RE: Character folding in the pretest

[Drew Adams <drew.adams@oracle.com>]

> > It would make sense to have the default based on the session's locale,
> > meaning that in a Swedish locale a, ä and å would be different and n and ñ
> > be different, but under a Spanish locale, the opposite would be true.
> 
> Character equivalence is based on the language(s) of whatever is in your
> buffer, which might be correlated with your locale, but not more than
> that.
> 
> Regardless, for the purpose of searching, my personal preference would
> be to make folding rather inclusive; I don't really care about the exact
> rules languages have come up for what letters are considered "the same",
> I just care for what I, as a user, would find the easiest to match.
> 
> So for instance, I'd like "angstrom" to match "Ångström" even though in
> Swedish, a/Å and o/ö are not the same. Somewhat similar to how
> languages' capitalization rules are ignored when searching
> case-insensitively. A few false positives are not much of problem.
> 
> That would also get my vote as a reasonable default for case-folding in
> searches. But I'll happily take any default, as long as there's a way to
> get the above behavior, preferably without having to change my locale.

Both of these posts (one saying that it should be possible to take
locale into account, perhaps even for default behavior; the other
adding that someone might have a personal preference) point to the
existence of multiple use cases and users needing to be able to
(easily) control the behavior.

We can fine-tune defaulting at design time, to try to provide a
reasonable behavior for most use cases/contexts, but users still
need to be able to easily customize the sets of equivalence classes,
and they should be able to have multiple sets of such sets, which
they can activate in different contexts (e.g. modes).

That is really where the design effort should be, at this point.
We have a basic char-folding mechanism, but we do not yet provide
an easy way for a user to customize the behavior, let alone to
define/get the various behaviors that s?he might want in different
contexts.