GNU bug report logs - #4016
23.1.50; docview: scrolling up breaks after setting a slice

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Message #5 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Paer Kurlberg <kurlberg <at> math.kth.se>
To: emacs-pretest-bug <at> gnu.org
Subject: 23.1.50; docview: scrolling up breaks after setting a slice
Date: Sun, 02 Aug 2009 16:07:35 +0200

Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the emacs-pretest-bug <at> gnu.org
mailing list.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:


View a dvi file (or pdf file for that matter) with DocView.

Set a slice by typing "ss" (invoking doc-view-set-slice) with x and y
coordinates zero, and maximum width and height, as suggested by the
prompt.  (In fact, any slice settings seems to trigger the phenomena.)

When hitting space (invoking doc-view-scroll-up-or-next-page), the
document is not scrolled up, and the following error message appears:

image-next-line: Invalid image specification

Note: By hitting "sr" (removing the slice) it is again possible to use
space to scroll up.

Remark: On a laptop with a small screen it would be very useful to set
slices to get rid of the large margins, and yet being able to scroll
through the document (even with a slice set, I cannot see the whole
page at once.)



If Emacs crashed, and you have the Emacs process in the gdb debugger,
please include the output from the following gdb commands:
    `bt full' and `xbacktrace'.
If you would like to further debug the crash, please read the file
/usr/share/emacs/23.1.50/etc/DEBUG for instructions.


In GNU Emacs 23.1.50.1 (i486-pc-linux-gnu, GTK+ Version 2.16.1)
 of 2009-07-31 on lansones, modified by Debian
 (emacs-snapshot package, version 1:20090730-1~jaunty1)
Windowing system distributor `The X.Org Foundation', version
 11.0.10600000
configured using `configure  '--build' 'i486-linux-gnu' '--host'
 'i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib'
 '--libexecdir=/usr/lib' '--localstatedir=/var'
 '--infodir=/usr/share/info' '--mandir=/usr/share/man'
 '--with-pop=yes'
 '--enable-locallisppath=/etc/emacs-snapshot:/etc/emacs:/usr/local/share/emacs/23.1.50/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.1.50/site-lisp:/usr/share/emacs/site-lisp'
 '--with-x=yes' '--with-x-toolkit=gtk' 'build_alias=i486-linux-gnu'
 'host_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN
 -DSITELOAD_PURESIZE_EXTRA=5000 -g -O2' 'LDFLAGS=-g -Wl,--as-needed'
 'CPPFLAGS=''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: DocView

Minor modes in effect:
  tooltip-mode: t
  tool-bar-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
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
C-x C-f a r n o l d . d v i <return> <return> s s 0 
<return> 0 <return> 9 2 6 <return> 1 3 1 0 <return> 
SPC <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <menu-bar> 
<help-menu> <send-emacs-bug-report>

Recent messages:
Loading
/usr/share/emacs-snapshot/site-lisp/planner-el/planner-autoloads.el
(source)...done
Loading /etc/emacs/site-start.d/51planner-el.el (source)...done
Loading /etc/emacs/site-start.d/52remember-el.el (source)...
Loading /usr/share/emacs/site-lisp/remember-el/remember-autoloads.el
(source)...done
Loading /etc/emacs/site-start.d/52remember-el.el (source)...done
Loading /etc/emacs/site-start.d/60hyperspec.el (source)...done
For information about GNU Emacs and the GNU system, type C-h C-a.
DocView: using cached files!
Type C-c C-c to toggle between editing or viewing the document.
No key given.  Assumed normal.
image-next-line: Invalid image specification

Load-path shadows:
/usr/share/emacs/23.1.50/site-lisp/auctex/tex-mik

Message #10 received at 4016 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Paer Kurlberg <kurlberg <at> math.kth.se>
To: 4016 <at> debbugs.gnu.org
Subject: Re: bug#4016: Acknowledgement (23.1.50; docview: scrolling up breaks after setting a slice)
Date: Sun, 02 Aug 2009 18:08:21 +0200

In case it might be helpful: below is a backtrace.  It seems that the
problem is that image-get-display-property (called in the function
image-next-line) returns the list

((slice 0 0 1100 1600) (image :type png :file
  "/tmp/docview1000/arnold.dvi-b04e9949bb98146d331479915a45fc5b/page-1.png"
  :pointer arrow))

and therefore image-size complains since a "proper image" should be a
list whose car equals 'image.


