bug#15841: Display bugs with cache-long-lines non-nil

[Michael Heerdegen]

Eli Zaretskii <eliz@gnu.org> writes:

> > I see something probably related.  Sometimes, evaluating
> > 
> >   (line-number-at-pos)
> > 
> > at the end of my .emacs (10000 lines) needs over a second.  Doing
> > 
> >   (setq cache-long-scans nil)
> > 
> > immediately fixes this.  Dunno yet how to provoke the problem.
>
> Please do try to find a recipe.  I just did that with xdisp.c (almost
> 30000 lines), and couldn't reproduce this.  line-number-at-pos is
> instantaneous, whether I try it at the beginning, the end, or the
> middle of the file.

Sorry, I was misguided.  What was slow wasn't `line-number-at-pos' but
redisplay (so only the result of evaluation showed up delayed).  This
long time for redisplay does only happen with some code I'm currently
developing, but also only when cache-long-scans is non-nil.  Anyway,
I'll tell you when I have a recipe.

Thanks,

Michael.