Function ensureFunctionPointers

OpenCSG/src/context.cpp:62–75

        static std::map<int, ContextData> gContextDataMap;

        void ensureFunctionPointers()
        {
            // In theory (and probably under Windows only), OpenGL function
            // pointers could be context specific. I.e., after changing to
            // a different context, it may be required to update the function
            // pointers again, or, to store them per context in the first place.
            // When changing from GLEW to glad, it turned out that this had
            // never been correctly considered. So I decided to ignore this
            // potential problem until I get concrete complaints.
            static bool sHaveOpenGLFunctions = false;
            if (!sHaveOpenGLFunctions)
                initExtensionLibrary();
            sHaveOpenGLFunctions = true;
        }

        OffscreenBuffer* getOffscreenBuffer(OffscreenType type) {
            int context = getContext();