Is it possible to call getWindowingSystemInterface() in a browser?

[HQidea]

Hey guys, I'm new to OSG. I added a getWindowingSystemInterface call in the osgemscripten.h's setupRendering function.

osg::GraphicsContext::WindowingSystemInterface* wsi = osg::GraphicsContext::getWindowingSystemInterface();

OpenSceneGraph/examples/osgemscripten/osgemscripten.h

Lines 155 to 163 in 2e4ae2e

	void setupRendering()
	{
	// Create OpenSceneGraph viewer.
	mViewer = new osgViewer::Viewer;
	// Use single thread: CRITICAL for Emscripten.
	mViewer->setThreadingModel(osgViewer::ViewerBase::SingleThreaded);
	// Create manipulator: CRITICAL for Emscripten.
	mViewer->setCameraManipulator(new osgGA::TrackballManipulator);
	}

After building and opening in the browser, there is a warning in the console:

OSG/I OSG/W Warning: GraphicsContext::WindowingSystemInterfaces::getWindowingSystemInterface() failed, no interfaces available.

Any ideas?