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

[João Távora]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Augusto Stoffel <arstoffel@gmail.com>
>> Cc: joaotavora@gmail.com,  61726@debbugs.gnu.org
>> Date: Sat, 25 Feb 2023 15:14:06 +0100
>> 
>> On Sat, 25 Feb 2023 at 15:47, Eli Zaretskii wrote:
>> 
>> >> > 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.
>>          ^^^^^^^
>
> Sorry.  Here:
>
>   (defun eglot-move-to-bytewise-column (column)
>     "Move to COLUMN as computed using the LSP `utf-8' criterion."
>     (let* ((bol (line-beginning-position))
>          (goal-byte (+ (position-bytes bol) column))
>          (eol (line-end-position)))
>       (goto-char bol)
>       (while (and (< (position-bytes (point)) goal-byte)
>                 (< (point) eol))
>       (if (>= (char-after) #x3fff80)  ; raw bytes take 2 bytes in the buffer
>           (setq goal-byte (1+ goal-byte)))
>       (forward-char 1))))

In eglot-move-to-lsp-abiding-column (the utf-16 sibling of this
function) we use a binary search instead of a linear search.  I remember
measuring a visible improvement.  I'm not sure the conditions are
exactly the same with this one.  Could/should we do the same here?

João