GNU bug report logs - #14780
Regression: C-n doesn't go to next line under simple circumstances

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Barry OReilly <gundaetiapo <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Regression: C-n doesn't go to next line under simple circumstances
Date: Wed, 3 Jul 2013 12:03:15 -0400

[Message part 1 (text/plain, inline)]

Let cant-next-line.el have file contents:

  (tool-bar-mode 0)
  (global-whitespace-mode 1)
  (set-face-attribute 'default nil :height 80)
  (setq scroll-margin 4)
  (setq scroll-conservatively 101)

Open up the attached cant-next-line.txt by:

  emacs -Q --load cant-next-line.el cant-next-line.txt

Move point to be immediately before the 'h' of "here". Try to reach the '-'
character at the end of the file using C-n. You can't. If I move point to
the beginning of line containing "here", then I can.

I checked emacs-24.3 and could not reproduce this, so it is a regression.

I witnessed this with latest trunk 68068a328a854998a0071f4714cbacdfed36fcc1
and for commit 20899d085afe62520113b5acbfe3dbba57823dc9 (Jun 5) which I use
day to day (because the commit immediately following broke Evil in a
critical way).

---

In GNU Emacs 24.3.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.10.4)
 of 2013-06-18 on psd15
Windowing system distributor `The X.Org Foundation', version 11.0.70101000
System Description:    Red Hat Enterprise Linux Client release 5.4 (Tikanga)

Configured using:
 `configure
 --prefix=/redacted/user/boreilly/sw/emacs-install-trunk-20899d085afe62520113b5acbfe3dbba57823dc9
 --with-gif=no'

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Text

Minor modes in effect:
  global-whitespace-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
M-x r e p o r t <tab> <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
None found.

Features:
(shadow sort nadvice gnus-util mail-extr emacsbug message format-spec
rfc822 mml easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse
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ietf-drums mm-util mail-prsvr mail-utils disp-table whitespace time-date
tooltip ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list newcomment lisp-mode
register page menu-bar rfn-eshadow timer select scroll-bar mouse
jit-lock font-lock syntax facemenu font-core frame cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev
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overlay sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process dbusbind
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty emacs)

[Message part 2 (text/html, inline)]

[cant-next-line.txt (text/plain, attachment)]

Message #8 received at 14780 <at> debbugs.gnu.org (full text, mbox):

From: Barry OReilly <gundaetiapo <at> gmail.com>
To: 14780 <at> debbugs.gnu.org
Subject: Re: bug#14780: Acknowledgement (Regression: C-n doesn't go to next
 line under simple circumstances)
Date: Fri, 19 Jul 2013 14:37:57 -0400

Git bisected the repo at Savannah to:

15cdf9527f5a78a5ea9aa0ba3fee8d7b84c3acf9 is the first bad commit
commit 15cdf9527f5a78a5ea9aa0ba3fee8d7b84c3acf9
Author: Eli Zaretskii <eliz <at> gnu.org>
Date:   Mon Dec 3 22:48:12 2012 +0200

    Fix bug #13055 with cursor positioning inside scroll-margin.

     src/xdisp.c (redisplay_window): If the cursor is visible, but inside
     the scroll margin, move point outside the margin.

Message #11 received at 14780 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Barry OReilly <gundaetiapo <at> gmail.com>
Cc: 14780 <at> debbugs.gnu.org
Subject: Re: bug#14780: Acknowledgement (Regression: C-n doesn't go to next
 line	under simple circumstances)
Date: Fri, 19 Jul 2013 22:14:28 +0300

> Date: Fri, 19 Jul 2013 14:37:57 -0400
> From: Barry OReilly <gundaetiapo <at> gmail.com>
> 
> Git bisected the repo at Savannah to:
> 
> 15cdf9527f5a78a5ea9aa0ba3fee8d7b84c3acf9 is the first bad commit
> commit 15cdf9527f5a78a5ea9aa0ba3fee8d7b84c3acf9
> Author: Eli Zaretskii <eliz <at> gnu.org>
> Date:   Mon Dec 3 22:48:12 2012 +0200
> 
>     Fix bug #13055 with cursor positioning inside scroll-margin.
> 
>      src/xdisp.c (redisplay_window): If the cursor is visible, but inside
>      the scroll margin, move point outside the margin.

