Re: AUCTeX and "builtin latex mode" integration

[Ikumi Keita]

Hi Stefan,

>>>>> Stefan Monnier <monnier@iro.umontreal.ca> writes:
> You may have seen an on-going discussion about the annoyance of the
> mixups between latex-mode and LaTeX-mode and such.

Could you tell us where that discussion takes place?

> I do think it would be good to try and "integrate" the two modes, for
> some definition of "integrate".  The question being indeed what
> "integration" is the best way forward.

I also want some improvements with regard to the "integration" because I
recently realized that emacs built-in `tex-mode' (accidentally?) shadows
AUCTeX `TeX-tex-mode' since emacs 28.1, to fail to enter LaTeX mode for
some cases[1][2]. (I'm not sure that the above discussion involves this
issue.)

[1] thread beginning with
https://lists.gnu.org/r/auctex/2022-08/msg00001.html
[2] 
https://tex.stackexchange.com/questions/648955/auctex-inconsistent-behavior-tex-vs-latex

> I'm wondering if it would be possible to turn AUCTeX into a minor mode.
> E.g. `LaTeX-mode` would then be redefined as

>     (define-derived-mode TeX-latex-mode latex-mode ...
>       (AUCTeX-mode 1))

> and `TeX-modes-set` would add/remove `AUCTeX-mode` from the hooks like
> `latex-mode-hook`.

It basically looks reasonable. I assume that you are thinking that
`AUCTeX-mode' actually chooses suitable behavior according to the value
of `major-mode' between `latex-mode', `plain-tex-mode', `doctex-mode'
and `texinfo-mode'.

> There's no doubt that it would introduce some (presumably minor or
> easy to fix) breakage in some corner cases for some exotic configs, of
> course, but I feel like in the long run it might be worth it.

+1

Here are some random thoughts.
1. There will be some overheads because it first runs initialization
codes of emacs built-in mode and then runs AUCTeX minor mode; I expect
that the associated cost is cheap enough.
2. AUCTeX still must retain some major modes, i.e., ConTeXt mode,
AmS-TeX mode, Japanese LaTeX mode and Japanese plain TeX mode because
there are no counterparts in emacs built-in modes.
3. Currently, there is defect in handling doc strings of AUCTeX LaTeX
mode, plain TeX mode and docTeX mode; C-h m and C-h f show doc string
of built-in modes, not AUCTeX modes. `AUCTeX-mode' should put suitable
`function-documentation' property for the respective major mode symbol.
4. `TeX-tex-mode' and `tex-mode' would need some special treatment.

> To be honest, I haven't looked very much at the code to see how
> realistic this is, but I think this could help clarify the situation
> for users. E.g. it would eliminate "lies" such as (setq major-mode
> 'latex-mode) in `latex.el`.

From the users' point of view, I don't think it matters much. They just
specify
%%% mode: latex
as the file local variable and think that they are using `latex-mode'.
I think that it would be only Elisp programmers that care about the
"lies".

Best regards,
Ikumi Keita
#StandWithUkraine #StopWarInUkraine