code: public JsHandlerRegistration addGeometryMergeStartHandler(final GeometryMergeStartHandler handler) {
  		org.geomajas.plugin.editing.client.merge.event.GeometryMergeStartHandler h;
  		h = new org.geomajas.plugin.editing.client.merge.event.GeometryMergeStartHandler() {
  
  			public void onGeometryMergingStart(GeometryMergeStartEvent event) {
  				org.geomajas.plugin.editing.jsapi.client.merge.event.GeometryMergeStartEvent e;
  				e = new org.geomajas.plugin.editing.jsapi.client.merge.event.GeometryMergeStartEvent();
  				handler.onGeometryMergeStart(e);
  			}
  		};
  		HandlerRegistration registration = delegate.addGeometryMergeStartHandler(h);
  		return new JsHandlerRegistration(new HandlerRegistration[] { registration });
  	}
docs: Register a {@link GeometryMergeStartHandler} to listen to events that signal the merging process has started.
  
  @param handler
  The {@link GeometryMergeStartHandler} to add as listener.
  @return The registration of the handler.