preamble,
> compilation will be significantly faster.
>
> If Timothy can come up with a patch some time soon, I’d prefer to have a
> more targeted preamble. Otherwise, the proposed approach is the way to
> go.

Yep, I’ve got something in my config currently that intercepts LaTeX preamble
creation and generates it only the fly from a list of detected features based on
the exported document and capability providers. I use this in my config to
automatically switch to LuaLaTeX when necessary and use pdfLaTeX the rest of the
time.

This should also be able to be able clean up some of the currently kludgy
preamble modifications like in oc-csl.el.

This has been on the back-burner for a while (I want to implement this is a way
that can be generalised across all output backends), but I’ll see if I can make
some progress and hopefully have a preliminary patch set in the next few weeks.

Lastly, there’s something extra I want to note. If we talk about including a
font customisation, I’d advocate for supporting font sets, not fonts. Once
again, this is something I’m a fan of from my config, and this could potentially
be supported across multiple export formats.

As an illustrative example, if I include this in one of my documents and create
a PDF:
┌────
│ #+options: fontset:biolinum
└────

Then I’ll get text with:
⁃ libertine roman as the serif font
⁃ biolinum as the serif, and default, font
⁃ source code pro as the mono font
⁃ newtxmath as the maths font

Similarly I can do `fontset:noto' and you can guess what that does.

All the best,
Timothy