Blender Git Loki

Merge branch 'master' into soc-2019-openxr

Fix compiling with external OpenXR SDK on Windows

Cleanup: Don't cast away const in GHOST C-API

Fix crash when no OpenXR runtime is found (or setup failed)

Remove bundled OpenXR-SDK sources from extern/

Removes the OPENXR_USE_BUNDLED_SRC option which allowed using the
OpenXR-SDK sources bundled in extern/. It would be too much hassle to
keept these updated.
Now these have to be provided on the system Blender is compiled on. I've
already added necessary bits to install_deps.sh and our Windows
maintainer is ready to provide builds with OpenXR-SDK linked.
Once this gets into master, platform maintainers will have to be
notified about the added dependency.

This also removes the JsonCpp dependency, it was only needed for the
OpenXR-SDK sources.

Linux: Add OpenXR-SDK to install_deps.sh

Silence warnings in OpenXR SDK API layer files

Quiet warning

Merge branch 'master' into soc-2019-openxr

Cleanup: Unused includes, better structuring for wm_xr.c

Cleanup: Remove unused support for non-OpenGL Windows

This was very useful for testing, but there's no current need for it.
Neither for VR code, nor for anything else in master.

Cleanup: Move secondary GHOST-context handle to XR surface data

This is used to refer to the DirectX context. For other (currently
non-existant) surfaces, this may not make much sense.

Don't swap buffers of offscreen surface OpenGL contexts

This does frame syncing to the regular screen, so hurts performance in
some cases.

Exit OpenXR context/session gracefully if the runtime reports loss pending

Handle XR_TYPE_EVENT_DATA_INSTANCE_LOSS_PENDING and
XR_SESSION_STATE_LOSS_PENDING according to the specification.

Disable specular highlights in the VR viewport

Fix xrDestroy calls to data already implicitly destroyed by OpenXR

Would effectifely result in null-ops, since the loader does good sanity
checks. The failing functions would still lead to error prints though.

Correctly request session end according to OpenXR 1.0 specification

Fix dark VR rendering on Windows Mixed Reality by appyling SRGB OETF

Discussed this in length with @sobotka, and it seems WMR has an utterly
broken pixel color pipeline. So we apply a SRGB OETF for this specific
runtime to compensate.

Allow querying OpenXR runtime ID

Useful in case special treatment is needed for certain runtimes.
Currently only WMR gets its ID assigned correctly, others are TODO.

Merge branch 'master' into soc-2019-openxr