bug#1517: cursor doesn't track shell output for very long lines

[Ken Olum]

In shell mode, with variable comint-scroll-show-maximum-output set to
nil, output with lines longer than the screen can cause the cursor to
be left behind instead of tracking the end of the output.  To reproduce:

Start emacs with emacs -Q
M-x shell
M-x set-variable
comint-scroll-show-maximum-output
nil
(Run csh if that isn't your usual shell)
repeat 10000 echo -n x ; echo

The cursor is now in the middle of the long line instead of on the next
line where it belongs.

                                        Ken Olum

In GNU Emacs 22.1.1 (x86_64-mandrake-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2008-10-27 on titan.mandriva.com, modified by Mandriva
Windowing system distributor `The Cygwin/X Project', version 11.0.60899901
configured using `configure  '--prefix=/usr' '--libexecdir=/usr/lib64' 
'--sharedstatedir=/var' '--with-gcc' '--with-pop' '--mandir=/usr/share/man' 
'--infodir=/usr/share/info' '--with-x-toolkit' 'x86_64-mandrake-linux' 
'--libdir=/usr/lib64' 'build_alias=x86_64-mandrake-linux' 
'host_alias=x86_64-mandrake-linux' 'target_alias=x86_64-mandrake-linux' 
'CFLAGS=-O2 -g -pipe -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector 
--param=ssp-buffer-size=4 -fexceptions -DNCURSES_OSPEED_T 
-fno-zero-initialized-in-bss' 'LDFLAGS=-s''

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

Major mode: Shell

Minor modes in effect:
  shell-dirtrack-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  auto-compression-mode: t
  line-number-mode: t

Recent input:
M-x s h e l l <return> M-x s e t - v a r <return> c 
o m i n <tab> s c <tab> m a <tab> <backspace> <backspace> 
s h o <tab> <return> n i l <return> <down-mouse-2> 
<mouse-2> <left> <left> <left> <left> <left> <left> 
<right> <backspace> <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> <backspace> 
<return> M-> <help-echo> M-x r e p o r t - e m a c 
s - b u g <return>

Recent messages:
("emacs" "-Q")
For information about the GNU Project and its goals, type C-h C-p.
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