Re: BIKESHED: completion faces

[Dmitry Gutov <dgutov@yandex.ru>]

On 05.11.2019 0:52, João Távora wrote:

> I don't agree with this reasoning at all.  First I think we agree Emacs
> would profit (in influx from users) from defaults that make it behave
> less like 90's Emacs and more like other younger editors.  However we
> also know that we can't just change the defaults without bothering
> users already relying on those defaults.

We agree, yes. Although I'm more in favor of changing the defaults, as 
soon as the kinks are worked out (e.g. flex is a bit slow when prefix is 
1-2 chars).

> So the next best thing is to add new functionality with a minimum of
> customization necessary.  So, IMO, it's nonsensical to ask users to
> customize the matching style to 'flex' AND also ask them customize a
> face so that that more-than-familiar matching strategy reveals its
> familiarity.

I disagree that it's a significant problem, though. Enabling 'flex' is 
one line. Customizing the face is just another line.

> This is better: I think this would lead you to my idea of a new
> `completion-relevant` face, which we would set to bold or something very
> prominent.  For the 'prefix' the relevant part is the "next character"
> and for the 'flex' style is whatever has matched.
> completions-first-difference could then be made an alias of that new
> face.

Hmm, I don't like this changing of terms, sorry. This way, the same 
highlighting would be applied to two fairly different things.

> 3. Completion styles decide which parts which faces to apply and when.
> Prefix uses both like it does now.  Flex should probably only use
> 'completion-relevant'.

With my proposal, the positions of the new face can be unambiguously 
determined by the current markings. So its application doesn't need to 
be implemented in completion styles. It can be done in one place: the 
code rendering the *Completions* buffer.