Give TreehouseView a generic for its Widget type (#1468)

redwood-treehouse-host-composeui/src/commonMain/kotlin/app/cash/redwood/treehouse/composeui/TreehouseContent.kt

@@ -47,7 +47,7 @@ import kotlinx.coroutines.flow.MutableStateFlow
 @Composable
 public fun <A : AppService> TreehouseContent(
   treehouseApp: TreehouseApp<A>,
-  widgetSystem: WidgetSystem,
+  widgetSystem: WidgetSystem<@Composable () -> Unit>,
   codeListener: CodeListener = CodeListener(),
   contentSource: TreehouseContentSource<A>,
 ) {
@@ -61,12 +61,12 @@ public fun <A : AppService> TreehouseContent(
   )
 
   val treehouseView = remember(widgetSystem) {
-    object : TreehouseView {
+    object : TreehouseView<@Composable () -> Unit> {
       override val children = ComposeWidgetChildren()
       override val uiConfiguration = MutableStateFlow(uiConfiguration)
       override val widgetSystem = widgetSystem
       override val readyForContent = true
-      override var readyForContentChangeListener: ReadyForContentChangeListener? = null
+      override var readyForContentChangeListener: ReadyForContentChangeListener<@Composable () -> Unit>? = null
       override var saveCallback: TreehouseView.SaveCallback? = null
       override val stateSnapshotId = StateSnapshot.Id(null)
       override fun reset() = children.remove(0, children.widgets.size)

redwood-treehouse-host/src/androidMain/kotlin/app/cash/redwood/treehouse/TreehouseLayout.kt

@@ -36,9 +36,9 @@ public typealias TreehouseWidgetView = TreehouseLayout
 @SuppressLint("ViewConstructor")
 public class TreehouseLayout(
   context: Context,
-  override val widgetSystem: WidgetSystem,
-) : RedwoodLayout(context), TreehouseView {
-  override var readyForContentChangeListener: ReadyForContentChangeListener? = null
+  override val widgetSystem: WidgetSystem<View>,
+) : RedwoodLayout(context), TreehouseView<View> {
+  override var readyForContentChangeListener: ReadyForContentChangeListener<View>? = null
     set(value) {
       check(value == null || field == null) { "View already bound to a listener" }
       field = value

redwood-treehouse-host/src/androidUnitTest/kotlin/app/cash/redwood/treehouse/TreehouseLayoutTest.kt

@@ -62,7 +62,7 @@ class TreehouseLayoutTest {
     val activity = Robolectric.buildActivity(Activity::class.java).resume().visible().get()
     val parent = activity.findViewById<ViewGroup>(android.R.id.content)
     val layout = TreehouseLayout(context, throwingWidgetSystem)
-    val listener = CountingReadyForContentChangeListener()
+    val listener = CountingReadyForContentChangeListener<View>()
 
     layout.readyForContentChangeListener = listener
     assertThat(listener.count).isEqualTo(0)
@@ -145,5 +145,5 @@ class TreehouseLayoutTest {
   }
 
   private val throwingWidgetSystem =
-    WidgetSystem { _, _ -> throw UnsupportedOperationException() }
+    WidgetSystem<View> { _, _ -> throw UnsupportedOperationException() }
 }

redwood-treehouse-host/src/commonMain/kotlin/app/cash/redwood/treehouse/ChangeListRenderer.kt

@@ -20,7 +20,6 @@ import app.cash.redwood.protocol.SnapshotChangeList
 import app.cash.redwood.protocol.widget.ProtocolBridge
 import app.cash.redwood.protocol.widget.ProtocolMismatchHandler
 import app.cash.redwood.protocol.widget.ProtocolNode
-import app.cash.redwood.widget.Widget
 import kotlinx.serialization.json.Json
 
 /**
@@ -38,12 +37,12 @@ public class ChangeListRenderer<W : Any>(
 
   @Suppress("UNCHECKED_CAST")
   public fun render(
-    view: TreehouseView,
+    view: TreehouseView<W>,
     changeList: SnapshotChangeList,
   ) {
     view.reset()
     val bridge = ProtocolBridge(
-      container = view.children as Widget.Children<W>,
+      container = view.children,
       factory = view.widgetSystem.widgetFactory(
         json,
         ProtocolMismatchHandler.Throwing,

redwood-treehouse-host/src/commonMain/kotlin/app/cash/redwood/treehouse/CodeListener.kt

@@ -23,13 +23,13 @@ public open class CodeListener {
    * Invoked when the initial code is still loading. This can be used to signal a loading state
    * in the UI before there is anything to display.
    */
-  public open fun onInitialCodeLoading(view: TreehouseView) {}
+  public open fun onInitialCodeLoading(view: TreehouseView<*>) {}
 
   /**
    * Invoked each time new code is loaded. This is called after the view's old children have
    * been cleared but before the children of the new code have been added.
    *
    * @param initial true if this is the first code loaded for this view's current content.
    */
-  public open fun onCodeLoaded(view: TreehouseView, initial: Boolean) {}
+  public open fun onCodeLoaded(view: TreehouseView<*>, initial: Boolean) {}
 }

redwood-treehouse-host/src/commonMain/kotlin/app/cash/redwood/treehouse/Content.kt

