Hi

I agree that this (C-p/C-n && <up> <down>) is the most intuitive in vertical and they shouldn't apply in non-vertical mode (cause <right> <left> is more intuitive then). C-s && C-r could do the same in both cases. For history navegation in vertical M-p and M-n could work fine.

If we want fido fully emulate ido; in the package ido-vertical there is something we could also provide somehow (maybe not exactly in the same way):

(defun ido-vertical-define-keys ()
(when ido-vertical-define-keys
(define-key ido-completion-map (kbd "C-n") 'ido-next-match)
(define-key ido-completion-map (kbd "C-p") 'ido-prev-match)
(define-key ido-completion-map (kbd "C-c C-t") 'ido-toggle-prefix))
(when (memq ido-vertical-define-keys '(C-n-C-p-up-and-down C-n-C-p-up-down-left-right))
(define-key ido-completion-map (kbd "<up>") 'ido-prev-match)
(define-key ido-completion-map (kbd "<down>") 'ido-next-match))
(when (eq ido-vertical-define-keys 'C-n-C-p-up-down-left-right)
(define-key ido-completion-map (kbd "<left>") 'ido-vertical-prev-match)
(define-key ido-completion-map (kbd "<right>") 'ido-vertical-next-match)))

-----Original Message-----
From: Kévin Le Gouguec <kevin.legouguec@gmail.com>
To: Dmitry Gutov <dgutov@yandex.ru>
Cc: Ergus <spacibba@aol.com>; emacs-devel@gnu.org <emacs-devel@gnu.org>; monnier@iro.umontreal.ca <monnier@iro.umontreal.ca>; Juri Linkov <juri@linkov.net>
Sent: Thu, Jun 18, 2020 10:22 am
Subject: Re: vertical fido-mode

Dmitry Gutov <dgutov@yandex.ru> writes:


> On 18.06.2020 00:50, Juri Linkov wrote:
>> Actually the hardest question is to decide what keys to use
>> to navigate completions in the vertical layout.  It would be
>> natural to use arrow keys and M-p/n, but there keys are used
>> for history navigation in the minibuffer.
>
> I think C-n/P-n is what users would expect. See Ivy, Helm, etc.
>
> Arrow keys, too.


As a former Ivy user who went back to icomplete and is now following
this thread with a lot of attention, my vote also goes for C-n/C-p for
next/previous candidate selection, and M-n/M-p for history navigation.

(Actually, I wouldn't mind C-n/C-p in regular (non-vertical) icomplete;
C-. is not super-ergonomic on AZERTY.  I liked C-M-i, but it's been
decommissioned in Emacs 27…)