interface MouseEvent : UIEvent {

    readonly attribute double offsetX;
    readonly attribute double offsetY;
    readonly attribute double clientX;
    readonly attribute double clientY;
    readonly attribute double x;
    readonly attribute double y;

    readonly attribute short button;

};

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;

};