RE: [External] : Re: Question about completion behavior

[Drew Adams]

> configure the Initial line in the Completions buffer
> ... add a sort of counter there to indicate the
> total number of candidates

I assume you mean the current number of candidates,
i.e., the matches of your current minibuffer input.
(For empty input this is the number of candidates
in the matching domain, i.e., all-completions.)

A better place for such a count, IMO, as well as
for other info about the current completion state
(completion style/mode, sort order etc.), is the
_mode-line_ of the `*Completions* window.

That's what Icicles does.  (In Icicles you can
change things like completion style/mode, and
sort order on the fly, and their defaults can be
configured per command.)

E.g., `M-x forw TAB' might show you this in the
*Completions* mode-line:

 18 candidates, vanilla completion, sorting alphabetical (reversed)
 ^^^^^^^^^^^^^

(Plus other completion status info.)

You can limit the number of candidates displayed,
in which case, e.g., "142 candidates shown/3247",
meaning that you're shown 142 out of 3247 total.

And (by default) when cycling, the *Completions*
mode-line briefly shows you short help about the
current candidate (it then returns to showing the
current general completion status).

E.g. `M-x forw TAB', with candidate `forward-char'
current (which means highlighted in *Completions*
and present in the minibuffer), briefly shows the
first line of its doc string:

 Move point N characters forward (backward if N is negative)

And `C-x C-f' foo TAB', might show this briefly
for the current file-name candidate:

 Bytes: 10083, Saved: 1/14/2022 12:52:46 PM, Access: 3/12/2022 11:05:27 AM, 
Perm: -rw-rw-rw-

More info about what's shown:

https://www.emacswiki.org/emacs/Icicles_-_Completions_Display#CompletionsModeLine