[Telepathy] Backward stream tube

[Alban Crequy]

Le Sat, 4 Jul 2009 02:01:32 +0100,
Alban Crequy <alban.crequy at collabora.co.uk> a écrit :

> So we discussed how to design and implement this feature in the
> Channel.Type.StreamTube interface.

There are other issues if we reuse the existing interface
Channel.Type.StreamTube for backward stream tubes: the 2 methods Offer's
and Accept's prototype assume that the direction of the tube is not
backward:

1. Called by the initiator:
Offer ( u: address_type, v: address, u: access_control, a{sv}:
parameters ) → nothing

2. Called by the recipient:
Accept ( u: address_type, u: access_control, v: access_control_param )
→ v

With backward stream tube, the semantic would be different, for example:
1. Called by the initiator:
Request ( u: address_type, u: access_control, a{sv}: parameters ) → v

2. Called by the recipient:
Offer ( u: address_type, v: address, u: access_control, a{sv}:
parameters ) → nothing

The field "v: address" is not at the same place.

Wjt suggested that telepathy-gabble can send the backward stream tube
request on the XMPP level to the contact directly when the channel is
created. But how can we handle the 'parameters' argument in this case?
Guillaume suggested the 'parameters' argument can be useful both on the
initiator side and on the side which offer the service. With normal
stream tubes, it is the same side, so it is set by the Offer() method.
But with backward stream tube, we have to decide which side set the
parameters, or if both side can set the parameters.

Cheers,
Alban