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Re: Calling internal-default-process-sentinel from another sentinel?
From: |
Stefan Monnier |
Subject: |
Re: Calling internal-default-process-sentinel from another sentinel? |
Date: |
Wed, 18 Nov 2020 09:44:18 -0500 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
>>> Such a use case doesn't seem uncommon and simply calling
>>> 'internal-default-process-sentinel' from a custom sentinel would seem a
>>> good solution, but the "internal-" prefix or the fact that such usage is
>>> completely absent from Emacs core and very rare even in 3rd party
>>> code[1] don't inspire confidence.
>>
>> `add-function` is your friend.
>>
>> (add-function :around (process-sentinel proc)
>> (lambda (orig-fun proc state)
>> (if (one particular case)
>> (do the thing)
>> (funcall orig-fun proc state))))
>
> Thanks, I've seen similar examples in the code base, but always advising
> an Elisp sentinel, not 'internal-default-process-sentinel', which is a C
> function, and IIUC also would/might be called from C (e.g. from
> status_notify ?). Or is the actual default sentinel some kind of a
> wrapper?
This is not advising 'internal-default-process-sentinel'. It just
replaces the sentinel by a new function which often delegates to the
previous function, whichever that previous function was and without
affecting that previous function's definition.
> And even for Elisp sentinels, I figured I'd rather avoid advice, as even
> when using a self-removing piece of advice, it still applies to all
> (even unrelated) calls of the same sentinel function occurring until the
> removal. Or am I missing something?
You're confused: this is not an "advice".
Stefan