Re: Introducing face in comments for various modes

[Thibaut Verron <thibaut.verron@gmail.com>]

On 13/12/2022 09:30, Heime wrote:
> ------- Original Message -------
> On Tuesday, December 13th, 2022 at 8:04 AM, Heime <heimeborgia@protonmail.com> wrote:
>
>
>> ------- Original Message -------
>> On Tuesday, December 13th, 2022 at 7:52 AM, Jean Louis bugs@gnu.support wrote:
>>
>>
>>
>>> Heime, I like the idea of highlighting comments, though I do it this
>>> way to specify (syntax comment-start) as that works for multiple
>>> modes.
>>>
>>> ; one
>>> ;; two
>>> ;;; three
>>> ;;;; and more
>>>
>>> ;;; Highlighting comments
>>>
>>> (setq rcd-regexp-comment (rx line-start
>>> (one-or-more (syntax comment-start))
>>> (one-or-more space)
>>> (group (one-or-more not-newline))
>>> line-end))
>>>
>>> ;; (highlight-regexp regexp nil 1)
>>> ;; (unhighlight-regexp regexp)
>>>
>>> Jean
> I would like to introduce (syntax comment-start) in place
> of ";;" in "^;;\s+\\[.+\\].*$".

It's not something you can "introduce" in your regexp, it only makes 
sense within the context of a regexp built with rx: 
https://www.gnu.org/software/emacs/manual/html_node/elisp/Rx-Notation.html

Rewriting your regexp as an rx regexp would not be too difficult if you 
want to go that route, Jean's example is a good template.

Otherwise, as an approximation of that feature, you could built your 
regex string using the value of the variable comment-start ( ";" in 
emacs-lisp-mode) instead of hardcoding ;; .

To be clear, the variable comment-start happens to have the same name as 
the symbol in (syntax comment-start), but they are not the same thing, 
the syntax classification can in theory be a lot smarter than simply 
regexp matching.