From 0.8 onwards we changed the update strategy of NiceGUI:
Prior to this release, we used and propagated the same strategy as JustPy: event handlers needed to return False to not trigger full page updates. This works good for small examples. But if your UI gets bigger, full page updates become a real performance bottle neck. Adding return False everywhere is quite cumbersome and error prone. Instead, NiceGUI now smartly updates only the element which changes. And for cases where it can not simply detect a change the user can use ui.update(...) to enforce an update. See our documentation for more details and examples.