bug#16526: 24.3.50; scroll-conservatively & c-mode regression

[Eli Zaretskii]

> Date: Sat, 25 Jan 2014 20:31:10 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: acm@muc.de, 16526@debbugs.gnu.org
> 
> >  > when it decides where
> >  > to place window-start.  This is triggered by redisplay after the move
> >  > to the end of the buffer.
> > 
> > But the `end-of-buffer' call terminates cleanly after a few seconds -
> > that's what the `sit-for' proves in my code.
> 
> Right, and that's when redisplay kicks in, which invokes JIT Lock.

More accurately, end-of-buffer calls recenter, which needs to compute
where to put window-start, which requires Emacs to examine the text
before point.  As part of this examination, we invoke functions that
simulate display, and those trigger JIT Lock, whose fontification
function starts the madness.