Re: Questions about isearch

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 27 Nov 2015 16:55:45 +0000
> From: Artur Malabarba <bruce.connor.am@gmail.com>
> Cc: emacs-devel <emacs-devel@gnu.org>
> 
> > Right, it does. I think I tried "ff", not "f". Is that supposed to
> > work?
> 
> No. We don't support having multiple characters match a single string. 
> 
> This is a design limitation. We can (and should) discuss improving this. But
> for now I think it should be documented as not supported. 

Is it reasonable to have ä match ä, but not the other way around?

> - ä now finds 'ä'. Because that is exactly its decomposition. 
> - ff doesn't find "ff", because the decomposition of ff is not exactly (f f),
> it's actually (compat f f). This was a decision, it's not a limitation. 

So you are saying we support canonical decompositions, but not
compatibility decompositions, I see.  However, it sounds inconsistent
to me, because searching for a does find ⓐ, although ⓐ's decomposition
is also "not exactly a".  I'm afraid it will be hard to explain to the
users why some of these match, while others don't.

Are there any downsides in adding compatibility decompositions to what
character folding supports?

> I figured that a character should only match its decomposition if the
> decomposition is strictly made of chars. Otherwise you get things like ¹
> matching 1 (which I thought we didn't want).

Well, I think we do want that.  At least MS Word does that by default,
so it isn't entirely silly or without precedent.