From 585dfff22b4df70ce3ae195ce394fdfcf6a79d2f Mon Sep 17 00:00:00 2001
From: David Vacca <dvacca@fb.com>
Date: Mon, 21 Oct 2019 11:45:43 -0700
Subject: [PATCH] Disable preallocation of views in Mounting layer of fabric

Summary:
This diff adds an experiment to disable the preallocation of views on the mounting layer of Fabric

Changelog:
Add a ReactNativeConfig to configure the preallocation of views in the mounting layer of Fabric

Reviewed By: shergin

Differential Revision: D17949681

fbshipit-source-id: 0af63df22aff9e94289bc8a8217c79222f1fd61c
---
 .../java/com/facebook/react/fabric/jni/Binding.cpp     | 10 ++++++++--
 .../main/java/com/facebook/react/fabric/jni/Binding.h  |  1 +
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.cpp b/ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.cpp
index 6f5921ae3a8..e1f5b6af696 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.cpp
+++ b/ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.cpp
@@ -238,6 +238,8 @@ void Binding::installFabricUIManager(
   reactNativeConfig_ = config;
   shouldCollateRemovesAndDeletes_ = reactNativeConfig_->getBool("react_fabric:enable_removedelete_collation_android");
 
+  disablePreallocateViews_ = reactNativeConfig_->getBool("react_fabric:disabled_view_preallocation_android");
+
   auto toolbox = SchedulerToolbox{};
   toolbox.contextContainer = contextContainer;
   toolbox.componentRegistryFactory = componentsRegistry->buildRegistryFunction;
@@ -602,7 +604,7 @@ void Binding::schedulerDidFinishTransaction(
 
     switch (mutation.type) {
       case ShadowViewMutation::Create: {
-        if (mutation.newChildShadowView.props->revision > 1 ||
+        if (disablePreallocateViews_ || mutation.newChildShadowView.props->revision > 1 ||
             deletedViewTags.find(mutation.newChildShadowView.tag) !=
                 deletedViewTags.end()) {
           mountItems[position++] =
@@ -683,7 +685,7 @@ void Binding::schedulerDidFinishTransaction(
           mountItems[position++] =
               createInsertMountItem(localJavaUIManager, mutation);
 
-          if (mutation.newChildShadowView.props->revision > 1 ||
+          if (disablePreallocateViews_ || mutation.newChildShadowView.props->revision > 1 ||
               deletedViewTags.find(mutation.newChildShadowView.tag) !=
                   deletedViewTags.end()) {
             mountItems[position++] =
@@ -780,6 +782,10 @@ void Binding::schedulerDidRequestPreliminaryViewAllocation(
     const SurfaceId surfaceId,
     const ShadowView &shadowView) {
 
+  if (disablePreallocateViews_) {
+    return;
+  }
+
   jni::global_ref<jobject> localJavaUIManager = getJavaUIManager();
   if (!localJavaUIManager) {
     LOG(ERROR) << "Binding::schedulerDidRequestPreliminaryViewAllocation: JavaUIManager disappeared";
diff --git a/ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.h b/ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.h
index 1840e023a7e..826b8fab714 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.h
+++ b/ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.h
@@ -105,6 +105,7 @@ class Binding : public jni::HybridClass<Binding>, public SchedulerDelegate {
 
   std::shared_ptr<const ReactNativeConfig> reactNativeConfig_{nullptr};
   bool shouldCollateRemovesAndDeletes_{false};
+  bool disablePreallocateViews_{false};
 };
 
 } // namespace react