Subject: Re: bug#47215: 28.0.50; Let M-x switch between M-x and M-X

From: Felician Nemeth <[email-masked]>
Date: Sat, 10 Apr 2021 19:56:49 +0200

Lars Ingebrigtsen <[email-masked]> writes:

> Felician Nemeth <[email-masked]> writes:
>
>>> I'm not quite sure how to implement this, though -- we basically end up
>>> in `completing-read', and `execute-extended-command-for-buffer' would
>>> have to define an `M-x' binding there, I guess...  and then somehow call
>>> `read-extended-command' with the text already in the minibuffer.
>>>
>>> Anybody got an idea as to how to implement this without rewriting
>>> `read-extended-command' completely?
>>
>> The execute-extended-commands have two undocumented optional arguments
>> (command-name and typed).  What are they used for?
>>
>> Anyway, following the fallback logic of `ido-find-file', I was able to
>> rebind `M-x' and save the content of the minibuffer with a non-standard
>> exit from `execute-extended-command'.  Maybe the ugly code below can
>> give ideas to someone more knowledgeable.
>
> Thanks -- I was wondering more about the situation where you've typed
>
> M-X foo|bar
>
> (| for point)
>
> and then hit `M-x' because you want to switch to the other mode.
> Ideally, `M-x' should do that, and also preserve the text the user has
> typed, and the cursor position.  I don't see an obvious simple way to do
> that... 

I've discovered that the initial-input argument of `completing-read` can
be written as (STRING . POSITION).  The attached patch makes use of it
and shows a simple implementation of my original wish.

However, the patch creates code duplication.  Also, I don't know how it
copes with recursive editing: maybe it's not a good idea to rebind M-x
when `enable-recursive-minibuffers' is t.  Finally, the docstring says
initial-input is deprecated.

I'm happy to work on the patch if you guide me to the right direction,
but this time I'd rather receive a fish instead of being taught how to
fish :)