Currently, GraphicsContext3D has direct calls for determining the presence of and using extensions. One example is supportsMapSubCHROMIUM() and mapBufferSubDataCHROMIUM(). In addition to being CHROMIUM specific, this sort of explicit extension functionality will eventually turn into a huge and unmanageable API. One possible solution is to replace all the 'supportsXXX' calls with a single supportsExtension() call. This would be passed a string with a unique extension name and would true if the extension is supported. Then there would be a getExtension() call which would return a platform specific Extension3D object. This would be statically cast into the platform specific subclass containing the API call(s). This can be nested. If the extension gives access to existing OpenGL functionality, there can be an Extension3DOpenGL subclass which gives access to the OpenGL version of the extension. This will reduce the amount of platform specific code needed. Since the platform specific code will have to be used to determine whether or not an extension is supported, it might be best for the supportedExtension() to be in Extension3D. So you would go: if (getExtension()->supportsExtension("GL_CHROMIUM_map_sub")) static_cast<const Extension3DChromium*>(getExtension())->mapBufferSubData(...);