Capturing mouse position outside of browser window?

Question

One major barrier to creating immersive experiences in the browser (using WebGL and similar) is the set of limitations placed on mouse control.

For instance a first per

Answer 1

A hint :

 function thumb_mouse_down(e) {
                       e.target.setCapture();
                       return false;
                   }

 function doc_mouse_up(e) {
                        e.target.releaseCapture();
}