docs: public static Component getSubScreen(Container container, Class<?> targetClass)
      {
          for (int i = container.getComponentCount() - 1; i >= 0; i--)
          {   // Go backwards to do toolbars, menubars last.
              Component component = container.getComponent(i);
              if (targetClass.isAssignableFrom(component.getClass()))
                  return component;
              if (component instanceof Container)
              {
                  component = JBasePanel.getSubScreen((Container)component, targetClass);
                  if (component != null)
                      return component;
              }
          }
          return null;
      }