Make suspending viewer threads the responsibility of the caller, not the shader manager.

apps/openmw/mwrender/renderingmanager.cpp

@@ -244,7 +244,8 @@ namespace MWRender
         for (auto itr = shadowDefines.begin(); itr != shadowDefines.end(); itr++)
             globalDefines[itr->first] = itr->second;
 
-        mResourceSystem->getSceneManager()->getShaderManager().setGlobalDefines(globalDefines, mViewer);
+        // It is unnecessary to stop/start the viewer as no frames are being rendered yet.
+        mResourceSystem->getSceneManager()->getShaderManager().setGlobalDefines(globalDefines);
 
         mPathgrid.reset(new Pathgrid(mRootNode));
 

components/shader/shadermanager.cpp

@@ -337,12 +337,9 @@ namespace Shader
         return DefineMap(mGlobalDefines);
     }
 
-    void ShaderManager::setGlobalDefines(DefineMap & defines, osg::ref_ptr<osgViewer::Viewer> viewer)
+    void ShaderManager::setGlobalDefines(DefineMap & globalDefines)
     {
-        mGlobalDefines = defines;
-        bool threadsStarted = viewer->areThreadsRunning();
-        if (threadsStarted)
-            viewer->stopThreading();
+        mGlobalDefines = globalDefines;
         for (auto shaderMapElement: mShaders)
         {
             std::string templateId = shaderMapElement.first.first;
@@ -358,8 +355,6 @@ namespace Shader
                 continue;
             shader->setShaderSource(shaderSource);
         }
-        if (threadsStarted)
-            viewer->startThreading();
     }
 
     void ShaderManager::releaseGLObjects(osg::State *state)

components/shader/shadermanager.hpp

@@ -39,7 +39,8 @@ namespace Shader
 
         /// Set the DefineMap used to construct all shaders
         /// @param defines The DefineMap to use
-        void setGlobalDefines(DefineMap & defines, osg::ref_ptr<osgViewer::Viewer> viewer);
+        /// @note This will change the source code for any shaders already created, potentially causing problems if they're being used to render a frame. It is recommended that any associated Viewers have their threading stopped while this function is running if any shaders are in use.
+        void setGlobalDefines(DefineMap & globalDefines);
 
         void releaseGLObjects(osg::State* state);