Ghost: Support drawing OpenGL framebuffers into a DirectX 11 buffer

Adds a minimal DirectX 11 Ghost context, plus some shared DirectX-OpenGL
resource interface using the NV_DX_interop2 WGL extension. From what I
know, this should be available on modern GPUs. If not, it should fail
gracefully.
There should be no user visible changes at this point.

Needed for DirectX-only OpenXR platforms (e.g. Windows Mixed Reality). I
heard there are other use-cases as well though.

It's known that this currently fails on some AMD systems, but that seems
to be fixable.

Most of this comes from the 2019 GSoC project, "Core Support of Virtual
Reality Headsets through OpenXR"
(https://wiki.blender.org/wiki/User:Severin/GSoC-2019/).

Reviewed by: Jeroen Bakker, Ray Molenkam, Brecht van Lommel

Differential Revision: https://developer.blender.org/D6190

1 files changed, 19 insertions, 0 deletions

diff --git a/intern/ghost/GHOST_C-api.h b/intern/ghost/GHOST_C-api.h
index ba46a868df6..a3cc9aa1df5 100644
--- a/intern/ghost/GHOST_C-api.h
+++ b/intern/ghost/GHOST_C-api.h
@@ -229,6 +229,25 @@ extern GHOST_ContextHandle GHOST_CreateOpenGLContext(GHOST_SystemHandle systemha
 extern GHOST_TSuccess GHOST_DisposeOpenGLContext(GHOST_SystemHandle systemhandle,
                                                  GHOST_ContextHandle contexthandle);
 
+#ifdef WIN32
+/**
+ * Create a new offscreen context.
+ * Never explicitly delete the context, use disposeContext() instead.
+ * \param systemhandle The handle to the system
+ * \return A handle to the new context ( == NULL if creation failed).
+ */
+GHOST_ContextHandle GHOST_CreateDirectXContext(GHOST_SystemHandle systemhandle);
+
+/**
+ * Dispose of a context.
+ * \param systemhandle The handle to the system
+ * \param contexthandle Handle to the context to be disposed.
+ * \return Indication of success.
+ */
+GHOST_TSuccess GHOST_DisposeDirectXContext(GHOST_SystemHandle systemhandle,
+                                           GHOST_ContextHandle contexthandle);
+#endif
+
 /**
  * Returns the window user data.
  * \param windowhandle The handle to the window