Reliably detecting controller disconnection.

So it would be good to have a simple cross platform method for determining if the current controller is still connected to the machine. To the best of my knowledge such a thing does not currently exist. Disconnected can mean a bunch of different things, so I'll enumerate the ones I know of:

• Controller out of bluetooth 'sight' (out of range, or shielded)
• Controller turned off manually or out of battery
• Controller unresponsive (broken)

I didn't find a concrete way of implementing it that was reliable on both OSX and Linux. The Current implementation of controller disconnection in Sportsfriends looks something like this:

bool connected = true;
if(!data.moves[i].api)
    connected = false;
else if(!data.moves[i].canUpdateLEDs)
    connected = false;
data.moves[i].timeSincePoll += dT;
if(data.moves[i].timeSincePoll > 1)
    connected = false;

So, to explain what is going on, for a controller to be seen as connected we must check:

• We have a valid move api handle for controller.
• We are able to successfully call psmove_update_leds on controller.
• We have successfully pulled input data from the controller within the last second.

Anything shy of those requirements doesn't seem to be robust enough.

This is of course a fair bit of a faff to go through, and as far as I can see these are all things that we might be able to handle on the api side. Thoughts?

Start by tracing the controller API around the move API handle, psmove_update_leds, and the input polling state described in the issue. Compare how these checks behave on OSX and Linux, then define a cross-platform connected-state contract and tests covering the listed disconnection cases.