Scope the FrameClock to a CodeSession

redwood-treehouse-host/src/androidInstrumentedTest/kotlin/app/cash/redwood/treehouse/AndroidChoreographerFrameClockTest.kt

@@ -20,7 +20,7 @@ import kotlinx.coroutines.runBlocking
 
 class AndroidChoreographerFrameClockTest : AbstractFrameClockTest() {
   // Tests run on a background thread but Choreographer can only be grabbed from the main thread.
-  override val frameClock = runBlocking(Dispatchers.Main) {
-    AndroidChoreographerFrameClock()
+  override val frameClockFactory = runBlocking(Dispatchers.Main) {
+    AndroidChoreographerFrameClock.Factory()
   }
 }

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

@@ -22,18 +22,11 @@ import kotlinx.coroutines.launch
 /**
  * A [FrameClock] that sends frames using [Choreographer].
  */
-internal class AndroidChoreographerFrameClock : FrameClock {
-  private val choreographer = Choreographer.getInstance()
-  private lateinit var scope: CoroutineScope
-  private lateinit var dispatchers: TreehouseDispatchers
-
-  override fun start(
-    scope: CoroutineScope,
-    dispatchers: TreehouseDispatchers,
-  ) {
-    this.scope = scope
-    this.dispatchers = dispatchers
-  }
+internal class AndroidChoreographerFrameClock private constructor(
+  private val choreographer: Choreographer,
+  private val scope: CoroutineScope,
+  private val dispatchers: TreehouseDispatchers,
+) : FrameClock {
 
   override fun requestFrame(appLifecycle: AppLifecycle) {
     choreographer.postFrameCallback { frameTimeNanos ->
@@ -42,4 +35,12 @@ internal class AndroidChoreographerFrameClock : FrameClock {
       }
     }
   }
+
+  class Factory : FrameClock.Factory {
+    private val choreographer = Choreographer.getInstance()
+    override fun create(
+      scope: CoroutineScope,
+      dispatchers: TreehouseDispatchers,
+    ) = AndroidChoreographerFrameClock(choreographer, scope, dispatchers)
+  }
 }

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

@@ -38,7 +38,7 @@ public fun TreehouseAppFactory(
   dispatchers = AndroidTreehouseDispatchers(),
   eventListener = eventListener,
   httpClient = httpClient.asZiplineHttpClient(),
-  frameClock = AndroidChoreographerFrameClock(),
+  frameClockFactory = AndroidChoreographerFrameClock.Factory(),
   manifestVerifier = manifestVerifier,
   embeddedDir = embeddedDir,
   embeddedFileSystem = embeddedFileSystem,

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

@@ -26,7 +26,7 @@ internal interface CodeSession<A : AppService> {
 
   val json: Json
 
-  fun start(sessionScope: CoroutineScope)
+  fun start(sessionScope: CoroutineScope, frameClock: FrameClock)
 
   fun addListener(listener: Listener<A>)
 

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

@@ -18,17 +18,16 @@ package app.cash.redwood.treehouse
 import kotlinx.coroutines.CoroutineScope
 
 internal interface FrameClock {
-  /** Run this clock until [scope] is canceled. */
-  fun start(
-    scope: CoroutineScope,
-    dispatchers: TreehouseDispatchers,
-  )
-
   /**
    * Request a call to [AppLifecycle.sendFrame]. It is an error to call [requestFrame] again before
    * that call is made.
    *
    * It is an error to call this before [start].
    */
   fun requestFrame(appLifecycle: AppLifecycle)
+
+  interface Factory {
+    /** Creates a new FrameClock that sends frames on [dispatchers] in [scope]. */
+    fun create(scope: CoroutineScope, dispatchers: TreehouseDispatchers): FrameClock
+  }
 }

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

@@ -212,7 +212,6 @@ public class TreehouseApp<A : AppService> private constructor(
         dispatchers = dispatchers,
         eventPublisher = eventPublisher,
         appScope = appScope,
-        frameClock = factory.frameClock,
         appService = appService,
         zipline = zipline,
       )
@@ -228,7 +227,10 @@ public class TreehouseApp<A : AppService> private constructor(
 
         session = next
         next.addListener(this@ZiplineCodeHost)
-        next.start(sessionScope)
+        next.start(
+          sessionScope = sessionScope,
+          frameClock = factory.frameClockFactory.create(sessionScope, dispatchers),
+        )
 
         for (listener in listeners) {
           listener.codeSessionChanged(next)
@@ -249,7 +251,7 @@ public class TreehouseApp<A : AppService> private constructor(
     public val dispatchers: TreehouseDispatchers,
     internal val eventListener: EventListener,
     internal val httpClient: ZiplineHttpClient,
-    internal val frameClock: FrameClock,
+    internal val frameClockFactory: FrameClock.Factory,
     internal val manifestVerifier: ManifestVerifier,
     internal val embeddedDir: Path?,
     internal val embeddedFileSystem: FileSystem?,

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

@@ -31,7 +31,6 @@ internal class ZiplineCodeSession<A : AppService>(
   private val dispatchers: TreehouseDispatchers,
   private val eventPublisher: EventPublisher,
   private val appScope: CoroutineScope,
-  private val frameClock: FrameClock,
   override val appService: A,
   val zipline: Zipline,
 ) : CodeSession<A>, AppLifecycle.Host {
@@ -41,20 +40,19 @@ internal class ZiplineCodeSession<A : AppService>(
   override val json: Json
     get() = zipline.json
 
