Move reset() function up to RedwoodView

redwood-compose/src/commonMain/kotlin/app/cash/redwood/compose/RedwoodComposition.kt

@@ -53,6 +53,8 @@ public fun <W : Any> RedwoodComposition(
   provider: Widget.Provider<W>,
   onEndChanges: () -> Unit = {},
 ): RedwoodComposition {
+  view.reset()
+
   return RedwoodComposition(scope, view.children, view.uiConfiguration, provider, onEndChanges)
 }
 

redwood-composeui/src/commonMain/kotlin/app/cash/redwood/composeui/RedwoodContent.kt

@@ -58,6 +58,9 @@ public fun RedwoodContent(
     object : RedwoodView<@Composable () -> Unit> {
       override val children = ComposeWidgetChildren()
       override val uiConfiguration = MutableStateFlow(uiConfiguration)
+      override fun reset() {
+        children.remove(0, children.widgets.size)
+      }
     }
   }
   LaunchedEffect(redwoodView, uiConfiguration) {

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

@@ -24,7 +24,6 @@ import android.view.ViewGroup.LayoutParams.MATCH_PARENT
 import app.cash.redwood.treehouse.TreehouseView.ReadyForContentChangeListener
 import app.cash.redwood.treehouse.TreehouseView.WidgetSystem
 import app.cash.redwood.widget.RedwoodLayout
-import app.cash.redwood.widget.ViewGroupChildren
 import java.util.UUID
 
 @Deprecated(
@@ -56,13 +55,6 @@ public class TreehouseLayout(
 
   override var saveCallback: TreehouseView.SaveCallback? = null
 
-  override fun reset() {
-    children.remove(0, (children as ViewGroupChildren).widgets.size)
-
-    // Ensure any out-of-band views are also removed.
-    removeAllViews()
-  }
-
   override fun onAttachedToWindow() {
     super.onAttachedToWindow()
     readyForContent = true

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

@@ -29,9 +29,6 @@ public interface TreehouseView<W : Any> : RedwoodView<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<W : Any> {
     /** Called when [TreehouseView.readyForContent] has changed. */

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

@@ -18,7 +18,6 @@ package app.cash.redwood.treehouse
 import app.cash.redwood.treehouse.TreehouseView.ReadyForContentChangeListener
 import app.cash.redwood.treehouse.TreehouseView.WidgetSystem
 import app.cash.redwood.widget.RedwoodUIView
-import app.cash.redwood.widget.UIViewChildren
 import kotlinx.cinterop.cValue
 import platform.CoreGraphics.CGRectZero
 import platform.UIKit.UITraitCollection
@@ -54,14 +53,6 @@ public class TreehouseUIView private constructor(
     (view as RootUiView).treehouseView = this
   }
 
-  override fun reset() {
-    children.remove(0, (children as UIViewChildren).widgets.size)
-
-    // Ensure any out-of-band views are also removed.
-    @Suppress("UNCHECKED_CAST") // Correct generic lost by cinterop.
-    (view.subviews as List<UIView>).forEach(UIView::removeFromSuperview)
-  }
-
   private fun superviewChanged() {
     readyForContentChangeListener?.onReadyForContentChanged(this)
   }

redwood-widget/src/androidMain/kotlin/app/cash/redwood/widget/RedwoodLayout.kt

@@ -38,6 +38,13 @@ public open class RedwoodLayout(
   override val uiConfiguration: StateFlow<UiConfiguration>
     get() = mutableUiConfiguration
 
+  override fun reset() {
+    _children.remove(0, _children.widgets.size)
+
+    // Ensure any out-of-band views are also removed.
+    removeAllViews()
+  }
+
   init {
     setOnWindowInsetsChangeListener { insets ->
       mutableUiConfiguration.value = computeUiConfiguration(insets = insets.safeDrawing)

redwood-widget/src/commonMain/kotlin/app/cash/redwood/widget/RedwoodView.kt

@@ -23,4 +23,11 @@ import kotlinx.coroutines.flow.StateFlow
 public interface RedwoodView<W : Any> {
   public val children: Widget.Children<W>
   public val uiConfiguration: StateFlow<UiConfiguration>
+
+  /**
+   * This should at minimum clear all [children].
+   *
+   * Invoke when switching the backing composition to prepare the view for an initial load.
+   */
+  public fun reset()
 }

redwood-widget/src/iosMain/kotlin/app/cash/redwood/widget/RedwoodUIView.kt

@@ -42,6 +42,14 @@ public open class RedwoodUIView(
   override val uiConfiguration: StateFlow<UiConfiguration>
     get() = mutableUiConfiguration
 
+  override fun reset() {
+    _children.remove(0, _children.widgets.size)
+
+    // Ensure any out-of-band views are also removed.
+    @Suppress("UNCHECKED_CAST") // Correct generic lost by cinterop.
+    (view.subviews as List<UIView>).forEach(UIView::removeFromSuperview)
+  }
+
   protected fun updateUiConfiguration() {
     mutableUiConfiguration.value = computeUiConfiguration(
       traitCollection = view.traitCollection,

redwood-widget/src/jsMain/kotlin/app/cash/redwood/widget/RedwoodHTMLElementView.kt

@@ -22,6 +22,7 @@ import app.cash.redwood.widget.Widget.Children
 import kotlinx.browser.window
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.update
+import kotlinx.dom.clear
 import org.w3c.dom.HTMLElement
 import org.w3c.dom.MediaQueryList
 
@@ -33,9 +34,10 @@ public fun HTMLElement.asRedwoodView(): RedwoodView<HTMLElement> {
 }
 
 private class RedwoodHTMLElementView(
-  element: HTMLElement,
+  private val element: HTMLElement,
 ) : RedwoodView<HTMLElement> {
-  override val children: Children<HTMLElement> = HTMLElementChildren(element)
+  private val _children = HTMLElementChildren(element)
+  override val children: Children<HTMLElement> get() = _children
   override val uiConfiguration = MutableStateFlow(
     UiConfiguration(
       darkMode = window.matchMedia("(prefers-color-scheme: dark)").matches,
@@ -61,4 +63,11 @@ private class RedwoodHTMLElementView(
     // TODO Watch size change
     //   https://developer.mozilla.org/en-US/docs/Web/API/ResizeObserver
   }
+
+  override fun reset() {
+    _children.remove(0, _children.widgets.size)
+
+    // Ensure any out-of-band nodes are also removed.
+    element.clear()
+  }
 }