Due to an oversight libsurvive events were only processed when inputs were updated.
If only triggering event processing when an event is needed, we would need to process
a random number of events, causing random overhead.
Rather, follow the model of other drivers and process events in a thread.
This required creating a local copy of the xrt_input arrays.
Fixes#113Fixes!679
v2: Use a mutex for get_tracked_pose and update_inputs
* Remove survive_device.{ctrl,hmd}::variant and use variant from config
* Use SurviveSimpleEventType_ConfigEvent to find connected devices
* Use SurviveSimpleEventType_PoseUpdateEvent for pose updates
Sometimes the Index is in weird hardware states and doesn't respond properly.
In such cases, time out after 5 seconds and continue with no HMD present.
Previously we also relied on the controller configs to be already available
once the HMD config was available. In rare cases they were not - wait for
the controller configs with the same timeout.
Each HMD driver now has to implement compute_distortion() which will be called
by the compositor implementation to generate a mesh (usually).
u_distortion_mesh contains implementations for the defaults (panotools, OpenHMD, vive).
Also adds compute_distortion function for Vive distortion
There are differences between OpenHMD and Panotools values, main differences for now:
* psvr has 5 pano coefficients, ohmd has 3
* psvr uses viewport size and lens center in pixels for distortion calculation, ohmd in meter
* psvr uses different distortion scaling than ohmd
Abandons the assumption that in oxr_system.xdevs[], index 0 is HMD,
1 is left controller, 2 is right controller.
Now to represent the dynamically assigned roles, oxr_system.role contains
the index for a device in oxr_system.xdevs[] for head, left and right.
This role assignment happens on the client side and currently can not be updated
from the server side.
Also adds an enum that device drivers set indicating allowed assignments
(many controllers are physically designed to be held in a specific hand).
This also adds support for configurations with only a HMD and a right controller.
