ubuntu-phone team mailing list archive

[Sebastien Bacher <seb128@xxxxxxxxxx>]

Hey everyone,

That's a topic that has been discussed between different groups of 
people recently, on merge requests [1] and bug reports, and it feels 
like we should have the discussion on a common place/together, to decide 
what is best, and all do the same thing.

Summary of the issue:
- in unity8 we use the greeter as a lock screen
- we want to have informations from the users available on the lock 
screen ("currently playing song" for example)
- we need a way to get those informations from the session to the greeter

We are currently using accountsservice to store "static" informations 
(e.g the background image for the user), that's needed because the user 
might not be logged/the directory not available to get the information 
otherwise. The case we are speaking about there is different and 
concerns "dynamic" informations (e.g the song currently playing in the 
user sessions)

We have some solutions which have been suggested:

1. using accountsservice there as well, maybe adding support for 
"volatile" informations which wouldn't get store.

That's the first suggestion made and some people started work using that 
approach. It feels suboptimal though, since it involves making 2 running 
processes talk by using a third process as proxy (which was not designed 
for that usecase).


We discussed it a bit on #ubuntu-desktop and came with those possible 
solutions as well


2. get lightdm to connect to the user-session bus and send back selected 
informations to the greeter.

That seems like the most flexible/powerful solution, giving access to 
the user session might be a concern for security though.


3. having a subdirectory in the user's XDG_RUNTIME_DIR, which is visible 
to the greter via a privileged protocol in lightdm (lightdm opening 
files and sending content, or using fds are possible options)

that should do the job, be easy enough and not risk exposing too much 
from the user session


Robert, what do you think of 2 and 3 from a lightdm perspective? Would 
you be happy to add support for one of those?


Everyone, I've you have comments or extra ideas, feedback is welcome ;-)

Cheers,
Sebastien Bacher


[1] 
https://code.launchpad.net/~ted/indicator-sound/account-service-support/+merge/205891