Re: BIKESHED: completion faces

[Eli Zaretskii <eliz@gnu.org>]

> From: João Távora <joaotavora@gmail.com>
> Date: Tue, 5 Nov 2019 19:16:00 +0000
> Cc: Stefan Monnier <monnier@iro.umontreal.ca>, Dmitry Gutov <dgutov@yandex.ru>, 
> 	emacs-devel <emacs-devel@gnu.org>
> 
> > The purpose of completion-first-difference is to help the user decide
> > what to type next.  
> 
> Indeed it does that. But there are equally efficient other ways to do the
> same, in my opinion.

If we have one efficient way, why do we need to consider others?

> One of them is to highlight the preceding character.

??? How does this help me to select what to type next?

> > What is the purpose of highlighting other parts of
> > the candidates? 
> 
> For a matching style such as flex or substring (as you would find in 
> many other editors) it's important to visually explain users to users
> why certain strings that don't start with the pattern they entered 
> are being shown on the screen.  I attach an image.

I don't see why it's important to explain how did the completion
algorithm arrive at a particular candidate.  The completion algorithm
is there to intuit what we mean in the most efficient way, but the
details of how it does that are immaterial.  The only ones who may be
interested are those who study completion algorithms ;-)

> completion-first-difference is at the very least a misnomer for
> other types of completion, because with flex there can be infinitely 
> many "first" differences. 

No, "first difference" is always the character to be typed after
point.  At least for the vastly important case that point is at the
end of what you typed, i.e. you don't move point back after typing
something.