CompositionObserver

fun onBeginComposition(
    composition: Composition,
    invalidationMap: Map<RecomposeScope, Set<Any>?>
): Unit

Called when the composition begins on the composition. The invalidationMap a map of invalid recompose scopes that are scheduled to be recomposed. The CompositionObserver will be called for the composition.

The scopes in the invalidationMap are not guaranteed to be composed. Some cases where they are not composed are 1) the scope is no longer part of the composition (e.g the parent scope no longer executed the code branch the scope was a part of) 2) the scope is part of movable content that was moved out of the composition.

In the case of movable content, the scope will be recomposed as part of a different composition when it is moved to that composition or it might be discarded if no other composition claims it.

fun onEndComposition(composition: Composition): Unit

Called after composition has been completed for composition.