@@ -47,7 +47,7 @@ public interface Content {
    *
    * This function may only be invoked on [TreehouseDispatchers.ui].
    */
-  public fun bind(view: TreehouseView)
+  public fun bind(view: TreehouseView<*>)
 
   /**
    * Suspends until content is available; either it is already in the view or it is preloaded and a call to [bind]

redwood-treehouse-host/src/commonMain/kotlin/app/cash/redwood/treehouse/ContentBinding.kt

@@ -25,8 +25,8 @@ import okio.Closeable
  *
  * Returns a closeable that unbinds from the content and stops tracking the ready state.
  */
-public fun Content.bindWhenReady(view: TreehouseView): Closeable {
-  val listener = ReadyForContentChangeListener {
+public fun <W : Any> Content.bindWhenReady(view: TreehouseView<W>): Closeable {
+  val listener = ReadyForContentChangeListener<W> {
     if (view.readyForContent) {
       bind(view)
     } else {
@@ -45,8 +45,8 @@ public fun Content.bindWhenReady(view: TreehouseView): Closeable {
   }
 }
 
-public fun <A : AppService> TreehouseContentSource<A>.bindWhenReady(
-  view: TreehouseView,
+public fun <A : AppService, W : Any> TreehouseContentSource<A>.bindWhenReady(
+  view: TreehouseView<W>,
   app: TreehouseApp<A>,
   codeListener: CodeListener = CodeListener(),
 ): Closeable {

redwood-treehouse-host/src/commonMain/kotlin/app/cash/redwood/treehouse/TreehouseAppContent.kt

@@ -51,7 +51,7 @@ private sealed interface ViewState {
   ) : ViewState
 
   class Bound(
-    val view: TreehouseView,
+    val view: TreehouseView<*>,
   ) : ViewState
 }
 
@@ -102,7 +102,7 @@ internal class TreehouseAppContent<A : AppService>(
     stateFlow.value = State(nextViewState, nextCodeState)
   }
 
-  override fun bind(view: TreehouseView) {
+  override fun bind(view: TreehouseView<*>) {
     treehouseApp.dispatchers.checkUi()
     val previousState = stateFlow.value
     val previousViewState = previousState.viewState
@@ -260,7 +260,7 @@ private class ViewContentCodeBinding<A : AppService>(
   private val bindingScope = CoroutineScope(SupervisorJob(appScope.coroutineContext.job))
 
   /** Only accessed on [TreehouseDispatchers.ui]. Null before [initView] and after [cancel]. */
-  private var viewOrNull: TreehouseView? = null
+  private var viewOrNull: TreehouseView<*>? = null
 
   /** Only accessed on [TreehouseDispatchers.ui]. Null before [initView] and after [cancel]. */
   private var bridgeOrNull: ProtocolBridge<*>? = null
@@ -282,7 +282,7 @@ private class ViewContentCodeBinding<A : AppService>(
 
   private var initViewCalled: Boolean = false
 
-  fun initView(view: TreehouseView) {
+  fun initView(view: TreehouseView<*>) {
     app.dispatchers.checkUi()
 
     require(!initViewCalled)

redwood-treehouse-host/src/commonMain/kotlin/app/cash/redwood/treehouse/TreehouseView.kt

@@ -24,22 +24,22 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.serialization.json.Json
 
 @ObjCName("TreehouseView", exact = true)
-public interface TreehouseView {
-  public val children: Widget.Children<*>
+public interface TreehouseView<W : Any> {
+  public val children: Widget.Children<W>
   public val uiConfiguration: StateFlow<UiConfiguration>
-  public val widgetSystem: WidgetSystem
+  public val widgetSystem: WidgetSystem<W>
   public val readyForContent: Boolean
-  public var readyForContentChangeListener: ReadyForContentChangeListener?
+  public var readyForContentChangeListener: ReadyForContentChangeListener<W>?
   public var saveCallback: SaveCallback?
   public val stateSnapshotId: StateSnapshot.Id
 
   /** Invoked when new code is loaded. This should at minimum clear all [children]. */
   public fun reset()
 
   @ObjCName("TreehouseViewReadyForContentChangeListener", exact = true)
-  public fun interface ReadyForContentChangeListener {
+  public fun interface ReadyForContentChangeListener<W : Any> {
     /** Called when [TreehouseView.readyForContent] has changed. */
-    public fun onReadyForContentChanged(view: TreehouseView)
+    public fun onReadyForContentChanged(view: TreehouseView<W>)
   }
 
   @ObjCName("TreehouseViewSaveCallback", exact = true)
@@ -49,11 +49,11 @@ public interface TreehouseView {
   }
 
