bug#6856: 24.0.50; fill-paragraph always marks buffer as modified

bug#6856: 24.0.50; fill-paragraph always marks buffer as modified

[Jose Antonio Ortega Ruiz]

1. emacs -Q
2. Open any file, go to a filled paragraph spawning more than 1 line
3. M-q. If the paragraph was already filled, no modification of the
   buffer occurs, but the buffer is marked as modified nonetheless.
3'. If the first M-q actually modified the text, save the buffer and go
    to 3: a second M-q does not change the text but marks the buffer as
    modified.


In GNU Emacs 24.0.50.1 (i486-pc-linux-gnu, GTK+ Version 2.20.1)
 of 2010-08-08 on elegiac, modified by Debian
 (emacs-snapshot package, version 1:20100808-1)
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/24.0.50/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.0.50/site-lisp:/usr/share/emacs/site-lisp' '--without-compress-info' '--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: Text

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
  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 / t m p / f o o . t x t RET a SPC b SPC c SPC 
d e C-x C-s ESC q C-a ESC q C-o C-x C-s a SPC d k f 
j l a SPC d k j f ESC q C-x C-s ESC q C-e RET a l d 
k f j SPC l s k d f j SPC a l k d j f RET l a k s d 
f j C-x C-s ESC q C-x C-s ESC q SPC s k d f j SPC a 
l s k j f SPC a l s k f j ESC q SPC a s l k ESC q C-x 
C-s ESC q C-x C-s ESC q C-x C-s C-h k ESC q ESC x r 
e p o r t - b u TAB RET

Recent messages:
Wrote /tmp/foo.txt
Saving file /tmp/foo.txt...
Wrote /tmp/foo.txt
Saving file /tmp/foo.txt...
Wrote /tmp/foo.txt
Saving file /tmp/foo.txt...
Wrote /tmp/foo.txt
Saving file /tmp/foo.txt...
Wrote /tmp/foo.txt
Type C-x 1 to delete the help window.

Load-path shadows:
/etc/emacs/site-start hides /usr/local/share/emacs/site-lisp/site-start
/usr/share/emacs/24.0.50/site-lisp/debian-startup hides /usr/share/emacs/site-lisp/debian-startup
/usr/local/share/emacs/site-lisp/cedet/speedbar/sb-image hides /usr/share/emacs/24.0.50/lisp/sb-image
/usr/local/share/emacs/site-lisp/cedet/speedbar/dframe hides /usr/share/emacs/24.0.50/lisp/dframe
/usr/local/share/emacs/site-lisp/cedet/speedbar/speedbar hides /usr/share/emacs/24.0.50/lisp/speedbar
/usr/local/share/emacs/site-lisp/cedet/common/ezimage hides /usr/share/emacs/24.0.50/lisp/ezimage
/usr/local/share/emacs/site-lisp/cedet/eieio/eieio hides /usr/share/emacs/24.0.50/lisp/emacs-lisp/eieio
/usr/local/share/emacs/site-lisp/cedet/eieio/eieio-base hides /usr/share/emacs/24.0.50/lisp/emacs-lisp/eieio-base
/usr/local/share/emacs/site-lisp/cedet/eieio/eieio-opt hides /usr/share/emacs/24.0.50/lisp/emacs-lisp/eieio-opt
/usr/local/share/emacs/site-lisp/cedet/eieio/eieio-datadebug hides /usr/share/emacs/24.0.50/lisp/emacs-lisp/eieio-datadebug
/usr/local/share/emacs/site-lisp/cedet/eieio/eieio-custom hides /usr/share/emacs/24.0.50/lisp/emacs-lisp/eieio-custom
/usr/local/share/emacs/site-lisp/cedet/eieio/eieio-comp hides /usr/share/emacs/24.0.50/lisp/emacs-lisp/eieio-comp
/usr/local/share/emacs/site-lisp/cedet/eieio/chart hides /usr/share/emacs/24.0.50/lisp/emacs-lisp/chart
/usr/local/share/emacs/site-lisp/cedet/eieio/eieio-speedbar hides /usr/share/emacs/24.0.50/lisp/emacs-lisp/eieio-speedbar
/usr/local/share/emacs/site-lisp/cedet/common/mode-local hides /usr/share/emacs/24.0.50/lisp/cedet/mode-local
/usr/local/share/emacs/site-lisp/cedet/common/inversion hides /usr/share/emacs/24.0.50/lisp/cedet/inversion
/usr/local/share/emacs/site-lisp/cedet/semantic/semantic hides /usr/share/emacs/24.0.50/lisp/cedet/semantic
/usr/local/share/emacs/site-lisp/cedet/common/cedet-global hides /usr/share/emacs/24.0.50/lisp/cedet/cedet-global
/usr/local/share/emacs/site-lisp/cedet/common/cedet-files hides /usr/share/emacs/24.0.50/lisp/cedet/cedet-files
/usr/local/share/emacs/site-lisp/cedet/srecode/srecode hides /usr/share/emacs/24.0.50/lisp/cedet/srecode
/usr/local/share/emacs/site-lisp/cedet/common/cedet hides /usr/share/emacs/24.0.50/lisp/cedet/cedet
/usr/local/share/emacs/site-lisp/cedet/common/cedet-idutils hides /usr/share/emacs/24.0.50/lisp/cedet/cedet-idutils
/usr/local/share/emacs/site-lisp/cedet/common/pulse hides /usr/share/emacs/24.0.50/lisp/cedet/pulse
/usr/local/share/emacs/site-lisp/cedet/ede/ede hides /usr/share/emacs/24.0.50/lisp/cedet/ede
/usr/local/share/emacs/site-lisp/cedet/common/cedet-cscope hides /usr/share/emacs/24.0.50/lisp/cedet/cedet-cscope
/usr/local/share/emacs/site-lisp/cedet/common/data-debug hides /usr/share/emacs/24.0.50/lisp/cedet/data-debug

