private synchronized void updateChildren() {

    // Collect all current mask layers
    LayerFilter layerFilter =
        layer -> {
          PropertySet conf = layer.getConfiguration();
          return conf.isPropertyDefined(MaskLayerType.PROPERTY_NAME_MASK)
              && conf.getValue(MaskLayerType.PROPERTY_NAME_MASK) != null;
        };
    List<Layer> maskLayers =
        LayerUtils.getChildLayers(
            LayerUtils.getRootLayer(this), LayerUtils.SEARCH_DEEP, layerFilter);
    HashMap<Mask, Layer> currentLayers = new HashMap<>();
    for (Layer maskLayer : maskLayers) {
      Mask mask = maskLayer.getConfiguration().getValue(MaskLayerType.PROPERTY_NAME_MASK);
      currentLayers.put(mask, maskLayer);
    }

    // Allign mask layers with available masks
    if (raster != null && getProduct() != null) {
      Mask[] availableMasks = getProduct().getMaskGroup().toArray(new Mask[0]);
      HashSet<Layer> unusedLayers = new HashSet<>(maskLayers);
      for (Mask availableMask : availableMasks) {
        // todo add all mask layers as soon as the masks have been scaled to fit the raster
        if (raster.getRasterSize().equals(availableMask.getRasterSize())) {
          Layer layer = currentLayers.get(availableMask);
          if (layer != null) {
            unusedLayers.remove(layer);
          } else {
            layer = createLayer(availableMask);
            getChildren().add(layer);
          }
          layer.setVisible(raster.getOverlayMaskGroup().contains(availableMask));
        }
      }

      // Remove unused layers
      for (Layer layer : unusedLayers) {
        layer.dispose();
        Layer layerParent = layer.getParent();
        if (layerParent != null) {
          layerParent.getChildren().remove(layer);
        }
      }
    }
  }
 @Override
 public void handleLayerPropertyChanged(Layer layer, PropertyChangeEvent event) {
   if ("visible".equals(event.getPropertyName())) {
     final Object value = layer.getConfiguration().getValue("mask");
     if (value instanceof Mask) {
       Mask mask = (Mask) value;
       final ProductNodeGroup<Mask> overlayMaskGroup = getRaster().getOverlayMaskGroup();
       if (layer.isVisible()) {
         if (!overlayMaskGroup.contains(mask)) {
           overlayMaskGroup.add(mask);
         }
       } else {
         overlayMaskGroup.remove(mask);
       }
     }
   }
 }