Re: Overlays as an AA-tree

[Eli Zaretskii <eliz@gnu.org>]

> From: Joakim Jalap <joakim.jalap@fastmail.com>
> Date: Wed, 23 Nov 2016 08:16:05 +0100
> 
> Evgeny Roubinchtein <zhenya1007@gmail.com> writes:
> 
> > This is really exciting work.
> >
> > I realize this is a politically-charged issue, but would it be
> > possible to reuse some of the design (if not the code) from XEmacs
> > extents?
> 
> It is not politically charged for me :) I have never used XEmacs, but I
> will have a look at the 'extents' feature. However, what I'm trying to
> do is just to change the underlying implementation, not change how
> overlays behave.
> 
> But I will have a look at extents, thanks for the tip!

Beware: we cannot use their code due to copyright issues, so it's
probably not wise to look at the code there.  Reading extents.texi in
the lispref/ directory is what I'd recommend.

I actually don't understand the request: what is meant by "design"
here?  If there are some features we lack in the overlays, then
corresponding feature requests (better yet, patches) would be
appreciated.  After reading extents.texi, I don't see any significant
features missing, except the ability to copy overlays with the text
(which AFAIR XEmacs implements somewhat inconsistently, as only some
of the primitives that process text support that).  Is there something
else?