code: function(evt) {
          var btn = evt.buttonElement;
          switch (btn.action) {
              case "panup": 
                  this.map.pan(0, -this.getSlideFactor("h"));
                  break;
              case "pandown": 
                  this.map.pan(0, this.getSlideFactor("h"));
                  break;
              case "panleft": 
                  this.map.pan(-this.getSlideFactor("w"), 0);
                  break;
              case "panright": 
                  this.map.pan(this.getSlideFactor("w"), 0);
                  break;
              case "zoomin": 
                  this.map.zoomIn(); 
                  break;
              case "zoomout": 
                  this.map.zoomOut(); 
                  break;
              case "zoomworld": 
                  this.map.zoomToMaxExtent(); 
                  break;
          }
      }
docs: Method: onButtonClick
  
  Parameters:
  evt - {Event}