code: public void extentChanged(double latMin, double lonMin, double latMax, double lonMax) {
              final Extent extent = Extent.forCoordinates(new Coordinate(latMin, lonMin), new Coordinate(latMax, lonMax));
              if (logger.isTraceEnabled()) {
                  logger.trace("JS reports extend change: {}", extent);
              }
              fireEvent(new MapViewEvent(MapViewEvent.MAP_BOUNDING_EXTENT, extent));
          }
docs: called when the map extent changed by changing the center or zoom of the map.
  
  @param latMin
  latitude of upper left corner
  @param lonMin
  longitude of upper left corner
  @param latMax
  latitude of lower right corner
  @param lonMax
  longitude of lower right corner