bug#22715: 25.0.91; Point randomly jumps during key entry

bug#22715: 25.0.91; Point randomly jumps during key entry

[Steve Revilak]

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First, please accept my apologies for the poor bug report.  I'm calling
it a poor bug report because I've been unable to find a simple recipe
that easily reproduces the behavior I'm seeing.

The behavior itself is easy to describe: while providing keyboard input,
sometimes point jumps to a (seemingly) random place in the buffer.

Some examples

  - while holding the UP arrow to slowly scroll upwards in the current
    buffer, point suddenly `jumps' up, over several screenfuls of text

  - while typing (ordinary alphanumeric text), point jumps to a line
    near the top of the file.  I've noticed this most often when using
    emacs to write java code.  I'll be typing away in the body of a
    method, and point will jump to a position in the file header
    comment, several hundred lines earlier.

This doesn't happen very often.  Perhaps 3--4 times during a work day.
I have not found a way to make it happen on demand.

I've experienced this behavior in 25.0.90 and 25.0.91, but not in
earlier versions.

I typically see this behavior in java-mode and org-mode.  That said, the
vast majority of my emacs usage involves java-mode and org-mode.

I've seen this behavior on two different x86_64 GNU/Linux systems.
One system runs Redhat 6.4, and the other runs OpenSUSE 13.2.  Both
systems have `standard' USB keyboards, and optical mice.

If I'm able to find a nice set of steps to reproduce, I'll add them to
this bug report.

If there are suggestions for gathering/providing more information,
please let me know, and I'll gladly try them.





In GNU Emacs 25.0.91.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.14.15)
  of 2016-02-16 built on sunny
Windowing system distributor 'The X.Org Foundation', version 11.0.11601000
System Description:	openSUSE 13.2 (Harlequin) (x86_64)

Configured using:
  'configure --prefix=/usr/local/emacs-25.0.91'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GCONF GSETTINGS NOTIFY
ACL GNUTLS LIBXML2 FREETYPE XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11

Important settings:
   value of $LC_COLLATE: C
   value of $LANG: en_US.UTF-8
   value of $XMODIFIERS: @im=ibus
   locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
   tooltip-mode: t
   global-eldoc-mode: t
   electric-indent-mode: t
   mouse-wheel-mode: t
   tool-bar-mode: t
   menu-bar-mode: t
   file-name-shadow-mode: t
   global-font-lock-mode: t
   font-lock-mode: t
   blink-cursor-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t
   line-number-mode: t
   transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message dired format-spec rfc822 mml
mml-sec epg epg-config gnus-util mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util help-fns help-mode easymenu cl-loaddefs pcase
cl-lib mail-prsvr mail-utils time-date mule-util tooltip eldoc electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list newcomment elisp-mode lisp-mode prog-mode register page
menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core frame cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese charscript case-table epa-hook jka-cmpr-hook help
simple abbrev minibuffer cl-preloaded nadvice loaddefs button faces
cus-face macroexp files text-properties overlay sha1 md5 base64 format
env code-pages mule custom widget hashtable-print-readable backquote
dbusbind inotify dynamic-setting system-font-setting font-render-setting
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 87179 5415)
  (symbols 48 19682 0)
  (miscs 40 38 110)
  (strings 32 14733 4487)
  (string-bytes 1 422301)
  (vectors 16 12267)
  (vector-slots 8 425290 4370)
  (floats 8 166 37)
  (intervals 56 198 0)
  (buffers 976 11)
  (heap 1024 44093 1008))

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bug#22715: 25.0.91; Point randomly jumps during key entry

[Andreas Schwab]

Try C-h l (view-lossage) to see the last few input events Emacs has
received.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

bug#22715: 25.0.91; Point randomly jumps during key entry

[Joakim Jalap]

FWIW, this happens to me too. Usually in c-mode, since that's what I
work with. I *think* I have seen a tendency for point to jump to
beginning-of-defun quite a lot of the time.

