RE: What is the most useful potential feature which Emacs lacks? A: Autocompletion

[Drew Adams]

> Lack of such simple but immensely useful feature
> is so disappointing

FWIW -

Icicles lets you control what you call autocompletion,
and what Icicles calls incremental completion, in a
few ways.

This page explains it:

https://www.emacswiki.org/emacs/Icicles_-_Icompletion#IncrementalCompletion

Option `icicle-incremental-completion' is the main
on/off control.

Options `icicle-incremental-completion-delay',
`icicle-incremental-completion-threshold', and
`icicle-show-completions-initially' determine
when it kicks in.

But one size doesn't fit all.  Different sets of
completion candidates (e.g. domain size), and
different kinds of completion, imply different
fits, in terms of such option values.

A given command that uses completion knows its
candidates domain and the kind(s) of completion.
It can bind such options to values that provide
appropriate default behavior for that command.

But just as importantly, you can change the
option values interactively, while completing:
increase or decrease the delay or threshold,
for example, or change the general on/off
behavior.

To me, easy user control is the most important
thing for such a feature.  A command knows what
kind of completion it's dealing with, but only
a user knows just what s?he wants/needs, during
any given invocation of a command that uses
completion.