Re: Questions about isearch

[Andreas Röhler]

Am 25.11.2015 um 19:41 schrieb Eli Zaretskii:
> These questions came out of review and extensive updates of the search
> and replace sections of the Emacs manual:
>
> 1. Character folding doesn't catch ligatures, such as æ (should it match
> the two characters "ae")?
>
> 2. It also doesn't match ä (a single character) with ä (2 characters,
> which Emacs correctly composes into 1 grapheme cluster).  Should it?
>
> 3. With the default value t of isearch-hide-immediately, one match in
> invisible text is not hidden, and remains on display.  To repro:
>
>    emacs -Q
>    C-x C-f etc/NEWS RET
>    C-c C-q
>    C-s require C-s <RIGHT>
>
> This leaves the match and its surrounding hidden text on screen.  I
> can understand the rationale, but the doc string doesn't say anything
> about this feature.  On the contrary, it says:
>
>    Whatever the value, all opened invisible text is hidden again after
>    exiting the search. ^^^
>
> 4. What is the equivalent of case-replace and the letter-case related
> behavior of replace commands to character folding?  E.g., if the
> replace command specifies to replace "foo" with "bar", and we found
> "föo", should we replace it with "bär" or something, by analogy with
> letter-case behavior?

Considering language special cases worldwide at core will run into infinity.

Would expect support of unicode-characters. Mapping them should be the 
task of special language-modes built upon, i.e. a text-norwegian etc.

In order to support languages, isearch might accept modifiers, like 
fill-paragraph does with fill-paragraph-function. Thus the regexps 
handed over may change.