bug#14567: These changes sometimes break plain text navigation

[Eli Zaretskii <eliz@gnu.org>]

> From: Stephen Berman <stephen.berman@gmx.net>
> Cc: Dima Kogan <dima@secretsauce.net>,  14567@debbugs.gnu.org
> Date: Wed, 10 Jul 2013 11:30:48 +0200
> 
> The changes in revision 113314 cause problems with repeated C-n:
> 
> 0. emacs -Q (any revision post 113313)
> 1. C-h n to visit NEWS
> 2. Type C-n and hold it.
> => Scrolling starts out fine, but around line 270 (sometimes earlier) it
> starts getting jerky and soon it appears to stop altogether, and only
> after releasing the keys is the display updated.  From this point on,
> holding down C-n shows this misbehavior.

I cannot reproduce this, sorry, not with the above recipe.  I tried
different fonts and different sizes of them, and never saw anything
like this.  If in your case Emacs cannot keep up due to some high
computational load (what does the CPU load say?), then I see no sign
of that on my system when I scroll through NEWS.  If you do see a
significant CPU load, please tell (in a new bug report, see below)
what kind of CPU do you have and whether the problem disappears if you
reduce the keyboard auto-repeat rate.

If you still see this after revision 113360 (where I made changes in
the same function as in 113314, although I think they are unrelated),
please report a new bug for this, as the problem you describe has
nothing to do whatsoever with this bug.  I will then try to give you
instructions how to instrument line-move-partial and report the
results.