bug#61726: [PATCH] Eglot: Support positionEncoding capability

[Eli Zaretskii]

> From: Augusto Stoffel <arstoffel@gmail.com>
> Cc: joaotavora@gmail.com,  61726@debbugs.gnu.org
> Date: Sat, 25 Feb 2023 12:29:02 +0100
> 
> On Sat, 25 Feb 2023 at 12:57, Eli Zaretskii wrote:
> 
> >> From: Augusto Stoffel <arstoffel@gmail.com>
> >> Cc: joaotavora@gmail.com,  61726@debbugs.gnu.org
> >> Date: Fri, 24 Feb 2023 19:08:14 +0100
> >> 
> >> I also didn't attempt to make 'eglot-move-to-bytewise-column' and
> >> 'eglot-bytewise-column' "correct" in the cases where 'json-serialize'
> >> throws an error.  I think it's clear that Eli and I have different
> >> definitions "correctness" in this context, but Eli's proposal requires
> >> substantial further work, including recovering from possible errors
> >> raising from 'json-serialize'.
> >
> > No, it doesn't.  All I'm asking for is to use encode-coding-string or
> > encode-coding-region to measure the actual number of bytes in a UTF-8
> > sequence that corresponds to a region of text.  Nothing else is
> > required or requested.
> >
> > Can you please humor me and implement eglot-bytewise-column like that?
> 
> I would be glad to do that, but unfortunately I'd have to ask your
> advice as to how to make the corresponding adaptation of
> eglot-move-to-bytewise-column.

Instead of this:

  (defun eglot-bytewise-column ()
    "Calculate current column using the LSP `utf-8' criterion."
    (- (position-bytes (point)) (position-bytes (line-beginning-position))))

use this:

  (defun eglot-bytewise-column ()
    "Calculate current column using the LSP `utf-8' criterion."
    (length (encode-coding-region (line-beginning-position) (point)
             'utf-8-unix t)))