Re: Using org-latex-preview in other major modes

[Karthik Chikmagalur <karthikchikmagalur@gmail.com>]

Hi Tony,

Just tried it out, it's very promising!  Thanks for taking the initiative
on this.

> I've prodded the code a little bit and, mostly just following [1],
> managed to implement basic previews in a relatively straightforward
> fashion. Attached is a proof-of-concept—aptly named
> latex-latex-preview.el :) The main user facing functions so far are
> 'latex-latex-preview' to preview the maths fragment at point, and
> 'latex-latex-preview-region' to preview all fragments in a region. Both
> functions currently ignore things like numbered equations and
> environments, though both do not seem exceptionally difficult to add
> back in.

There are two issues with numbering:
- providing an Org-agnostic API point to attach a numbering table to, and
- calculating the new numbering table in LaTeX (or other major-modes).

For The first issue, we need a way to provide an updated numbering table
during the auto-regeneration of edited fragments.  Currently this is
done implicitly by calling `org-latex-preview--place-from-elements' from
the `--regenerate-overlay` function.

The second requires fast numbering table updates.  We do it in Org by
mapping over the org-element cache (see
`org-latex-preview--get-numbered-environments').  Even this is too slow
sometimes, so we suspend numbering updates when live-previewing until
the cursor exits the fragment.  Parsing the LaTeX buffer from point to
the end when (re)generating each preview is going to be too slow, so
you'll have to create some kind of cache and update it incrementally.

> There's also a stub 'latex-latex-preview-auto-mode' minor mode. Stepping
> in and out of already rendered environments works fine, with the preview
> being regenerated if needed; only the implementation of
> 'org-latex-preview-auto--regenerate-overlay' had to change for that.

This was a pleasant surprise, I was expecting more trouble here.

> The mode does not currently feature live-previews. The innards of
> 'org-latex-preview-auto--detect-fragments-in-change' and
> 'org-latex-preview-live--setup' look a bit more org-specific, with
> queries to 'org-element-*' functions all over the place, but all of
> that looks fixable—at least from afar. I will continue prodding the
> code a little bit and will report back with any bumps that are hit
> along the way.

`org-latex-preview-auto--detect-fragments-in-change' is written for
speed. It only does quick text-matching and is thus mostly Org-agnostic,
except for a call to a numbering calculation near the end.  This should
be easy to adapt.  The problem is the function it calls,
`org-latex-preview-auto--maybe-track-element-here', which finds the
bounds of the inserted LaTeX fragment using org-element and
conditionally sets up a preview overlay.  You will need an equivalent of
this for LaTeX-mode.

Since you have auto-mode working already, live previews should be quite
easy to add.  From what I can see, you only need to provide your own
`org-latex-preview-live--ensure-overlay'.  This function creates the
preview overlay next to or under the LaTeX fragment.  All the other live
preview code only changes overlay properties or calls
`--regenerate-overlay`, which you've already implemented.

Karthik