From: Anders Lindgren <andlind@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: 16129-done@debbugs.gnu.org
Subject: bug#16129: 24.3.50; Emacs slow with follow-mode when buffer ends before last window
Date: Tue, 7 Jan 2014 09:13:19 +0100 [thread overview]
Message-ID: <CABr8ebY10KMZTWfrkvk7afNgXwSMkR0mqPWkrq6FYy_dMjtG5g@mail.gmail.com> (raw)
In-Reply-To: <8338l1t6ip.fsf@gnu.org>
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Hi!
Thanks, I tried it out on the trunk, and it seems to be working correctly!
I'm open to reimplementing follow-mode in another way, if you think that
it's necessary. However, there are two different uses of set-window-start,
and maybe we don't need to change both:
* Normally, when the position of the active window change, the start of the
other windows are updated. This occurs very infrequent, and it would
require a redisplay anyway.
* When a window shows the empty tail of a buffer, point-max is "hammered"
into window-start to ensure that the display engine doesn't recenter the
window.
Of the two uses, I only consider the second a problem. However, it would
probably be easy to handle if there would be a windows-specific option or
call-back that could control if the window should be recentered or not.
While I'm at it, I realized today that the responsiveness when using
follow-mode was better when running the cursor up and down compared to left
and right. When looking into the details I saw that the arrow keys no
longer were bound to previous- and next-char, so we need to apply the patch
below to follow-mode (I don't have write-access to the archives).
Thanks for your help,
Anders
=== modified file 'lisp/follow.el'
--- lisp/follow.el 2014-01-01 07:43:34 +0000
+++ lisp/follow.el 2014-01-07 07:48:40 +0000
@@ -311,7 +311,7 @@
(set-default symbol value)))
(defvar follow-cache-command-list
- '(next-line previous-line forward-char backward-char)
+ '(next-line previous-line forward-char backward-char right-char
left-char)
"List of commands that don't require recalculation.
In order to be able to use the cache, a command should not change the
On Mon, Jan 6, 2014 at 5:33 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> > Date: Mon, 6 Jan 2014 09:20:03 +0100
> > From: Anders Lindgren <andlind@gmail.com>
> > Cc: Stefan Monnier <monnier@iro.umontreal.ca>, 16129@debbugs.gnu.org
> >
> > I think the incorrect state occurs when the new early exit occurs from
> > redsplay_window. When I added the condition "&& PT == w->last_point",
> both
> > the recentering problem and speed issues were solved.
>
> Indeed, this was my conclusion as well. (Except that PT is not quite
> right, as the window could be displaying a buffer that is not the
> current one at that early point in redisplay_window.)
>
> What this caused was that the window redisplay was mistakenly skipped,
> but then we marked that window's display "accurate", which confused
> the heck out of the display engine.
>
> So I installed the patch below to fix this regression, and I'm marking
> this bug done. Feel free to reopen if there are any leftovers.
>
> Btw, I strongly recommend against messing with window-start (or
> anything else that potentially requires redisplay) in a
> post-command-hook: doing so disables some important redisplay
> optimizations, and can easily trigger subtle misfeatures. I suggest
> to look for a better method to do what follow-mode needs to do, even
> if that means we'd have to implement a special hook we don't yet have.
>
> Thanks.
>
> === modified file 'src/xdisp.c'
> --- src/xdisp.c 2014-01-01 17:44:48 +0000
> +++ src/xdisp.c 2014-01-06 16:21:39 +0000
> @@ -15621,7 +15621,8 @@ redisplay_window (Lisp_Object window, bo
> && REDISPLAY_SOME_P ()
> && !w->redisplay
> && !f->redisplay
> - && !buffer->text->redisplay)
> + && !buffer->text->redisplay
> + && BUF_PT (buffer) == w->last_point)
> return;
>
> /* Make sure that both W's markers are valid. */
>
>
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next prev parent reply other threads:[~2014-01-07 8:13 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-13 14:34 bug#16129: 24.3.50; Emacs slow with follow-mode when buffer ends before last window Anders Lindgren
2013-12-13 15:32 ` Eli Zaretskii
2013-12-13 15:36 ` Eli Zaretskii
2013-12-13 16:38 ` Stefan Monnier
2013-12-13 17:55 ` Anders Lindgren
2014-01-02 13:55 ` Anders Lindgren
2014-01-02 18:39 ` Anders Lindgren
2014-01-05 23:13 ` Anders Lindgren
2014-01-06 3:45 ` Eli Zaretskii
2014-01-06 8:20 ` Anders Lindgren
2014-01-06 16:33 ` Eli Zaretskii
2014-01-07 8:13 ` Anders Lindgren [this message]
2014-01-10 9:31 ` Eli Zaretskii
2014-01-10 18:52 ` Anders Lindgren
2014-01-10 19:00 ` Eli Zaretskii
2014-01-13 11:41 ` Anders Lindgren
2014-01-13 14:47 ` Stefan Monnier
2014-01-13 16:16 ` Eli Zaretskii
2014-01-14 12:34 ` Anders Lindgren
2014-01-14 16:25 ` Eli Zaretskii
2014-01-16 12:24 ` Anders Lindgren
2014-01-16 14:42 ` Stefan Monnier
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