anchor.diff:      _init(true);
     }
   
  -  void _init(bool value) {
  -    _forward = value;
  +  void _init(bool forward) {
  +    _forward = forward;
       enabled = false;
   
       spark.navigationManager.onNavigate.listen((_) {
  
positive.code:     } else {
        spark.navigationManager.goBack();
      }
    }
  }
  
  
negative.code: 
      // Ctrl-1 to Ctrl-8. The user types in a 1-based key event; we convert that
      // into a 0-based into into the tabs.
      spark.editorArea.focusTab(spark.editorArea.tabs[_binding.index - 1]);
    }
  }
  
  