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

[Steve Revilak <steve@srevilak.net>]

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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:
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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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