ComposableView: custom Android views and Compose functions

[colemancda]

The library's UIViewRepresentable-equivalent. Because a @Composable (or an Android View) can never be authored in Swift, the seam is a named registry: Kotlin registers name → composable factories once at startup, and Swift references one by name.

API

Swift — ComposableView(_ name:props:content:) emits a node that references a registered factory, forwarding typed props and an optional slot of SwiftUI child content:

ComposableView("RatingBar", props: ["rating": .double(stars), "max": 5])
ComposableView("DashedBorder", props: ["color": .color(.blue)]) {
    Text("These SwiftUI views sit inside a Compose-drawn border")
}

PropValue gained literal conveniences, so props read as a plain dictionary (["url": "…", "zoom": 1.5, "on": true]).

Kotlin — ComposableRegistry.register(name) { props, children -> … }. A factory that wraps a legacy Android View (maps, WebView, an ad SDK) uses Compose's own AndroidView inside; props is a typed accessor (props.float("rating")), so app authors never touch the JSON layer. Unregistered names render a visible diagnostic.

The interesting bug

Child content initially rendered nothing. Root cause (found by bisecting the render path on-device): a nested call to a public composable from a dynamically-invoked factory slot has its restart group skipped by the Compose runtime — the subtree silently fails to compose. Fixed by routing the registry slot through an internal RenderChild entry point; the public Render now delegates to it. (Also: the registry now stores a plain composable function type rather than a fun interface.)

Verification

• swift test — 2 new emission tests (typed props + child forwarding), 60 total passing
• Emulator (new Custom Views screen): a native android.widget.RatingBar that reactively updates as the Swift @State changes (3.5 → 4.5 via ±½ buttons); a Compose DashedBorder drawing around two SwiftUI Texts in its slot; and the red unregistered-name diagnostic

Deferred

Two-way callbacks from a custom composable back into Swift state (props flow Swift→Kotlin only for now); desktop registration of Android-view factories (they're Android-only by nature).