Support custom compose views in the desktop rig

Demo/App.swiftpm/Sources/Catalog.swift

@@ -69,10 +69,9 @@ struct CatalogEntry: Identifiable {
             CatalogEntry(id: "form", title: "Form", screen: AnyCatalogScreen(FormPlayground())),
             CatalogEntry(id: "modifier", title: "Modifiers", screen: AnyCatalogScreen(ModifierPlayground())),
         ]
-        // Android-only: native-view interop through the composable registry
-        #if !DESKTOP_RIG
+        // Custom views through the composable registry — cross-platform: each
+        // host (Android app, desktop rig) registers its own factories.
         entries.append(CatalogEntry(id: "representable", title: "Custom Views", screen: AnyCatalogScreen(RepresentablePlayground())))
-        #endif
         entries += [
             CatalogEntry(id: "appearance", title: "Appearance", screen: AnyCatalogScreen(AppearancePlayground())),
             CatalogEntry(id: "animation", title: "Animation", screen: AnyCatalogScreen(AnimationPlayground())),

Demo/desktop/src/jvmMain/kotlin/com/pureswift/swiftui/desktop/DemoComposables.kt

@@ -0,0 +1,107 @@
+package com.pureswift.swiftui.desktop
+
+import androidx.compose.foundation.gestures.detectDragGestures
+import androidx.compose.foundation.gestures.detectTapGestures
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.drawBehind
+import androidx.compose.ui.draw.drawWithContent
+import androidx.compose.ui.geometry.CornerRadius
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.PathEffect
+import androidx.compose.ui.graphics.drawscope.Stroke
+import androidx.compose.ui.graphics.drawscope.clipRect
+import androidx.compose.ui.input.pointer.pointerInput
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import com.pureswift.swiftui.ComposableRegistry
+import kotlin.math.roundToInt
+
+/// Registers the desktop rig's custom composables into the interpreter's
+/// registry — the desktop counterpart to the Android demo's `registerDemo
+/// Composables`. Called once before the first render. It shows that the
+/// composable registry is a cross-platform extension point: `DashedBorder` is
+/// the identical pure-Compose function used on Android, and `RatingBar` is a
+/// pure Compose-Multiplatform reimplementation of what the Android demo bridges
+/// to `android.widget.RatingBar`.
+fun registerDemoComposables() {
+
+    // A pure Compose-Multiplatform star rating — no native widget. Tapping or
+    // dragging across the stars reports a half-step rating back to Swift; the
+    // `rating` prop drives the fill so two-way binding round-trips.
+    ComposableRegistry.register("RatingBar") { props, _ ->
+        val rating = props.float("rating") ?: 0f
+        val max = props.int("max") ?: 5
+        val onChanged = props.doubleAction("onRatingChanged")
+
+        // Maps a horizontal position within the row to the nearest half-star.
+        fun report(x: Float, width: Int) {
+            if (width <= 0 || onChanged == null) return
+            val fraction = (x / width).coerceIn(0f, 1f)
+            val stepped = (fraction * max * 2).roundToInt() / 2.0
+            onChanged.invoke(stepped.coerceIn(0.0, max.toDouble()))
+        }
+
+        Box(
+            modifier = Modifier
+                .pointerInput(max) { detectTapGestures { report(it.x, size.width) } }
+                .pointerInput(max) {
+                    detectDragGestures { change, _ -> report(change.position.x, size.width) }
+                },
+        ) {
+            androidx.compose.foundation.layout.Row {
+                for (index in 0 until max) {
+                    val fill = (rating - index).coerceIn(0f, 1f)
+                    Star(fill)
+                }
+            }
+        }
+    }
+
+    // The same pure Compose function the Android demo registers: a dashed border
+    // drawn around whatever SwiftUI child content lands in the slot.
+    ComposableRegistry.register("DashedBorder") { props, children ->
+        val color = props.color("color") ?: Color(0xFF6750A4.toInt())
+        Box(
+            modifier = Modifier
+                .drawBehind {
+                    drawRoundRect(
+                        color = color,
+                        style = Stroke(
+                            width = 5f,
+                            pathEffect = PathEffect.dashPathEffect(floatArrayOf(24f, 14f)),
+                        ),
+                        cornerRadius = CornerRadius(20f, 20f),
+                    )
+                }
+                .padding(18.dp),
+        ) {
+            children()
+        }
+    }
+}
+
+/// One star, filled left-to-right by `fill` (0…1) so halves render exactly.
+/// A clipped filled glyph is layered over an empty one — no icon dependency.
+@Composable
+private fun Star(fill: Float) {
+    val style = TextStyle(fontSize = 34.sp, textAlign = TextAlign.Center)
+    Box(modifier = Modifier.size(40.dp), contentAlignment = Alignment.Center) {
+        Text("☆", style = style, color = Color(0xFFB0B0B0)) // ☆
+        Text(
+            "★", // ★
+            style = style,
+            color = Color(0xFFFFC107),
+            modifier = Modifier.drawWithContent {
+                clipRect(right = size.width * fill) { this@drawWithContent.drawContent() }
+            },
+        )
+    }
+}

Demo/desktop/src/jvmMain/kotlin/com/pureswift/swiftui/desktop/Main.kt

@@ -87,6 +87,7 @@ private fun LiveContent() {
     val store = remember {
         TreeStore().also {
             com.pureswift.swiftui.SwiftBridge.sink = com.pureswift.swiftui.JextractCallbackSink()
+            registerDemoComposables()
             SwiftRuntime().start(it)
         }
     }

Package.swift

@@ -119,15 +119,16 @@ let package = Package(
             ],
             // `Playgrounds` symlinks the Android demo's shared sources; the rig
             // reuses them verbatim on desktop. Excluded: the app entry point (it
-            // needs the Android host or Apple's App/Scene), and the three
-            // Android-only screens — Map (schematic), Video (Media3), and Custom
-            // Views (the native-view composable registry) — which have no desktop
-            // rendering. Their catalog entries are `#if canImport(AndroidSwiftUI)`.
+            // needs the Android host or Apple's App/Scene) and the two Android-
+            // only screens — Map (schematic) and Video (Media3) — which have no
+            // desktop rendering; their catalog entries are gated on `DESKTOP_RIG`.
+            // The Custom Views screen (the composable registry) IS included: the
+            // registry is a cross-platform extension point, and the desktop rig
+            // registers pure-Compose factories for it (see DemoComposables.kt).
             exclude: [
                 "Playgrounds/App.swift",
                 "Playgrounds/MapPlaygrounds.swift",
                 "Playgrounds/VideoPlaygrounds.swift",
-                "Playgrounds/RepresentablePlaygrounds.swift",
             ],
             swiftSettings: [
               .swiftLanguageMode(.v5),