code: function(e) {
          var min = this.minSlider,
              max = this.maxSlider,
              minLocked = min.isLocked() || !min.backgroundEnabled,
              maxLocked = max.isLocked() || !min.backgroundEnabled,
              Ev  = YAHOO.util.Event,
              d;
  
          if (minLocked || maxLocked) {
              this.activeSlider = minLocked ? max : min;
          } else {
              if (this.isHoriz) {
                  d = Ev.getPageX(e)-min.thumb.initPageX-min.thumbCenterPoint.x;
              } else {
                  d = Ev.getPageY(e)-min.thumb.initPageY-min.thumbCenterPoint.y;
              }
                      
              this.activeSlider = d*2 > max.getValue()+min.getValue() ? max : min;
          }
      }
docs: A background click will move the slider thumb nearest to the click.
  Override if you need different behavior.
  @method selectActiveSlider
  @param e {Event} the mousedown event
  @private