// https://w3c.github.io/uievents/#mouseevent [Exposed=Window] interface MouseEvent : UIEvent { readonly attribute double offsetX; readonly attribute double offsetY; readonly attribute double clientX; readonly attribute double clientY; readonly attribute double screenX; readonly attribute double screenY; readonly attribute double x; readonly attribute double y; readonly attribute double pageX; readonly attribute double pageY; readonly attribute short button; readonly attribute unsigned short buttons; }; dictionary MouseEventInit : EventModifierInit { // FIXME: offsetX and offsetY shouldn't be here. double offsetX = 0; double offsetY = 0; double clientX = 0; double clientY = 0; short button = 0; };