Re: How to determine (from Elisp) whether the Emacs frame has focus?

[Marcin Borkowski <mbork@mbork.pl>]

On 2015-11-14, at 14:40, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Marcin Borkowski <mbork@mbork.pl>
>> Cc: help-gnu-emacs@gnu.org
>> Date: Sat, 14 Nov 2015 13:34:06 +0100
>> 
>> > Then I don't understand why the solution of focus-in/out-hook was
>> > rejected as "hackish".  These hooks are there precisely for situations
>> > like these, AFAIK.  IMO, there's nothing hackish about that.
>> 
>> AFAIU, these hooks are best suited to situations like "run LaTeX on
>> switching to a pdf viewer".  That does not require global variables; my
>> use case does.
>
> Sorry, I still don't understand: why cannot the hook modify values of
> global variables, and thus serve your needs in this context?

Well, you're probably right, I'm just overthinking it.

>> Would it be possible to introduce a function like (emacs-has-focus-p)
>> for that?  Would it make sense?
>
> What would that function do except test the value of some global
> variable, set by the focus-in and focus-out hooks?

Well, it could do it without using those hooks, if it were in C.  But
you're probably right (again), there's no need to add that to the core.

>> For starters, I only want to know whether it is Emacs which has focus or
>> not.  Then, I would like to know e.g. the mode of the current buffer; in
>> that case, I'm not sure what I should do when the current buffer is the
>> minibuffer or something.  But this is less important for me now.
>
> There's only one current buffer in the entire Emacs session, and it
> doesn't change when Emacs loses focus.  Its value is returned by the
> function current-buffer, as I'm sure you know.

Of course.  However, what I really mean is not exactly (current-buffer),
but "the buffer I'm working in now".  This means that if
e.g. current-buffer is the minibuffer (as might be the case during
search or M-x or whatever), I would prefer /the buffer I'll get back to
when I finish doing whatever I'm doing in the minibuffer/, or /the
buffer I was in when I switched to the minibuffer/ (these two need not
coincide, of course, e.g. in case of C-x b - in such a case I'm fine
with whichever one).  This might be the other-buffer, I'm not sure -
I'll have to study the docs a bit more.

Best,

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University