Drive shared animation backend from Fabric frame callback

Summary:
In this diff we drop the custom choreographer for the backend on Android and instead plug into the one in `FabricUIManager`. This reduces the area for possible mistakes, makes it clearer how Fabric interacts with animation on a per-frame basis, and simplifies the flow around invalidation and cleanup of the React instance.

The crash this is meant to avoid comes from having two separate frame callback lifecycles. The old `AnimationBackendChoreographer` owned a self-reposting callback that could keep driving `FabricUIManagerBinding.driveAnimationBackend` independently from Fabric's own lifecycle. During React instance teardown, `FabricUIManager.invalidate()` pauses Fabric's frame callback and then unregisters the native binding. If a separate backend callback survives that sequence, it can invoke the binding after the native side has been uninstalled.

The shared animation backend is now driven from Fabric's existing `DISPATCH_UI` frame callback after mount items are dispatched. The Android `AnimationChoreographer` implementation only owns backend pause/resume state and conditionally forwards active frames to the shared backend.

Threading-wise:
- If invalidation happens before a frame starts, `mDestroyed` makes the frame no-op.
- If invalidation races with an already-running frame, `ReactChoreographer.removeFrameCallback` is serialized with callback execution via the `callbackQueues` monitor, so `onHostPause()` waits for the current `DISPATCH_UI` callback to finish before `unregister()` tears down the native binding.
- If the frame reposts itself in `schedule()`, the blocked removal observes and removes that callback before teardown continues.

Changelog:
[Android][Fixed] - Drive the shared animation backend from Fabric's frame callback during React instance teardown

Differential Revision: D110321362

Author: Bartlomiej Bloniarz

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/AnimationBackendChoreographer.kt

@@ -1620,6 +1620,10 @@ public void doFrameGuarded(long frameTimeNanos) {
         //   2. In case there are no view commands or mount items, wait until next frame.
         mMountItemDispatcher.dispatchPreMountItems(frameTimeNanos);
         mMountItemDispatcher.tryDispatchMountItems();
+        FabricUIManagerBinding binding = mBinding;
+        if (ReactNativeFeatureFlags.useSharedAnimatedBackend() && binding != null) {
+          binding.driveAnimationBackend(frameTimeNanos);
+        }
       } catch (Exception ex) {
         FLog.e(TAG, "Exception thrown when executing UIFrameGuarded", ex);
         mIsMountingEnabled = false;

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/FabricUIManager.java

@@ -79,16 +79,12 @@ internal class FabricUIManagerBinding : HybridClassBase() {
 
   external fun driveCxxAnimations()
 
-  external fun driveAnimationBackend(frameTimeMs: Double)
+  external fun driveAnimationBackend(frameTimeNanos: Long)
 
   external fun drainPreallocateViewsQueue()
 
   external fun reportMount(surfaceId: Int)
 
-  external fun setAnimationBackendChoreographer(
-      animationBackendChoreographer: AnimationBackendChoreographer
-  )
-
   external fun mergeReactRevision(surfaceId: Int)
 
   fun register(
@@ -97,13 +93,8 @@ internal class FabricUIManagerBinding : HybridClassBase() {
       fabricUIManager: FabricUIManager,
       eventBeatManager: EventBeatManager,
       componentFactory: ComponentFactory,
-      animationBackendChoreographer: AnimationBackendChoreographer,
   ) {
     fabricUIManager.setBinding(this)
-    animationBackendChoreographer.frameCallback = AnimationFrameCallback { frameTimeMs: Double ->
-      driveAnimationBackend(frameTimeMs)
-    }
-    setAnimationBackendChoreographer(animationBackendChoreographer)
 
     installFabricUIManager(
         runtimeExecutor,

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/FabricUIManagerBinding.kt

@@ -58,16 +58,13 @@ public class FabricUIManagerProviderImpl(
     val runtimeExecutor = catalystInstance?.runtimeExecutor
     val runtimeScheduler = catalystInstance?.runtimeScheduler
 
-    val animationBackendChoreographer = AnimationBackendChoreographer(context)
-
     if (runtimeExecutor != null && runtimeScheduler != null) {
       binding.register(
           runtimeExecutor,
           runtimeScheduler,
           fabricUIManager,
           eventBeatManager,
           componentFactory,
-          animationBackendChoreographer,
       )
     } else {
       throw IllegalStateException(

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/FabricUIManagerProviderImpl.kt

@@ -44,7 +44,6 @@ import com.facebook.react.common.annotations.UnstableReactNativeAPI
 import com.facebook.react.devsupport.InspectorFlags.getIsProfilingBuild
 import com.facebook.react.devsupport.StackTraceHelper
 import com.facebook.react.devsupport.interfaces.DevSupportManager
-import com.facebook.react.fabric.AnimationBackendChoreographer
 import com.facebook.react.fabric.ComponentFactory
 import com.facebook.react.fabric.FabricUIManager
 import com.facebook.react.fabric.FabricUIManagerBinding
@@ -259,16 +258,13 @@ internal class ReactInstance(
     // Misc initialization that needs to be done before Fabric init
     DisplayMetricsHolder.initDisplayMetricsIfNotInitialized(context)
 
