Flutter is implemented in layers. The RenderObject layer looks very much like a traditional retained mode UI. It's possible to write Flutter entirely at this le

Flutter is implemented in layers. The RenderObject layer looks very much like a traditional retained mode UI. It's possible to write Flutter entirely at this level, nobody forces you to use the Widget layer above it. The Widget layer is basically React-style, where the API looks fairly similar to immediate mode, but it uses caching and diff computation to reflect everything into the retained RenderObjects below it.