code: function(e) {
          this.logger.log("background drag");
          if (this.backgroundEnabled && !this.isLocked()) {
              var x = Event.getPageX(e),
                  y = Event.getPageY(e);
              this.moveThumb(x, y, true, true);
              this.fireEvents();
          }
      }
docs: Handles the onDrag event for the slider background
  @method onDrag
  @private