bug#11099: 23.2; Filter function causes flickering in minibuffer

[Sean McLaughlin]

1) Create a file count.sh

#!/bin/bash

ctr=0

while true; do
    sleep 1
    echo "ctr = $ctr"
    ctr=$(( ctr + 1 ))
done

2) Create a buffer called *count*

3) Start count asyncronously from a clean emacs (-q)

(defun Tmp.filter-fun (proc s)
  (with-current-buffer "*count*"
    (insert s)))

(defun Tmp.count ()
  (interactive)
  (let ((process
         (start-process
          "count"
          "*count*"
          "/home/seanmcl/bin/count")))
    (set-process-filter process 'Tmp.filter-fun)))

4) Type C-x

This will cause C-x to show up in the minibuffer.  Every time a
line is filtered from count, the C-x flickers in the minibuffer,
sometimes moving a character to the right and then back to the
left.


In GNU Emacs 23.2.1 (i486-pc-linux-gnu, GTK+ Version 2.20.0)
 of 2010-12-11 on raven, modified by Debian
Windowing system distributor `The X.Org Foundation', version 11.0.10707000
configured using `configure  '--build' 'i486-linux-gnu' '--build'
'i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib'
'--libexecdir=/usr/lib' '--localstatedir=/var/lib'
'--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-pop=yes'
'--enable-locallisppath=/etc/emacs23:/etc/emacs:/usr/local/share/emacs/23.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.2/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/23.2/leim'
'--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars'
'build_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g -O2' 'LDFLAGS=-g'
'CPPFLAGS=''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.utf8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Fundamental

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

Recent input:
<escape> x r e p o r t SPC e m SPC <return>

Recent messages:
Loading /etc/emacs/site-start.d/50git-core.el (source)...done
Loading /etc/emacs/site-start.d/50haskell-mode.el (source)...
Loading /usr/local/share/emacs/23.2/site-lisp/haskell-mode/haskell-site-file.el
(source)...done
Loading /etc/emacs/site-start.d/50haskell-mode.el (source)...done
Loading /etc/emacs/site-start.d/50psvn.el (source)...done
Loading /etc/emacs/site-start.d/50python-docutils.el (source)...done
Loading /etc/emacs/site-start.d/50sml-mode.el (source)...
Loading /usr/local/share/emacs/23.2/site-lisp/sml-mode/sml-mode-startup.el
(source)...done
Loading /etc/emacs/site-start.d/50sml-mode.el (source)...done
For information about GNU Emacs and the GNU system, type C-h C-a.

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hides 
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Features:
(shadow sort mail-extr message sendmail regexp-opt ecomplete rfc822 mml
easymenu mml-sec password-cache mm-decode mm-bodies mm-encode mailcap
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gnus-util netrc time-date mm-util mail-prsvr gmm-utils wid-edit
mailheader canlock sha1 hex-util hashcash mail-utils emacsbug
emacs-goodies-el emacs-goodies-custom emacs-goodies-loaddefs easy-mmode
tooltip ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd
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format env code-pages mule custom widget hashtable-print-readable
backquote make-network-process dbusbind system-font-setting
font-render-setting gtk x-toolkit x multi-tty emacs)