Re: Introducing face in comments for various modes

[Thibaut Verron]

On 13/12/2022 10:46, Heime wrote:
> ------- Original Message -------
> On Tuesday, December 13th, 2022 at 9:35 AM, Thibaut Verron 
> <thibaut.verron@gmail.com> wrote:
>
>
> > 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 ;; .
> How can one specify two comment characters next to each other?

Using the variable, the same way you would normally do for a regexp, by 
putting \{2\} after the matched regexp.

E.g.

ELISP> (format "\\(%s\\)\\{2\\}" comment-start)
"\\(;\\)\\{2\\}"

(don't trust me for the number of escape characters)

But I don't think it's really what you want: for example, in a mode 
where comment-start is "# " (e.g. org or python), this will match "# # " 
but not "##".

Using the syntax table is better here, as the character # alone has the 
syntax of a comment-start.

I had forgotten about the simplest option, that is the regexp equivalent 
of the rx syntax: \s< in a regexp will match exactly a character with 
the syntax of a comment-start.

So: "\s<\{2\}" should be exactly what you want (at least in languages 
where comments start with a single character).