Re: New multi-command facility displays in the wrong echo area.

[Gregory Heytings via "Emacs development discussions." <emacs-devel@gnu.org>]

>
> Thanks.  So I think your change is a definite improvement, and I 
> therefore installed it on the emacs-27 branch.
>

Thank you.  Alas, it's not the only bug of this new feature.  A recipe:

emacs -Q
(progn
   (set-frame-width nil 80)
   (setq max-mini-window-height 1)
   (setq default-directory (concat "/" (make-string 67 ?a)))
   (call-interactively 'find-file))
press C-x o
press C-s

At this point you see no indication that I-search has been started.  (If 
you look close enough, the only thing you can see is a curly arrow in the 
right fringe of the miniwindow.)  Likewise, if you press C-x C-s, you see 
no indication that changes have been saved (or not).  And so forth.

I suggest the following fourth condition in set-minibuffer-message:

(< (buffer-size (window-buffer (active-minibuffer-window))) (/ (frame-width (window-frame (active-minibuffer-window))) 2))

Of course it's a heuristic (it could still fail when the face used in the 
miniwindow is different, and larger than, the default face), but it should 
catch 99.99% of the remaining error cases.

It is amazing that such a feature got accepted, was included in an 
official Emacs release, and became Emacs' default behavior, without even 
trying the two obvious cases to test: what happens when there is not 
enough free space in the minibuffer? and what happens when the active 
minibuffer is not on the same frame?

It is even more amazing that, at the same time, my proposed solution to 
display completion candidates in the minibuffer is rejected on the grounds 
that it could cause "potential problems", when so far no one has managed 
to show a case in which it would create an actual problem.