[debbugs-tracker] bug#22395: closed (25.0.50; 'C-v' scrolls only a half of the window height)

[GNU bug Tracking System]

Your message dated Mon, 18 Jan 2016 18:25:24 +0200
with message-id <address@hidden>
and subject line Re: bug#22395: 25.0.50; 'C-v' scrolls only a half of the 
window height
has caused the debbugs.gnu.org bug report #22395,
regarding 25.0.50; 'C-v' scrolls only a half of the window height
to be marked as done.

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-- 
22395: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=22395
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--- Begin Message --- Subject: 25.0.50; 'C-v' scrolls only a half of the window height Date: Sun, 17 Jan 2016 21:50:16 +0100

Recipe from "emacs -Q":

1. Eval:
    (setq scroll-preserve-screen-position t)
    (setq scroll-margin 2)

2. Visit the attached file.

On my system, I initially see lines 1 to 33.

3. Type 'C-v'

I observe that 'C-v' has scrolled the buffer vertically, but only by
about a half of the window height (I now see lines 16 to 48).
Subsequent 'C-v' commands do the same: they scroll the buffer by a
half of the window.

This seems wrong.  The amount of scrolling should be "a near full
screen", as described in 'C-h k C-v'.

I observe this bug also in the last 24.5 release.

In GNU Emacs 25.0.50.1 (i686-pc-mingw32)
 of 2016-01-17 built on LEG570
Repository revision: a0d5b7ae3bb014bb0b1c205d123c597df0e76411
Windowing system distributor 'Microsoft Corp.', version 10.0.10586
Configured using:
 'configure --host=i686-pc-mingw32 --enable-checking=yes,glyphs'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS

Important settings:
  value of $LANG: ENU
  locale-coding-system: cp1252

-- 
Dani Moncayo

f1
Description: Binary data

--- End Message ---

> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: bug#22395: 25.0.50; 'C-v' scrolls only a half of the window height
>
>
>
>
> Date: 
>
> Mon, 18 Jan 2016 18:25:24 +0200
>
>
>
>
> > Date: Sun, 17 Jan 2016 21:50:16 +0100
> > From: Dani Moncayo <address@hidden>
> > 
> > 1. Eval:
> >     (setq scroll-preserve-screen-position t)
> >     (setq scroll-margin 2)
> > 
> > 2. Visit the attached file.
> > 
> > On my system, I initially see lines 1 to 33.
> > 
> > 3. Type 'C-v'
> > 
> > I observe that 'C-v' has scrolled the buffer vertically, but only by
> > about a half of the window height (I now see lines 16 to 48).
> > Subsequent 'C-v' commands do the same: they scroll the buffer by a
> > half of the window.
> > 
> > This seems wrong.  The amount of scrolling should be "a near full
> > screen", as described in 'C-h k C-v'.
>
> Start the same recipe from line #3 or greater, and the "bug" goes
> away.
>
> You asked Emacs to do the impossible: preserve the screen position of
> point at the first window line and also not to allow point to enter
> the first 2 lines of the window.  Emacs didn't know what to do with
> this conflict.  Now it does.
>
>
> --- End Message ---