Re: VOTE: Changing completions-common-part face's default

[Dmitry Gutov <dgutov@yandex.ru>]

On 07.11.2019 17:08, Stefan Monnier wrote:

>> which brings back the main objection to using it for prefix completion.
> 
> To be honest, I'm not completely sure what is the main objection.
> I chose `blue3` so far because while noticeable it seems to me that it
> doesn't affect the overall legibility nor makes the first-diff
> less noticeable.

Excessive highlighting is something we've been normally avoiding in 
Emacs, for its distracting properties.

> So, yes, it's "useless" highlighting for basic/prefix-completion, but
> that's pretty much a given.  "useless" is compatible with "harmless".

That's also true.

>> I recognize others feel differently, though.
>> So if blue4 also works for your stated goal, which is
> 
> I could live with "blue4" but it's significantly less visible, so
> I think the only role it could play is to advertise the existence of the
> face, but nothing else: I expect that very few people who want to see
> the common-part (e.g. because they're using flex) will find it
> sufficient, whereas I suspect that `blue3` would be "good enough" for
> a non-negligible fraction of those users.

Like Joao said, blue4 will seem like a half-measure, and I generally 
don't support those. So while I'd prefer my first suggestion (wait until 
flex is used universally), I'd like to retract my personal objection here.

blue3 is a good enough color, and it fits the default theme. So unless 
we can agree on a better idea, and unless other people object, let's go 
with blue3 and call it a day.

> It is better than what we have, IMO, so I'm willing to "retreat" to
> `blue4` for this "first step" if you really think `blue3` harms the
> basic/prefix-completion case.

If we have more time to think on this, I'd try to consider how to better 
help the pcmpl/flex cases by using completions-first-difference on more 
characters instead. And/or adding an extra face for the other 
"non-matching" characters.

For "fabrobazor" example and input "foo",

"abr", "b" and "az" would be highlighted with that new face. And "r" 
still with first-difference.

Information-wise, the result should be the same as highlighting the 
common part.

Not quite sure what colors to use, though.