bug#29374: patch for lisp/pixel-scroll

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 22 Nov 2017 08:08:17 +0900 (JST)
> Cc: 29374@debbugs.gnu.org, tkk@misasa.okayama-u.ac.jp
> From: Tak Kunihiro <tkk@misasa.okayama-u.ac.jp>
> 
> >> Date: Tue, 21 Nov 2017 13:35:07 +0900 (JST)
> >> From: Tak Kunihiro <tkk@misasa.okayama-u.ac.jp>
> >> Cc: tkk@misasa.okayama-u.ac.jp
> >>
> >> I'm sending a patch for lisp/pixel-scroll.el.
> >>
> >> This patch fixes movement of cursor to stay away from the top of the
> >> line and the end of the line on a screen.
> >
> > Thanks, but please tell more about the problem, and perhaps show a
> > recipe to reproduce it.
> 
> First of all, expression of my previous message was not correct.
> Let me rephrase as below.
> 
>    This patch fixes movement of cursor to stay away from the top and
>    the bottom of a screen.
> 
> Before fix, sudden scope-jump happened on certain cases.  Let's
> consider a case with cursor is located at the bottom and about to
> scroll down (move scope up).
> 
> There is a condition where
>  bob is shown on the top of screen
>  and window-vscroll is non-zero.
> 
> On this condition, (scroll-up 1) would be called without
> (vertical-motion -1).  As a consequence screen jumps.
> 
> After the fix, cursor will be moved by vertical-motion before calling
> scroll-down or pixel-scroll-pixel-down.

Thanks, I pushed your changes.