GNU bug report logs - #29374
patch for lisp/pixel-scroll

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Tak Kunihiro <tkk <at> misasa.okayama-u.ac.jp>
Subject: bug#29374: closed (Re: bug#29374: patch for lisp/pixel-scroll)
Date: Fri, 01 Dec 2017 08:59:02 +0000

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Your bug report

#29374: patch for lisp/pixel-scroll

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 29374 <at> debbugs.gnu.org.

-- 
29374: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=29374
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Tak Kunihiro <tkk <at> misasa.okayama-u.ac.jp>
Cc: 29374-done <at> debbugs.gnu.org
Subject: Re: bug#29374: patch for lisp/pixel-scroll
Date: Fri, 01 Dec 2017 10:58:12 +0200

> Date: Wed, 22 Nov 2017 08:08:17 +0900 (JST)
> Cc: 29374 <at> debbugs.gnu.org, tkk <at> misasa.okayama-u.ac.jp
> From: Tak Kunihiro <tkk <at> misasa.okayama-u.ac.jp>
> 
> >> Date: Tue, 21 Nov 2017 13:35:07 +0900 (JST)
> >> From: Tak Kunihiro <tkk <at> misasa.okayama-u.ac.jp>
> >> Cc: tkk <at> 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.

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From: Tak Kunihiro <tkk <at> misasa.okayama-u.ac.jp>
To: bug-gnu-emacs <at> gnu.org
Cc: tkk <at> misasa.okayama-u.ac.jp
Subject: patch for lisp/pixel-scroll
Date: Tue, 21 Nov 2017 13:35:07 +0900 (JST)

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.

ChangeLog entry and a patch are attached.

* ChangeLog

2017-11-21 Tak Kunihiro <tkk <at> misasa.okayama-u.ac.jp>

        Fix cursor movement to stay away from the top of line and the end of line on a screen

        * lisp/pixel-scroll.el (pixel-scroll-up): Move cursor down regardless eob is shown on the top.
        (pixel-scroll-down) Move cursor up regardless bob is shown on the top.

* Patch
diff --git a/lisp/pixel-scroll.el b/lisp/pixel-scroll.el
old mode 100644
new mode 100755
index 2213a02..556613d
--- a/lisp/pixel-scroll.el
+++ b/lisp/pixel-scroll.el
@@ -110,11 +110,11 @@ This is an alternative of `scroll-up'.  Scope moves downward."
                        pixel-resolution-fine-flag
                      (frame-char-height))
                  (pixel-line-height))))
-      (if (pixel-eob-at-top-p)            ; when end-of-the-buffer is close
-          (scroll-up 1)                   ; relay on robust method
-        (while (pixel-point-at-top-p amt) ; prevent too late (multi tries)
-          (vertical-motion 1))            ; move point downward
-        (pixel-scroll-pixel-up amt)))))   ; move scope downward
+      (while (pixel-point-at-top-p amt) ; prevent too late (multi tries)
+        (vertical-motion 1))            ; move point downward
+      (if (pixel-eob-at-top-p)          ; when end-of-the-buffer is close
+          (scroll-up 1)                 ; relay on robust method
+        (pixel-scroll-pixel-up amt))))) ; move scope downward
 
 (defun pixel-scroll-down (&optional arg)
   "Scroll text of selected window down ARG lines.
@@ -127,11 +127,11 @@ This is and alternative of `scroll-down'.  Scope moves upward."
                        pixel-resolution-fine-flag
                      (frame-char-height))
                  (pixel-line-height -1))))
-      (if (or (pixel-bob-at-top-p amt) ; when beginning-of-the-buffer is seen
-              (pixel-eob-at-top-p))    ; for file with a long line
-          (scroll-down 1)              ; relay on robust method
-        (while (pixel-point-at-bottom-p amt) ; prevent too late (multi tries)
-          (vertical-motion -1))
+      (while (pixel-point-at-bottom-p amt) ; prevent too late (multi tries)
+        (vertical-motion -1))              ; move point upward
+      (if (or (pixel-bob-at-top-p amt)     ; when beginning-of-the-buffer is seen
+              (pixel-eob-at-top-p))        ; for file with a long line
+          (scroll-down 1)                  ; relay on robust method
         (pixel-scroll-pixel-down amt)))))
 
 (defun pixel-bob-at-top-p (amt)

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