function onPointerEnter( tracker, event ) {
        //$.console.log('pointerenter ' + (tracker.userData ? tracker.userData.toString() : ''));

        var gPoint = {
            id: getPointerId( event ),
            type: getPointerType( event ),
            isPrimary: getIsPrimary( event ),
            currentPos: getMouseAbsolute( event ),
            currentTime: $.now()
        };

        // pointerenter doesn't bubble and is not cancelable, but we call
        //   preProcessEvent() so it's dispatched to preProcessEventHandler
        //   if necessary
        var eventInfo = {
            originalEvent: event,
            eventType: 'pointerenter',
            pointerType: gPoint.type,
            isEmulated: false
        };
        preProcessEvent( tracker, eventInfo );

        updatePointerEnter( tracker, eventInfo, gPoint );
    }
Note: Called for both pointer events and legacy mouse events
        ($.MouseTracker.havePointerEvents determines which)

@private
@inner