I cannot reproduce the bug on my system.  Unless I don't understand
what you mean by "cannot reach the '-' character".  I can reach every
line in the buffer by using C-n, using your recipe (or what I
understand of it).

Message #14 received at 14780 <at> debbugs.gnu.org (full text, mbox):

From: Barry OReilly <gundaetiapo <at> gmail.com>
To: 14780 <at> debbugs.gnu.org
Subject: Re: bug#14780: Acknowledgement (Regression: C-n doesn't go to next
 line under simple circumstances)
Date: Fri, 19 Jul 2013 15:53:35 -0400

Use this /tmp/cant-next-line.el to automate a little more.

(tool-bar-mode 0)
(global-whitespace-mode 1)
(set-face-attribute 'default nil :height 80)
(setq scroll-margin 4)
(setq scroll-conservatively 101)
(add-hook 'emacs-startup-hook (lambda ()
                                (re-search-forward "here")
                                (trace-redisplay)
                                ;; Doesn't reproduce it, have to C-n manually
                                ;; (run-at-time "1 sec" 1 (lambda ()
                                ;;
(call-interactively 'next-line)))
                                ))

Reproduction won't happen if you:
  - resize the window
  - use M-x next-line instead of C-n
  - press and hold C-n
  - navigate in ways other than prescribed

I can see it everytime I follow the recipe.

Here is the trace-redisplay resulting from:
  ./src/emacs -r -Q --load /tmp/cant-next-line.el /tmp/cant-next-line.txt
  Then C-n 5 times

redisplay_internal 0
0x110d9a0 (cant-next-line.txt): same window start
0x110d9a0 (cant-next-line.txt): 1
0x110d9a0 (cant-next-line.txt): same window start
0x110d9a0 (cant-next-line.txt): 1
redisplay_preserve_echo_area (8)
redisplay_internal 0
redisplay_internal 0
0x110d9a0 (cant-next-line.txt): cursor movement
0x110d9a0 (cant-next-line.txt): try_scrolling
redisplay_internal 0
0x110d9a0 (cant-next-line.txt): forced window start
redisplay_preserve_echo_area (7)
redisplay_internal 0
redisplay_internal 0
0x110d9a0 (cant-next-line.txt): forced window start
redisplay_preserve_echo_area (7)
redisplay_internal 0
redisplay_internal 0
0x110d9a0 (cant-next-line.txt): forced window start
redisplay_preserve_echo_area (7)
redisplay_internal 0
redisplay_internal 0
0x110d9a0 (cant-next-line.txt): forced window start
redisplay_preserve_echo_area (7)
redisplay_internal 0
redisplay_preserve_echo_area (8)
redisplay_internal 0
redisplay_preserve_echo_area (8)
redisplay_internal 0

Message #17 received at 14780 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Barry OReilly <gundaetiapo <at> gmail.com>
Cc: 14780 <at> debbugs.gnu.org
Subject: Re: bug#14780: Regression: C-n doesn't go to next line	under simple
 circumstances
Date: Fri, 19 Jul 2013 23:30:29 +0300

> Date: Fri, 19 Jul 2013 15:53:35 -0400
> From: Barry OReilly <gundaetiapo <at> gmail.com>
> 
> Use this /tmp/cant-next-line.el to automate a little more.
> 
> (tool-bar-mode 0)
> (global-whitespace-mode 1)
> (set-face-attribute 'default nil :height 80)
> (setq scroll-margin 4)
> (setq scroll-conservatively 101)
> (add-hook 'emacs-startup-hook (lambda ()
>                                 (re-search-forward "here")
>                                 (trace-redisplay)
>                                 ;; Doesn't reproduce it, have to C-n manually
>                                 ;; (run-at-time "1 sec" 1 (lambda ()
>                                 ;;
> (call-interactively 'next-line)))
>                                 ))
> 
> Reproduction won't happen if you:
>   - resize the window
>   - use M-x next-line instead of C-n
>   - press and hold C-n
>   - navigate in ways other than prescribed
> 
> I can see it everytime I follow the recipe.
> 
> Here is the trace-redisplay resulting from:
>   ./src/emacs -r -Q --load /tmp/cant-next-line.el /tmp/cant-next-line.txt

I get 'Search failed: "here"'.

