Subject: Re: bug#78006: Improving `TeX-electric-math' behavior

From: "Paul D. Nelson" <[email-masked]>
Date: Thu, 24 Apr 2025 11:55:44 +0200

>   User Option: TeX-electric-math
>
>   In addition, when the variable is non-nil and there is an active
>   region outside math mode, typing $ will put around the active region
>   symbols for opening and closing inline equation and keep the region
>   active, leaving point after the closing symbol.  By pressing
>   repeatedly $ while the region is active you can toggle between an
>   inline equation, a display equation, and no equation.  To be precise,
>   ‘$...$’ is replaced by ‘$$...$$’, whereas ‘\(...\)’ is replaced by
>   ‘\[...\]’.
>
> Using $$...$$ in LaTeX is discouraged, so I think AUCTeX shouldn't
> promote this as well, so I suggest this change to
> `TeX-insert-dollar-electric-region':

Looks good to me overall.

One counterintuitive edge case: if I mark x and hit $ repeatedly, then I
get $x$ -> \[x\] -> x -> etc.  On the other hand, if I mark $x$ and hit
$, then I get $$x$$ -> $x$ -> etc.

I also wonder then whether TeX-insert-dollar (x2) should then similarly
insert $$|$$ or \[|\] according to mode?

Tangentially, I wonder whether this feature might be more useful if it
worked not just when operating on a region for the first time, but more
generally on any math region, as a way to cycle between inline and
displayed math.  I've had "make-inline" and "make-displayed" functions
in my config for a long time now that I've tried unsuccessfully to think
of an elegant way to package and contribute.