bug#48545: 28.0.50; `icomplete-vertical-mode` does not support the `group-function`

[João Távora]

Dmitry Gutov <dgutov@yandex.ru> writes:
> On 19.08.2021 14:18, João Távora wrote:

>> completion-all-sorted-completions in minibuffer.el if a table supplies
>> `group-function`.  A patch for this is after my sig.
>
> We discussed this problem when group-function was introduced. Another
> approach is to just change the method of grouping: first the
> completions are sorted, and then they are sorted into groups.

That's a possiblity. But it might be performing too much work, at least
at first sight.  For the C-x 8 RET case and the xref table (the only
tables I know which use this) things seem to be naturally put into
groups already.  So sorting them alphabetically, by length, by history,
and _then_ destroying most (but not all) with the grouping could be not
so interesting if the there's a big a price to pay.

I recommend whatever is done that some quantitative benchmarking is
performed to the before/after.  Enabling fido-vertical-mode and pressing
C-u C-x C-e C-m after

   (benchmark-run (call-interactively 'insert-char))

Seems to be a decent way to measure.

Currently, with the alpha/length/history sorting, it takes about 1
second in my machine.  Without any sorting (and the natural grouping),
takes about 0.6 seconds.  You should measure what the re-grouping
sorting does.

João