The X Window System generates a LeaveWindow event whenever the pointer passes out of your widget. In order for traversal to work properly, your widget must call the PrimitiveLeave action of XmPrimitive. This action encapsulates the appropriate Motif response to a LeaveWindow event. In short, this action does the following:
You can invoke PrimitiveLeave either from within the actions array or by enveloping it inside an action.