GNU bug report logs - #662
23.0.60; Constant recentering with scroll-margin set

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Message #5 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Ralf Angeli <angeli <at> caeruleus.net>
To: emacs-pretest-bug <at> gnu.org
Subject: 23.0.60; Constant recentering with scroll-margin set
Date: Wed, 06 Aug 2008 23:16:24 +0200

Start Emacs with
emacs -Q -eval "(progn (setq scroll-margin 1) (dotimes (i 100) (newline)))"
and start typing in the scratch buffer.  With nearly every new line
which is inserted, the buffer is recentered.


In GNU Emacs 23.0.60.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.12.11)
 of 2008-08-06 on photon
Windowing system distributor `The X.Org Foundation', version 11.0.10402000
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.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  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
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
M-x r e p o r t - e m <tab> <return>

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Message #10 received at 662 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Chong Yidong <cyd <at> stupidchicken.com>
To: Ralf Angeli <angeli <at> caeruleus.net>
Cc: 662 <at> debbugs.gnu.org
Subject: Re: 23.0.60; Constant recentering with scroll-margin set
Date: Wed, 06 Aug 2008 21:26:30 -0400

> Start Emacs with emacs -Q -eval "(progn (setq scroll-margin 1)
> (dotimes (i 100) (newline)))" and start typing in the scratch buffer.
> With nearly every new line which is inserted, the buffer is
> recentered.

Could you try to provide a more precise recipe?  I'm not sure what you
mean.

Message #15 received at 662 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Chong Yidong <cyd <at> stupidchicken.com>
To: Ralf Angeli <angeli <at> caeruleus.net>
Cc: 662 <at> debbugs.gnu.org
Subject: Re: 23.0.60; Constant recentering with scroll-margin set
Date: Wed, 06 Aug 2008 21:54:49 -0400

Actually, I see the bug now.  I've made some changes to CVS that ought
to fix it.  Does it work for you now?

Message #22 received at 662 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Ralf Angeli <angeli <at> caeruleus.net>
To: Chong Yidong <cyd <at> stupidchicken.com>
Cc: 662 <at> debbugs.gnu.org
Subject: Re: 23.0.60; Constant recentering with scroll-margin set
Date: Thu, 07 Aug 2008 20:21:47 +0200

* Chong Yidong (2008-08-07) writes:

> Actually, I see the bug now.  I've made some changes to CVS that ought
> to fix it.  Does it work for you now?

It's better, but it doesn't seem to be totally fixed.  There is still
some recentering happening when scrolling a long article in Gnus.  If
you type <RET> to scroll, the bottom of the article will be reached
eventually and once this happens, the buffer will be recentered and the
last line jumps to the middle of the window.

-- 
Ralf

Message #27 received at 662 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Ralf Angeli <angeli <at> caeruleus.net>
To: Chong Yidong <cyd <at> stupidchicken.com>
Cc: 662 <at> debbugs.gnu.org
Subject: Re: 23.0.60; Constant recentering with scroll-margin set
Date: Thu, 07 Aug 2008 20:41:50 +0200

* Ralf Angeli (2008-08-07) writes:

> * Chong Yidong (2008-08-07) writes:
>
>> Actually, I see the bug now.  I've made some changes to CVS that ought
>> to fix it.  Does it work for you now?
>
> It's better, but it doesn't seem to be totally fixed.  There is still
> some recentering happening when scrolling a long article in Gnus.  If
> you type <RET> to scroll, the bottom of the article will be reached
> eventually and once this happens, the buffer will be recentered and the
> last line jumps to the middle of the window.

It could also be that this has to be fixed in Gnus.  I'm not sure, but I
remember that there was a similar issue back in 2005 where some changes
hat to be made in `gnus-article-next-page' and related functions in
order to deal with some changes in the handling of `scroll-margin'.

-- 
Ralf

Message #32 received at 662 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Ralf Angeli <angeli <at> caeruleus.net>
To: Chong Yidong <cyd <at> stupidchicken.com>
Cc: 662 <at> debbugs.gnu.org
Subject: Re: 23.0.60; Constant recentering with scroll-margin set
Date: Fri, 08 Aug 2008 20:32:12 +0200

* Ralf Angeli (2008-08-07) writes:

> It could also be that this has to be fixed in Gnus.  I'm not sure, but I
> remember that there was a similar issue back in 2005 where some changes
> hat to be made in `gnus-article-next-page' and related functions in
> order to deal with some changes in the handling of `scroll-margin'.

Okay, the problem is the statement
(move-to-window-line -1)
in `gnus-article-next-page'.  If `scroll-margin' is set and greater than
0 it will lead to a recentering.  This is usually countered by
`gnus-article-next-page-1', but not at the end of an article where
`gnus-article-next-page-1' will not be called.

The problem can be circumvented by changing the above statement to
(move-to-window-line (- -1 scroll-margin))

Let me know if the recentering behavior will stay like it is now, then I
can report this to the Gnus maintainers.

-- 
Ralf

Message #37 received at 662 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Ralf Angeli <angeli <at> caeruleus.net>
Cc: 662 <at> debbugs.gnu.org, Chong Yidong <cyd <at> stupidchicken.com>
Subject: Re: bug#662: 23.0.60; Constant recentering with scroll-margin set
Date: Fri, 08 Aug 2008 16:56:06 -0400

>> It could also be that this has to be fixed in Gnus.  I'm not sure, but I
>> remember that there was a similar issue back in 2005 where some changes
>> hat to be made in `gnus-article-next-page' and related functions in
>> order to deal with some changes in the handling of `scroll-margin'.

> Okay, the problem is the statement
> (move-to-window-line -1)
> in `gnus-article-next-page'.  If `scroll-margin' is set and greater than
> 0 it will lead to a recentering.  This is usually countered by
> `gnus-article-next-page-1', but not at the end of an article where
> `gnus-article-next-page-1' will not be called.

> The problem can be circumvented by changing the above statement to
> (move-to-window-line (- -1 scroll-margin))

> Let me know if the recentering behavior will stay like it is now, then I
> can report this to the Gnus maintainers.

BTW, shouldn't Gnus "just" set scroll-margin (and such things)
buffer-locally in its article buffer, so as to isolate it from
such problems?
Or maybe not buffer-locally but let-bound around a call to redisplay?


        Stefan

Message #42 received at 662 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Ralf Angeli <angeli <at> caeruleus.net>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>, ding <at> gnus.org
Cc: 662 <at> debbugs.gnu.org, Chong Yidong <cyd <at> stupidchicken.com>
Subject: Re: bug#662: 23.0.60; Constant recentering with scroll-margin set
Date: Tue, 12 Aug 2008 20:51:51 +0200

* Stefan Monnier (2008-08-08) writes:

> BTW, shouldn't Gnus "just" set scroll-margin (and such things)
> buffer-locally in its article buffer, so as to isolate it from
> such problems?
> Or maybe not buffer-locally but let-bound around a call to redisplay?

I guess this is something to decide for the Gnus developers, so I am
forwarding the message to the Gnus list.

Note that this discussion is centered around the recentering bug I
reported earlier on the Gnus list, so this is not related to a new bug.

-- 
Ralf

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