Re: [WIP PATCH] Controlling Isearch from the minibuffer

[Augusto Stoffel]

On Sun,  9 May 2021 at 13:36, Alan Mackenzie <acm@muc.de> wrote:

> Hello, Augusto.

Hi Alan,

>
> On Sat, May 08, 2021 at 12:13:52 +0200, Augusto Stoffel wrote:
>> I've attached a draft implementation of a minibuffer-controlled mode for
>> Isearch, as described for instance in
>> https://lists.gnu.org/archive/html/emacs-devel/2020-01/msg00447.html
>> To enable the feature, set `isearch-from-minibuffer' to t.
>
>> The basic trade-off is that this makes it easier to edit the search
>> string, and harder to quit the search.
>
> You mean, the patch makes incompatible changes to isearch, yes?

I wouldn't dare to suggest turning this on by default :-).

The *slight* incompatible changes are all in `isearch-edit-string'.
This seems like a quite unpolished command anyway, but of course I can
leave it untouched.  I suggest discussing the details in a future
subthread.

>
>> It also drops some of the eccentricities of regular Isearch.  For
>> instance, DEL deletes and C-g quits.
>
> What to you are eccentricities, are features to other people.  I'm very
> satisfied with the current workings of C-g, and would protest vehemently
> were they to be changed.  I'm not sure what you mean by "DEL deletes" -
> what does it delete, and in which circumstances?

I am sure most of the regulars in this thread share your view.
Otherwise, something like this proposal would have surfaced much
earlier.  But this doesn't mean this feature won't be appreciated by
other people.

In the minbuffer-controlled Isearch mode, DEL is simply
`delete-backward-char', not some kind of undo.  It deletes in all
circumstances.

>
>> I'm sharing this preliminary version because two important questions can
>> already be answered:
>
>> - Does the approach taken here seem sufficiently robust?  Note in
>>   particular the `with-isearch-window' macro, which is now needed around
>>   several functions, as well as the somewhat hacky `run-with-idle-timer'
>>   call inside the `isearch-mode' function.
>
>> - Are the slightly backwards incompatible keybinding changes in
>>   `isearch-edit-string' acceptable?
>
> It depends what you mean by "slightly".  I suspect the answer to the
> question is no.  Any changes here which aren't simply additions are
> going to disturb somebody's workflow.
>
>> If any of these answers is no, then I would provide a package for the
>> same feature.  But I think the feature is interesting enough to be built
>> in isearch.el.  Moreover, it would benefit from being official because
>> many third-party extensions to Isearch will need to take into account
>> the possibility that the search is being controlled remotely from a
>> minibuffer.
>
> Skimming through your patch (it is too large for me to take in every
> detail at the moment), it seems it could make isearch.el even more
> difficult to maintain than it currently is.  For example, the two
> defmacros `with-...' are the sort that force somebody debugging (or
> trying to read a patch) to look somewhere else to find out what they
> mean.  This is irksome and tedious.  There are already macros like this
> in isearch.el, and it would seem wise to minimise any further
> proliferation.  Each of these macros expands the ,@body twice for every
> invocation.  Would it not be possible to rearrange things, just to
> expand them once?

My difficulty in understanding Isearch is the very complicated internal
state.  This patch is just a UI thing and doesn't interact at lot with
the search state.

As to the duplication of ,@body, sure, once can always use a lambda to
avoid this.  However, I would rather break up a very long function that
requires being wrap in these macros (they will be very few, anyway) into
shorter and simpler pieces.

>
> In one hunk in the patch, I see a condition-case containing a funcall,
> containing a catch, containing a minibuffer-with-setup-hook, which in
> its turn contains a lambda function and an unwind-protect.  The lambda
> function sets functions onto both after-change-functions and
> post-command-hook.  Whew!  Each one of these constructs on its own
> causes difficulty in debugging, but they have their justification.  Must
> they really all appear together in this fashion?

The condition-case complicated, really.  The tag in question is thrown
at just one place (`with-isearch-window-quitting-edit') and caught at
just one place (`isearch-edit-string').  No spaghetti logic here at all.
It just passes a continuation, hence the funcall.

I admit the after-change function and post-command hook are hairy,
because they interact with the Isearch state.

>
> The biggest question, which may have been answered somewhere in the
> thread already, is why?  What is wrong with isearch at the moment that
> the patch will fix, or enable to be fixed?  The emacs-devel post you
> cite above (from 2020) doesn't seem to motivate this change.  Could you
> possibly answer this question, or cite a post which answers it, please?
>

I used Isearch for many years and never really understood/cared to
figure out why sometimes trying to delete a character jumped around the
buffer.  Or in which circumstances I had to press C-g once or twice to
quit (I still don't, but in the meanwhile I found `isearch-cancel').  I
would also inadvertently quit the search all the time when trying to
edit the string.  This is too complicated to my taste.

Only after an interlude using Swiper I realized that Isearch isn't even
using the minibuffer, like any other command that reads a string does.

This patch is supposed to provide a simple, intuitive mode of operation
for Isearch.

>> Some further remarks:
>
>> - The minibuffer-controlled mode is supposed to depend on the proposed
>>   `isearch-buffer-local' feature.  This will make the hack used to
>>   deactivate the `overriding-terminal-local-map' unnecessary.
>
>> - It seems necessary to let-bind `inhibit-redisplay' to nil in
>>   `with-isearch-window' in order to avoid flicker in the cursor.  This
>>   seems related to the recent thread "Temporarily select-window, without
>>   updating mode-line face and cursor fill?" in this list.  Any better
>>   solutions?
>
>> - I don't like the `with-isearch-window-quitting-edit' macro, but I
>>   don't see a different way of achieving the necessary effect.
>
>> - I don't use/know of all Isearch features, so let me know if you spot
>>   some incompatibility.
>
>> What do you think?
>
> The patch is ~500 lines long.  This makes me worried.  I'm afraid I can
> only react negatively and defensively at the moment.
>

That's because I didn't reindent anything yet :-)

Now seriously, the bulk of the change is to rewrite
`isearch-edit-string'.  Apart from that, it (1) wraps a bunch of
commands in a macro that does nothing when `isearch-from-minibuffer' is
nil, and (2) adds a condition at the end of `isearch-mode' to possibly
call `isearch-edit-string'.  That's about it.  Maybe with this short
summary the patch becomes easier to digest.

> [ patch snipped ].