bug#2295: Viewing images with image-mode changes directory time

bug#2295: Viewing images with image-mode changes directory time

[Juri Linkov]

Using image-mode to visit image files touches directory modification
dates.  This is especially annoying when image files are in an old
archive.  The problem is in the function `add-text-properties' that
temporarily modifies the image buffer causing lock-file to create a lock
file in the current directory that modifies the directory timestamp.

As a solution I propose to let-bind `buffer-file-truename' to nil
around the call to `add-text-properties' to prevent directory time
modification:

Index: lisp/image-mode.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/image-mode.el,v
retrieving revision 1.55
diff -c -r1.55 image-mode.el
*** lisp/image-mode.el	7 Feb 2009 15:29:14 -0000	1.55
--- lisp/image-mode.el	11 Feb 2009 22:52:35 -0000
***************
*** 457,464 ****
  	   (buffer-undo-list t)
  	   (modified (buffer-modified-p)))
        (image-refresh image)
!       (add-text-properties (point-min) (point-max) props)
!       (set-buffer-modified-p modified)
        ;; Inhibit the cursor when the buffer contains only an image,
        ;; because cursors look very strange on top of images.
        (setq cursor-type nil)
--- 457,465 ----
  	   (buffer-undo-list t)
  	   (modified (buffer-modified-p)))
        (image-refresh image)
!       (let ((buffer-file-truename nil)) ; avoid changing dir mtime by lock_file
!         (add-text-properties (point-min) (point-max) props)
!         (set-buffer-modified-p modified))
        ;; Inhibit the cursor when the buffer contains only an image,
        ;; because cursors look very strange on top of images.
        (setq cursor-type nil)

-- 
Juri Linkov
http://www.jurta.org/emacs/

bug#2295: Viewing images with image-mode changes directory time

[Stefan Monnier]

> As a solution I propose to let-bind `buffer-file-truename' to nil
> around the call to `add-text-properties' to prevent directory time
> modification:

That sounds OK.  We should provide at least a macro for that.
BTW, while you're there, change set-buffer-modified-p to
restore-buffer-modified-p.


        Stefan

bug#2295: marked as done (Viewing images with image-mode changes directory time)

[Emacs bug Tracking System]

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Your message dated Thu, 12 Feb 2009 23:49:52 +0200
with message-id <878wob496n.fsf@jurta.org>
and subject line Re: bug#2295: Viewing images with image-mode changes directory time
has caused the Emacs bug report #2295,
regarding Viewing images with image-mode changes directory time
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
bug report if necessary, and/or fix the problem forthwith.

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-- 
2295: http://emacsbugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=2295
Emacs Bug Tracking System
Contact owner@emacsbugs.donarmstrong.com with problems

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From: Juri Linkov <juri@jurta.org>
To: emacs-pretest-bug@gnu.org
Subject: Viewing images with image-mode changes directory time
Date: Thu, 12 Feb 2009 00:55:48 +0200
Message-ID: <873aepkksk.fsf@jurta.org>

Using image-mode to visit image files touches directory modification
dates.  This is especially annoying when image files are in an old
archive.  The problem is in the function `add-text-properties' that
temporarily modifies the image buffer causing lock-file to create a lock
file in the current directory that modifies the directory timestamp.

As a solution I propose to let-bind `buffer-file-truename' to nil
around the call to `add-text-properties' to prevent directory time
modification:

Index: lisp/image-mode.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/image-mode.el,v
retrieving revision 1.55
diff -c -r1.55 image-mode.el
*** lisp/image-mode.el	7 Feb 2009 15:29:14 -0000	1.55
--- lisp/image-mode.el	11 Feb 2009 22:52:35 -0000
***************
*** 457,464 ****
  	   (buffer-undo-list t)
  	   (modified (buffer-modified-p)))
        (image-refresh image)
!       (add-text-properties (point-min) (point-max) props)
!       (set-buffer-modified-p modified)
        ;; Inhibit the cursor when the buffer contains only an image,
        ;; because cursors look very strange on top of images.
        (setq cursor-type nil)
--- 457,465 ----
  	   (buffer-undo-list t)
  	   (modified (buffer-modified-p)))
        (image-refresh image)
!       (let ((buffer-file-truename nil)) ; avoid changing dir mtime by lock_file
!         (add-text-properties (point-min) (point-max) props)
!         (set-buffer-modified-p modified))
        ;; Inhibit the cursor when the buffer contains only an image,
        ;; because cursors look very strange on top of images.
        (setq cursor-type nil)

