bug#16621: 24.3.50; Periodic timer + overlays = flickering near point

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: dgutov@yandex.ru,  16621@debbugs.gnu.org
> Date: Mon, 03 Feb 2014 22:28:43 -0500
> 
> >> But in the current case at hand, "absolutely nothing" happened.
> > Something did happen (in the isearch recipe): we've redisplayed the
> > echo area.
> 
> But nothing "absolutely nothing happened" to the window where the
> text flickers.

That's the issue with redrawing the cursor that I mentioned.  If we
can find a way to avoid that, we will probably solve most of the
problem, if not all of it.

> And even the "redisplayed echo area" itself was done despite the
> fact that "absolutely nothing" happened (between the end of the
> previous redisplay and the beginning of the next).

Yes, but there could be some message "shown through", like from an
input method or GC or whatever.  That's why echo area is redisplayed
when it is active, I guess.