GNU bug report logs - #2295
Viewing images with image-mode changes directory time

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

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

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/

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

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Juri Linkov <juri <at> jurta.org>
Cc: 2295 <at> debbugs.gnu.org, emacs-pretest-bug <at> gnu.org
Subject: Re: bug#2295: Viewing images with image-mode changes directory time
Date: Wed, 11 Feb 2009 21:40:54 -0500

> 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

Message #20 received at 2295-done <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Juri Linkov <juri <at> jurta.org>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 2295-done <at> debbugs.gnu.org
Subject: Re: bug#2295: Viewing images with image-mode changes directory time
Date: Thu, 12 Feb 2009 23:49:52 +0200

>> 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/

Message #27 received at 2295 <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> jurta.org>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 2295 <at> debbugs.gnu.org
Subject: Re: bug#2295: Viewing archives with arc-mode changes directory time
Date: Fri, 28 Sep 2012 19:59:19 +0300

>> 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))))
 
 (defvar tar-mode-map
   (let ((map (make-keymap)))

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