Re: emacs-27 027da65: Fix display of minibuffer prompt in ido.el

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: emacs-devel@gnu.org,  Eli Zaretskii <eliz@gnu.org>
> Date: Thu, 13 Feb 2020 18:39:40 -0500
> 
> >> +@item minibuffer-message
> >> +@kindex minibuffer-message @r{(text property)}
> >> +This text property tells where to display temporary messages in an
> >> +active minibuffer.
> >
> > TBH, I'm wary of documenting this variable in the manual, since we might
> > prefer to do away with it later, if a sufficiently stable fix for the 
> > overlay-based solution is found.
> 
> I tend to agree.

I don't, at least not for the reasons described by Dmitry.  Display of
overlay strings is quite messy, especially at EOB; it already causes
quite a few complex and sometimes inelegant code fragments in the
display engine, in particular related to cursor positioning.  So
anything that allows us to avoid using overlay strings, and simply
insert text into a buffer, is a win from my POV.

And using a special text property to guide display (and other
important features) is a technique we use elsewhere in Emacs.
Granted, we don't always document such text properties, but in this
case, we are talking about an area where quite a few external packages
tend to offer all kinds of add-ons and improvements, so I thought it
was important to document it, so that they could play well with the
new set-message-function feature.

That said, if you (or someone else) have other good reasons we would
like not to publish this property, which are stronger than the
considerations that led me to document it, I'm all ears.

Thanks.