public void registerInstalledAddOn(final AddOnProperties addOn) {
installedAddOns.add(addOn);
final ResourceController resourceController = ResourceController.getResourceController();
if (addOn.getDefaultProperties() != null)
resourceController.addDefaults(addOn.getDefaultProperties());
if (addOn.getPreferencesXml() != null) {
final ModeController modeController = Controller.getCurrentModeController();
if (modeController instanceof MModeController) {
((MModeController)modeController).getOptionPanelBuilder().load(new StringReader(addOn.getPreferencesXml()));
}