Signal subscriptions dead on upgrade to Ubuntu Raring (13.04)

[Kip Warner]

On Mon, 2013-05-13 at 11:46 +0100, Simon McVittie wrote:
> On 11/05/13 20:10, Kip Warner wrote:
> > It works now and thank you again. I just want to make sure that it is
> > working for the right reason. If I want the sender to own the bus, emit
> > the signals, but allow anyone to listen, then those semantics for the
> > sender are correct, along with the recipient's below?
> 
> Broadcast signals (no/NULL destination) are nearly always correct. Their
> semantics are "hey, if anyone cares, something just happened". Think of
> them as like email to a mailing list - anyone who is paying attention
> can act on them.
> 
> Unicast signals (non-NULL destination) are rarely used on D-Bus. If
> broadcasts are like a mailing list, unicast signals are like private
> email: they are a notification to one specific recipient (and, perhaps
> stretching the analogy a bit, it's best to send to the mailing list even
> if you are basically only talking to Thiago, to give others like me a
> chance to join in :-)
> 
> To continue the email analogy, eavesdropping (setting a match rule with
> eavesdrop=true) is like your mail-server administrator monitoring your
> messages.
> 
> This was changed between 1.4 and 1.6 to make eavesdropping's intended
> semantics more obvious: in 1.4 and older, it was too easy to eavesdrop
> on the session bus without intending to.

Hey Simon. That explanation was very clear and thank you very much for
providing that. I'm glad the default eavesdropping behaviour was altered
in 1.6 which was distributed with Raring, otherwise I may not have
caught this issue in time.

One other question. Isn't libdbus only the reference implementation? I
thought glib's GDBus API was a new implementation not dependent on the
former? If so, was the change in the default eavesdropping behaviour I
observed due to the latter having been patched to reflect the new
thinking in the reference implementation?

-- 
Kip Warner -- Software Engineer
OpenPGP encrypted/signed mail preferred
http://www.thevertigo.com
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