code: function(evt) {
          var pxCenter = this.rectPxBounds.getCenterPixel();
          var deltaX = evt.xy.x - pxCenter.x;
          var deltaY = evt.xy.y - pxCenter.y;
          var top = this.rectPxBounds.top;
          var left = this.rectPxBounds.left;
          var height = Math.abs(this.rectPxBounds.getHeight());
          var width = this.rectPxBounds.getWidth();
          var newTop = Math.max(0, (top + deltaY));
          newTop = Math.min(newTop, this.ovmap.size.h - height);
          var newLeft = Math.max(0, (left + deltaX));
          newLeft = Math.min(newLeft, this.ovmap.size.w - width);
          this.setRectPxBounds(new OpenLayers.Bounds(newLeft,
                                                     newTop + height,
                                                     newLeft + width,
                                                     newTop));
          this.updateMapToRect();
      }
docs: Method: mapDivClick
  Handle browser events
  
  Parameters:
  evt - {<OpenLayers.Event>} evt