Unwanted Focus Shift when Clicking Menu Functions in Emacs Mode Line

Question

I am experiencing an issue in Emacs where clicking on a function name in a menu displayed on the mode line not only triggers the desired function but also has an unintended effect on the window or buffer below, interfering with the intended functionality.

Creating a Minimal Working Example (MWE) for the menus, as they were generated using minor modes and easy-menu-define, would be challenging.

I would appreciate any insights or suggestions on how to diagnose and resolve this issue. If you've encountered a similar problem or have experience with focus shifts when using menus in the mode line, please share your insights. Thank you!

I thought that introducing a delay, let's say half a second, between the moment I click on the function name in the menu and its actual execution might solve the problem. Unfortunately, I have no idea how to implement this delay.

Edit. This is my MWE:

(defun mwe-function-1 ()
  "MWE function 1"
  (interactive)
  (unwind-protect
      (query-replace "foo" "bar" nil (point-min) (point-max))
    ;; UNWINDFORMS
    (read-string "function 1 executed")))

(defun mwe-function-2 ()
  "MWE function 2"
  (interactive)
  (unwind-protect
      (query-replace "foo" "bar" nil (point-min) (point-max))
    ;; UNWINDFORMS
    (read-string "function 2 executed")))

(defun mwe-function-3 ()
  "MWE function 3"
  (interactive)
  (unwind-protect
      (query-replace "foo" "bar" nil (point-min) (point-max))
    ;; UNWINDFORMS
    (read-string "function 3 executed")))

(define-minor-mode mwe-mode
  "MWE mode"
  :init-value nil
  :lighter (:eval (propertize " MWE "
                              'face '(:foreground "RoyalBlue" :background "DarkGoldenrod1")))

  :keymap
  `(
    (,(kbd "<C-kp-1>") . mwe-function)
    )

  (if mwe-mode
      (easy-menu-define mwe-menu mwe-mode-map
        "MWE"
        '("MWE mode"
          ;; I want the menu on mode-line only:
          :visible (not (eq (framep (selected-frame)) 'x))
          ["mwe-function-1" mwe-function-1
           :help "mwe-function 1"]
          ["mwe-function-2" mwe-function-2
           :help "mwe-function 2"]
          ["mwe-function-3" mwe-function-3
           :help "mwe-function 3"]))
    t))

emacs --version
GNU Emacs 29.1
Development version 28fb02492c24 on master branch; build date 2023-12-10.

$ uname -a
Linux ---- 5.4.0-169-generic #187-Ubuntu SMP Thu Nov 23 14:52:28 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
$ echo $XDG_CURRENT_DESKTOP
MATE

When I click on the function mwe-function in the menu, it doesn't get executed because the mouse event interrupts query-replace. The issue doesn't occur consistently and is quite random.

I would try to add a dalay between the mouse event on the menu and the function execution.

Edit 2. I updated my MWE adding an UNWINDFORM to my functions and my Emacs version. Now I am on Emacs 29.1.

It continues to happen, randomly, that query-replace gets interrupted by mouse capture within the buffer window.

Indeed (from the manual):

Aside from this, any other character exits the query-replace, and is then reread as part of a key sequence. Thus, if you type C-k, it exits the query-replace and then kills to end of line. In particular, C-g simply exits the query-replace.

However, the UNWIND-FORM is always executed.

Answer 1

I opened a bug ticket for this issue (bug#69236) and a developer asked to me to

show the output of "C-h l" in both cases, i.e. when things work and when they don't.

I got:

<help-echo> <down-mouse-1> ;; mouse-minor-mode-menu
q <return>                 ;; exit-minibuffer
<help-echo> C-h l          ;; view-lossage

when things work and:

<help-echo> <down-mouse-1>           ;; mouse-minor-mode-menu
<mouse-1> <mouse-1>                  ;; mouse-select-window
<help-echo> C-x o                    ;; other-window
<return>                             ;; exit-minibuffer
C-h l                                ;; view-lossage

when things do not work.

So I implemented a workaround to solve my problem (bug?):

1. First of all I builded this macro:

(defmacro with-ignore-mouse-events (&rest body)
  "Macro to ignore mouse events before evaluating BODY."
  `(progn
     (when (input-pending-p)
       (let ((event (read-event)))
         (if (mouse-event-p event)
             (let ((button (event-basic-type event)))
               (if (eq button 'mouse-1)
                   (ignore)
                 (setq unread-command-events (list event))))
           (setq unread-command-events (list event)))))
     ,@body))

to intercept and "unread" the mouse-1 event.

2. Then I prepared this function to create a modified version of the functions I intend to use in the menu:

(defun generate-IME-star-functions (functions)
  "Generate starred versions of the given functions, where the original
functions are wrapped with the `with-ignore-mouse-events' macro"
  (dolist (func functions)
    (let* ((func-name (symbol-name func))
           (starred-func-name (intern (format "%s*" func-name))))
      (unless (fboundp starred-func-name)
        (defalias starred-func-name
          `(lambda ()
             (interactive)
             (with-ignore-mouse-events
              (funcall ',func)))
          (format "Starred version of the function `%s', where the original
function is wrapped with the `with-ignore-mouse-events' macro" func-name))))))

3. I built a list of the functions used in the menu:

(defvar mwe-function-names '(mwe-function-1 mwe-function-2 mwe-function-3))

4. And, finally, I built the minor-mode menu in this way

(define-minor-mode mwe-mode
  "MWE mode"
  :init-value nil
  :lighter (:eval (propertize " MWE "
                              'face '(:foreground "RoyalBlue" :background "DarkGoldenrod1")))

  :keymap
  `(
    (,(kbd "<C-kp-1>") . mwe-function)
    )

  (if mwe-mode
      (progn
        (generate-IME-star-functions mwe-function-names)
        (easy-menu-define mwe-menu mwe-mode-map
          "MWE"
          '("MWE mode"
            ;; I want the menu on mode-line only:
            :visible (not (eq (framep (selected-frame)) 'x))
            ["mwe-function-1" mwe-function-1*
             :help "mwe-function 1"]
            ["mwe-function-2" mwe-function-2*
             :help "mwe-function 2"]
            ["mwe-function-3" mwe-function-3*
             :help "mwe-function 3"])))
    t))

A better solution would have been to automatically wrap all functions, when launched from the menu, with my macro, but I have no idea how to accomplish that.