Blender Git Loki

Support DirectX Ghost context creation

Adds support for creating a DirectX 11 Ghost context. It's not used yet
and more stuff besides creation is needed. Also, other versions than 11
should probably be supported.
We need a DirectX context to support the Windows Mixed Reality OpenXR
Runtime, a rather important one to support. Idea is to use an extension
for OpenGL-DirectX interoperability for drawing the OpenGL offscreen
viewport render using DirectX.

Split wm_xr.c into multiple files

Similar to gizmo/ and message_bus/, there's now a xr/ directory
containing header files and a intern/ directory for source and internal
header files.

Guess this is reasonable to do. And better to do early on to avoid
loosing much git history.

Fix compile errors and crashes on Windows

* Include needed Windows/DirectX headers
* Disable zero sized arraz (GCC extension)
* Add missing break causing failling assert
* Add missing semicolon in Win only code :)

Fix compile error with system OpenXR SDK

Graphics binding types were disabled by a compiler flag then.

Cleanup: Rename graphics-lib to graphics-binding

Merge branch 'master' into soc-2019-openxr

Proper management of OpenXR graphics bindings for session setup

OpenXR needs to interface with some graphics library (OpenGL, Vulkan,
DirectX, etc.). This is done through graphics binding extensions. The
OpenXR specification requires these to be properly set up before a
session is created.

Adds the following:
* Support priority list of multiple graphics binding extensions (e.g.
check OpenGL extension availability first, DirectX on Windows second,
etc.)
* Barebones for passing graphics library data to OpenXR session
creation. This is highly system dependent, e.g. it requires GLX data
for OpenGL on X11 systems (XrGraphicsBindingOpenGLXlibKHR). More work,
including additions to GHOST, will be needed once I get to the more
graphics related stuff.
* Create an own graphics context for the VR session. It's not doing
anything useful yet. This is just to fool the Monado OpenXR runtime
so that it actually attempts to create the OpenXR session.
* Had to add two CMake modules for platform dependent #define's required
by the OpenXR specification.

Cleanup: Move OpenXRData struct out of wmXRContext

Just to make access a bit more convenient.

Fix wrong enum-type used for switch

Why doesn't MSVC warn about this, grr...

Fix CMake errors after merge (?)

Not sure if this is caused by changes just merged in, or by a system
upgrade I just did. Either way, fixed it now.

Merge branch 'master' into soc-2019-openxr

Silence warning, fix mem-leak, don't destroy NULL session

Initial session state handling

To correctly start a session, a graphics extension specific object needs
to be passed to the OpenXR runtime. E.g. for the Windows Mixed Reality
runtime, XrGraphicsBindingD3D11KHR needs to be passed with a valid
DirectX device. Since we don't have any DirectX compatibility working,
I can't test this on Windows yet.
So to test this I finally need to get Monado to work on Linux and
correctly setup the OpenGL extension there.

Barebones for managing session changes

Adds initial OpenXR event querying so that session state change events
can be handled. Doesn't do any handling yet.

Enable graphics extensions if available

Check if available extensions includes the GL one, or the DirectX one on
Windows. Enable them if available.

Cleanup: Correct local variable name

Fix layer and extension count not stored as intended

Print OpenXR runtime name once connected

Merge branch 'master' into soc-2019-openxr

Initial VR-session starting/ending

Adds operator to toggle a VR session, exposed in the Window top-bar
menu. It triggers the needed calls for session creation and destruction.
Setting up the XR-system (a configuration of related devices) is also
done now.

Calling WMR runtime functions fails currently. Not sure why. So while
this executes required routines, it doesn't really work.