bug#367: compilation-scroll-output not working on certain long line

[Kevin Ryde <user42@zip.com.au>]

[-- Attachment #1: Type: text/plain, Size: 2139 bytes --]

With foo.el and foo.pl below, running

	emacs -Q foo.el
	M-x eval-buffer

produces a compilation window showing only "xxx.xx" bits, where I hoped
setting compilation-scroll-output to `t' in foo.el would make it follow
the further output after that, ie. the "bar" lines (which you can see by
switching to the *compilation* buffer and scrolling down).

The foo.pl script is merely to print the provoking output.  It's a long
line arriving as its first 1024 bytes and then enough to just fill the
10-line compilation window.  During the second sleep the end of the
"xxx.xx" is the last line in the window.

I get the problem on both a console tty and under gtk X, and in both the
debian packaged 22.2 and my build of the current cvs.  It seems to
depend on the sleeps, ie. pauses in the output, so if you don't get the
effect you might try increasing them a bit.




In GNU Emacs 22.2.1 (i486-pc-linux-gnu, GTK+ Version 2.12.9)
 of 2008-04-27 on raven, modified by Debian
configured using `configure  '--build=i486-linux-gnu' '--host=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/emacs22:/etc/emacs:/usr/local/share/emacs/22.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/22.2/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/22.2/leim' '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 'build_alias=i486-linux-gnu' 'host_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_AU
  locale-coding-system: iso-8859-1
  default-enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  show-paren-mode: t
  encoded-kbd-mode: t
  file-name-shadow-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  auto-compression-mode: t
  line-number-mode: t


[-- Attachment #2: foo.el --]
[-- Type: application/emacs-lisp, Size: 95 bytes --]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #3: foo.pl --]
[-- Type: text/x-perl, Size: 1353 bytes --]

#!/usr/bin/perl

sleep 2;
$| = 1;

print 'xxxxxxxx: xxx.xx xxx.xx xxx.xx xxxxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxxxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxxxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxxxx.xx xxxxx.xx xxxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxxxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxxxx.xx xxx.xx xxx.xx xxx.xx xxxxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxxxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxxxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx';
sleep 2;

print ' xxx.xx xxxxx.xx xxxxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxx.xx xxxxx.xx xxx.xx xxx.xx xxx.xx xxx.xx
';
sleep 2;

foreach (1..100) { print "bar\n"; }
exit 0;