ScreenUi

Marks a @Composable function as the Android renderer for a screen presenter, so the codegen processor can wire it into the consumer's UI multibinding at compile time.

Without this annotation the consumer would have to manually write a Metro @BindingContainer that @Provides @IntoSet a ScreenContent, with a matches predicate that downcasts the active navigation child and a content lambda that invokes the composable. With this annotation the processor emits all of that next to the composable.

Example

@Composable
@ScreenUi(presenter = ShowsPresenter::class, parentScope = ActivityScope::class)
fun ShowsScreen(
    presenter: ShowsPresenter,
    modifier: Modifier = Modifier,
) {
    // ... compose UI here
}

The processor emits one file (ShowsScreenUiBinding.kt) into the same module's <package>.di sub package. The file contains a @BindingContainer @ContributesTo(parentScope) object whose single @Provides @IntoSet function returns a ScreenContent that:

• tests whether the active navigation child is a ScreenDestination<*> whose presenter is an instance of presenter;

• invokes the annotated composable with the cast presenter and the incoming Modifier.

Composable signature requirement

The annotated function must match the signature @Composable fun <Name>(presenter: <PresenterType>, modifier: Modifier = Modifier). The processor does not enforce the parameter names or default expression at parse time, but the generated code calls the composable with presenter = ..., modifier = modifier. A function whose parameters are out of order or named differently will fail to compile after generation, not during processing.

When to use it

Pair this with @NavDestination(kind = SCREEN) on the matching presenter. The pair lives in two modules: the presenter (Kotlin Multiplatform, with @NavDestination) and the composable (Android only, with @ScreenUi). The processor emits one binding for each so they wire together at runtime through Metro multibindings.