From: Alan Mackenzie <acm@muc.de>
To: Eli Zaretskii <eliz@gnu.org>
Cc: Gerald Wildgruber <wildgruber@tu-berlin.de>, emacs-devel@gnu.org
Subject: Re: follow-mode: extremely slow in combination with org-mode
Date: Sun, 17 Jun 2018 11:13:33 +0000 [thread overview]
Message-ID: <20180617111333.GA12093@ACM> (raw)
In-Reply-To: <83lgbdu8zs.fsf@gnu.org>
Hello, Eli.
On Sun, Jun 17, 2018 at 11:12:39 +0300, Eli Zaretskii wrote:
> > From: Gerald Wildgruber <wildgruber@tu-berlin.de>
> > CC: <emacs-devel@gnu.org>
> > Date: Sun, 17 Jun 2018 08:57:22 +0200
> > - follow-windows-start-end 17606 57%
> > - if 17606 57%
> > - let 17603 57%
> > - let 17603 57%
> > - while 17603 57%
> > - setq 17599 57%
> > - cons 17599 57%
> > - cons 17599 57%
> > - cons 17599 57%
> > - follow-calc-win-end 17591 57%
> > - let* 17591 57%
> > - if 9229 30%
> > + let 1115 3%
> > + pos-visible-in-window-p 26 0%
> > posn-point 8350 27%
> > + window-inside-pixel-edges 12 0%
> Alan, why doesn't follow-calc-win-end doesn't just use window-end with
> last argument non-nil? AFAU, that should allow you to compute the
> result using 1/4 of the processing time you now invest. Why do you
> need all the rest in that function? What am I missing?
I honestly don't know for sure. But on 2014-04-27 I made a note in my
personal log:
"In follow-calc-win-end, we check for EOB being visible in the
window, rather than being the window-end. There needs to be a
comment here about what the last element means."
. I wish I could decipher what I meant, then. I think I might have
encountered a corner case, where EOB is _inside_ a window, possibly not
even the last window, and using window-end failed for some reason.
But I think follow-calc-win-end was in the original follow.el written by
Anders Lindgren. Maybe, back in the mists of time, window-end didn't
work for some reason - maybe it hadn't yet acquired it's UPDATE
argument, or something like that.
follow-calc-win-end was much longer in Emacs-21.4, and carried the
comment "This function is optimized function for speed!". It had got
shorter some time up to Emacs-24.5, where it had already started using
posn-point. This rewrite was probably this:
commit c93b886f957b55df4fe45d986c34242832ec4a28
Author: Chong Yidong <cyd@gnu.org>
Date: Sun Apr 29 09:48:23 2012 +0800
Fix Follow mode's calculation of window ends.
* lisp/follow.el (follow-calc-win-end): Rewrite to handle partial
screen lines correctly.
(follow-avoid-tail-recenter): Minor cleanup.
Fixes: debbugs:8390
Why we don't just use window-end, I don't know. Maybe the sequence of
people who've modified follow-calc-win-end have all assumed their
predecessors understood why a simple window-end wasn't used. If it is
something to do with EOB messing things up, maybe we could amend
window-end better to handle EOB.
Sorry I can't do any more than speculate, here.
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2018-06-17 11:13 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-16 10:25 follow-mode: extremely slow in combination with org-mode Gerald Wildgruber
2018-06-16 11:41 ` Eli Zaretskii
2018-06-16 13:06 ` Gerald Wildgruber
2018-06-16 16:25 ` Eli Zaretskii
2018-06-16 21:05 ` Gerald Wildgruber
2018-06-17 6:57 ` Gerald Wildgruber
2018-06-17 8:12 ` Eli Zaretskii
2018-06-17 11:13 ` Alan Mackenzie [this message]
2018-06-17 13:02 ` Eli Zaretskii
2018-06-17 14:56 ` Gerald Wildgruber
2018-06-17 15:10 ` Eli Zaretskii
2018-06-19 12:08 ` Gerald Wildgruber
2018-06-19 16:55 ` Eli Zaretskii
2018-06-19 13:53 ` Gerald Wildgruber
2018-06-17 15:13 ` Eli Zaretskii
2018-06-21 8:25 ` Anders Lindgren
2018-06-27 16:43 ` Gerald Wildgruber
2018-07-09 20:12 ` Anders Lindgren
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