code: void onDataSetLookupChanged(@Observes DataSetLookupChangedEvent event) {
          DataSetLookup dataSetLookup = event.getDataSetLookup();
          displayerSettings.setDataSet(null);
          displayerSettings.setDataSetLookup(dataSetLookup);
          removeStaleSettings();
          initDisplayer();
          initSettingsEditor();
          showDisplayer();
      }
docs: Widget listeners callback notifications