[weekly report] Music sharing in Banshee using Telepathy

[Neil Loknath <neil loknath gmail com>]

So, SoC week 1 has come to an end. I'd say it's been quite a
productive week. Although I haven't really followed my schedule
outlined in my proposal, things are going well. I had initially
planned to be finishing up the bindings to the Telepathy API at the
end of week 1. But, during the community bonding period, I just
couldn't help myself and starting playing with things by writing some
tests: http://github.com/nloko/telepathy-sharp/tree/master
I also spent some time during the community bonding period
familiarizing myself with Banshee code. So, as SoC officially started,
I was armed and ready.

Since a picture speaks a thousand words, I've decided to go one up and
post some video. I made a screencast of what's been done so far. As
shown in the video, when the new Telepathy extension loads, there is a
new source category in Banshee called 'Contacts.' So, here's the
play-by-play:

- Banshee looks for active Telepathy connections, loads up the contact
roster for each connection, and represents each contact as a new child
source of the 'Contacts' source
- Presence changes are reflected
- Membership changes such as removing/adding a contact are accounted for
- If a connection goes away, the sources representing the contacts are
cleaned up.
- When a connection becomes active, contacts are again loaded as sources.

Cool stuff! But, don't take my word for it, see for yourself!
http://www.youtube.com/watch?v=o_wk1zYMJaI

For some added excitement, I added the option to announce what Banshee
is currently playing to all of your contacts. The work was slated for
more towards the end of the project. But, I decided to do it now, as
it was fairly easy and was a good introduction into how to play some
GUI stuff in Banshee.

Now, I will be taking some time look over what I've done so far. My
awesome mentor, Bertrand Lorentz, has already given me some tips that
I need to incorporate. In addition to that, I've got a bit of a
problem I need to figure out. It looks like I've run into a Mono bug:
https://bugzilla.novell.com/show_bug.cgi?id=481687 The problem is, I
can't unbox an IConvertible object NDesk.DBus returns when a DBus
object returns a complex variant. For simple types, I can unbox just
fine. But, if the original data type is a struct or array of structs,
it's an issue. Apparently, the issue is resolved in Mono 2.4. Right
now, all signs are pointing to upgrading from Mono 2.0.1 to Mono 2.4,
as the Telepathy API returns variants in few places. So, if I find a
way to simply workaround my current problem, I will probably run into
this bug again at another point. For example:

   public struct IPv4Address
   {
       public string address;
       public uint port;
   }

   System.Object addr = ift.ProvideFile (socket_type, socket_ac, "");
       if (socket_type == SocketAddressType.IPv4) {
           Console.WriteLine (MSG_PREFIX + "Boxed object is {0}",
addr.ToString ());
           IPv4Address socket_addr = (IPv4Address)Convert.ChangeType
(addr, typeof (IPv4Address));
       }

Results in an explosion!

[FileTransfer] Boxed object is (su)

Unhandled Exception: System.Reflection.TargetInvocationException:
Exception has been thrown by the target of an invocation. --->
System.InvalidCastException: Unknown target convertion type from
NDesk.DBus.DValue to tests.IPv4Addres
 at System.Convert.ToType (System.Object value, System.Type
conversionType, IFormatProvider provider) [0x00000]

So, as you can see, I've got plenty to keep me busy! What's next?
- review what I've already done
- figure out what do about this Mono bug and possibly install Mono 2.4
(a drag because Banshee won't have a 2.4 requirement for awhile,
AFAIK)
- filter connection to the ones that support tubes and file transfers
(that result in Jabber only, but don't want to hard code that. Will be
using the API to query)
- filter the contacts so only the ones that support the Banshee
extension are displayed.

That's all for now! In the meantime, feel free to take a peek at my
Github repository, if you'd like:
http://github.com/nloko/banshee/tree/gsoc

Neil