* bug#38316: 26.1; Undo with undo-inhibit-record-point set doesn't restore unmodified state
@ 2019-11-21 21:18 Braun Gábor
2020-11-01 14:50 ` Lars Ingebrigtsen
0 siblings, 1 reply; 2+ messages in thread
From: Braun Gábor @ 2019-11-21 21:18 UTC (permalink / raw)
To: 38316
1. Start Emacs:
emacs -Q --eval '(setq undo-inhibit-record-point t)'
I see the scratch buffer with -- in the modeline indicating it is not
modified.
2. Enter 'abc' in the scratch buffer: press keys a b c.
3. Press C-_.
The inserted 'abc' is deleted, but in the modeline I see ** indicating
that the buffer is modified. The expectation is that the buffer is no
longer modified.
Do the same as above but start Emacs with 'emacs -Q', no additional
options. Now after C-_ I see -- in the modeline indicating that the
buffer is not modified, as expected.
Discussion:
1. The value of buffer-undo-list is (as shown by C-h v buffer-undo-list)
in the first case
(nil
(#("abc" 0 3
(fontified t))
. 146)
(#<marker at 146 in *scratch*> . -3)
nil
(146 . 149)
nil
(1 . 146))
while in the second case
(nil
(#("abc" 0 3
(fontified t))
. 146)
(#<marker at 146 in *scratch*> . -3)
nil
(146 . 149)
(t . 0)
nil
(1 . 146)
(t . 0))
The only change I see is the additional (t . 0) entries in buffer-undo-
list.
2. The difference in buffer-undo-list is explained by the function
record_point in src/undo.c, which I include here in an abbreviated form
with ... denoting omissions:
static void
record_point (ptrdiff_t beg)
{
/* Don't record position of pt when undo_inhibit_record_point holds.
*/
if (undo_inhibit_record_point)
return;
...
/* If this is the first change since save, then record this.*/
if (MODIFF <= SAVE_MODIFF)
record_first_change ();
/* We may need to record point ...*/
if (at_boundary
&& point_before_last_command_or_undo != beg
&& buffer_before_last_command_or_undo == current_buffer )
bset_undo_list (current_buffer,
Fcons (make_fixnum (point_before_last_command_or_undo),
BVAR (current_buffer, undo_list)));
}
here the call to record_first_change() is responsible for adding the
(t . ...) entries. Note that record_first_change() is called only if
undo-inhibit-record-point is nil regardles of whether point actually
gets recorded in buffer-undo-list (i.e. the condition of the last `if'
is true).
By the way, functions record_insert and record_delete seem to rely on
record_point adding necessary (t . ...) entries. So these functions
never add (t . ...) entries when undo-inhibit-record-point is t,
and that's why they are missing in the first example above.
Best wishes,
Gábor
System information:
In GNU Emacs 26.1 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.5)
of 2019-09-23, modified by Debian built on x86-grnet-01
Windowing system distributor 'The X.Org Foundation', version
11.0.12004000
System Description: Debian GNU/Linux 10 (buster)
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Undo!
Type C-x 1 to delete the help window, C-M-v to scroll help.
Configured using:
'configure --build x86_64-linux-gnu --prefix=/usr
--sharedstatedir=/var/lib --libexecdir=/usr/lib
--localstatedir=/var/lib --infodir=/usr/share/info
--mandir=/usr/share/man --enable-libsystemd --with-pop=yes
--enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.1/site-
lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.1/site-lisp:/
usr/share/emacs/site-lisp
--with-sound=alsa --without-gconf --with-mailutils --build
x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
--libexecdir=/usr/lib --localstatedir=/var/lib
--infodir=/usr/share/info --mandir=/usr/share/man --enable-libsystemd
--with-pop=yes
--enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.1/site-
lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.1/site-lisp:/
usr/share/emacs/site-lisp
--with-sound=alsa --without-gconf --with-mailutils --with-x=yes
--with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g -O2
-fdebug-prefix-map=/build/emacs-StqULU/emacs-26.1+1=. -fstack-
protector-strong
-Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
-D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'
Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 THREADS LIBSYSTEMD LCMS2
Important settings:
value of $LANG: hu_HU.UTF-8
locale-coding-system: utf-8-unix
Major mode: Lisp Interaction
Minor modes in effect:
tooltip-mode: t
global-eldoc-mode: t
eldoc-mode: t
electric-indent-mode: t
mouse-wheel-mode: t
tool-bar-mode: t
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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
Load-path shadows:
None found.
Features:
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Memory information:
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(symbols 48 20553 1)
(miscs 40 55 104)
(strings 32 30980 919)
(string-bytes 1 777673)
(vectors 16 15007)
(vector-slots 8 501086 9156)
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(intervals 56 290 0)
(buffers 992 12))
^ permalink raw reply [flat|nested] 2+ messages in thread
* bug#38316: 26.1; Undo with undo-inhibit-record-point set doesn't restore unmodified state
2019-11-21 21:18 bug#38316: 26.1; Undo with undo-inhibit-record-point set doesn't restore unmodified state Braun Gábor
@ 2020-11-01 14:50 ` Lars Ingebrigtsen
0 siblings, 0 replies; 2+ messages in thread
From: Lars Ingebrigtsen @ 2020-11-01 14:50 UTC (permalink / raw)
To: Braun Gábor; +Cc: 38316
Braun Gábor <braungb88@gmail.com> writes:
> 1. Start Emacs:
>
> emacs -Q --eval '(setq undo-inhibit-record-point t)'
>
> I see the scratch buffer with -- in the modeline indicating it is not
> modified.
>
> 2. Enter 'abc' in the scratch buffer: press keys a b c.
>
> 3. Press C-_.
>
> The inserted 'abc' is deleted, but in the modeline I see ** indicating
> that the buffer is modified. The expectation is that the buffer is no
> longer modified.
I can confirm that this bug is still present in Emacs 28.
> Do the same as above but start Emacs with 'emacs -Q', no additional
> options. Now after C-_ I see -- in the modeline indicating that the
> buffer is not modified, as expected.
Yup. (The bug report then goes on to discuss the differences in
buffer-undo-list, which is probably the cause of this bug.)
Does anybody have any insight here into what's going wrong here?
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
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2019-11-21 21:18 bug#38316: 26.1; Undo with undo-inhibit-record-point set doesn't restore unmodified state Braun Gábor
2020-11-01 14:50 ` Lars Ingebrigtsen
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