code: function() {
          var activated = false;
          if(this.map) {
              if(OpenLayers.Control.prototype.activate.apply(this)) {
                  if(this.listeners == null) {
                      this.setListeners();
                  }
                  for(var type in this.listeners) {
                      this.map.events.register(type, this, this.listeners[type]);
                  }
                  activated = true;
                  if(this.previousStack.length == 0) {
                      this.initStack();
                  }
              }
          }
          return activated;
      }
docs: APIMethod: activate
  Activate the control.  This registers any listeners.
  
  Returns:
  {Boolean} Control successfully activated.