Joakim

bug#22715: 25.0.91; Point randomly jumps during key entry

[Eli Zaretskii]

> Date: Tue, 16 Feb 2016 20:39:49 -0500
> From: Steve Revilak <steve@srevilak.net>
> 
> First, please accept my apologies for the poor bug report.  I'm calling
> it a poor bug report because I've been unable to find a simple recipe
> that easily reproduces the behavior I'm seeing.
> 
> The behavior itself is easy to describe: while providing keyboard input,
> sometimes point jumps to a (seemingly) random place in the buffer.
> 
> Some examples
> 
>   - while holding the UP arrow to slowly scroll upwards in the current
>     buffer, point suddenly `jumps' up, over several screenfuls of text
> 
>   - while typing (ordinary alphanumeric text), point jumps to a line
>     near the top of the file.  I've noticed this most often when using
>     emacs to write java code.  I'll be typing away in the body of a
>     method, and point will jump to a position in the file header
>     comment, several hundred lines earlier.
> 
> This doesn't happen very often.  Perhaps 3--4 times during a work day.
> I have not found a way to make it happen on demand.
> 
> I've experienced this behavior in 25.0.90 and 25.0.91, but not in
> earlier versions.
> 
> I typically see this behavior in java-mode and org-mode.  That said, the
> vast majority of my emacs usage involves java-mode and org-mode.
> 
> I've seen this behavior on two different x86_64 GNU/Linux systems.
> One system runs Redhat 6.4, and the other runs OpenSUSE 13.2.  Both
> systems have `standard' USB keyboards, and optical mice.
> 
> If I'm able to find a nice set of steps to reproduce, I'll add them to
> this bug report.
> 
> If there are suggestions for gathering/providing more information,
> please let me know, and I'll gladly try them.

Thanks.

It's indeed hard to do anything with this without more details.  Some
questions:

 . Are the problems in java-mode and org-mode similar?  It doesn't
   sound like that, but I'm not sure.

 . Do you have similar Emacs customizations on both systems where you
   see this?

 . Can you make this happen in "emacs -Q"?

Thanks.

bug#22715: 25.0.91; Point randomly jumps during key entry

[Eli Zaretskii]

> From: Joakim Jalap <joakim.jalap@fastmail.com>
> Date: Wed, 17 Feb 2016 10:26:45 +0100
> 
> FWIW, this happens to me too. Usually in c-mode, since that's what I
> work with. I *think* I have seen a tendency for point to jump to
> beginning-of-defun quite a lot of the time.

Vanilla C Mode, or do you have some customizations there?

bug#22715: 25.0.91; Point randomly jumps during key entry

[Joakim Jalap]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Joakim Jalap <joakim.jalap@fastmail.com>
>> Date: Wed, 17 Feb 2016 10:26:45 +0100
>> 
>> FWIW, this happens to me too. Usually in c-mode, since that's what I
>> work with. I *think* I have seen a tendency for point to jump to
>> beginning-of-defun quite a lot of the time.
>
> Vanilla C Mode, or do you have some customizations there?

I have no customizations to c-mode, but I do use a c-style I've defined.

And I have a lot of minor modes active, like ggtags, cscope, and so on.
But I have those enabled in emacs 24 as well, and I've never seen this
behaviour there.

bug#22715: 25.0.91; Point randomly jumps during key entry

[Eli Zaretskii]

> From: Joakim Jalap <joakim.jalap@fastmail.com>
> Cc: 22715@debbugs.gnu.org
> Date: Wed, 17 Feb 2016 17:52:19 +0100
> 
> > Vanilla C Mode, or do you have some customizations there?
> 
> I have no customizations to c-mode, but I do use a c-style I've defined.
> 
> And I have a lot of minor modes active, like ggtags, cscope, and so on.
> But I have those enabled in emacs 24 as well, and I've never seen this
> behaviour there.

I asked this to have an idea of what factors could be at work here.
One of the customizations might expose some bug, and it would be good
to know which one is that, because it will make looking for the bug
easier.

So if you have a way of finding out which optional feature causes the
buggy behavior, it will help.

Thanks.

bug#22715: 25.0.91; Point randomly jumps during key entry

[Joakim Jalap]

Eli Zaretskii <eliz@gnu.org> writes:

> I asked this to have an idea of what factors could be at work here.
> One of the customizations might expose some bug, and it would be good
> to know which one is that, because it will make looking for the bug
> easier.
>
> So if you have a way of finding out which optional feature causes the
> buggy behavior, it will help.
>
> Thanks.

Sure, I will try to disable as much as possible and see if it
disappears, and the enable the stuff one by one if it does.

If I recall correctly there was some talk of something like this on the
ML a while back (I can't find it right now) which had something to do
with a rewrite of the undo system? I've rebuilt Emacs several time since
then, with 'make clean' in between, but is it possible I still have some
byte compiled files laying around form back then? Is there a way to
check?

Thanks for looking in to this.

Joakim

bug#22715: 25.0.91; Point randomly jumps during key entry

[Eli Zaretskii]

> From: Joakim Jalap <joakim.jalap@fastmail.com>
> Cc: 22715@debbugs.gnu.org
> Date: Wed, 17 Feb 2016 22:13:09 +0100
> 
> If I recall correctly there was some talk of something like this on the
> ML a while back (I can't find it right now) which had something to do
> with a rewrite of the undo system? I've rebuilt Emacs several time since
> then, with 'make clean' in between, but is it possible I still have some
> byte compiled files laying around form back then? Is there a way to
> check?

