From 8f38f0536c1505cb4b784963eb9cab8cfa1eee9d Mon Sep 17 00:00:00 2001
From: Mads Buvik Sandvei <madssandvei@protonmail.com>
Date: Tue, 2 Jun 2020 21:46:22 +0200
Subject: [PATCH] Separate GLRC for OpenXR to ensure uncontested access. Safety
 check on predictions to police that they are made only once per frame.

---
 apps/openmw/mwvr/openxrmanagerimpl.cpp | 30 +++++++++++++++++++++++---
 apps/openmw/mwvr/openxrmanagerimpl.hpp |  3 +++
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/apps/openmw/mwvr/openxrmanagerimpl.cpp b/apps/openmw/mwvr/openxrmanagerimpl.cpp
index 7cc58b8bb..eae8626a1 100644
--- a/apps/openmw/mwvr/openxrmanagerimpl.cpp
+++ b/apps/openmw/mwvr/openxrmanagerimpl.cpp
@@ -93,10 +93,16 @@ namespace MWVR
 
         { // Create Session
             // TODO: Platform dependent
+            auto DC = wglGetCurrentDC();
+            auto GLRC = wglGetCurrentContext();
+            auto XRGLRC = wglCreateContext(DC);
+            wglShareLists(GLRC, XRGLRC);
+            wglMakeCurrent(DC, XRGLRC);
+
             mGraphicsBinding.type = XR_TYPE_GRAPHICS_BINDING_OPENGL_WIN32_KHR;
             mGraphicsBinding.next = nullptr;
-            mGraphicsBinding.hDC = wglGetCurrentDC();
-            mGraphicsBinding.hGLRC = wglGetCurrentContext();
+            mGraphicsBinding.hDC = DC;
+            mGraphicsBinding.hGLRC = XRGLRC;
 
             if (!mGraphicsBinding.hDC)
                 std::cout << "Missing DC" << std::endl;
@@ -108,6 +114,7 @@ namespace MWVR
             createInfo.systemId = mSystemId;
             CHECK_XRCMD(xrCreateSession(mInstance, &createInfo, &mSession));
             assert(mSession);
+            wglMakeCurrent(DC, GLRC);
         }
 
         LogLayersAndExtensions();
@@ -315,7 +322,11 @@ namespace MWVR
             int64_t predictedDisplayTime,
             TrackedSpace space)
     {
-
+        if (!mPredictionsEnabled)
+        {
+            Log(Debug::Error) << "Prediction out of order";
+            throw std::logic_error("Prediction out of order");
+        }
         std::array<XrView, 2> views{ {{XR_TYPE_VIEW}, {XR_TYPE_VIEW}} };
         XrViewState viewState{ XR_TYPE_VIEW_STATE };
         uint32_t viewCount = 2;
@@ -339,6 +350,11 @@ namespace MWVR
 
     MWVR::Pose OpenXRManagerImpl::getPredictedLimbPose(int64_t predictedDisplayTime, TrackedLimb limb, TrackedSpace space)
     {
+        if (!mPredictionsEnabled)
+        {
+            Log(Debug::Error) << "Prediction out of order";
+            throw std::logic_error("Prediction out of order");
+        }
         XrSpaceLocation location{ XR_TYPE_SPACE_LOCATION };
         XrSpaceVelocity velocity{ XR_TYPE_SPACE_VELOCITY };
         location.next = &velocity;
@@ -500,6 +516,14 @@ namespace MWVR
             referenceSpace = mReferenceSpaceView;
         return referenceSpace;
     }
+    void OpenXRManagerImpl::enablePredictions()
+    {
+        mPredictionsEnabled = true;
+    }
+    void OpenXRManagerImpl::disablePredictions()
+    {
+        mPredictionsEnabled = false;
+    }
 }
 
 namespace osg
diff --git a/apps/openmw/mwvr/openxrmanagerimpl.hpp b/apps/openmw/mwvr/openxrmanagerimpl.hpp
index ed58b186c..8ad78e28e 100644
--- a/apps/openmw/mwvr/openxrmanagerimpl.hpp
+++ b/apps/openmw/mwvr/openxrmanagerimpl.hpp
@@ -65,8 +65,11 @@ namespace MWVR
         void HandleSessionStateChanged(const XrEventDataSessionStateChanged& stateChangedEvent);
         XrFrameState frameState();
         XrSpace getReferenceSpace(TrackedSpace space);
+        void enablePredictions();
+        void disablePredictions();
 
         bool initialized = false;
+        bool mPredictionsEnabled = false;
         long long mFrameIndex = 0;
         XrInstance mInstance = XR_NULL_HANDLE;
         XrSession mSession = XR_NULL_HANDLE;