Called when this window or a child window receives a mouse event. The on-subwindow-event method of the receiver's top-level window is called first (see get-top-level-window); if the return value is #f, the on-subwindow-event method is called for the next child in the path to the receiver, and so on. Finally, if the receiver's on-subwindow-event method returns #f, the event is passed on to the receiver's normal mouse-handling mechanism.
The event argument is the event that was generated for the receiver window. Returns #f.