bug#1713: follow-mode with three vertical windows causes Emacs to hang

bug#1713: follow-mode with three vertical windows causes Emacs to hang

[Teemu Likonen]

Emacs hangs when follow-mode is used with three vertically split windows
and the buffer/window text is scrolled. The "hang" means that Emacs
stops responding and takes nearly all the CPU time.

Steps to reproduce:

    $ emacs -Q

    C-h r           (Emacs manual)
    C-x 3
    C-x 3
    C-x +
    M-x follow-mode RET

Now press C-n (next-line) down and keep it down. The cursor moves and
the buffer text scrolls but at some point Emacs just hangs.

This is always reproducible with my Emacs 22.2.1 (Debian package) and
Emacs 23 (http://emacs.orebokech.com/).

bug#1713: marked as done (follow-mode with three vertical windows causes Emacs to hang)

[Emacs bug Tracking System]

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with message-id <87sko5bpcy.fsf@cyd.mit.edu>
and subject line Re: follow-mode with three vertical windows causes Emacs to hang
has caused the Emacs bug report #1713,
regarding follow-mode with three vertical windows causes Emacs to hang
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
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-- 
1713: http://emacsbugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=1713
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From: Teemu Likonen <tlikonen@iki.fi>
To: bug-gnu-emacs@gnu.org
Subject: follow-mode with three vertical windows causes Emacs to hang
Date: Sat, 27 Dec 2008 17:31:14 +0200
Message-ID: <874p0p8wjh.fsf@iki.fi>

Emacs hangs when follow-mode is used with three vertically split windows
and the buffer/window text is scrolled. The "hang" means that Emacs
stops responding and takes nearly all the CPU time.

Steps to reproduce:

    $ emacs -Q

    C-h r           (Emacs manual)
    C-x 3
    C-x 3
    C-x +
    M-x follow-mode RET

Now press C-n (next-line) down and keep it down. The cursor moves and
the buffer text scrolls but at some point Emacs just hangs.

This is always reproducible with my Emacs 22.2.1 (Debian package) and
Emacs 23 (http://emacs.orebokech.com/).




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From: Chong Yidong <cyd@stupidchicken.com>
To: Teemu Likonen <tlikonen@iki.fi>
Cc: 1713-done@emacsbugs.donarmstrong.com
Subject: Re: follow-mode with three vertical windows causes Emacs to hang
Date: Tue, 30 Dec 2008 11:27:09 -0500
Message-ID: <87sko5bpcy.fsf@cyd.mit.edu>

Alas, Follow mode is not well-maintained, and does not handle
variable-height text terribly well.  I've checked in several fixes to
prevent this and some other related bugs.  The hang should be resolved
now.  Thanks for the report.