Re: Detect window switches?

[Eli Zaretskii]

> From: Dan Espen <despen@verizon.net>
> Date: Thu, 26 Sep 2013 15:22:58 -0400
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: Dan Espen <despen@verizon.net>
> >> Date: Thu, 26 Sep 2013 14:22:15 -0400
> >> 
> >> My mode line changes color when a buffer changes from active/inactive.
> >> Isn't that what the OP is looking for?
> >
> > That's done on the C level, and Lisp programs cannot hook into this.
> 
> Hmm, starting to sound like a bug.
> Here's an event that Emacs acts on but doesn't make the
> event visible to ELisp.

No, Emacs doesn't act on this as an event.  What happens is that the
next redisplay after a window switch redraws the mode line in a
different face.  The redisplay isn't triggered by an event (because
there is no such event), it is triggered by other means, mostly
because Emacs becomes idle.  That could happen many seconds after the
switch, if Emacs becomes busy calculating something, for example.