Widgets topic

The bridge between the reactive graph and the widget tree.

Observer runs its builder under dependency tracking: every reactive value read inside subscribes the widget, and the subscriptions are rediscovered on every build, so conditional reads stay correct. Observer.withChild keeps a heavy static subtree out of the rebuilt region.

In debug mode an observer whose builder tracks nothing throws, since it would never rebuild.

Classes

Observer

A widget that rebuilds when any reactive value read in its builder changes.