function startTrackingPointer( pointsList, gPoint ) {
        //$.console.log('startTrackingPointer *** ' + pointsList.type + ' ' + gPoint.id.toString());
        gPoint.speed = 0;
        gPoint.direction = 0;
        gPoint.contactPos = gPoint.currentPos;
        gPoint.contactTime = gPoint.currentTime;
        gPoint.lastPos = gPoint.currentPos;
        gPoint.lastTime = gPoint.currentTime;

        return pointsList.add( gPoint );
    }
@function
@private
@inner
@param {OpenSeadragon.MouseTracker.GesturePointList} pointsList
    The GesturePointList to track the pointer in.
@param {OpenSeadragon.MouseTracker.GesturePoint} gPoint
     Gesture point to track.
@returns {Number} Number of gesture points in pointsList.