I’ve got a view/composable structure like this:

@Composable Foo() {
    Providers(MyAmbient provides foo) {
        // <-- [REF] Capture the composition here…
        AndroidView(R.layout.bar) { view ->
            view.setContent {
                // <-- [DEREF] …and resume it here.
                Baz(MyAmbient.current)
            }
        }
    }
}

And I want that innermost composable to be able to access ambients from the outer one.

The way to do this is first to call compositionReference() on the line commented [REF], and then use it to create the composition on the line above [DEREF]. compositionReference() is a public function, and works as expected. Compose APIs such compositionFor() and subcomposeInto() accept a CompositionReference parameter, but are lower-level than is convenient to use from regular view code (they require dealing with ComponentNodes). There's currently no way to pass the CompositionReference into the child composition.

The simplest way to support this would be for ViewGroup.setContent to take an optional CompositionReference parameter and plumb it through to the deepest compositionFor call. I've proven this works using reflection to access private APIs here.

This was initially discussed in this Slack thread.