Are you using a recent trunk?  I'm using today's trunk.

> redisplay_internal 0
> 0x110d9a0 (cant-next-line.txt): same window start
> 0x110d9a0 (cant-next-line.txt): 1
> 0x110d9a0 (cant-next-line.txt): same window start
> 0x110d9a0 (cant-next-line.txt): 1
> redisplay_preserve_echo_area (8)
> redisplay_internal 0
> redisplay_internal 0
> 0x110d9a0 (cant-next-line.txt): cursor movement
> 0x110d9a0 (cant-next-line.txt): try_scrolling
> redisplay_internal 0
> 0x110d9a0 (cant-next-line.txt): forced window start
> redisplay_preserve_echo_area (7)
> redisplay_internal 0
> redisplay_internal 0
> 0x110d9a0 (cant-next-line.txt): forced window start
> redisplay_preserve_echo_area (7)
> redisplay_internal 0
> redisplay_internal 0
> 0x110d9a0 (cant-next-line.txt): forced window start
> redisplay_preserve_echo_area (7)
> redisplay_internal 0
> redisplay_internal 0
> 0x110d9a0 (cant-next-line.txt): forced window start
> redisplay_preserve_echo_area (7)
> redisplay_internal 0
> redisplay_preserve_echo_area (8)
> redisplay_internal 0
> redisplay_preserve_echo_area (8)
> redisplay_internal 0

I see nothing extraordinary here.

Message #20 received at 14780 <at> debbugs.gnu.org (full text, mbox):

From: Barry OReilly <gundaetiapo <at> gmail.com>
To: 14780 <at> debbugs.gnu.org
Subject: Re: bug#14780: Regression: C-n doesn't go to next line under simple
 circumstances
Date: Fri, 19 Jul 2013 16:37:30 -0400

> I get 'Search failed: "here"'.

Are you using the cant-next-line.txt attached to the bug report? It
clearly contains "here".

> Are you using a recent trunk?  I'm using today's trunk.

I'm using:
  commit 3961bd5799169d6e24e151a8fc06d637c348eb93
  Author: Paul Eggert <eggert <at> cs.ucla.edu>
  Date:   Fri Jul 19 11:09:23 2013 -0700

Message #23 received at 14780 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Barry OReilly <gundaetiapo <at> gmail.com>
Cc: 14780 <at> debbugs.gnu.org
Subject: Re: bug#14780: Regression: C-n doesn't go to next line under
 simple	circumstances
Date: Sat, 20 Jul 2013 09:42:03 +0300

> Date: Fri, 19 Jul 2013 16:37:30 -0400
> From: Barry OReilly <gundaetiapo <at> gmail.com>
> 
> > I get 'Search failed: "here"'.
> 
> Are you using the cant-next-line.txt attached to the bug report?

Yes.

> It clearly contains "here".

Maybe Emacs searches for it before it visits the file?

> > Are you using a recent trunk?  I'm using today's trunk.
> 
> I'm using:
>   commit 3961bd5799169d6e24e151a8fc06d637c348eb93
>   Author: Paul Eggert <eggert <at> cs.ucla.edu>
>   Date:   Fri Jul 19 11:09:23 2013 -0700

Strange.

Message #26 received at 14780 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: gundaetiapo <at> gmail.com
Cc: 14780 <at> debbugs.gnu.org
Subject: Re: bug#14780: Regression: C-n doesn't go to next line
 under	simple	circumstances
Date: Sat, 20 Jul 2013 11:33:07 +0300

Does the following fix the problem for you?

