bug#49999: 27.2; save-mark-and-excursion does not save mark-active

bug#49999: 27.2; save-mark-and-excursion does not save mark-active

[Peter Münster]

Hi,

It seems, that save-mark-and-excursion does not restore the mark state.

Here is a test function:

(defun my-test-func ()
  "Test if save-mark-and-excursion is working."
  (interactive)
  (with-current-buffer "test-buf"
    (save-mark-and-excursion
      (goto-char (point-min))
      (add-face-text-property
       (point) (1+ (point)) (list :background "orange")))))

Test case:
- "emacs -Q"
- evaluate my-test-func
- open a new buffer "test-buf"
- type some characters
- mark a region somewhere
- M-x my-test-func

Result: point is restored, but mark-active is nil.

Kind regards, Peter



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-- 
           Peter

bug#49999: 27.2; save-mark-and-excursion does not save mark-active

[Lars Ingebrigtsen]

Peter Münster <pm@a16n.net> writes:

> It seems, that save-mark-and-excursion does not restore the mark state.
>
> Here is a test function:
>
> (defun my-test-func ()
>   "Test if save-mark-and-excursion is working."
>   (interactive)
>   (with-current-buffer "test-buf"
>     (save-mark-and-excursion
>       (goto-char (point-min))
>       (add-face-text-property
>        (point) (1+ (point)) (list :background "orange")))))
>
> Test case:
> - "emacs -Q"
> - evaluate my-test-func
> - open a new buffer "test-buf"
> - type some characters
> - mark a region somewhere
> - M-x my-test-func
>
> Result: point is restored, but mark-active is nil.

I can reproduce this, but I'm not quite sure what's going on.  I tweaked
your function:

(defun my-test-func ()
  "Test if save-mark-and-excursion is working."
  (interactive)
  (save-mark-and-excursion
    (goto-char (point-min))
    (add-face-text-property
     (point) (1+ (point)) (list :background "orange")))
  (message "%s" mark-active))

This messages t -- but evaling mark-active afterwards shows that it's
nil.  So something is deactivating the mark after the command has run,
apparently?  Hm...  this sounds vaguely familiar to me...  Anybody know
what could be going on here?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#49999: 27.2; save-mark-and-excursion does not save mark-active

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> I can reproduce this, but I'm not quite sure what's going on.  I tweaked
> your function:
>
> (defun my-test-func ()
>   "Test if save-mark-and-excursion is working."
>   (interactive)
>   (save-mark-and-excursion
>     (goto-char (point-min))
>     (add-face-text-property
>      (point) (1+ (point)) (list :background "orange")))
>   (message "%s" mark-active))
>
> This messages t -- but evaling mark-active afterwards shows that it's
> nil.  So something is deactivating the mark after the command has run,
> apparently?  Hm...  this sounds vaguely familiar to me...  Anybody know
> what could be going on here?

Oh, right -- it's transient mark mode that does this stuff?  That is, if
you run a command that inserts something in the buffer, then it'll
switch the region off?

So `save-mark-and-excursion' works exactly as it should.  But if you
don't want transient-mark-mode to switch itself off, you have to say
something like:

(defun my-test-func ()
  "Test if save-mark-and-excursion is working."
  (interactive)
  (save-mark-and-excursion
    (goto-char (point-min))
    (with-silent-modifications
      (add-face-text-property
       (point) (1+ (point)) (list :background "orange")))))

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#49999: 27.2; save-mark-and-excursion does not save mark-active

[Peter Münster]

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On Wed, Aug 11 2021, Lars Ingebrigtsen wrote:

> So `save-mark-and-excursion' works exactly as it should.  But if you
> don't want transient-mark-mode to switch itself off, you have to say
> something like:

Thanks for your explanation. Please find attached a patch, that uses
your solution.

-- 
           Peter

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From 8e0d6c4e787ecb56ef8eede83ea5c5d8ed0db5e1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Peter=20M=C3=BCnster?= <pm@a16n.net>
Date: Fri, 13 Aug 2021 11:13:43 +0200
Subject: [PATCH] Minor enhancements for image-dired.el

* lisp/image-dired.el (image-dired-thumb-visible-marks): Add the group.
(image-dired-thumb-update-marks): Keep the mark state when changing faces.
---
 lisp/image-dired.el | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/lisp/image-dired.el b/lisp/image-dired.el
index 76c7ae91f0..34bf1d02a9 100644
--- a/lisp/image-dired.el
+++ b/lisp/image-dired.el
@@ -465,6 +465,7 @@ This is where you see the cursor."
 If non-nil, apply the `image-dired-thumb-mark' face to marked
 images."
   :type 'boolean
+  :group 'image-dired
   :version "28.1")
 
 (defface image-dired-thumb-mark
@@ -2360,20 +2361,18 @@ non-nil."
 
 (defun image-dired-thumb-update-marks ()
   "Update the marks in the thumbnail buffer."
-  ;; TODO: only called by image-dired-mouse-toggle-mark but there are
-  ;; certainly other places, where it should be called too.
   (when image-dired-thumb-visible-marks
     (with-current-buffer image-dired-thumbnail-buffer
-      (save-excursion
+      (save-mark-and-excursion
         (goto-char (point-min))
         (let ((inhibit-read-only t))
           (while (not (eobp))
-            (if (image-dired-thumb-file-marked-p)
-                (add-face-text-property
-                 (point) (1+ (point))
-                 'image-dired-thumb-mark)
-              (remove-text-properties (point) (1+ (point))
-                                      '(face image-dired-thumb-mark)))
+            (with-silent-modifications
+              (if (image-dired-thumb-file-marked-p)
+                  (add-face-text-property (point) (1+ (point))
+                                          'image-dired-thumb-mark)
+                (remove-text-properties (point) (1+ (point))
+                                        '(face image-dired-thumb-mark))))
             (forward-char)))))))
 
 (defun image-dired-mouse-toggle-mark-1 ()
-- 
2.26.2


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bug#49999: 27.2; save-mark-and-excursion does not save mark-active

[Lars Ingebrigtsen]

Peter Münster <pm@a16n.net> writes:

> Thanks for your explanation. Please find attached a patch, that uses
> your solution.

Thanks; applied with one change:

> +  :group 'image-dired

We don't normally add :group to defcustoms these days -- the `defgroup'
at the start of the file says what group they belong in.

(I've now removed all the :group things from the defcustoms in the
file.)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no