GNU bug report logs - #34710
the mode line flicks on set-window-vscroll

Previous Next

Full log

View this message in rfc822 format

From: Robert Pluim <rpluim <at> gmail.com>
To: Alan Third <alan <at> idiocy.org>
Cc: Tak Kunihiro <tkk <at> misasa.okayama-u.ac.jp>, 34710 <at> debbugs.gnu.org
Subject: bug#34710: the mode line flicks on set-window-vscroll
Date: Mon, 04 Mar 2019 22:07:25 +0100

Alan Third <alan <at> idiocy.org> writes:

> On Mon, Mar 04, 2019 at 10:06:20AM +0100, Robert Pluim wrote:
>> Alan Third <alan <at> idiocy.org> writes:
>> 
>> > I believe it’s a problem with running redisplay rapidly (sit-for) and
>> > the way we’re drawing in NS. We end up with macOS demanding a screen
>> > update, and Emacs unable to deliver due to there being another
>> > redisplay coming up.
>> >
>> > The patch attached to this discussion doesn’t have the problem:
>> >
>> > https://lists.gnu.org/archive/html/emacs-devel/2019-02/msg00354.html
>> >
>> > However Robert Pluim reported serious performance problems with it. I
>> > haven’t been able to replicate them.
>> 
>> I can try it again. Perhaps something in my configuration is causing
>> this.
>
> If you can try and track it down that would be very helpful.
>
> The only thing I can think of that could make it very slow is drawing
> the buffer to the screen, but that really shouldn’t be as slow as
> you’re experiencing, it is, after all, just drawing an image to the
> screen.

To be clear: the slowness I experience does not seem wholly related to
redisplay: if I move down in a file using 'C-n', without the buffer
scrolling, the movement is very slow. Then when it does actually
update the screen because Iʼve moved point off the bottom, it is again
slow (by a rough measurement, moving from the top to the bottom of my
org file using C-v is approximately twice as slow).

(this is all with 'emacs -Q')

Iʼve just run another test where I scroll my org file programmatically
rather than interactively, and then your patch makes no discernable
difference:

(benchmark-run 1000
               (goto-char (point-min))
               (condition-case nil
                   (while t
                     (scroll-up-command))
                 (error nil)))
                 
takes ~15 seconds in both vanilla emacs-26 and with your patch.

Are there any other tests you'd like me to run? (I know nothing about
macOS profiling tools)

Robert

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.