Re: Questions about isearch

[Artur Malabarba]

On 27 Nov 2015 2:36 pm, "Eli Zaretskii" <address@hidden> wrote:
> > It does for me. In this very buffer, if I isearch for 'f' I can get to
> > the ligature above.
>
> 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.

> > >> > 2. It also doesn't match ä (a single character) with ä (2 characters,
> > >> > which Emacs correctly composes into 1 grapheme cluster). Should it?
> >
> > Done now.
>
> Thanks.
>
> But if this now work, why doesn't "ff" find ff or vice versa?  Isn't
> that the same case?

No. Each one is a different scenario here.

-  "ff" not finding ff is a case of multiple chars in the search string can't be collapsed as a single thing (see above). It's the same reason why 'ä' still doesn't match ä.
- 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.
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).