-- 
Juri Linkov
http://www.jurta.org/emacs/



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From: Juri Linkov <juri@jurta.org>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: 2295-done@emacsbugs.donarmstrong.com
Subject: Re: bug#2295: Viewing images with image-mode changes directory time
Date: Thu, 12 Feb 2009 23:49:52 +0200
Message-ID: <878wob496n.fsf@jurta.org>

>> As a solution I propose to let-bind `buffer-file-truename' to nil
>> around the call to `add-text-properties' to prevent directory time
>> modification:
>
> That sounds OK.  We should provide at least a macro for that.

Maybe it would be better (after the release) to improve
`add-text-properties' to not modify the current buffer
(with a new flag to keep the default behavior unchanged).
This is an old problem with buffers that don't save text properties,
so modifying them is meaningless and sometimes harmful.

> BTW, while you're there, change set-buffer-modified-p to
> restore-buffer-modified-p.

Done.

-- 
Juri Linkov
http://www.jurta.org/emacs/

bug#2295: Viewing archives with arc-mode changes directory time

[Juri Linkov]

>> Using image-mode to visit image files touches directory modification
>> dates.  This is especially annoying when image files are in an old
>> archive.  The problem is in the function `add-text-properties' that
>> temporarily modifies the image buffer causing lock-file to create a lock
>> file in the current directory that modifies the directory timestamp.
>>
>> As a solution I propose to let-bind `buffer-file-truename' to nil
>> around the call to `add-text-properties' to prevent directory time
>> modification:
>
> That sounds OK.  We should provide at least a macro for that.

I don't know how this macro could look, but there is exactly the same
problem in arc-mode and tar-mode.el.  Visiting an archive file modifies
the mtime of its directory.  This can be fixed with the same method
as used to fix image-mode (by binding buffer-file-truename to nil):

=== modified file 'lisp/arc-mode.el'
--- lisp/arc-mode.el	2012-05-04 06:13:18 +0000
+++ lisp/arc-mode.el	2012-09-28 16:51:56 +0000
@@ -787,7 +789,8 @@ (defun archive-summarize (&optional shut
 Optional argument SHUT-UP, if non-nil, means don't print messages
 when parsing the archive."
   (widen)
-  (let ((inhibit-read-only t))
+  (let ((buffer-file-truename nil) ; avoid changing dir mtime by lock_file
+	(inhibit-read-only t))
     (setq archive-proper-file-start (copy-marker (point-min) t))
     (set (make-local-variable 'change-major-mode-hook) 'archive-desummarize)
     (or shut-up

=== modified file 'lisp/tar-mode.el'
--- lisp/tar-mode.el	2012-08-13 10:34:25 +0000
+++ lisp/tar-mode.el	2012-08-20 01:25:16 +0000
@@ -518,12 +518,13 @@ (defun tar-summarize-buffer ()
         (progress-reporter-done progress-reporter)
       (message "Warning: premature EOF parsing tar file"))
     (goto-char (point-min))
-    (let ((inhibit-read-only t)
+    (let ((buffer-file-truename nil) ; avoid changing dir mtime by lock_file
+	  (inhibit-read-only t)
           (total-summaries
            (mapconcat 'tar-header-block-summarize tar-parse-info "\n")))
-      (insert total-summaries "\n"))
+      (insert total-summaries "\n")
     (goto-char (point-min))
-    (restore-buffer-modified-p modified)))
+      (restore-buffer-modified-p modified))))
 \f
 (defvar tar-mode-map
   (let ((map (make-keymap)))