bug#26513: 25.2; pop-up-frames and *Completions* buffer

[charles@aurox.ch (Charles A. Roelli)]

On Sat, Apr 15 2017 at 09:49:28 am, Drew Adams wrote:

> FWIW, I reported such problems a couple of decades ago.
> Unfortunately (for me at least), there is not enough
> use or interest in using separate frames by default,
> including for *Completions*, so this kind of thing has
> not gotten the love it would really need for progress.

Maybe it's time for some change?  :-)  Especially in light of the
boatload of new frame stuff that was added recently (thanks to Martin
for that).

> I've tried to do what I can in my own environment to
> handle this, especially in the context of a standalone 
> minibuffer frame.  And Martin has been helpful wrt
> problems that resulted from changes in the Emacs code
> over the years.
>
> Here's what I do for *Completions*, FWIW:
>
> I add an entry to `special-display-buffer-names* that
> has a function, `1on1-display-*Completions*-frame',
> which takes care of displaying the *Completions* frame.
>
> The main thing that function does is redirect the
> focus of the *Completions* frame to the standalone
> minibuffer frame (if the minibuffer is active) or
> (if not) to the buffer that was current before
> *Completions* display was requested:
>
> (let ((redirect
>        (if (active-minibuffer-window)
>            1on1-minibuffer-frame
>          (and completion-reference-buffer
>               (get-buffer-window
>                 completion-reference-buffer 'visible)
>                 (not (eq (get-buffer "*Completions*") 
>                          completion-reference-buffer))
>                 (window-frame
>                   (get-buffer-window
>                     completion-reference-buffer t))))))
>       (when redirect
>         (redirect-frame-focus (selected-frame)
>                               redirect)))

1) Does this still work without a standalone minibuffer frame?  I'm
   interested in using one, but I'd rather fix the *Completions* frame
   problem first before adding on a minibuffer-only frame to my setup.
2) I don't understand why vanilla Emacs puts the *Completions* buffer in
   focus when it's popped into a new frame -- but I know that this is
   the reason you have to redirect the focus from *Completions* to the
   minibuffer or the completion-reference-buffer frame.  On Mac OS,
   though, redirecting frame focus results in a lot of flicker and lag
   on each keypress -- sometimes up to a second or two long.  (Will save
   the rest for another bug report someday.)  Wouldn't a simpler
   alternative to frame redirection be to just put point back in the
   minibuffer or completion-reference-buffer?

> I've said it before, but I think it is relevant:
> Back in the early 1990s the Emacs implementation
> named `Epoch' worked very well with a standalone
> minibuffer frame, out of the box.
>
> All I've done is try to work around Emacs's poor
> (non-existent) support for this kind of use case -
> essentially trying to emulate Epoch behavior.

Standalone minibuffer frames are meant to work correctly almost out of
the box, though, right?  (IIRC you just have to fiddle with
`initial-frame-alist' to remove the minibuffer from the first
frame).  It's only when *Completions* is displayed in a separate frame
that there are issues.

> But frames remain the poor cousin to windows in
> Emacs.  Part of that is likely due to the fact that
> Emacs cannot completely control the behavior of
> frames for all window managers.  Window mgrs are
> different, and they have ultimate control.

Yes, this seems like it's the main issue here.  But still, sane frame
behavior doesn't seem too far off.