Unable to register dbus method

Unable to register dbus method

[Lluís]

Hi,

After getting a working implementation for providing GNOME Shell's calendar
widget with info from org-mode events, it looks like this suddenly stopped
working:

#v+
(dbus-register-method :session
                      "org.gnome.Shell.CalendarServer"
                      "/org/gnome/Shell/CalendarServer"
                      "org.gnome.Shell.CalendarServer"
                      "GetEvents"
                      'ogc:--dbus-get-events)
#v-

The callback never gets invoked, while "dbus-monitor" shows a method call is
actually sent by the widget, but only the evolution server responds to it:

#v+
method call sender=:1.17 -> dest=:1.52 serial=309 path=/org/gnome/Shell/CalendarServer; interface=org.gnome.Shell.CalendarServer; member=GetEvents
   int64 1353928320
   int64 1357557120
   boolean true
method call sender=:1.52 -> dest=:1.41 serial=27 path=/org/gnome/evolution/dataserver/Calendar/3912/6; interface=org.gnome.evolution.dataserver.Calendar; member=open
   boolean true
method return sender=:1.41 -> dest=:1.52 reply_serial=27
   uint32 18
signal sender=:1.41 -> dest=(null destination) serial=97 path=/org/gnome/evolution/dataserver/Calendar/3912/6; interface=org.gnome.evolution.dataserver.Calendar; member=readonly
   boolean false
signal sender=:1.41 -> dest=(null destination) serial=98 path=/org/gnome/evolution/dataserver/Calendar/3912/6; interface=org.gnome.evolution.dataserver.Calendar; member=online
   boolean true
signal sender=:1.41 -> dest=(null destination) serial=99 path=/org/gnome/evolution/dataserver/Calendar/3912/6; interface=org.gnome.evolution.dataserver.Calendar; member=opened
   array [
      string "org.gnome.evolution.dataserver.Calendar.NoSuchCal"
      string "No existeix el calendari"
   ]
signal sender=:1.41 -> dest=(null destination) serial=100 path=/org/gnome/evolution/dataserver/Calendar/3912/6; interface=org.gnome.evolution.dataserver.Calendar; member=open_done
   uint32 18
   string "org.gnome.evolution.dataserver.Calendar.NoSuchCal"
   string "No es pot obrir el calendari: No existeix el calendari"
method return sender=:1.52 -> dest=:1.17 reply_serial=309
   array [
   ]
#v-

Is it maybe that evolution registered for that method first and thus further
registrations simply take no effect? If so, why was this not happening before?

I'm using emacs-snapshot version 2:20121209-1.

For the curious, code is available at
https://github.com/llvilanova/org-gnome-calendar.


Thanks,
  Lluis

-- 
 "And it's much the same thing with knowledge, for whenever you learn
 something new, the whole world becomes that much richer."
 -- The Princess of Pure Reason, as told by Norton Juster in The Phantom
 Tollbooth

Re: Unable to register dbus method

[Michael Albinus]

Lluís <xscript@gmx.net> writes:

> Hi,

Hi Lluís,

> After getting a working implementation for providing GNOME Shell's calendar
> widget with info from org-mode events, it looks like this suddenly stopped
> working:
>
> The callback never gets invoked, while "dbus-monitor" shows a method call is
> actually sent by the widget, but only the evolution server responds to it:
>
> Is it maybe that evolution registered for that method first and thus further
> registrations simply take no effect?

Maybe. Or Evolution has replaced your registration by its own. D-Bus
life is hard.

Note, that you cannot register for just one method; you can register
only for a whole service. `dbus-register-method' does it silently for
you.

Install d-feet (very useful anyway!), and check, which application has
registered for the service org.gnome.Shell.CalendarServer.

In order to bring your application in front of the service, you could
use `dbus-register-service' with the `:replace-existing' flag.

> Thanks,
>   Lluis

Best regards, Michael.

Re: Unable to register dbus method

[Lluís]

Michael Albinus writes:

> Lluís <xscript@gmx.net> writes:
>> Hi,

> Hi Lluís,

>> After getting a working implementation for providing GNOME Shell's calendar
>> widget with info from org-mode events, it looks like this suddenly stopped
>> working:
>> 
>> The callback never gets invoked, while "dbus-monitor" shows a method call is
>> actually sent by the widget, but only the evolution server responds to it:
>> 
>> Is it maybe that evolution registered for that method first and thus further
>> registrations simply take no effect?

> Maybe. Or Evolution has replaced your registration by its own. D-Bus
> life is hard.

> Note, that you cannot register for just one method; you can register
> only for a whole service. `dbus-register-method' does it silently for
> you.

> Install d-feet (very useful anyway!), and check, which application has
> registered for the service org.gnome.Shell.CalendarServer.

> In order to bring your application in front of the service, you could
> use `dbus-register-service' with the `:replace-existing' flag.

Aha! The `:replace-existing' did the trick and it's now working again.

Does this mean I should resend the method invocation through DBus to whomever is
not the "primary owner"? Sorry for the DBus-centric questions.


Thanks a lot,
  Lluis

-- 
 "And it's much the same thing with knowledge, for whenever you learn
 something new, the whole world becomes that much richer."
 -- The Princess of Pure Reason, as told by Norton Juster in The Phantom
 Tollbooth

Re: Unable to register dbus method

[Michael Albinus]

Lluís <xscript@gmx.net> writes:

Hi Lluís,

>> In order to bring your application in front of the service, you could
>> use `dbus-register-service' with the `:replace-existing' flag.
>
> Aha! The `:replace-existing' did the trick and it's now working again.

Good.

> Does this mean I should resend the method invocation through DBus to whomever is
> not the "primary owner"? Sorry for the DBus-centric questions.

No. D-Bus uses a queue of registered applications for every service. Every
application, like Evolution or Emacs, can register for a service. First
request wins. All other applications are queued for the service.

If the application, which "owns" the service, is stopped, the next
waiting application in the queue becomes the owner, until the queue is
empty.

The `:replace-existing' flag breaks this rule. Your application is not
queued at the end, but becomes the service name owner immediately.

> Thanks a lot,
>   Lluis

Best regards, Michael.