Re: dbus problem: "notifications-notify :on-action" stops working

[Michael Albinus]

Peter Münster <pmlists@free.fr> writes:

> Hi Michael,

Hi Peter,

sorry for the delay, it took some hours to walk through the dbus-monitor
traces.

> Sometimes, I've started another "emacs -Q -l /tmp/init.el" just to see,
> if it works or not. Now, the problem appears again, at timestamp
> "1330414472". Here the "*Messages*":

According to the traces, you have two Emacs sessions running, sending
notifications to the notification service. It looks, like a notification
daemon wants to be unique for a given client, sending the
notifications. As long as you send notifications from the same client
(aka Emacs session), the daemon stays alive, and does the work.

If another client sends a notification message, the running daemon is
disabled in the D-Bus name owner queue, and a new notification daemon is
started for that client. The point is, that this new daemon is still
reachable via the known name "org.freedesktop.Notifications", but is has
another unique D-Bus name (like ":1.5" or so).

notifications.el registers for signals from the D-Bus service
"org.freedesktop.Notifications". But during registration, this service
name is translated into the D-Bus unique name of the daemon, running at
*this* time. When another daemon takes over the service name
"org.freedesktop.Notifications", it has another D-Bus unique name, for
which notifications.el has not registered. That's why you don't see the
signals anymore.

I have prepared a patch, which shall handle this situation. Could you,
please, check?

--8<---------------cut here---------------start------------->8---
*** /home/albinus/src/emacs/lisp/notifications.el.~107473~      2012-03-01 
15:08:08.000000000 +0100
--- /home/albinus/src/emacs/lisp/notifications.el       2012-03-01 
15:08:09.000000000 +0100
***************
*** 91,107 ****
  (defvar notifications-on-close-map nil
    "Mapping between notification and close callback functions.")

  (defun notifications-on-action-signal (id action)
    "Dispatch signals to callback functions from `notifications-on-action-map'."
    (let ((entry (assoc id notifications-on-action-map)))
!     (when entry
        (funcall (cadr entry) id action)
        (remove entry 'notifications-on-action-map))))

  (when (fboundp 'dbus-register-signal)
    (dbus-register-signal
     :session
!    notifications-service
     notifications-path
     notifications-interface
     notifications-action-signal
--- 91,114 ----
  (defvar notifications-on-close-map nil
    "Mapping between notification and close callback functions.")

+ (defvar notifications-service-name ""
+   "Unique service name of notification daemon.
+ This must be kept, because the notification daemon could be
+ restarted, and the registered signals cannot be identified anymore.")
+
  (defun notifications-on-action-signal (id action)
    "Dispatch signals to callback functions from `notifications-on-action-map'."
    (let ((entry (assoc id notifications-on-action-map)))
!     (when (and entry
!              (string-equal notifications-service-name
!                            (dbus-event-service-name last-input-event)))
        (funcall (cadr entry) id action)
        (remove entry 'notifications-on-action-map))))

  (when (fboundp 'dbus-register-signal)
    (dbus-register-signal
     :session
!    nil
     notifications-path
     notifications-interface
     notifications-action-signal
***************
*** 113,119 ****
    ;; make it optional, and assume `undefined' as default.
    (let ((entry (assoc id notifications-on-close-map))
        (reason (or reason 4)))
!     (when entry
        (funcall (cadr entry)
               id (cadr (assoc reason notifications-closed-reason)))
        (remove entry 'notifications-on-close-map))))
--- 120,128 ----
    ;; make it optional, and assume `undefined' as default.
    (let ((entry (assoc id notifications-on-close-map))
        (reason (or reason 4)))
!     (when (and entry
!              (string-equal notifications-service-name
!                            (dbus-event-service-name last-input-event)))
        (funcall (cadr entry)
               id (cadr (assoc reason notifications-closed-reason)))
        (remove entry 'notifications-on-close-map))))
***************
*** 121,127 ****
  (when (fboundp 'dbus-register-signal)
    (dbus-register-signal
     :session
!    notifications-service
     notifications-path
     notifications-interface
     notifications-closed-signal
--- 130,136 ----
  (when (fboundp 'dbus-register-signal)
    (dbus-register-signal
     :session
!    nil
     notifications-path
     notifications-interface
     notifications-closed-signal
***************
*** 277,282 ****
--- 286,295 ----
                              (or hints '(:array :signature "{sv}"))
                              :int32 (or timeout -1)))

+     ;; Remember daemon unique service name.
+     (setq notifications-service-name
+         (dbus-get-name-owner :session notifications-service))
+
      ;; Register close/action callback function
      (let ((on-action (plist-get params :on-action))
            (on-close (plist-get params :on-close)))
--8<---------------cut here---------------end--------------->8---

> Thanks for your efforts,

Best regards, Michael.