bug#27896: [External] : Re: bug#27896: 25.2; `C-M-%' with `rectangle-mark-mode'

[Juri Linkov <juri@linkov.net>]

>>> But we could somewhat easily change `C-M-%' to be slightly less
>>> surprising, and document its limitations.  That is, we say that no
>>> multi-line matches are impossible in rectangle mode, and we implement it
>>
>> The current limitation is inability to use some greedy
>> regexps in rectangle mode.  This is not much worse than
>> limiting query-replace to non-multi-line matches only.
>
> Aren't multi-line replacements already disallowed in rectangle mode by
> the filtering function?

Except in a degenerate case when a rectangular region covers lines
completely from beginning to end.

>>> by just narrowing to each successive line part, and executing the
>>> query-replace-regexp once per line.  (With some magic to handle `!' etc,
>>> I guess.)
>>
>> Actually not narrowing in the sense of narrow-to-region,
>> but temporarily setting the LIMIT arg of 'replace-search'
>> to the end of the region of the current line.
>
> Yup.
>
> But I guess it's not that easy to get this to work sensibly -- it'd only
> highlight matches in one line at a time, which would be odd.

Maybe it's possible to add special handling for lazy-highlighting
as well, but unfortunately implementing all this takes too much time.

So this is a question of priorities: does it make sense to spend
much time implementing this.  Are there any users of this feature?

I mean the feature of regexp and multi-line replacements in rectangle mode,
because non-regexp single-line string replacements already work fine
in rectangle mode.

Or it's enough to explain the current limitation in the documentation.