-  /** Only accessed on [TreehouseDispatchers.zipline]. */
+  // These vars only accessed on TreehouseDispatchers.zipline.
   private lateinit var sessionScope: CoroutineScope
-
-  /** Only accessed on [TreehouseDispatchers.zipline]. */
+  private lateinit var frameClock: FrameClock
   private lateinit var appLifecycle: AppLifecycle
 
   private var canceled = false
 
-  override fun start(sessionScope: CoroutineScope) {
+  override fun start(sessionScope: CoroutineScope, frameClock: FrameClock) {
     dispatchers.checkUi()
+
     sessionScope.launch(dispatchers.zipline) {
       this@ZiplineCodeSession.sessionScope = sessionScope
-
-      frameClock.start(sessionScope, dispatchers)
+      this@ZiplineCodeSession.frameClock = frameClock
 
       val service = appService.withScope(ziplineScope).appLifecycle
       appLifecycle = service
@@ -73,11 +71,11 @@ internal class ZiplineCodeSession<A : AppService>(
   }
 
   override fun cancel() {
+    dispatchers.checkUi()
+
     if (canceled) return
     canceled = true
 
-    dispatchers.checkUi()
-
     val listenersArray = listeners.toTypedArray() // onCancel mutates.
     for (listener in listenersArray) {
       listener.onCancel(this)

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

@@ -28,7 +28,7 @@ import kotlinx.coroutines.test.runTest
 
 @OptIn(ExperimentalCoroutinesApi::class)
 abstract class AbstractFrameClockTest {
-  internal abstract val frameClock: FrameClock
+  internal abstract val frameClockFactory: FrameClock.Factory
 
   @Test fun ticksWithTime() = runTest {
     val dispatchers = object : TreehouseDispatchers {
@@ -38,7 +38,7 @@ abstract class AbstractFrameClockTest {
       override fun checkZipline() {}
       override fun close() {}
     }
-    frameClock.start(this, dispatchers)
+    val frameClock = frameClockFactory.create(this, dispatchers)
 
     val frameTimes = Channel<Long>(Channel.UNLIMITED)
     val appLifecycle = object : AppLifecycle {

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

@@ -46,7 +46,7 @@ internal class FakeCodeHost(
       previous?.cancel()
 
       if (value != null) {
-        value.start(CoroutineScope(EmptyCoroutineContext))
+        value.start(CoroutineScope(EmptyCoroutineContext), FakeFrameClock())
         for (listener in listeners) {
           listener.codeSessionChanged(value)
         }

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

@@ -32,7 +32,7 @@ internal class FakeCodeSession(
 
   private var canceled = false
 
-  override fun start(sessionScope: CoroutineScope) {
+  override fun start(sessionScope: CoroutineScope, frameClock: FrameClock) {
     eventLog += "$name.start()"
   }
 

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

@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2023 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package app.cash.redwood.treehouse
+
+class FakeFrameClock : FrameClock {
+  override fun requestFrame(appLifecycle: AppLifecycle) {
+  }
+}

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

@@ -21,24 +21,19 @@ import kotlinx.coroutines.launch
 import platform.posix.CLOCK_MONOTONIC_RAW
 import platform.posix.clock_gettime_nsec_np
 
-internal class IosDisplayLinkClock : FrameClock {
-  private lateinit var scope: CoroutineScope
-  private lateinit var dispatchers: TreehouseDispatchers
-  private lateinit var displayLinkTarget: DisplayLinkTarget
-
+internal class IosDisplayLinkClock private constructor(
+  private val scope: CoroutineScope,
+  private val dispatchers: TreehouseDispatchers,
+) : FrameClock {
   /** Non-null if we're expecting a call to [AppLifecycle.sendFrame]. */
   private var appLifecycle: AppLifecycle? = null
 
-  override fun start(scope: CoroutineScope, dispatchers: TreehouseDispatchers) {
-    this.scope = scope
-    this.dispatchers = dispatchers
-    this.displayLinkTarget = DisplayLinkTarget {
-      unsubscribe()
-      scope.launch(dispatchers.zipline) {
-        val nanos = clock_gettime_nsec_np(CLOCK_MONOTONIC_RAW.convert()).convert<Long>()
-        appLifecycle?.sendFrame(nanos)
-        appLifecycle = null
-      }
+  private val displayLinkTarget = DisplayLinkTarget {
+    unsubscribe()
+    scope.launch(dispatchers.zipline) {
+      val nanos = clock_gettime_nsec_np(CLOCK_MONOTONIC_RAW.convert()).convert<Long>()
+      appLifecycle?.sendFrame(nanos)
+      appLifecycle = null
     }
   }
 
@@ -48,4 +43,11 @@ internal class IosDisplayLinkClock : FrameClock {
       displayLinkTarget.subscribe()
     }
   }
+
+  companion object : FrameClock.Factory {
+    override fun create(
+      scope: CoroutineScope,
+      dispatchers: TreehouseDispatchers,
+    ) = IosDisplayLinkClock(scope, dispatchers)
+  }
 }

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

@@ -35,7 +35,7 @@ public fun TreehouseAppFactory(
   dispatchers = IosTreehouseDispatchers(),
   eventListener = eventListener,
   httpClient = httpClient,
-  frameClock = IosDisplayLinkClock(),
+  frameClockFactory = IosDisplayLinkClock,
   manifestVerifier = manifestVerifier,
   embeddedDir = embeddedDir,
   embeddedFileSystem = embeddedFileSystem,

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

@@ -19,5 +19,6 @@ import kotlin.test.Ignore
 
 @Ignore // TODO Does not work without linking XCTest and showing a XCUIApplication.
 class IosDisplayLinkClockTest : AbstractFrameClockTest() {
-  override val frameClock = IosDisplayLinkClock()
+  override val frameClockFactory: FrameClock.Factory
+    get() = IosDisplayLinkClock
 }