title: What are the correct min and max values for Gluon maps zooming?
body: <p>I am trying out Gluon maps.  As I understand it, Gluon maps uses OpenStreetMap which has a zoom range of 0 to 20 (but this value is not mentioned in the MapView javadoc).  I create this code:</p>
  <pre><code>public class MapTest2 extends Application
  {
      MapView mapView = new MapView();
      MapPoint mapPoint = new MapPoint(51.509865d,-0.118092d);    // London, England
          
      @Override
      public void start(Stage stage) throws Exception {
          StackPane sp = new StackPane();
          sp.getChildren().add(mapView);
          
          mapView.setCenter(mapPoint);
          mapView.setZoom(42.8);          // ? and -1.1 works but -1.3 fails
          
          Scene  scene = new Scene(sp, 500, 300);
          stage.setScene(scene);
          stage.show();
      }
      
      public static void main(String[] args) {
          MapTest2.launch(MapTest2.class, args);
      }
  }
  </code></pre>
  <p>where I can set the positive zoom value far higher than 20.  Some considerable zooming out on the mouse wheel returns me to a reasonable view.  A zoom value of -1.1 works but -1.3 fails with:</p>
  <pre><code>Exception in thread &quot;main&quot; java.lang.RuntimeException: Exception in Application start method
  :
  Caused by: java.lang.ArrayIndexOutOfBoundsException: Index -2 out of bounds for length 20
      at com.gluonhq.impl.maps.BaseMap.loadTiles(BaseMap.java:347)
      at com.gluonhq.impl.maps.BaseMap.layoutChildren(BaseMap.java:490)
  :
  </code></pre>
  <p>What are the real minimum and maximum zoom ranges, and should I use only integer values for zoom as there seems to be some rounding going on?</p>