subscribe

Subscribes the composing scope to the widget's value changing under its declaration, so that a change the caller does not adopt brings the pass that puts the declaration back. Answers nothing: what a subscribed scope does about a change is read the widget on the pass after it.

A change a settle made and recorded the widget's answer to is the one kind this does not carry: it is where the declaration was already heading, and the pass that made it has already been told where it landed.

declare does this for the declaration it settles. Call it directly where a component derives something from the widget in its own body rather than through a declaration.