From 663e0a10551fbd394d27aa4aa31321cda88b382b Mon Sep 17 00:00:00 2001
From: madsbuvi <madssandvei@zoho.com>
Date: Tue, 26 Jan 2021 19:28:09 +0100
Subject: [PATCH] Fix a race condition in loading screen.

---
 apps/openmw/mwgui/loadingscreen.cpp | 49 ++---------------------------
 apps/openmw/mwgui/loadingscreen.hpp |  2 --
 2 files changed, 2 insertions(+), 49 deletions(-)

diff --git a/apps/openmw/mwgui/loadingscreen.cpp b/apps/openmw/mwgui/loadingscreen.cpp
index 7ddc8c5507..aeaacaa638 100644
--- a/apps/openmw/mwgui/loadingscreen.cpp
+++ b/apps/openmw/mwgui/loadingscreen.cpp
@@ -45,8 +45,6 @@ namespace MWGui
         , mNestedLoadingCount(0)
         , mProgress(0)
         , mShowWallpaper(true)
-        , mOldCallback(nullptr)
-        , mHasCallback(false)
     {
         mMainWidget->setSize(MyGUI::RenderManager::getInstance().getViewSize());
 
@@ -147,35 +145,11 @@ namespace MWGui
 
         void operator () (osg::RenderInfo& renderInfo) const override
         {
-            {
-                std::unique_lock<std::mutex> lock(mMutex);
-                mOneshot = false;
-            }
-            mSignal.notify_all();
-
             int w = renderInfo.getCurrentCamera()->getViewport()->width();
             int h = renderInfo.getCurrentCamera()->getViewport()->height();
             mTexture->copyTexImage2D(*renderInfo.getState(), 0, 0, w, h);
 
-            {
-                std::unique_lock<std::mutex> lock(mMutex);
-                mOneshot = false;
-            }
-            mSignal.notify_all();
-        }
-
-        void wait()
-        {
-            std::unique_lock<std::mutex> lock(mMutex);
-            while (mOneshot)
-                mSignal.wait(lock);
-        }
-
-        void waitUntilInvoked()
-        {
-            std::unique_lock<std::mutex> lock(mMutex);
-            while (mOneshot)
-                mSignal.wait(lock);
+            mOneshot = false;
         }
 
         void reset()
@@ -185,8 +159,6 @@ namespace MWGui
 
     private:
         mutable bool mOneshot;
-        mutable std::mutex mMutex;
-        mutable std::condition_variable mSignal;
         osg::ref_ptr<osg::Texture2D> mTexture;
     };
 
@@ -362,14 +334,12 @@ namespace MWGui
         }
 
 #if OSG_VERSION_GREATER_OR_EQUAL(3, 5, 10)
+        mViewer->getCamera()->removeInitialDrawCallback(mCopyFramebufferToTextureCallback);
         mViewer->getCamera()->addInitialDrawCallback(mCopyFramebufferToTextureCallback);
 #else
-        // TODO: Remove once we officially end support for OSG versions pre 3.5.10
-        mOldCallback = mViewer->getCamera()->getInitialDrawCallback();
         mViewer->getCamera()->setInitialDrawCallback(mCopyFramebufferToTextureCallback);
 #endif
         mCopyFramebufferToTextureCallback->reset();
-        mHasCallback = true;
 
         mBackgroundImage->setBackgroundImage("");
         mBackgroundImage->setVisible(false);
@@ -412,21 +382,6 @@ namespace MWGui
         mViewer->renderingTraversals();
         mViewer->advance(mViewer->getFrameStamp()->getSimulationTime());
 
-        if (mHasCallback)
-        {
-            mCopyFramebufferToTextureCallback->waitUntilInvoked();
-
-            // Note that we are removing the callback before the draw thread has returned from it.
-            // This is OK as we are retaining the ref_ptr.
-#if OSG_VERSION_GREATER_OR_EQUAL(3, 5, 10)
-            mViewer->getCamera()->removeInitialDrawCallback(mCopyFramebufferToTextureCallback);
-#else
-            // TODO: Remove once we officially end support for OSG versions pre 3.5.10
-            mViewer->getCamera()->setInitialDrawCallback(mOldCallback);
-#endif
-            mHasCallback = false;
-        }
-
         mLastRenderTime = mTimer.time_m();
     }
 
diff --git a/apps/openmw/mwgui/loadingscreen.hpp b/apps/openmw/mwgui/loadingscreen.hpp
index 5d86ed3896..e1c652386d 100644
--- a/apps/openmw/mwgui/loadingscreen.hpp
+++ b/apps/openmw/mwgui/loadingscreen.hpp
@@ -87,8 +87,6 @@ namespace MWGui
 
         osg::ref_ptr<osg::Texture2D> mTexture;
         osg::ref_ptr<CopyFramebufferToTextureCallback> mCopyFramebufferToTextureCallback;
-        osg::ref_ptr<osg::Camera::DrawCallback> mOldCallback;
-        bool mHasCallback;
         std::unique_ptr<MyGUI::ITexture> mGuiTexture;
 
         void changeWallpaper();