anchor.diff:     * If swipe duration is less than [durationThreshold] (in ms), a swipe is  
      * detected (regardless of swipe distance).
      * 
  -   * The [draggingClassSwiper] is the css class set to the [swiperElement] 
  -   * while a user is dragging.
  +   * The [draggingClass] is the css class set to the [swiperElement] 
  +   * while a user is dragging. If set to null, no such css class is added.
      * 
      * The [draggingClassBody] is the css class set to the html body tag
  -   * while a user is dragging.
  +   * while a user is dragging. If set to null, no such css class is added.
      */
     Swiper(Element swiperElement, 
         { int startIndex: 0, 
           int speed: 300, 
           bool autoWidth: true, 
           double autoHeightRatio: null, 
  -        this.distanceThreshold: 20,
  -        this.durationThreshold: 250,
  +        int distanceThreshold: 20,
  +        int durationThreshold: 250,
           bool disableTouch: false, 
           bool disableMouse: false,
           String handle: null, 
  -        String cancel: 'input,textarea,button,select,option',
  -        String draggingClassSwiper: 'swiper-dragging',
  +        String cancel: 'input, textarea, button, select, option',
  +        String draggingClass: 'swiper-dragging',
           String draggingClassBody: 'swiper-drag-occurring'})
           
         : this._swiperElement = swiperElement,
           this._speed = speed, 
           this._autoWidth = autoWidth,
  -        this._autoHeightRatio = autoHeightRatio {
  +        this._autoHeightRatio = autoHeightRatio,
  +        this._distanceThreshold = distanceThreshold, 
  +        this._durationThreshold = durationThreshold {
       
       _log.fine('Initializing Swiper');
       
  
positive.code:   /// The aspect ratio of the Swiper if it should be automatically applied.
    final double _autoHeightRatio;
    
    /// The [DragDetector] used to track drags on the [_containerElement].
    DragDetector _dragDetector;
    
    /// Stops the time between a drag start and a drag end to determine if the
    /// duration was below the [durationThreshold].
    Stopwatch _dragStopwatch;
    
    /// Width of one slide. 
  
negative.code:    * Fired when the user ends the dragging. 
     * 
     * Is also fired when the user clicks the 'esc'-key or the window loses focus. 
     */
    Stream<DragEvent> get onDragEnd => _dragDetector.onDragEnd;
    
  