CEGUI的设计模式:

像其中的单件模式比较容易理解.

但是像如下的设计不知道为什么要这样?
class CEGUIEXPORT DragContainer : public Window
    {
    public:
        /*************************************************************************
            Constants
        *************************************************************************/
        static const String WidgetTypeName;     //!< Type name for DragContainer.
        static const String EventNamespace;     //!< Namespace for global events
        static const String EventDragStarted;   //!< Name of the event fired when the user begins dragging the thumb.
        static const String EventDragEnded;     //!< Name of the event fired when the user releases the thumb.
        static const String EventDragPositionChanged;   //!< Event fired when the drag position has changed.
        static const String EventDragEnabledChanged;    //!< Event fired when dragging is enabled or disabled.
        static const String EventDragAlphaChanged;      //!< Event fired when the alpha value used when dragging is changed.
        static const String EventDragMouseCursorChanged;//!< Event fired when the mouse cursor used when dragging is changed.
        static const String EventDragThresholdChanged;  //!< Event fired when the drag pixel threshold is changed.
        static const String EventDragDropTargetChanged; //!< Event fired when the drop target changes.
       ...
       ...
       ...
    private:
        /*************************************************************************
            Static properties for the Spinner widget
        *************************************************************************/
        static DragContainerProperties::DragAlpha       d_dragAlphaProperty;
        static DragContainerProperties::DragCursorImage d_dragCursorImageProperty;
        static DragContainerProperties::DraggingEnabled d_dragEnabledProperty;
        static DragContainerProperties::DragThreshold   d_dragThresholdProperty;
};
为什么上面的有的设计为public,有的又是private,
为什么又要设计为静态的呢???谁帮我解释下?