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Re: Callbacks from modules

From: Ivan Andrus
Subject: Re: Callbacks from modules
Date: Fri, 27 Nov 2015 10:30:41 -0700

On Nov 27, 2015, at 1:29 AM, Eli Zaretskii <address@hidden> wrote:
>> From: Ivan Andrus <address@hidden>
>> Date: Thu, 26 Nov 2015 20:23:48 -0700
>> Cc: address@hidden
>>> Then one way would be to have that callback set a flag,
>>> provide a Lisp-callable function that returns the flag, and then start
>>> a timer that will test the flag and call your Lisp callback when the
>>> flag is set.
>> I was hoping to avoid polling, since the use case I have would like to start 
>> reading again as soon as the previous version finishes.
> You could do that on the C level, no?  You don't need anything from
> Lisp to start reading again.

I should have said I want the option of continuing to read.  I wanted that 
logic (along with what to read next) in lisp.

>>> Another, perhaps simpler, possibility would be to have the module
>>> provide a Lisp-callable function that will register a Lisp callback.
>>> Then your C callback will simply call that Lisp function.
>> I don’t understand how I would implement this option, though it sounds like 
>> what I was hoping for.  In order to call a lisp function, don’t I need an 
>> emacs_env?
> Forget it, it probably won't work anyway, because your C callback runs
> in another thread, right?  Module code cannot run in any thread but
> the main thread.

Okay, I was wondering about that.  Based on the back trace it did look like it 
was running in the same thread, but it’s probably best to not rely on that.


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