bug#6455: 23.2; Backspace in view mode

bug#6455: 23.2; Backspace in view mode

[Francis Wright]

This bug report will be sent to the Free Software Foundation,
not to your local site managers!
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 bug-gnu-emacs@gnu.org mailing list,
and to the gnu.emacs.bug news group.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug.  If you can, give
a recipe starting from `emacs -Q':

Run emacs -Q.
Open a file using view-file (or v in dired mode).
Move to a point well away from the beginning of the buffer.
Press the backspace key.
The error message generated is "Beginning of buffer", which is not true.
I think the error message should be the same as generated by pressing
(say) the delete key, namely "Buffer is read-only: #<buffer prizes.sh>".
This error is not mode specific.

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'.
For information about debugging Emacs, please read the file
c:/NTEmacs/emacs-23.2/etc/DEBUG.


In GNU Emacs 23.2.1 (i386-mingw-nt6.0.6002)
 of 2010-05-08 on G41R2F1
Windowing system distributor `Microsoft Corp.', version 6.0.6002
configured using `configure --with-gcc (3.4) --no-opt --cflags -Ic:/xpm/include'

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: ENG
  value of $XMODIFIERS: nil
  locale-coding-system: cp1252
  default enable-multibyte-characters: t

Major mode: Shell-script

Minor modes in effect:
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-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-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t
  view-mode: t

Recent input:
<help-echo> M-x v i e w - f SPC <return> <help-echo> 
C-y C-u C-SPC <delete> <end> <return> <down-mouse-1> 
<mouse-1> <backspace> <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> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <menu-bar> <help-menu> <se
nd-emacs-bug-report>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
prizes.sh has auto save data; consider M-x recover-this-file
Setting up indent for shell type sh
setting up indent stuff
Indentation variables are now local.
Indentation setup for shell type sh
View mode: type C-h for help, h for commands, q to quit.
view-scroll-lines: Beginning of buffer

Load-path shadows:
c:/NTEmacs/emacs-23.2/../site-lisp/woman hides c:/NTEmacs/emacs-23.2/lisp/woman
c:/NTEmacs/emacs-23.2/../site-lisp/whitespace hides
c:/NTEmacs/emacs-23.2/lisp/whitespace
c:/NTEmacs/emacs-23.2/../site-lisp/ruler-mode hides
c:/NTEmacs/emacs-23.2/lisp/ruler-mode
c:/NTEmacs/emacs-23.2/../site-lisp/ls-lisp hides
c:/NTEmacs/emacs-23.2/lisp/ls-lisp

Features:
(shadow sort mail-extr message ecomplete rfc822 mml easymenu mml-sec
password-cache mm-decode mm-bodies mm-encode mailcap mail-parse rfc2231
rfc2047 rfc2045 qp ietf-drums mailabbrev nnheader gnus-util netrc
time-date mm-util mail-prsvr gmm-utils wid-edit mailheader canlock sha1
hex-util hashcash mail-utils emacsbug regexp-opt sh-script executable
view tooltip ediff-hook vc-hooks lisp-float-type mwheel dos-w32
disp-table ls-lisp w32-win w32-vars tool-bar dnd fontset image fringe
lisp-mode register page menu-bar rfn-eshadow timer select scroll-bar
mldrag 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 loaddefs button minibuffer faces cus-face files text-properties
overlay md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process multi-tty emacs)

bug#6455: 23.2; Backspace in view mode

[Glenn Morris]

"Francis Wright" wrote:

> Run emacs -Q.
> Open a file using view-file (or v in dired mode).
> Move to a point well away from the beginning of the buffer.
> Press the backspace key.
> The error message generated is "Beginning of buffer", which is not true.
> I think the error message should be the same as generated by pressing
> (say) the delete key, namely "Buffer is read-only: #<buffer prizes.sh>".

This is a confusing report. The backspace key in View-mode runs
View-scroll-page-backward, which scrolls the buffer backwards until it
bumps into the start of the buffer. It seems to me that it is doing
the right thing. Try it on a buffer where the whole buffer does not
fit into the window at once, after first moving to the end of the
buffer.

Why should it instead say that the buffer is read-only, when it is not
trying to modify the buffer in any way?

bug#6455: 23.2; Backspace in view mode

[Francis Wright]

> From: Glenn Morris [mailto:rgm@gnu.org]
> Sent: Friday, June 18, 2010 7:54 PM
> To: Francis Wright
> Cc: 6455@debbugs.gnu.org
> Subject: Re: bug#6455: 23.2; Backspace in view mode
> 
> "Francis Wright" wrote:
> 
> > Run emacs -Q.
> > Open a file using view-file (or v in dired mode).
> > Move to a point well away from the beginning of the buffer.
> > Press the backspace key.
> > The error message generated is "Beginning of buffer", which is not true.
> > I think the error message should be the same as generated by pressing
> > (say) the delete key, namely "Buffer is read-only: #<buffer prizes.sh>".
> 
> This is a confusing report. The backspace key in View-mode runs
> View-scroll-page-backward, which scrolls the buffer backwards until it
> bumps into the start of the buffer. It seems to me that it is doing
> the right thing. Try it on a buffer where the whole buffer does not
> fit into the window at once, after first moving to the end of the
> buffer.
> 
> Why should it instead say that the buffer is read-only, when it is not
> trying to modify the buffer in any way?

Sorry, you're right. I overlooked the binding of the backspace key; I assumed it
was supposed to delete characters backwards.