anchor.diff:    /// The reading direction is given by [textDirection].
     ///
     /// See also:
  +  /// 
     ///  * [decreasedValue], describes what [value] will be after performing
     ///    [SemanticsAction.decrease]
     ///  * [increasedValue], describes what [value] will be after performing
  
positive.code:   /// registered.
    ///
    /// See also:
    ///  * [addAction] to add an action.
    VoidCallback getActionHandler(SemanticsAction action) => _actions[action];
  
  
negative.code:   /// would like to contribute to the semantics tree.
    ///
    /// See also:
    ///
    /// * [addAction] to add an action.
    final Map<SemanticsAction, VoidCallback> _actions = <SemanticsAction, VoidCallback>{};
  
  