Adds internal API for creating and managing OpenXR actions at the
GHOST and WM layers. Does not bring about any changes for users since
XR action functionality is not yet exposed in the Python API (will be
added in a subsequent patch).
OpenXR actions are a means to communicate with XR input devices and
can be used to retrieve button/pose states or apply haptic feedback.
Actions are bound to device inputs via a semantic path binding
(https://www.khronos.org/registry/OpenXR/specs/1.0/html/xrspec.html#semantic-path-interaction-profiles),
which serves as an XR version of keymaps.
Main features:
- Abstraction of OpenXR action management functions to GHOST-XR,
WM-XR APIs.
- New "xr_session_start_pre" callback for creating actions at
appropriate point in the XR session.
- Creation of name-identifiable action sets/actions.
- Binding of actions to controller inputs.
- Acquisition of controller button states.
- Acquisition of controller poses.
- Application of controller haptic feedback.
- Carefully designed error handling and useful error reporting
(e.g. action set/action name included in error message).
Reviewed By: Julian Eisel
Differential Revision: http://developer.blender.org/D10942
Blender's main loop puts the main thread to sleep for 5ms if no user input was
received from the OS. We never want that to happen while the VR session is
running, which runs on the main thread too.
For simpler scenes, where the viewport already draws fast, this may have quite
some impact. E.g. in my tests, the classroom scene went from ~55 to quite
stable 90 FPS in solid mode (total render time as measured and averaged by
Windows Mixed Reality utilities). With Eevee, it only went from 41 to 47 FPS.
In complex files, there's barely a difference. E.g. less than 1 FPS increase in
a Spring file (both Solid mode and Eevee).
Splits up wm_xr.c into multiple files in their own folder:
source/blender/windowmanager/xr. So this matches how the message bus and
gizmo code have their own folder and files.
This allows better structuring and should make the code scale better.
I rather do this early on than to wait until we end up with a single,
huge file.
Also improves a bit how data is prepared and updated for drawing.
