code: function(event) {
          this.feature = event.feature;
          var loc = this.layer.map.getLonLatFromViewPortPx(event.pixel);
          this.considerSnapping(
              event.vertex, new OpenLayers.Geometry.Point(loc.lon, loc.lat)
          );
      }
docs: Method: onVertexModified
  Registered as a listener for the vertexmodified event on the editable
  layer.
  
  Parameters:
  event - {Object} The vertex modified event.