code: function(iUp, iDown, iTickSize) {
          this.logger.log("setYConstraint: " + iUp + "," + iDown + "," + iTickSize);
          this.topConstraint = parseInt(iUp, 10);
          this.bottomConstraint = parseInt(iDown, 10);
  
          this.minY = this.initPageY - this.topConstraint;
          this.maxY = this.initPageY + this.bottomConstraint;
          if (iTickSize) { this.setYTicks(this.initPageY, iTickSize); }
  
          this.constrainY = true;
          
          this.logger.log("initPageY:" + this.initPageY + " minY:" + this.minY + 
                  " maxY:" + this.maxY);
      }
docs: By default, the element can be dragged any place on the screen.  Set
  this to limit the vertical travel of the element.  Pass in 0,0 for the
  parameters if you want to lock the drag to the x axis.
  @method setYConstraint
  @param {int} iUp the number of pixels the element can move up
  @param {int} iDown the number of pixels the element can move down
  @param {int} iTickSize optional parameter for specifying that the
  element should move iTickSize pixels at a time.