bug#12799: 24.3.50; `scroll-conservatively', I-search and `C-g'

bug#12799: 24.3.50; `scroll-conservatively', I-search and `C-g'

[Dani Moncayo]

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Recipe from "emacs -nw -Q" (the "-nw" part is not strictly needed, but
it is cleaner for showing the problem):

1. Visit the attached file.
2. Adjust the vertical space (empty lines) between "first line" and
"last visible line" until the latter becomes indeed the last visible
line in the window.
3. Go to the start of the buffer: M-<
4. Advance one line: C-n
5. C-s 1
6. C-g

I observe that after step #5 the window is scrolled (OK), and that
scrolling is cancelled after step #6 (OK - like it should be).

But if I set `scroll-conservatively' to 1 and repeat the experiment
(from step #3), I observe that the vertical scrolling made in step #5
is not cancelled in step #6.  IMO it should be cancelled, because
"C-g" should leave the view (not just the point) where it was before
the Isearch.


In GNU Emacs 24.3.50.1 (i386-mingw-nt6.1.7601)
 of 2012-11-04 on MS-W7-DANI
Bzr revision: 110794 rgm@gnu.org-20121104041313-7j1z7vaqtrgopt26
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -I../../libs/libXpm-3.5.10/include -I../../libs/libXpm-3.5.10/src
 -I../../libs/libpng-1.2.37-lib/include -I../../libs/zlib-1.2.5
 -I../../libs/giflib-4.1.4-1-lib/include
 -I../../libs/jpeg-6b-4-lib/include
 -I../../libs/tiff-3.8.2-1-lib/include
 -I../../libs/libxml2-2.7.8-w32-bin/include/libxml2
 -I../../libs/gnutls-3.0.9-w32-bin/include
 -I../../libs/libiconv-1.9.2-1-lib/include'

Important settings:
  value of $LANG: ESN
  locale-coding-system: cp1252
  default enable-multibyte-characters: t


-- 
Dani Moncayo

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first line





























last visible line
1
2
3
4
5
6

bug#12799: 24.3.50; `scroll-conservatively', I-search and `C-g'

[Marcin Borkowski]

On 2012-11-04, at 19:07, Dani Moncayo <dmoncayo@gmail.com> wrote:

> Recipe from "emacs -nw -Q" (the "-nw" part is not strictly needed, but
> it is cleaner for showing the problem):
>
> 1. Visit the attached file.
> 2. Adjust the vertical space (empty lines) between "first line" and
> "last visible line" until the latter becomes indeed the last visible
> line in the window.
> 3. Go to the start of the buffer: M-<
> 4. Advance one line: C-n
> 5. C-s 1
> 6. C-g
>
> I observe that after step #5 the window is scrolled (OK), and that
> scrolling is cancelled after step #6 (OK - like it should be).
>
> But if I set `scroll-conservatively' to 1 and repeat the experiment
> (from step #3), I observe that the vertical scrolling made in step #5
> is not cancelled in step #6.  IMO it should be cancelled, because
> "C-g" should leave the view (not just the point) where it was before
> the Isearch.

Hi everyone,

I can confirm that this behavior is still present in GNU Emacs
25.1.50.1.  I am not 100% sure, however, whether this is really
a bug.

Best,

-- 
Marcin Borkowski
http://mbork.pl/en

bug#12799: 24.3.50; `scroll-conservatively', I-search and `C-g'

[Eli Zaretskii]

> Date: Sat, 30 Jan 2016 20:49:02 +0100
> Cc: 12799@debbugs.gnu.org
> 
> On 2012-11-04, at 19:07, Dani Moncayo <dmoncayo@gmail.com> wrote:
> 
> > Recipe from "emacs -nw -Q" (the "-nw" part is not strictly needed, but
> > it is cleaner for showing the problem):
> >
> > 1. Visit the attached file.
> > 2. Adjust the vertical space (empty lines) between "first line" and
> > "last visible line" until the latter becomes indeed the last visible
> > line in the window.
> > 3. Go to the start of the buffer: M-<
> > 4. Advance one line: C-n
> > 5. C-s 1
> > 6. C-g
> >
> > I observe that after step #5 the window is scrolled (OK), and that
> > scrolling is cancelled after step #6 (OK - like it should be).
> >
> > But if I set `scroll-conservatively' to 1 and repeat the experiment
> > (from step #3), I observe that the vertical scrolling made in step #5
> > is not cancelled in step #6.  IMO it should be cancelled, because
> > "C-g" should leave the view (not just the point) where it was before
> > the Isearch.
> 
> Hi everyone,
> 
> I can confirm that this behavior is still present in GNU Emacs
> 25.1.50.1.  I am not 100% sure, however, whether this is really
> a bug.

No, it isn't a bug, but the intended behavior: contrary to the OP's
expectations C-g is _not_ supposed to cancel the scroll, it is
supposed to return point to where the search started.  And setting
scroll-conservatively to 1 means that if point is 1 line above or
below the window, Emacs should scroll the window only by 1 line in
order to bring point into view.  Which is what Emacs does in this
case.

So I'm closing the bug.  I apologize for not noticing it when it was
originally reported.

Thanks.