From: Marcin Borkowski <mbork@mbork.pl>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: help-gnu-emacs@gnu.org
Subject: Re: How to define a (derived) minor mode inaccessible to the user
Date: Thu, 28 Jan 2021 08:42:50 +0100 [thread overview]
Message-ID: <87v9bhik1x.fsf@mbork.pl> (raw)
In-Reply-To: <jwvv9bpro14.fsf-monnier+emacs@gnu.org>
On 2021-01-22, at 16:38, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>>> The `interactive-form` property is virtually never used. Instead, the
>>> interactive form is traditionally stored within the function.
>> So how does `execute-extended-command' know what to list, then?
>
> You can use `commandp` to know if it's got an interactive form or not,
> and `interactive-form` (the function) to extract it from a function.
>
>> A cursory look told me that it uses `read-extended-command', which uses
>> `commandp'. So, how does `commandp' know? (I'm not well versed in C,
>> but do I guess correctly that it checks the `interactive-form' property,
>> and if nil, it (somehow) looks for `(interactive ...)' in its
>> definition?)
>
> Pretty much, yes (with the extra handling for the cases where the
> function is not a `(lambda ...)` list but a byte-compiled object, or an
> autoloaded function, or a function implemented in C).
OK, thanks.
>>> If you *really* care about hiding the major mode from the user
>>> I suggest you use an "obscure" or "scary" name.
>> Well, the convention is to use two dashes, but how can the end-user (not
>> knowing Elisp and the conventions) know that?
>
> That's indeed the convention for functions. For commands we don't
> really have a convention for "commands that should be hidden from `M-x".
> We used to prevent completion from revealing obsolete commands.
> It's been reverted recently (to my disappointment), but we could add
> a similar feature for "commands not to be used via M-x" (could be used
> for those commands that only work when bound to a mouse event, for
> example).
>
> Maybe `smex` offers something like that. When I rewrote
> `execute-extended-command' into Elisp, I hoped that it would encourage
> people to hack on it and add features to it (like this one), but sadly
> it doesn't seem to have had much effect of this kind so far.
>
> We could add some property that holds a predicate function which
> `execute-extended-command' could use to filter out commands which can't
> be used in the current context (e.g. the predicate could check the
> major mode, for those commands which only work in a given major mode).
>
>> So, basically you move the function definition from the function cell to
>> the value cell of `my-mode', right? Clever! Is it actually used
>> anywhere in Emacs?
>
> No, and I don't recommend it.
> E.g `C-h m` will then fail to show the proper docstring of the major mode.
I see. Still interesting.
Thanks,
--
Marcin Borkowski
http://mbork.pl
next prev parent reply other threads:[~2021-01-28 7:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-22 5:11 How to define a (derived) minor mode inaccessible to the user Marcin Borkowski
2021-01-22 5:34 ` [External] : " Drew Adams
2021-01-22 15:01 ` Marcin Borkowski
2021-01-22 14:19 ` Stefan Monnier
2021-01-22 15:23 ` Marcin Borkowski
2021-01-22 15:38 ` Stefan Monnier
2021-01-28 7:42 ` Marcin Borkowski [this message]
2021-01-28 14:31 ` Stefan Monnier
2021-01-23 13:08 ` Michael Heerdegen
2021-01-28 7:45 ` Marcin Borkowski
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