BACKTRACE: 

Debugger entered--Lisp error: (error "Invalid image specification")
  image-size(((slice 0 0 1100 1600) (image :type png :file
  "/tmp/docview1000/arnold.dvi-b04e9949bb98146d331479915a45fc5b/page-1.png"
  :pointer arrow)))
  image-next-line(36)
  image-scroll-up(nil)
  doc-view-scroll-up-or-next-page()
  call-interactively(doc-view-scroll-up-or-next-page nil nil)

Message #15 received at 4016 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Tassilo Horn <tassilo <at> member.fsf.org>
To: Paer Kurlberg <kurlberg <at> math.kth.se>
Cc: 4016 <at> debbugs.gnu.org
Subject: Re: bug#4016: Acknowledgement (23.1.50; docview: scrolling up breaks after setting a slice)
Date: Mon, 03 Aug 2009 08:46:27 +0200

Paer Kurlberg <kurlberg <at> math.kth.se> writes:

> In case it might be helpful: below is a backtrace.  It seems that the
> problem is that image-get-display-property (called in the function
> image-next-line) returns the list
>
> ((slice 0 0 1100 1600) (image :type png :file
>   "/tmp/docview1000/arnold.dvi-b04e9949bb98146d331479915a45fc5b/page-1.png"
>   :pointer arrow))
>
> and therefore image-size complains since a "proper image" should be a
> list whose car equals 'image.

I can reproduce the error.  But I'm not too sure where the bug is
located.  According to the docs, the display property may be a single
display spec, or a list or vector of such.

,----[ (info "(elisp)Display Property") ]
| The value of the `display' property should be a display specification,
| or a list or vector containing several display specifications.
`----

So in that respect the slice + image spec are ok.

I think that maybe the C function

  int valid_image_p (object) Lisp_Object object;

in image.c should be adapted to accept lists/vectors including one image
spec.

Bye,
Tassilo

Message #18 received at 4016 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Paer Kurlberg <kurlberg <at> math.kth.se>
Cc: 4016 <at> debbugs.gnu.org
Subject: Re: bug#4016: 23.1.50; docview: scrolling up breaks after setting a
 slice
Date: Sun, 18 Jul 2021 21:10:58 +0200

Paer Kurlberg <kurlberg <at> math.kth.se> writes:

> View a dvi file (or pdf file for that matter) with DocView.
>
> Set a slice by typing "ss" (invoking doc-view-set-slice) with x and y
> coordinates zero, and maximum width and height, as suggested by the
> prompt.  (In fact, any slice settings seems to trigger the phenomena.)
>
> When hitting space (invoking doc-view-scroll-up-or-next-page), the
> document is not scrolled up, and the following error message appears:
>
> image-next-line: Invalid image specification

(I'm going through old bug reports that unfortunately weren't resolved
at the time.)

I tried reproducing this in Emacs 28, but I got no errors when doing
this.  (The slice command is `c s' now(?), though.)

Are you still seeing this issue in recent Emacs versions?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #23 received at 4016 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: kurlberg <kurlberg <at> math.kth.se>
Cc: 4016 <at> debbugs.gnu.org
Subject: Re: bug#4016: 23.1.50; docview: scrolling up breaks after setting a
 slice
Date: Sun, 18 Jul 2021 22:07:13 +0200

kurlberg <kurlberg <at> math.kth.se> writes:

> I just tried it on emacs 26.3, and the problem seems to be gone, I think
> the bug thus can be marked as resolved. Thanks for looking into this.

Thanks for checking; closing this bug report then.

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