Ghost: Ghost-XR API to abstract away and access OpenXR functionality

Extends Ghost to include an abstraction for OpenXR, which I refer to as
Ghost-XR. Such an API is the base for the following commit, which introduces VR
support to Blender.

Main features:
* Simple and high-level interface for Blender specific code to call.
* Extensible for muliple graphics backends, currently OpenGL and a DirectX
  compatibility layer are supported.
* Carefully designed error handling strategy allowing Blender to handle errors
  gracefully and with useful error messages.
* OpenXR extension and API-layer management.
* OpenXR session management.
* Basic OpenXR event management.
* Debug utilities for Ghost-XR and OpenXR

For more information on this API, check
https://wiki.blender.org/wiki/Source/Interface/XR.

Reviewed by: Brecht Van Lommel

Differential Revision: https://developer.blender.org/D6188

1 files changed, 42 insertions, 0 deletions

diff --git a/intern/ghost/GHOST_IXrContext.h b/intern/ghost/GHOST_IXrContext.h
new file mode 100644
index 00000000000..362bc923ee8
--- /dev/null
+++ b/intern/ghost/GHOST_IXrContext.h
@@ -0,0 +1,42 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup GHOST
+ */
+
+#ifndef __GHOST_IXRCONTEXT_H__
+#define __GHOST_IXRCONTEXT_H__
+
+#include "GHOST_Types.h"
+
+class GHOST_IXrContext {
+ public:
+  virtual ~GHOST_IXrContext() = default;
+
+  virtual void startSession(const GHOST_XrSessionBeginInfo *begin_info) = 0;
+  virtual void endSession() = 0;
+  virtual bool isSessionRunning() const = 0;
+  virtual void drawSessionViews(void *draw_customdata) = 0;
+
+  virtual void dispatchErrorMessage(const class GHOST_XrException *) const = 0;
+
+  virtual void setGraphicsContextBindFuncs(GHOST_XrGraphicsContextBindFn bind_fn,
+                                           GHOST_XrGraphicsContextUnbindFn unbind_fn) = 0;
+  virtual void setDrawViewFunc(GHOST_XrDrawViewFn draw_view_fn) = 0;
+};
+
+#endif  // __GHOST_IXRCONTEXT_H__