code: public void onMapViewChanged(MapViewChangedEvent event) {
  		refreshPixelLength();
  		// Note: if this.mapWidget is null, pixelLength must be valid
  		if ( !Double.isNaN(pixelLength) && (0.0 != pixelLength)) {
  			if (!isScaleItemInitialized) {
  				scaleItem.clearValue();
  				updateResolutions();
  				setDisplayScale(mapView.getCurrentScale() * pixelLength);
  			} else 	if (scaleItem.getValueAsString() == null || "".equals(scaleItem.getValueAsString())) {
  				setDisplayScale(mapView.getCurrentScale() * pixelLength);
  			} else if (event.isMapResized()) {
  				updateScaleList();
  				setDisplayScale(mapView.getCurrentScale() * pixelLength);
  			} else if (!event.isSameScaleLevel() || scaleItem.getDisplayValue() == null
  					|| "".equals(scaleItem.getDisplayValue())) {
  				setDisplayScale(mapView.getCurrentScale() * pixelLength);
  			}
  		}
  	}
docs: Will be called when the MapView changes (caused by e.g zooming); updates the select item to the correct scale.
  
  Note: This method implements MapViewChangedHandler's (only) method, this handler is registered in this.init())
  
  @see org.geomajas.gwt.client.map.event.MapViewChangedHandler#onMapViewChanged
  (org.geomajas.gwt.client.map.event.MapViewChangedEvent)