Add inert Java plumbing for the Android pull model

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

@@ -27,6 +27,7 @@
 import androidx.annotation.AnyThread;
 import androidx.annotation.Nullable;
 import androidx.annotation.UiThread;
+import androidx.annotation.VisibleForTesting;
 import androidx.core.view.ViewCompat.FocusDirection;
 import com.facebook.common.logging.FLog;
 import com.facebook.infer.annotation.Assertions;
@@ -65,6 +66,7 @@
 import com.facebook.react.fabric.mounting.mountitems.MountItem;
 import com.facebook.react.fabric.mounting.mountitems.MountItemFactory;
 import com.facebook.react.fabric.mounting.mountitems.PrefetchResourcesMountItem;
+import com.facebook.react.fabric.mounting.mountitems.PullTransactionMountItem;
 import com.facebook.react.fabric.mounting.mountitems.SynchronousMountItem;
 import com.facebook.react.internal.featureflags.ReactNativeFeatureFlags;
 import com.facebook.react.internal.featureflags.ReactNativeNewArchitectureFeatureFlags;
@@ -1009,6 +1011,26 @@ public void runGuarded() {
     }
   }
 
+  /**
+   * Pull model: called from C++ via JNI (usually on the commit thread) to signal that a transaction
+   * is available for {@code surfaceId}. Enqueues a PullTransactionMountItem so the UI thread pulls
+   * and applies the transaction itself, preserving mount-item ordering.
+   */
+  @SuppressWarnings("unused")
+  @AnyThread
+  @ThreadConfined(ANY)
+  @VisibleForTesting
+  void onTransactionAvailable(int surfaceId) {
+    FabricUIManagerBinding binding = mBinding;
+    if (binding == null) {
+      return;
+    }
+    mMountItemDispatcher.addMountItem(new PullTransactionMountItem(surfaceId, binding));
+    if (UiThreadUtil.isOnUiThread()) {
+      mMountItemDispatcher.tryDispatchMountItems();
+    }
+  }
+
   @SuppressWarnings("unused")
   @AnyThread
   @ThreadConfined(ANY)

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

@@ -85,6 +85,8 @@ internal class FabricUIManagerBinding : HybridClassBase() {
 
   external fun reportMount(surfaceId: Int)
 
+  external fun pullAndExecuteTransaction(surfaceId: Int)
+
   external fun mergeReactRevision(surfaceId: Int)
 
   fun register(

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/mountitems/PullTransactionMountItem.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.fabric.mounting.mountitems
+
+import com.facebook.proguard.annotations.DoNotStripAny
+import com.facebook.react.fabric.FabricUIManagerBinding
+import com.facebook.react.fabric.mounting.MountingManager
+
+/**
+ * Pull model mount item. Enqueued (on the commit thread) when C++ notifies that a transaction is
+ * available for a surface. When it executes on the UI thread it asks C++ to pull the surface's
+ * pending transaction and apply it synchronously, so the diff + batch construction happens on the
+ * UI thread instead of the commit thread (matching iOS).
+ */
+@DoNotStripAny
+internal class PullTransactionMountItem(
+    private val surfaceId: Int,
+    private val binding: FabricUIManagerBinding,
+) : MountItem {
+
+  override fun execute(mountingManager: MountingManager) {
+    binding.pullAndExecuteTransaction(surfaceId)
+  }
+
+  override fun getSurfaceId(): Int = surfaceId
+
+  override fun toString(): String = "PullTransactionMountItem [surfaceId: $surfaceId]"
+}

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlags.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<df3f81d0083a8ebe9d0fbcb86e652405>>
+ * @generated SignedSource<<8508c768e49199737ce5fd1071ca1d68>>
  */
 
 /**
@@ -252,6 +252,12 @@ public object ReactNativeFeatureFlags {
   @JvmStatic
   public fun enableModuleArgumentNSNullConversionIOS(): Boolean = accessor.enableModuleArgumentNSNullConversionIOS()
 
+  /**
+   * When enabled, Android mounts transactions with the pull model (like iOS): the commit thread no longer pulls and builds the mount batch in schedulerShouldRenderTransactions. Instead the UI thread pulls the transaction itself via a PullTransactionMountItem enqueued in the MountItemDispatcher, builds the IntBufferBatchMountItem, and applies it synchronously. Implies rawProps accumulation (enableAccumulatedUpdatesInRawPropsAndroid behavior).
+   */
+  @JvmStatic
+  public fun enableMountingCoordinatorPullModelAndroid(): Boolean = accessor.enableMountingCoordinatorPullModelAndroid()
+
   /**
    * Enables the MutationObserver Web API in React Native.
    */

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsCxxAccessor.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<c31110405f1c9cd5ae0627fb114585a6>>
+ * @generated SignedSource<<eeb2c4625ae5039dc087f364713050fe>>
  */
 