-    val animationBackendChoreographer = AnimationBackendChoreographer(context)
-
     val binding = FabricUIManagerBinding()
     binding.register(
         getBufferedRuntimeExecutor(),
         getRuntimeScheduler(),
         fabricUIManager,
         eventBeatManager,
         componentFactory,
-        animationBackendChoreographer,
     )
 
     // Initialize the FabricUIManager

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/runtime/ReactInstance.kt

@@ -7,32 +7,32 @@
 
 #pragma once
 
-#include <fbjni/fbjni.h>
 #include <react/renderer/animationbackend/AnimationChoreographer.h>
-
-#include "JAnimationBackendChoreographer.h"
+#include <atomic>
 
 namespace facebook::react {
 
 class AndroidAnimationChoreographer : public AnimationChoreographer {
  public:
-  explicit AndroidAnimationChoreographer(jni::alias_ref<JAnimationBackendChoreographer> jChoreographer)
-      : jChoreographer_(jni::make_global(jChoreographer))
+  void resume() override
   {
+    active_.store(true);
   }
 
-  void resume() override
+  void pause() override
   {
-    jChoreographer_->resume();
+    active_.store(false);
   }
 
-  void pause() override
+  void onAnimationFrameIfActive(AnimationTimestamp timestamp) const
   {
-    jChoreographer_->pause();
+    if (active_.load()) {
+      onAnimationFrame(timestamp);
+    }
   }
 
  private:
-  jni::global_ref<JAnimationBackendChoreographer> jChoreographer_;
+  std::atomic_bool active_{false};
 };
 
 } // namespace facebook::react

packages/react-native/ReactAndroid/src/main/jni/react/fabric/AndroidAnimationChoreographer.h

@@ -61,8 +61,10 @@ void FabricUIManagerBinding::driveCxxAnimations() {
   scheduler->animationTick();
 }
 
-void FabricUIManagerBinding::driveAnimationBackend(jdouble frameTimeMs) {
-  animationChoreographer_->onAnimationFrame(AnimationTimestamp{frameTimeMs});
+void FabricUIManagerBinding::driveAnimationBackend(jlong frameTimeNanos) {
+  auto frameTimeMs = static_cast<double>(frameTimeNanos) / 1000000.0;
+  animationChoreographer_->onAnimationFrameIfActive(
+      AnimationTimestamp{frameTimeMs});
 }
 
 void FabricUIManagerBinding::drainPreallocateViewsQueue() {
@@ -572,6 +574,8 @@ void FabricUIManagerBinding::installFabricUIManager(
 
   contextContainer->insert("FabricUIManager", globalJavaUiManager);
 
+  animationChoreographer_ = std::make_shared<AndroidAnimationChoreographer>();
+
   auto toolbox = SchedulerToolbox{};
   toolbox.contextContainer = contextContainer;
   toolbox.componentRegistryFactory = componentsRegistry->buildRegistryFunction;
@@ -583,9 +587,6 @@ void FabricUIManagerBinding::installFabricUIManager(
 
   toolbox.eventBeatFactory = eventBeatFactory;
 
-  react_native_assert(
-      animationChoreographer_ != nullptr &&
-      "AnimationChoreographer is nullptr");
   toolbox.animationChoreographer = animationChoreographer_;
 
   animationDriver_ = std::make_shared<LayoutAnimationDriver>(
@@ -604,6 +605,7 @@ void FabricUIManagerBinding::uninstallFabricUIManager() {
   std::unique_lock lock(installMutex_);
   animationDriver_ = nullptr;
   scheduler_ = nullptr;
+  animationChoreographer_ = nullptr;
   mountingManager_ = nullptr;
 }
 
@@ -875,19 +877,9 @@ void FabricUIManagerBinding::registerNatives() {
       makeNativeMethod(
           "getRelativeAncestorList",
           FabricUIManagerBinding::getRelativeAncestorList),
-      makeNativeMethod(
-          "setAnimationBackendChoreographer",
-          FabricUIManagerBinding::setAnimationBackendChoreographer),
       makeNativeMethod(
           "mergeReactRevision", FabricUIManagerBinding::mergeReactRevision),
   });
 }
 
-void FabricUIManagerBinding::setAnimationBackendChoreographer(
-    jni::alias_ref<JAnimationBackendChoreographer::javaobject>
-        animationBackendChoreographer) {
-  animationChoreographer_ = std::make_shared<AndroidAnimationChoreographer>(
-      animationBackendChoreographer);
-}
-
 } // namespace facebook::react

packages/react-native/ReactAndroid/src/main/jni/react/fabric/FabricUIManagerBinding.cpp

@@ -127,7 +127,7 @@ class FabricUIManagerBinding : public jni::HybridClass<FabricUIManagerBinding>,
 
   void driveCxxAnimations();
 
-  void driveAnimationBackend(jdouble frameTimeMs);
+  void driveAnimationBackend(jlong frameTimeNanos);
 
   void drainPreallocateViewsQueue();
 
@@ -168,8 +168,6 @@ class FabricUIManagerBinding : public jni::HybridClass<FabricUIManagerBinding>,
   bool enableFabricLogs_{false};
 
   std::shared_ptr<AndroidAnimationChoreographer> animationChoreographer_;
-
-  void setAnimationBackendChoreographer(jni::alias_ref<JAnimationBackendChoreographer::javaobject> animationBackend);
 };
 
 } // namespace facebook::react