[Shotwell] Proposed Ubuntu Online Accounts integration

[David King]

Hello Shotwell list!

I have been working on UOA (Ubuntu Online Accounts) at Canonical for a 
while, and this is an update on some work that was done to integrate 
Shotwell with UOA, after I chatted with Lucas, Eric and Adam about it at 
GUADEC a few weeks ago.

UOA is similar to GOA (GNOME Online Accounts) in that it is a way to 
give out access tokens for online services (such as Flickr, Picasa and 
Facebook) to applications.

Alberto Mardegan ported Shotwell to use UOA for account authentication 
for publishing accounts. You can see the source code changes at 
Launchpad:

https://code.launchpad.net/~online-accounts/online-accounts-shotwell/accounts-only3

There is a Shotwell bug open about adding UOA support:

http://redmine.yorba.org/issues/5596

I would be very grateful if a Shotwell developer could cast an eye over 
the changes so far and let us know if the approach is broadly acceptable 
for merging into Shotwell. Please let me know if there are any problems, 
and I will try to get them fixed as soon as possible.

Before UOA support is ready for merging to Shotwell upstream (and I 
would really like that!), there are a few things that should be done.  
Firstly, it should be made optional, likely at compile time. This will 
make it easier for distributions to choose whether to enable the support 
in Shotwell packages. Secondly, there are some minimal UI changes that 
would improve the user experience, such as removing the ‘Login’ and 
‘Logout’ buttons from the publishing dialogue, as those are redundant 
if UOA is being used to get the authentication token. There are some 
other minor UI changes that would make sense, such as adding a button to 
call out to the UOA configuration panel to configure a new account, and 
another button to re-authenticate an account if there is an error. 
Another change might be to hide the publishing plugins from the 
preferences, as whether an account is enabled can be controlled for the 
UOA settings panel.

Would the UI and build changes that I suggested be broadly acceptable, 
and is there a good way that I could demonstrate those, or would you 
just like a branch with the changes so that you can test for yourselves? 
There is already a PPA containing a Shotwell version with the above 
changes (but without the suggested changes):

https://launchpad.net/~webapps/+archive/preview/

Looking forward to some good discussion!

David