   @ObjCName("TreehouseViewWidgetSystem", exact = true)
-  public fun interface WidgetSystem {
+  public fun interface WidgetSystem<W : Any> {
     /** Returns a widget factory for encoding and decoding changes to the contents of [view]. */
     public fun widgetFactory(
       json: Json,
       protocolMismatchHandler: ProtocolMismatchHandler,
-    ): ProtocolNode.Factory<*>
+    ): ProtocolNode.Factory<W>
   }
 }

redwood-treehouse-host/src/commonTest/kotlin/app/cash/redwood/treehouse/CountingReadyForContentChangeListener.kt

@@ -17,10 +17,10 @@ package app.cash.redwood.treehouse
 
 import app.cash.redwood.treehouse.TreehouseView.ReadyForContentChangeListener
 
-class CountingReadyForContentChangeListener : ReadyForContentChangeListener {
+class CountingReadyForContentChangeListener<W : Any> : ReadyForContentChangeListener<W> {
   var count = 0
 
-  override fun onReadyForContentChanged(view: TreehouseView) {
+  override fun onReadyForContentChanged(view: TreehouseView<W>) {
     count++
   }
 }

redwood-treehouse-host/src/iosMain/kotlin/app/cash/redwood/treehouse/TreehouseUIView.kt

@@ -33,13 +33,13 @@ public typealias TreehouseUIKitView = TreehouseUIView
 
 @ObjCName("TreehouseUIView", exact = true)
 public class TreehouseUIView private constructor(
-  override val widgetSystem: WidgetSystem,
+  override val widgetSystem: WidgetSystem<UIView>,
   view: UIView,
-) : TreehouseView, RedwoodUIView(view) {
+) : TreehouseView<UIView>, RedwoodUIView(view) {
   override var saveCallback: TreehouseView.SaveCallback? = null
   override var stateSnapshotId: StateSnapshot.Id = StateSnapshot.Id(null)
 
-  override var readyForContentChangeListener: ReadyForContentChangeListener? = null
+  override var readyForContentChangeListener: ReadyForContentChangeListener<UIView>? = null
     set(value) {
       check(value == null || field == null) { "View already bound to a listener" }
       field = value
@@ -48,7 +48,7 @@ public class TreehouseUIView private constructor(
   override val readyForContent: Boolean
     get() = view.superview != null
 
-  public constructor(widgetSystem: WidgetSystem) : this(widgetSystem, RootUiView())
+  public constructor(widgetSystem: WidgetSystem<UIView>) : this(widgetSystem, RootUiView())
 
   init {
     (view as RootUiView).treehouseView = this

redwood-treehouse-host/src/iosTest/kotlin/app/cash/redwood/treehouse/TreehouseUIViewTest.kt

@@ -52,7 +52,7 @@ class TreehouseUIViewTest {
   @Test fun attachAndDetachSendsStateChange() {
     val parent = UIView()
     val layout = TreehouseUIView(throwingWidgetSystem)
-    val listener = CountingReadyForContentChangeListener()
+    val listener = CountingReadyForContentChangeListener<UIView>()
 
     layout.readyForContentChangeListener = listener
     assertThat(listener.count).isEqualTo(0)
@@ -138,5 +138,5 @@ class TreehouseUIViewTest {
   }
 
   private val throwingWidgetSystem =
-    WidgetSystem { _, _ -> throw UnsupportedOperationException() }
+    WidgetSystem<UIView> { _, _ -> throw UnsupportedOperationException() }
 }

samples/emoji-search/ios-shared/src/commonMain/kotlin/com/example/redwood/emojisearch/ios/exposed.kt

@@ -42,7 +42,7 @@ fun exposedTypes(
   treehouseUIView: TreehouseUIView,
   uiViewRedwoodLayoutWidgetFactory: UIViewRedwoodLayoutWidgetFactory,
   uiViewRedwoodLazyLayoutWidgetFactory: UIViewRedwoodLazyLayoutWidgetFactory,
-  widgetSystem: WidgetSystem,
+  widgetSystem: WidgetSystem<*>,
   widgetFactories: EmojiSearchWidgetFactories<*>,
 ) {
   throw AssertionError()
@@ -54,5 +54,5 @@ fun modifier(): Modifier = Modifier
 
 fun <A : AppService> bindWhenReady(
   content: Content,
-  view: TreehouseView,
+  view: TreehouseView<*>,
 ): Closeable = content.bindWhenReady(view)

test-app/android-views/src/main/kotlin/com/example/redwood/testing/android/views/TestAppActivity.kt

@@ -16,6 +16,7 @@
 package com.example.redwood.testing.android.views
 
 import android.os.Bundle
+import android.view.View
 import androidx.activity.ComponentActivity
 import app.cash.redwood.compose.AndroidUiDispatcher.Companion.Main
 import app.cash.redwood.layout.view.ViewRedwoodLayoutWidgetFactory
@@ -50,7 +51,7 @@ class TestAppActivity : ComponentActivity() {
     val treehouseApp = createTreehouseApp()
     val treehouseContentSource = TreehouseContentSource(TestAppPresenter::launch)
 
-    val widgetSystem = object : TreehouseView.WidgetSystem {
+    val widgetSystem = object : TreehouseView.WidgetSystem<View> {
       override fun widgetFactory(
         json: Json,
         protocolMismatchHandler: ProtocolMismatchHandler,