 /**
@@ -57,6 +57,7 @@ internal class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAcces
   private var enableLayoutAnimationsOnAndroidCache: Boolean? = null
   private var enableLayoutAnimationsOnIOSCache: Boolean? = null
   private var enableModuleArgumentNSNullConversionIOSCache: Boolean? = null
+  private var enableMountingCoordinatorPullModelAndroidCache: Boolean? = null
   private var enableMutationObserverByDefaultCache: Boolean? = null
   private var enableNativeCSSParsingCache: Boolean? = null
   private var enableNetworkEventReportingCache: Boolean? = null
@@ -441,6 +442,15 @@ internal class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAcces
     return cached
   }
 
+  override fun enableMountingCoordinatorPullModelAndroid(): Boolean {
+    var cached = enableMountingCoordinatorPullModelAndroidCache
+    if (cached == null) {
+      cached = ReactNativeFeatureFlagsCxxInterop.enableMountingCoordinatorPullModelAndroid()
+      enableMountingCoordinatorPullModelAndroidCache = cached
+    }
+    return cached
+  }
+
   override fun enableMutationObserverByDefault(): Boolean {
     var cached = enableMutationObserverByDefaultCache
     if (cached == null) {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsCxxInterop.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<87b76f5c2af82462dc66c7721cd66ac4>>
+ * @generated SignedSource<<9a171a03d15885e64b84f03442b304b4>>
  */
 
 /**
@@ -102,6 +102,8 @@ public object ReactNativeFeatureFlagsCxxInterop {
 
   @DoNotStrip @JvmStatic public external fun enableModuleArgumentNSNullConversionIOS(): Boolean
 
+  @DoNotStrip @JvmStatic public external fun enableMountingCoordinatorPullModelAndroid(): Boolean
+
   @DoNotStrip @JvmStatic public external fun enableMutationObserverByDefault(): Boolean
 
   @DoNotStrip @JvmStatic public external fun enableNativeCSSParsing(): Boolean

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsDefaults.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<8a117541421f413e517e1be1acf8be7d>>
+ * @generated SignedSource<<4fd762a8e3ab6de1276a15368075f40c>>
  */
 
 /**
@@ -97,6 +97,8 @@ public open class ReactNativeFeatureFlagsDefaults : ReactNativeFeatureFlagsProvi
 
   override fun enableModuleArgumentNSNullConversionIOS(): Boolean = false
 
+  override fun enableMountingCoordinatorPullModelAndroid(): Boolean = false
+
   override fun enableMutationObserverByDefault(): Boolean = false
 
   override fun enableNativeCSSParsing(): Boolean = false

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsLocalAccessor.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<9a2806b3934d130010954a92a7b48e0f>>
+ * @generated SignedSource<<4a4a234004196595b5fb2949bd91f9c4>>
  */
 
 /**
@@ -61,6 +61,7 @@ internal class ReactNativeFeatureFlagsLocalAccessor : ReactNativeFeatureFlagsAcc
   private var enableLayoutAnimationsOnAndroidCache: Boolean? = null
   private var enableLayoutAnimationsOnIOSCache: Boolean? = null
   private var enableModuleArgumentNSNullConversionIOSCache: Boolean? = null
+  private var enableMountingCoordinatorPullModelAndroidCache: Boolean? = null
   private var enableMutationObserverByDefaultCache: Boolean? = null
   private var enableNativeCSSParsingCache: Boolean? = null
   private var enableNetworkEventReportingCache: Boolean? = null
@@ -482,6 +483,16 @@ internal class ReactNativeFeatureFlagsLocalAccessor : ReactNativeFeatureFlagsAcc
     return cached
   }
 
+  override fun enableMountingCoordinatorPullModelAndroid(): Boolean {
+    var cached = enableMountingCoordinatorPullModelAndroidCache
+    if (cached == null) {
+      cached = currentProvider.enableMountingCoordinatorPullModelAndroid()
+      accessedFeatureFlags.add("enableMountingCoordinatorPullModelAndroid")
+      enableMountingCoordinatorPullModelAndroidCache = cached
+    }
+    return cached
+  }
+
   override fun enableMutationObserverByDefault(): Boolean {
     var cached = enableMutationObserverByDefaultCache
     if (cached == null) {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsProvider.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<49c76b8072c1bd29135086c9e0a5da2f>>
+ * @generated SignedSource<<0b4bf7de06ad677b0868640c98ff0aa9>>
  */
 
 /**
@@ -97,6 +97,8 @@ public interface ReactNativeFeatureFlagsProvider {
 
   @DoNotStrip public fun enableModuleArgumentNSNullConversionIOS(): Boolean
 
+  @DoNotStrip public fun enableMountingCoordinatorPullModelAndroid(): Boolean
+
   @DoNotStrip public fun enableMutationObserverByDefault(): Boolean
 