=== modified file 'src/xdisp.c'
--- src/xdisp.c	2013-07-16 21:35:45 +0000
+++ src/xdisp.c	2013-07-20 08:21:36 +0000
@@ -15592,7 +15592,8 @@ redisplay_window (Lisp_Object window, in
 	     Move it back to a fully-visible line.  */
 	  new_vpos = window_box_height (w);
 	}
-      else if (w->cursor.vpos >=0)
+      else if (w->cursor.vpos >=0
+	       && PT >= BEGV && PT < ZV)
 	{
 	  /* Some people insist on not letting point enter the scroll
 	     margin, even though this part handles windows that didn't
@@ -15619,7 +15620,16 @@ redisplay_window (Lisp_Object window, in
 	      if (header_line)
 		window_height += CURRENT_HEADER_LINE_HEIGHT (w);
 	      if (w->cursor.y >= window_height - pixel_margin)
-		new_vpos = window_height - pixel_margin;
+		{
+		  struct text_pos pos;
+
+		  SET_TEXT_POS (pos, PT, PT_BYTE);
+		  start_display (&it, w, pos);
+		  it.current_y = it.vpos = 0;
+		  move_it_to (&it, ZV, -1, -1, -1, MOVE_TO_POS);
+		  if (it.vpos > margin)
+		    new_vpos = window_height - pixel_margin;
+		}
 	    }
 	}
 

Message #29 received at 14780 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: gundaetiapo <at> gmail.com
Cc: 14780 <at> debbugs.gnu.org
Subject: Re: bug#14780: Regression: C-n doesn't go to next
 line	under	simple	circumstances
Date: Sat, 20 Jul 2013 12:09:32 +0300

> Date: Sat, 20 Jul 2013 11:33:07 +0300
> From: Eli Zaretskii <eliz <at> gnu.org>
> Cc: 14780 <at> debbugs.gnu.org
> 
> Does the following fix the problem for you?

Sorry, that change had a bug.  Please try this instead:

=== modified file 'src/xdisp.c'
--- src/xdisp.c	2013-07-16 21:35:45 +0000
+++ src/xdisp.c	2013-07-20 09:05:11 +0000
@@ -15608,10 +15608,11 @@ redisplay_window (Lisp_Object window, in
 	     the Y coordinate of the _next_ row, see the definition of
 	     MATRIX_ROW_BOTTOM_Y.  */
 	  if (w->cursor.vpos < margin + header_line)
-	    new_vpos
-	      = pixel_margin + (header_line
-				? CURRENT_HEADER_LINE_HEIGHT (w)
-				: 0) + frame_line_height;
+	    {
+	      w->cursor.vpos = -1;
+	      clear_glyph_matrix (w->desired_matrix);
+	      goto try_to_scroll;
+	    }
 	  else
 	    {
 	      int window_height = window_box_height (w);
@@ -15619,7 +15620,11 @@ redisplay_window (Lisp_Object window, in
 	      if (header_line)
 		window_height += CURRENT_HEADER_LINE_HEIGHT (w);
 	      if (w->cursor.y >= window_height - pixel_margin)
-		new_vpos = window_height - pixel_margin;
+		{
+		  w->cursor.vpos = -1;
+		  clear_glyph_matrix (w->desired_matrix);
+		  goto try_to_scroll;
+		}
 	    }
 	}
 

Message #32 received at 14780 <at> debbugs.gnu.org (full text, mbox):

From: Barry OReilly <gundaetiapo <at> gmail.com>
Cc: 14780 <at> debbugs.gnu.org
Subject: Re: bug#14780: Regression: C-n doesn't go to next line under simple
 circumstances
Date: Mon, 22 Jul 2013 16:37:49 -0400

On Sat, Jul 20, 2013 at 5:09 AM, Eli Zaretskii <eliz <at> gnu.org> wrote:
> Sorry, that change had a bug.  Please try this instead:

That fixes the issue. Thanks.

Message #37 received at 14780-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Barry OReilly <gundaetiapo <at> gmail.com>
Cc: 14780-done <at> debbugs.gnu.org
Subject: Re: bug#14780: Regression: C-n doesn't go to next line under
 simple	circumstances
Date: Wed, 24 Jul 2013 20:38:12 +0300

> Date: Mon, 22 Jul 2013 16:37:49 -0400
> From: Barry OReilly <gundaetiapo <at> gmail.com>
> Cc: 14780 <at> debbugs.gnu.org
> 
> On Sat, Jul 20, 2013 at 5:09 AM, Eli Zaretskii <eliz <at> gnu.org> wrote:
> > Sorry, that change had a bug.  Please try this instead:
> 
> That fixes the issue. Thanks.

Thanks, committed as trunk revision 113532.

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