bug#24109: 24.5; Long lines in message mode make Emacs irresponsive

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 02 Oct 2016 10:09:53 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 24109@debbugs.gnu.org, djcb@djcbsoftware.nl,
> 	Christophe.Troestler@umons.ac.be
> 
> > From: Yuri D'Elia <wavexx@thregr.org>
> > Cc: 24109@debbugs.gnu.org, djcb@djcbsoftware.nl, Christophe.Troestler@umons.ac.be
> > Date: Sat, 01 Oct 2016 20:25:57 +0200
> > 
> > Ok, after some testing, I was able to get a self-contained test case.
> > I was successfully able to test this into the current git's master with
> > emacs -q, built with lucid as the main toolkit.
> > 
> > Please load-file the attached sample. It will create a *test* buffer,
> > using a quoted representation of (buffer-substring) which is sufficient
> > to recreate the problem.
> > 
> > It will move the point to the beginning of the last line, as well as
> > switching on truncate-lines. Having the point on the beginning of the
> > line is important.
> > 
> > Switch to the *test* buffer and move up. It will hang at the "Luciaine"
> > line. I'm also attaching a screenshot of my current window state.
> > 
> > If you toggle auto-hscroll-mode instead, before scrolling, you'll see
> > how the cursor disappears instead when exactly at the beginning of the
> > line.
> 
> Thanks, I will look into this soon.

Tis is now fixed on the emacs-25 branch.