docs: function(options) {
          var mapBounds = this.getMapBounds();
          if (mapBounds !== null && ((options && options.force) ||
            (this.layer.visibility && this.layer.calculateInRange() && this.invalidBounds(mapBounds)))) {
              this.calculateBounds(mapBounds);
              this.resolution = this.layer.map.getResolution(); 
              this.triggerRead(options);
          }
      }