Gumbo FxScroller - Functional and Design Specification

public class FxScroller extends FxComponent implements IFocusManagerComponent
{
    [SkinPart] public var horizontalScrollBar:FxHScrollBar;
    [SkinPart] public var verticalScrollBar:FxVScrollBar;
    
    [Bindable]
    /**
     *  The viewport component to be scrolled.
     * 
     *  The viewport is added to the FXScroller component's skin 
     *  which lays out both the viewport and scrollbars.
     * xs
     *  When the viewport property is set, the viewport's clipContent property is 
     *  set to true to enable scrolling.
     * 
     *  Scroller does not support rotating the viewport directly.  The viewport's
     *  contents can be transformed arbitrarily but the viewport itself can not.
     */
    public function get viewport():IViewport
    public function set viewport(value:IViewport):void

    [Bindable]
    [Inspectable(enumeration="off,on,auto", defaultValue="auto")]
    /**
     *  Indicates under what conditions the vertical scrollbar is displayed.
     * 
     *  ScrollPolicy.ON ("on") - the scrollbar is always displayed.
     * 
     *  ScrollPolicy.OFF ("off") - the scrollbar is never displayed.
     *  The viewport can still be scrolled programmatically, by setting its
     *  verticalScrollPosition property.
     * 
     *  ScrollPolicy.AUTO ("auto") - the scrollbar is displayed when 
     *  the viewport's contentHeight is larger than its height.
     * 
     *  The scroll policy affects the measured size of the FxScroller component.
     * 
     *  @default ScrollPolicy.AUTO
     */ 
    public function get verticalScrollPolicy():String
    public function set verticalScrollPolicy(value:String):void
    
    [Bindable]
    [Inspectable(enumeration="off,on,auto", defaultValue="auto")]
    /**
     *  Indicates under what conditions the horizontal scrollbar is displayed.
     * 
     *  ScrollPolicy.ON ("on") - the scrollbar is always displayed.
     *  
     *  ScrollPolicy.OFF ("off") - the scrollbar is never displayed.
     *  The viewport can still be scrolled programmatically, by setting its
     *  horizontalScrollPosition property.
     *  
     *  ScrollPolicy.AUTO ("auto") - the scrollbar is displayed when 
     *  the viewport's contentWidth is larger than its width.
     * 
     *  The scroll policy affects the measured size of the FxScroller component.
     * 
     *  @default ScrollPolicy.AUTO
     */ 
    public function get horizontalScrollPolicy():String
    public function set horizontalScrollPolicy(value:String):void
}

    /**
     *  The viewport controlled by this scrollbar.  If a viewport is
     *  specified, then changes to its actual size, content size, and
     *  scroll position, cause the corresponding ScrollBar methods to
     *  run:
     * 
     *  - viewportResizeHandler()
     *  - contentWidthChangeHandler()
     *  - contentHeightChangeHandler()
     *  - viewportVerticalScrollPositionChangeHandler()
     *  - viewportHorizontalScrollPositionChangeHandler()
     * 
     *  The FxVScrollBar and FxHScrollBar classes override these methods to 
     *  keep their pageSize, maximum, and value properties in sync with the
     *  viewport.   Similarly, they override their page and step methods to
     *  use the viewport's scrollPositionDelta methods to compute page and
     *  and step offsets.
     *    
     *  @default null
     */
    public function get viewport():IViewport
    public function set viewport(value:IViewport):void

   /**
    *  Called when the viewport's width or height changes, does nothing by default.
    */
    protected function viewportResizeHandler(event:ResizeEvent):void
    
   /**
    *  Called when the viewport's contentWidth changes, does nothing by default.
    */
    protected function viewportContentWidthChangeHandler(event:PropertyChangeEvent):void
    
    /**
     *  Called when the viewport's contentHeight changes, does nothing by default.
     */
    protected function viewportContentHeightChangeHandler(event:PropertyChangeEvent):void
    
    /**
     *  Called when the viewport's horizontalScrollPosition changes, does nothing by default.
     */
    protected function viewportHorizontalScrollPositionChangeHandler(event:PropertyChangeEvent):void
    
    /**
     *  Called when the viewport's verticalScrollPosition changes, does nothing by default. 
     */
    protected function viewportVerticalScrollPositionChangeHandler(event:PropertyChangeEvent):void