code: function(e) {
          if (!this.backgroundEnabled || this.isLocked()) {
              return false;
          }
  
          this._mouseDown = true;
  
          var x = Event.getPageX(e),
              y = Event.getPageY(e);
  
  
          this.focus();
          this._slideStart();
          this.moveThumb(x, y);
      }
docs: Handles the mousedown event for the slider background
  @method onMouseDown
  @private