I don't think this should matter, but if you want to be sure, you can
always delete all the *.elc files and say "make" to rebuild them all.

bug#22715: 25.0.91; Point randomly jumps during key entry

[Joakim Jalap]

Eli Zaretskii <eliz@gnu.org> writes:

> I don't think this should matter, but if you want to be sure, you can
> always delete all the *.elc files and say "make" to rebuild them all.

Right, I will try that too.

bug#22715: 25.0.91; Point randomly jumps during key entry

[Steve Revilak]

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Thanks, Eli and Andreas, for your suggestions.

I began by collecting `view-lossage' after several instances of
point-jumping.  Here is a representative example:

      > [self-insert-command]
      SPC [self-insert-command]
      a [self-insert-command]
      l [self-insert-command]
      l [self-insert-command]
      R [self-insert-command]
      e [self-insert-command]
      q [self-insert-command]
      u [self-insert-command]
      e [self-insert-command]
      s [self-insert-command]  <<< HERE
      t [self-insert-command]
      I [self-insert-command]
      M-x [execute-extended-command]
      v [self-insert-command]
      i [self-insert-command]
      e [self-insert-command]
      w [self-insert-command]
      - [self-insert-command]
      l [self-insert-command]
      o [self-insert-command]
      <tab> [minibuffer-complete]
      <return> [minibuffer-complete-and-exit]

I'd been typing on line 494 of a .java file.  The characters "stI"
ended up on line 464.  I don't see any unexpected characters in
view-lossage; the characters that appear are those I actually typed.


Next, I tried to reproduce this behavior in a "almost emacs -Q"
configuration, which was

   emacs -q --no-site-file --no-site-lisp --no-splash

and the smallest ~/.emacs I could get away with.  I was not able to
reproduce the point-jumping behavior in this configuration.


Looking through the emacs-devel archives, I came across

   https://lists.gnu.org/archive/html/emacs-devel/2015-11/msg01687.html

which describes behavior nearly identical to what I've observed.


A later post suggests a patch

   https://lists.gnu.org/archive/html/emacs-devel/2016-01/msg00029.html

and another suggests that point-jumping might be related to timers

   https://lists.gnu.org/archive/html/emacs-devel/2015-11/msg02127.html


As an experiment, I went back to my "normal emacs", but with a few
lines in ~/.emacs commented out:

   ;(semantic-mode 1)
   ;(semantic-stickyfunc-mode t)

I also commented out `setq' definitions for
semanticdb-default-save-directory and semanticdb-project-roots.  With
those elements commented out, I couldn't reproduce the point-jumping
behavior.  (I'll continue to test in this configuration, to be more
certain that the non-reproduce isn't just a coincidence.)


If it would help, I can restore the aforementioned `semantic' pieces,
and see if I can correlate point-jumping with specific timer events.
I can also try the save-excursion patch in
https://lists.gnu.org/archive/html/emacs-devel/2016-01/msg00029.html.


Finally, 

   https://lists.gnu.org/archive/html/emacs-devel/2016-01/msg00031.html

suggests this might be related to Bug #15045.


Steve

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bug#22715: 25.0.91; Point randomly jumps during key entry

[Eli Zaretskii]

> Date: Thu, 18 Feb 2016 21:22:40 -0500
> From: Steve Revilak <steve@srevilak.net>
> 
> As an experiment, I went back to my "normal emacs", but with a few
> lines in ~/.emacs commented out:
> 
>    ;(semantic-mode 1)
>    ;(semantic-stickyfunc-mode t)
> 
> I also commented out `setq' definitions for
> semanticdb-default-save-directory and semanticdb-project-roots.  With
> those elements commented out, I couldn't reproduce the point-jumping
> behavior.  (I'll continue to test in this configuration, to be more
> certain that the non-reproduce isn't just a coincidence.)
> 
> If it would help, I can restore the aforementioned `semantic' pieces,
> and see if I can correlate point-jumping with specific timer events.
> I can also try the save-excursion patch in
> https://lists.gnu.org/archive/html/emacs-devel/2016-01/msg00029.html.

That would help, thanks.  Eventually, we need to establish what chain
of events causes redisplay when point is in a temporary location.

> Finally, 
> 
>    https://lists.gnu.org/archive/html/emacs-devel/2016-01/msg00031.html
> 
> suggests this might be related to Bug #15045.

