From freedesktop-dbus  Tue Jun 13 16:20:02 2006
From: Thiago Macieira <thiago.macieira () trolltech ! com>
Date: Tue, 13 Jun 2006 16:20:02 +0000
To: freedesktop-dbus
Subject: Re: Targetted signals
Message-Id: <200606131820.02844.thiago.macieira () trolltech ! com>
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Ross Burton wrote:
>I'd really like it if signals could be send to specific addresses.=20

I don't really agree with that. You're thinking of signals like a kind=20
of "broadcast": all parties receive it.

However, signals are more like "multicast": only interested parties=20
receive it. You just have to craft the signal emission so that the=20
receivers can make up a rule to match them.

Since you can't influence the service name, nor the interface name or the=20
signal name, you're left with two items: the object path and the=20
arguments (and signature). You've tried to construct the rule based on=20
the arguments: I would recomment the opposite approach: make the signals=20
distinct based on the object path.

>My=20
>use-case is the DBus port of evolution-data-server.  When a live book
>view is updated a signal needs to be sent to interested parties, but as
>there can be multiple book views with different queries and the message
>arguments can be large (up to 40 vcards), restricting the sending of the
>signals to only the relevant clients would be a good idea. =20

Without understanding what "relevant clients" means, there isn't much more=
=20
we can help you with.

But, for example, if this meant that "relevant clients" means "clients=20
that have open queries on the book view that got updated", one solution=20
would be to have one object path per book view. That means clients would=20
listen to the signals coming only from the book views that they queried,=20
because they would have queried according to the object path.

>At the=20
>moment the server calls methods on the server, but this causes a method
>return to be sent, which is not required.

You can make a call with the "no reply needed" flag set. The receiver side=
=20
can opt to not send a reply in that case.

=2D-=20
Thiago Jos=E9 Macieira - thiago.macieira AT trolltech.com
Trolltech AS - Sandakerveien 116, NO-0402 Oslo, Norway

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