code: function(pixel) {
          var res = this.map.getResolution();
          this.feature.geometry.move(res * (pixel.x - this.lastPixel.x),
                                     res * (this.lastPixel.y - pixel.y));
          this.layer.drawFeature(this.feature);
          this.lastPixel = pixel;
          this.onDrag(this.feature, pixel);
      }
docs: Method: moveFeature
  Called when the drag handler detects a mouse-move.  Also calls the
  optional onDrag method.
  
  Parameters:
  pixel - {<OpenLayers.Pixel>} Location of the mouse event.