   @DoNotStrip public fun enableNativeCSSParsing(): Boolean

packages/react-native/ReactAndroid/src/main/jni/react/featureflags/JReactNativeFeatureFlagsCxxInterop.cpp

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<42f1901c8b7cb568cc761a791991a333>>
+ * @generated SignedSource<<a795068a8d53ac4385bf77461792fd70>>
  */
 
 /**
@@ -261,6 +261,12 @@ class ReactNativeFeatureFlagsJavaProvider
     return method(javaProvider_);
   }
 
+  bool enableMountingCoordinatorPullModelAndroid() override {
+    static const auto method =
+        getReactNativeFeatureFlagsProviderJavaClass()->getMethod<jboolean()>("enableMountingCoordinatorPullModelAndroid");
+    return method(javaProvider_);
+  }
+
   bool enableMutationObserverByDefault() override {
     static const auto method =
         getReactNativeFeatureFlagsProviderJavaClass()->getMethod<jboolean()>("enableMutationObserverByDefault");
@@ -750,6 +756,11 @@ bool JReactNativeFeatureFlagsCxxInterop::enableModuleArgumentNSNullConversionIOS
   return ReactNativeFeatureFlags::enableModuleArgumentNSNullConversionIOS();
 }
 
+bool JReactNativeFeatureFlagsCxxInterop::enableMountingCoordinatorPullModelAndroid(
+    facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop> /*unused*/) {
+  return ReactNativeFeatureFlags::enableMountingCoordinatorPullModelAndroid();
+}
+
 bool JReactNativeFeatureFlagsCxxInterop::enableMutationObserverByDefault(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop> /*unused*/) {
   return ReactNativeFeatureFlags::enableMutationObserverByDefault();
@@ -1142,6 +1153,9 @@ void JReactNativeFeatureFlagsCxxInterop::registerNatives() {
       makeNativeMethod(
         "enableModuleArgumentNSNullConversionIOS",
         JReactNativeFeatureFlagsCxxInterop::enableModuleArgumentNSNullConversionIOS),
+      makeNativeMethod(
+        "enableMountingCoordinatorPullModelAndroid",
+        JReactNativeFeatureFlagsCxxInterop::enableMountingCoordinatorPullModelAndroid),
       makeNativeMethod(
         "enableMutationObserverByDefault",
         JReactNativeFeatureFlagsCxxInterop::enableMutationObserverByDefault),

packages/react-native/ReactAndroid/src/main/jni/react/featureflags/JReactNativeFeatureFlagsCxxInterop.h

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<9967d87b794ba46797ed78a845683dc7>>
+ * @generated SignedSource<<5ffd2340bcfdeb6919f215f494040fb9>>
  */
 
 /**
@@ -141,6 +141,9 @@ class JReactNativeFeatureFlagsCxxInterop
   static bool enableModuleArgumentNSNullConversionIOS(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
 
+  static bool enableMountingCoordinatorPullModelAndroid(
+    facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
+
   static bool enableMutationObserverByDefault(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
 

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlags.cpp

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<6f2362e9844cab731ca01e4af563fde9>>
+ * @generated SignedSource<<28cc44042e02c3521b40c6c2ba005888>>
  */
 
 /**
@@ -174,6 +174,10 @@ bool ReactNativeFeatureFlags::enableModuleArgumentNSNullConversionIOS() {
   return getAccessor().enableModuleArgumentNSNullConversionIOS();
 }
 
+bool ReactNativeFeatureFlags::enableMountingCoordinatorPullModelAndroid() {
+  return getAccessor().enableMountingCoordinatorPullModelAndroid();
+}
+
 bool ReactNativeFeatureFlags::enableMutationObserverByDefault() {
   return getAccessor().enableMutationObserverByDefault();
 }

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlags.h

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<f871b2203c86dd7f25640cd3a6ea7d00>>
+ * @generated SignedSource<<66d7e8a85d0925fc03660ac22f2fb500>>
  */
 
 /**
@@ -224,6 +224,11 @@ class ReactNativeFeatureFlags {
    */
   RN_EXPORT static bool enableModuleArgumentNSNullConversionIOS();
 
+  /**
+   * When enabled, Android mounts transactions with the pull model (like iOS): the commit thread no longer pulls and builds the mount batch in schedulerShouldRenderTransactions. Instead the UI thread pulls the transaction itself via a PullTransactionMountItem enqueued in the MountItemDispatcher, builds the IntBufferBatchMountItem, and applies it synchronously. Implies rawProps accumulation (enableAccumulatedUpdatesInRawPropsAndroid behavior).
+   */
+  RN_EXPORT static bool enableMountingCoordinatorPullModelAndroid();
+
   /**
    * Enables the MutationObserver Web API in React Native.
    */