How best to pass event down from a parent presenter to a child presenter

[ElliotSknr]

I currently have a setup where I create a navigator and provide it to NavigableCircuitContent at the root of my application. The initial screen, let's call it HomeScreen launches another CircuitContent(), providing the existing navigator to this function. Within the home screen I have a scaffold which displays a bottom bar with nav destinations that are swapped out in the via the CircuitContent's screen parameter.

The trouble I am having is how best to inform one of these child screens/presenter that the navbar has been pressed in the event that the navbar is clicked on the currently active tab, where I would want to perform a custom action such as refresh of content or scroll to the top of the child screen.

I access a kotlin object between these presenters to listen to this, but I was hoping to first understand if there is a more idiomatic way to perform this within circuit.

Root

// navigator/backstack created via remember functions here, the backstack is created with `HomeScreen`
NavigableCircuitContent(
  navigator = navigator,
  backStack = backStack,
  decoration = GestureNavigationDecoration(
    onBackInvoked = {
      navigator.pop()
    }
  ),
)

Home Presenter

override fun present(): HomeState {
  var currentTabScreen: Screen by rememberRetained { mutableStateOf(ChildTabScreenOne) }
  return HomeState(
    selectedScreen = currentTabScreen,
    navigator = navigator,
    eventSink = { event ->
      when (event) {
        is HomeEvent.ChangeScreen -> {
          currentTabScreen = event.screen
/*...*/
}})}}

Home Ui

Scaffold (
  /*bottom bar with code to send ChangeScreen via the eventSink */
) { scaffoldPadding ->
  AnimatedContent(state.selectedScreen) { targetScreen ->
    CircuitContent(
      screen = targetScreen,
      navigator = state.navigator,
      modifier = Modifier
        .padding(scaffoldPadding)
        .consumeWindowInsets(scaffoldPadding)
        .fillMaxSize(),
    )
  }
}

[ZacSweers]

I would make your home scaffold be backed by a presenter that is composed of its nested presenters. You can then pass state to their current states' sinks. You can't pass state through CircuitContent directly as it's intentionally opaque.