Features:
(shadow sort gnus-util mail-extr message sendmail regexp-opt rfc822 mml
mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mailabbrev mail-utils gmm-utils mailheader
emacsbug help-fns help-mode easymenu view tooltip ediff-hook vc-hooks
lisp-float-type mwheel x-win x-dnd 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 dbusbind
dynamic-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty emacs)

bug#6856: 24.0.50; fill-paragraph always marks buffer as modified

[Eli Zaretskii]

> From: Jose Antonio Ortega Ruiz <jaortega@gmail.com>
> Date: Sat, 14 Aug 2010 15:50:44 +0200
> Cc: rfrancoise@debian.org
> 
> 1. emacs -Q
> 2. Open any file, go to a filled paragraph spawning more than 1 line
> 3. M-q. If the paragraph was already filled, no modification of the
>    buffer occurs, but the buffer is marked as modified nonetheless.
> 3'. If the first M-q actually modified the text, save the buffer and go
>     to 3: a second M-q does not change the text but marks the buffer as
>     modified.

That's how M-q worked since day one.  It has no way of testing whether
a paragraph is already filled, so it always refills it, which causes
the buffer to become modified, because the text is being moved around
(you just don't see it because text is usually not displayed until
completely refilled).

bug#6856: 24.0.50; fill-paragraph always marks buffer as modified

[Jose Antonio Ortega Ruiz]

On Sat, Aug 14 2010, Eli Zaretskii wrote:

>> From: Jose Antonio Ortega Ruiz <jaortega@gmail.com>
>> Date: Sat, 14 Aug 2010 15:50:44 +0200
>> Cc: rfrancoise@debian.org
>> 
>> 1. emacs -Q
>> 2. Open any file, go to a filled paragraph spawning more than 1 line
>> 3. M-q. If the paragraph was already filled, no modification of the
>>    buffer occurs, but the buffer is marked as modified nonetheless.
>> 3'. If the first M-q actually modified the text, save the buffer and go
>>     to 3: a second M-q does not change the text but marks the buffer as
>>     modified.
>
> That's how M-q worked since day one.  It has no way of testing whether
> a paragraph is already filled, so it always refills it, which causes
> the buffer to become modified, because the text is being moved around
> (you just don't see it because text is usually not displayed until
> completely refilled).

Yes, i knew this is not a regression, but was hoping that there was an
easy way to "fix" it. Sounds like there isn't. Thanks for the
clarification.

jao