code: protected void registerAttributes() {
          // Building attributes. Parsed before actor creation.
          registerBuildingAttributes();
  
          // Regular attributes. Parsed after the actor is constructed.
          registerCommonAttributes();
          registerListenerAttributes();
  
          registerAnimatedImageAttributes();
          registerButtonAttributes();
          registerButtonGroupAttributes();
          registerContainerAttributes();
          registerDialogAttributes();
          registerHorizontalGroupAttributes();
          registerImageAttributes();
          registerLabelAttributes();
          registerListAttributes();
          registerProgressBarAttributes();
          registerScrollBarAttributes();
          registerSplitPaneAttributes();
          registerSelectBoxAttributes();
          registerTableAttributes();
          registerTextFieldAttributes();
          registerTooltipAttributes();
          registerTouchpadAttributes();
          registerTreeAttributes();
          registerVerticalGroupAttributes();
          registerWindowAttributes();
      }
docs: Warning: invoked by the constructor. Registers known default attributes. Since processors registration might
  override previous settings, this method - if overridden - should call super BEFORE registering new attributes (or
  replacing the old ones).