Give the composable registry typed props and a reliable child slot

Author: colemancda

Demo/swiftui/src/commonMain/kotlin/com/pureswift/swiftui/ComposableRegistry.kt

@@ -4,22 +4,36 @@ import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.graphics.Color
 import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.JsonPrimitive
+import kotlinx.serialization.json.booleanOrNull
+import kotlinx.serialization.json.doubleOrNull
+import kotlinx.serialization.json.intOrNull
+import kotlinx.serialization.json.longOrNull
+
+/// Typed access to a custom composable's props, so app authors read values
+/// without touching the underlying JSON layer (or depending on it).
+class Props internal constructor(private val json: JsonObject) {
+    fun string(key: String): String? = (json[key] as? JsonPrimitive)?.content
+    fun double(key: String): Double? = (json[key] as? JsonPrimitive)?.doubleOrNull
+    fun float(key: String): Float? = double(key)?.toFloat()
+    fun int(key: String): Int? = (json[key] as? JsonPrimitive)?.intOrNull
+    fun bool(key: String): Boolean? = (json[key] as? JsonPrimitive)?.booleanOrNull
+    /// A color passed from Swift as `PropValue.color(_:)` (an ARGB int).
+    fun color(key: String): Color? = (json[key] as? JsonPrimitive)?.longOrNull?.let { Color(it.toInt()) }
+}
 
 /// The library's single extension point: Kotlin registers named composables;
-/// Swift emits a `Composable(name:props:)` node referencing one. A registered
-/// factory receives the node's props and its rendered children slot. Entries
-/// registered from common code work on both Android and desktop; a factory
-/// that wraps an Android-only view simply isn't registered on desktop.
+/// Swift emits a `ComposableView(name:props:)` node referencing one. A factory
+/// receives typed props and a slot rendering the SwiftUI child content. Entries
+/// registered from common code work on both Android and desktop; a factory that
+/// wraps an Android-only view simply isn't registered on desktop.
 object ComposableRegistry {
 
-    fun interface Factory {
-        @Composable
-        fun Content(props: JsonObject, children: @Composable () -> Unit)
-    }
-
-    private val factories = mutableMapOf<String, Factory>()
+    // A registered factory: given props and a slot rendering the SwiftUI child
+    // content, it emits composables. Stored as a plain composable function type.
+    private val factories = mutableMapOf<String, @Composable (props: Props, children: @Composable () -> Unit) -> Unit>()
 
-    fun register(name: String, factory: Factory) {
+    fun register(name: String, factory: @Composable (props: Props, children: @Composable () -> Unit) -> Unit) {
         factories[name] = factory
     }
 
@@ -28,9 +42,13 @@ object ComposableRegistry {
         val name = node.string("name") ?: return
         val factory = factories[name]
         if (factory != null) {
-            factory.Content(node.props) {
+            factory(Props(node.props)) {
+                // RenderChild, not the public Render: a nested call to a public
+                // composable from this dynamically-invoked factory slot has its
+                // restart group skipped by the runtime and silently renders
+                // nothing.
                 for (child in node.children) {
-                    Render(child)
+                    RenderChild(child)
                 }
             }
         } else {