That bug was resolved.  So if this is related, there should be some
other place in Semantic that needs to take advantage of the changes
made to resolve that bug.

Thanks.

bug#22715: 25.0.91; Point randomly jumps during key entry

[David Engster]

Eli Zaretskii writes:
>>    https://lists.gnu.org/archive/html/emacs-devel/2016-01/msg00031.html
>> 
>> suggests this might be related to Bug #15045.
>
> That bug was resolved.

No, it turned out that #22287 was another issue than #15045, and it's
not yet resolved. I really have to apologize for the delay here. I'll
push a fix to emacs-25 over the weekend.

-David

bug#22715: 25.0.91; Point randomly jumps during key entry

[David Engster]

David Engster writes:
> Eli Zaretskii writes:
>>>    https://lists.gnu.org/archive/html/emacs-devel/2016-01/msg00031.html
>>> 
>>> suggests this might be related to Bug #15045.
>>
>> That bug was resolved.
>
> No, it turned out that #22287 was another issue than #15045, and it's
> not yet resolved. I really have to apologize for the delay here. I'll
> push a fix to emacs-25 over the weekend.

Done. I hope this fixes this bug as well.

-David

bug#22715: 25.0.91; Point randomly jumps during key entry

[Eli Zaretskii]

> From: David Engster <deng@randomsample.de>
> Cc: 22715@debbugs.gnu.org,  Steve Revilak <steve@srevilak.net>
> Date: Sun, 21 Feb 2016 17:27:28 +0100
> 
> David Engster writes:
> > Eli Zaretskii writes:
> >>>    https://lists.gnu.org/archive/html/emacs-devel/2016-01/msg00031.html
> >>> 
> >>> suggests this might be related to Bug #15045.
> >>
> >> That bug was resolved.
> >
> > No, it turned out that #22287 was another issue than #15045, and it's
> > not yet resolved. I really have to apologize for the delay here. I'll
> > push a fix to emacs-25 over the weekend.
> 
> Done. I hope this fixes this bug as well.

Thanks.  Steve, please test.

bug#22715: 25.0.91; Point randomly jumps during key entry

[Steve Revilak]

Eli and David,

Thanks for you help!  I have one small question about testing.

Should I `git clone git://git.savannah.gnu.org/emacs.git', check out
the emacs-25 branch, then build and test there?  Or, is there a patch
I should apply to the 25.0.91 pretest sources?

Steve

bug#22715: 25.0.91; Point randomly jumps during key entry

[Eli Zaretskii]

> Date: Mon, 22 Feb 2016 12:22:18 -0500
> From: Steve Revilak <steve@srevilak.net>
> Cc: David Engster <deng@randomsample.de>, 22715@debbugs.gnu.org
> 
> Should I `git clone git://git.savannah.gnu.org/emacs.git', check out
> the emacs-25 branch, then build and test there?  Or, is there a patch
> I should apply to the 25.0.91 pretest sources?

It's up to you.  If you want to go the patch way, simply apply the
patch you see in David's changeset.

bug#22715: 25.0.91; Point randomly jumps during key entry

[Steve Revilak]

I patched the 29.0.91 pretest sources with diffs from these two
commits:

---------------------------------
commit aa5a7948431437fc09931ac21eb05f365e1f8876
Author: David Engster <deng@...>
Date:   Sun Feb 21 17:16:45 2016 +0100

     Remove `semanticdb-save-all-db-idle' from `auto-save-hook'

     * lisp/cedet/semantic/db-mode.el (semanticdb-hooks): Do not put
       `semanticdb-save-all-db-idle' into `auto-save-hook'. The latter is
       not an idle hook, so it's not appropriate to call it there. It will
       already be called in the `semantic-idle-work-core-handler', which
       runs when Emacs is actually idle.

commit 2d8b2fd034ccc61f949b408373342b5f9f8ba592
Author: David Engster <deng@...>
Date:   Sun Feb 21 17:11:01 2016 +0100

     Restore point when writing semantic table to disk

     * lisp/cedet/semantic/db-file.el (object-write): Wrap call to
       `semantic-fetch-tags' in `save-excursion', since it might move point
       in current buffer. (Bug #22287)
---------------------------------

I'll work with these changes for a while, and report back with my
findings.

bug#22715: 25.0.91; Point randomly jumps during key entry

[Steve Revilak]

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After applying

   commit aa5a7948431437fc09931ac21eb05f365e1f8876
   commit 2d8b2fd034ccc61f949b408373342b5f9f8ba592

to the emacs-25.0.91 pretest, the `point-jumping' no longer occurs.

Thanks again for your help!

Steve

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