bug#14744: 24.3.50; Flickering mouse-face on process output

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Christopher Schmidt <christopher@ch.ristopher.com>,  14744@debbugs.gnu.org
> Date: Sat, 29 Jun 2013 11:08:51 -0400
> 
> I consider it a bug because some part of the screen flickers.
> I understand the underlying technical reason why Emacs does that, but
> it's still a misfeature.

See my other message, where I explained the reasons for this specific
case.  Not surprisingly, it's use of overlays.

> Ideally we should refrain from redrawing things that haven't
> changed

We do, but not with mouse-highlight.

> the second best fix is to use some kind of double buffering so the
> intermediate "drawn but not depressed" state is kept hidden.

I admit that I have no idea what you have in mind here, but patches
are most welcome.