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

[Eli Zaretskii]

> From: Augusto Stoffel <arstoffel@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  61726@debbugs.gnu.org
> Date: Fri, 24 Feb 2023 12:01:48 +0100
> 
> On Fri, 24 Feb 2023 at 10:20, João Távora wrote:
> 
> > The second thing I don't like is also due to the late-binding idea.
> > This is a hotspot in Eglot, some of these functions are called
> > many many times, for each LSP server interaction depending
> > on how many document positions are exchanged (and they can
> > be a lot).  I do remember benchmarking strategies at the time
> > and seeing a perceptible difference.  Plus, this late-binding is
> > really useless as a server will guaranteedly _not_ change its
> > column-counting standard during the LSP session.
> 
> `eglot-lsp-abiding-column' allocates a new string!

If that is a concern, eglot.el could use a private temporary buffer
into which the encoded text is inserted, eliminating the need to call
'length'.  The impact of that in performance should be measured, of
course, to make sure it doesn't make code slower; it will definitely
improve the GC pressure aspect.