Scrolling line per line: bug

[Eduardo Ochs]

> Try  (setq scroll-step 1)
>
> > -----Original Message-----
> > From: "Baenninger, Dominik" [SMTP:dominik.baenninger@ito.umnw.ethz.ch]
> > Sent: Monday, January 22, 2001 5:27 PM
> > To: help-gnu-emacs@gnu.org
> > Subject: Scrolling line per line
> >
> > Can anyone say, how I can tell emacs, that when I scroll with the
> > cursor, he should not forwarding several lines per step but only
> > line by line?
> >
> > Thanks
> > Dominik
> >
> > _______________________________________________
> > Help-gnu-emacs mailing list
> > Help-gnu-emacs@gnu.org
> > http://mail.gnu.org/mailman/listinfo/help-gnu-emacs

  (Info-goto-node "(elisp)Vertical Scrolling")
  (setq scroll-step 1)
  (setq scroll-conservatively 1)

But this behaves somewhat strangely if we have wrapped lines. Example:

Suppose that we have a very long line, "foo....bar....baz....quux",
but with many more dots, between a line that says "(recenter -1)" and
one that says "(recenter 0)", i.e.,

(recenter -1)
foo.............................................................................bar.............................................................................baz.............................................................................quux
(recenter 0)

This would appear like

  +------------------+
  |                  |
  |                  |
  |                  |
  |(recenter -1)     |
  |foo..............\|
  |.bar.............\|
  |..baz............\|
  |...quux           |
  |(recenter 0)      |
  |                  |
  |                  |
  +------------------+

in a text window. Then in the following two situations we get a
half-screen of scrolling even with `scroll-step' (or
`scroll-conservatively' in newer Emacsen; see the info node "Vertical
Scrolling" in the Emacs Lisp manual) set to 1:


I) +------------------+       II) +------------------+ 
   |                  |           |(recenter 0)      |
   |                  |           |                  |
   |                  |           |                  |
   |                  |           |                  |
   |                  |           |                  |
   |                  |           |                  |
   |                  |           |                  |
   |                  |           |                  |
   |                  |           |                  |
   |(recenter -1)     |           |                  |
   |foo..............\|           |                  |
   +------------------+           +------------------+

with the cursor in the last     with the cursor in the
line and going down, and...     top line and going up.


Is there a known workaround for this? If not, should I file a bug
report? Or should I consider that this message will be already taken
as a bug report, even if it is being sent to the wrong list?

  Cheers,
  Buenas Salenas Cronopio Cronopio,
    Eduardo Ochs
    http://angg.twu.net/
    edrx@inx.com.br


P.S.: I've tested this on GNU Emacsen 19.34, 20.7.2 and 21.0.93, on an
i386 that runs a rather standard Debian 2.2 GNU/Linux distribution.