"spurious scrolling bug"

"spurious scrolling bug"

[Glenn Morris]

Does anyone know what the FOR-RELEASE item "spurious scrolling bug"
actually refers to?

Perhaps

http://lists.gnu.org/archive/html/bug-gnu-emacs/2007-04/msg00003.html
?

If so, can anyone reproduce the problem? Is it Windows-only?

I can't reproduce it, so IMO it's a "spurious scrolling-bug", rather
than a "spurious-scrolling bug".

Re: "spurious scrolling bug"

[Richard Stallman]

    Does anyone know what the FOR-RELEASE item "spurious scrolling bug"
    actually refers to?

This bug causes a spurious scroll that centers point in the window.
Sometimes it seems to happen while Emacs is idle, which leads
me to suspect that an idle timer is doing it, or else that the
code in keyboard.c that does things like auto-save and GC when Emacs
is idle.

I have tried to find ways to reproduce it, but no success yet.

Re: "spurious scrolling bug"

[Chong Yidong]

Richard Stallman <rms@gnu.org> writes:

>     Does anyone know what the FOR-RELEASE item "spurious scrolling bug"
>     actually refers to?
>
> This bug causes a spurious scroll that centers point in the window.
> Sometimes it seems to happen while Emacs is idle, which leads
> me to suspect that an idle timer is doing it, or else that the
> code in keyboard.c that does things like auto-save and GC when Emacs
> is idle.
>
> I have tried to find ways to reproduce it, but no success yet.

I haven't seen anything like this.  Any clues?

>From inspecting timer-list and timer-idle-list, I see only that the
only active timer is the idle timer jit-lock-context-fontify, which
doesn't move point.  Do you have stealth fontification on, or any
relevant customizations that might cause this?

Re: "spurious scrolling bug"

[Thien-Thi Nguyen]

() Chong Yidong <cyd@stupidchicken.com>
() Thu, 12 Apr 2007 22:27:57 -0400

   Do you have stealth fontification on, or any
   relevant customizations that might cause this?

i have seen spurious scrolling when the mouse wheel
(yes, i succumbed in late 2006 and got a mouse, blech)
is jammed between low-potential positions.  it seems to
send out alternating scroll-up and scroll-down signals
at high frequency causing emacs to spaz out.

maybe this is not related to the above problem.

thi

Re: "spurious scrolling bug"

[Jason Rumney]

Thien-Thi Nguyen wrote:
> i have seen spurious scrolling when the mouse wheel
> (yes, i succumbed in late 2006 and got a mouse, blech)
> is jammed between low-potential positions.  it seems to
> send out alternating scroll-up and scroll-down signals
> at high frequency causing emacs to spaz out.
>
> maybe this is not related to the above problem.
>   

I don't think that is related to this bug. I have seen it occur 
occasionally, and it recenters the cursor, usually resulting in a half 
page jump, rather than scrolling by the few lines you'd expect if it was 
the scroll wheel.

Re: "spurious scrolling bug"

[Richard Stallman]

    i have seen spurious scrolling when the mouse wheel
    (yes, i succumbed in late 2006 and got a mouse, blech)
    is jammed between low-potential positions.  it seems to
    send out alternating scroll-up and scroll-down signals
    at high frequency causing emacs to spaz out.

    maybe this is not related to the above problem.

It can't explain my problem.  It could be a second bug.

Re: "spurious scrolling bug"

[Richard Stallman]

I think someone sent a bug report about spurious scrolling (when
scrolling should not occur), during the past few weeks.  I do not know
how to find that message, though.  I searched my outgoing mail to
emacs-devel, and it seems I did not send a response to it there.
Maybe it was sent to emacs-pretest-bug.

    >From inspecting timer-list and timer-idle-list, I see only that the
    only active timer is the idle timer jit-lock-context-fontify, which
    doesn't move point.  Do you have stealth fontification on, or any
    relevant customizations that might cause this?

I think these are all my settings that might be relevant:

    (setq transient-mark-mode t)
    (setq mark-even-if-inactive t)
    (global-font-lock-mode 1)
    (setq jit-lock-stealth-verbose t)
    (setq jit-lock-defer-contextually t)

    (setq scroll-conservatively 10000)
    (setq garbage-collection-messages t)

It doesn't have to be a timer.   It could be the code
in keyboard.c that sleeps and then does auto-save or GC.

I think I have sometimes seen this problem in recent weeks when I 
type C-c C-c to send a message, and the RMAIL buffer expands to
fill the whole screen.  After that, I sometimes see it scroll.

Re: "spurious scrolling bug"

[Chong Yidong]

Richard Stallman <rms@gnu.org> writes:

> I think someone sent a bug report about spurious scrolling (when
> scrolling should not occur), during the past few weeks.  I do not know
> how to find that message, though.  I searched my outgoing mail to
> emacs-devel, and it seems I did not send a response to it there.
> Maybe it was sent to emacs-pretest-bug.

You probably mean this thread, which is (apparently) unrelated to the
current bug:

From: Warren L Dodge <warrend@mdhost.cse.tek.com>
Subject: Re: C-a acts different in 22.0.90 then past versions
To: storm@cua.dk (Kim F. Storm)
Cc: emacs-pretest-bug@gnu.org, warren.l.dodge@tektronix.com

  I'll try emacs-22.0.96 as soon as I can get it built. In the mean time here
  is the answers to all the other questions.

  emacs-22.0.90 -Q
  c-xc-f /etc/termcap 

  c-xc-q     To make it writable
  c-kc-kc-y  kill the first line and put it back. 
             It will not do it without this line kill

  c-s the    do this until you leave the first screen displayed. This will
             recenter the buffer on the "the" found. Then c-s for one more
             "the" below but on the same display screen. For the GNU/Linux on
             the redhat 4.0 release it was about 16 additional c-s commands to
             get it. I think near the bottom will work also. 

  c-a        this will recent the screen on the line where the "the" was at.


From: Richard Stallman <rms@gnu.org>
Subject: Re: C-a acts different in 22.0.90 then past versions
Newsgroups: gmane.emacs.pretest.bugs
To: Chong Yidong <cyd@stupidchicken.com>
Cc: emacs-pretest-bug@gnu.org

    > Aha, I could reproduce this reliably with a June 20th version of CVS
    > as well.  However, I cannot reproduce it using the latest version in
    > CVS, following the exact same steps.  I guess this bug has already
    > been solved.

    The problem shows up in 22.0.90, but is solved in 22.0.96.

  I believe this is a bug I fixed.  I think the fix was in isearch.el,
  though that part of the memory is not clear.

  However, I still get spurious undesirable scrolling once in a while,
  not associated with isearch.  I don't know what causes that.

Re: "spurious scrolling bug"

[Richard Stallman]

    You probably mean this thread, which is (apparently) unrelated to the
    current bug:

Indeed, that is the bug that I already fixed.

I noted spurious scrolling on a few occasions.  One was on exiting
from C-s.  Eventually I found a reproducible case, so I tracked down
the cause and fixed it.

Another was after waiting for periods on the order of a minute,
particularly in Rmail.  I never figured out the cause of that, and I
think I never found a way to reproduce it.  Typically it happens after
I have used SPC, C-v or M-v to scroll through the message, so that
point is at the top or bottom line.  I think it was mainly after
scrolling down, but I am not sure.

Another case where I have seen it is immediately after typing C-c C-c
to send a message in Mail mode.  I noticed that a few times over the
past few weeks.

I will try to keep an eye out for whether these problems still happen.