New lens tutorial

[Ivan Sagalaev]

> The reason why we
> provide the Quickly lens template and python-unity-singlet is simply to
> ease Unity Lenses development. That also means that we will be able to
> better support developers with their questions on the code we recommend
> and we know best.

And for the same reason I'd say there wouldn't be much value in having 
another tutorial using the same technology. OTOH, having one operating 
on a lower level of abstraction is useful for some people to get better 
understanding (it was for me anyway). And yes, publishing it on 
developer.ubuntu.com was my intention from the beginning.

> Most Ubuntu software is distributed under various versions of the GPL
> license. Which particular controversy are you referring to?

I'm referring to its often criticized "viral" nature[1]. This may not be 
as big of a problem for applications but python-unity-singlet is a 
library, and GPL requires any lens built with it to be licensed also 
under GPL. This is the restriction I didn't want to impose on the 
readers of the tutorial who may have reasons to use more permissive 
licenses. I myself am going to release my lens under BSD license, for 
example.

>> - The library currently has a bug that doesn't allow a lens to react on
>> searches from the Dash home.
>
> Would you mind pointing us to the bug?

Just filed: https://bugs.launchpad.net/singlet/+bug/1057539

> Michael Hall (on CC) is the main Singlet developer.

He's not on CC, btw :-). But I believe I can reach him through Launchpad 
anyway. Thanks!

> You'll find some API documentation here:
>
> http://developer.ubuntu.com/api/ubuntu-12.10/python/Gio-2.0.html
> http://developer.ubuntu.com/api/ubuntu-12.10/python/GLib-2.0.html
>
> And here:
>
> http://developer.gnome.org/gio
> http://developer.gnome.org/glib

An API reference is a lousy way to learn stuff :-). I'll try to dig 
around those docs on gnome.org as they seem to have at least some 
explanatory prose and code examples. And I'll try to reach Michael, as 
he was the one who wrote `run_lens` after all…


[1]: http://en.wikipedia.org/wiki/Viral_license