scroll-margin woes

scroll-margin woes

[David]

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I've recently set my scroll-margin value to >0 and immediately had
problems using Gnus. First, I would recommend to apply the patch that
sets the scroll-margin to zero in summary buffers:

http://article.gmane.org/gmane.emacs.devel/85300

Even if this patch may only cure the symptom of a bug in Emacs I'd still
think it should be applied since a) it does no harm and b) the summary
buffer is otherwise practically unusable if scroll-margin > 0 and
Emacs 22 or newer.

Additionally, I noticed that when I hit ENTER in the summary buffer to
scroll the currently displayed article by one line, it often scrolls by
nearly a full page. This frequently happens in shimbun groups, but not
always - I can't really say why. My guess is this is due to

(move-to-window-line -1) 

in gnus-article-next-page. I fixed this behavior by putting the cursor
in the middle of the article buffer before calling
gnus-article-next-page-1 (see attached patch). This works for me, but I
don't know if this is the correct thing to do. Scrolling in Emacs is a
deep mystery to me...

-David


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--- gnus-art.el	2008-03-13 15:51:23.000000000 +0100
+++ gnus-art.el-patched	2008-03-13 15:52:31.000000000 +0100
@@ -6100,6 +6100,9 @@
 	(gnus-narrow-to-page 1)		;Go to next page.
 	nil)
     ;; More in this page.
+    (when (and (boundp 'scroll-margin)
+	       (not (zerop scroll-margin)))
+      (move-to-window-line nil))
     (gnus-article-next-page-1 lines)
     nil))
 

Re: scroll-margin woes

[Ralf Angeli]

* David (2008-03-13) writes:

> the summary
> buffer is otherwise practically unusable if scroll-margin > 0 and
> Emacs 22 or newer.

Get rid of your outdated Gnus installation and try again.

-- 
Ralf

Re: scroll-margin woes

[David]

Ralf Angeli <angeli@caeruleus.net> writes:
> * David (2008-03-13) writes:
>
>> the summary
>> buffer is otherwise practically unusable if scroll-margin > 0 and
>> Emacs 22 or newer.
>
> Get rid of your outdated Gnus installation and try again.

I'm using Gnus from CVS.

-David

Re: scroll-margin woes

[Ralf Angeli]

* David (2008-03-14) writes:

> Ralf Angeli <angeli@caeruleus.net> writes:
>> * David (2008-03-13) writes:
>>
>>> the summary
>>> buffer is otherwise practically unusable if scroll-margin > 0 and
>>> Emacs 22 or newer.
>>
>> Get rid of your outdated Gnus installation and try again.
>
> I'm using Gnus from CVS.

Hm, then I don't know what the problem is.  I've been using the CVS
version as well with Emacs 22 and I haven't encountered any problems
with `scroll-margin' set to 1.

-- 
Ralf

Re: scroll-margin woes

[David]

Ralf Angeli <angeli@caeruleus.net> writes:
>> I'm using Gnus from CVS.
>
> Hm, then I don't know what the problem is.  I've been using the CVS
> version as well with Emacs 22 and I haven't encountered any problems
> with `scroll-margin' set to 1.

My scroll-margin is set to 7. The problem is not that easy to reproduce
since it seems to depend on the size of the summary buffer and is worst
with a threaded display (though it also occurs with disabled
threads). See also this post:

http://article.gmane.org/gmane.emacs.gnus.general/66402

I made a little screencast which shows the bug:

http://m61s02.vlinux.de/vid/gnus-scroll-margin.ogg

I open the group and continuously hit 'd' to mark posts as read. As you
can see, the summary buffer doesn't update correctly; you can see in the
status line that articles are actually marked:

-David