Fabric: Introducing MountingTransaction

Summary:
`MountingTransaction` encapsulates all artifacts of `ShadowTree` commit, particularly list of mutations and meta-data.
We will rely on this heavily in the coming diffs.

Reviewed By: JoshuaGross

Differential Revision: D15021795

fbshipit-source-id: 811da7afd7b929a34a81aa66566193d46bbc34f8

React/Fabric/Mounting/RCTMountingManager.h

@@ -11,8 +11,8 @@
 #import <React/RCTPrimitives.h>
 #import <react/core/ComponentDescriptor.h>
 #import <react/core/ReactPrimitives.h>
+#import <react/mounting/MountingTransaction.h>
 #import <react/mounting/ShadowView.h>
-#import <react/mounting/ShadowViewMutation.h>
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -27,10 +27,10 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, strong) RCTComponentViewRegistry *componentViewRegistry;
 
 /**
- * Schedule mutations to be performed on the main thread.
+ * Schedule a mounting transaction to be performed on the main thread.
  * Can be called from any thread.
  */
-- (void)scheduleMutations:(facebook::react::ShadowViewMutationList const &)mutations rootTag:(ReactTag)rootTag;
+- (void)scheduleTransaction:(facebook::react::MountingTransaction &&)mountingTransaction;
 
 /**
  * Suggests preliminary creation of a component view of given type.

React/Fabric/Mounting/RCTMountingManager.mm

@@ -211,23 +211,23 @@ static void RNPerformMountInstructions(ShadowViewMutationList const &mutations,
   return self;
 }
 
-- (void)scheduleMutations:(ShadowViewMutationList const &)mutations rootTag:(ReactTag)rootTag
+- (void)scheduleTransaction:(facebook::react::MountingTransaction &&)mountingTransaction;
 {
   if (RCTIsMainQueue()) {
     // Already on the proper thread, so:
     // * No need to do a thread jump;
     // * No need to do expensive copy of all mutations;
     // * No need to allocate a block.
-    [self mountMutations:mutations rootTag:rootTag];
+    [self mountMutations:mountingTransaction.getMutations() rootTag:mountingTransaction.getSurfaceId()];
     return;
   }
 
-  // We need a non-reference for `mutations` to allow copy semantic.
-  auto mutationsCopy = mutations;
+  // We need a non-reference for `mountingTransaction` to allow copy semantic.
+  __block auto mountingTransactionCopy = MountingTransaction{mountingTransaction};
 
   RCTExecuteOnMainQueue(^{
     RCTAssertMainQueue();
-    [self mountMutations:mutationsCopy rootTag:rootTag];
+    [self mountMutations:mountingTransactionCopy.getMutations() rootTag:mountingTransactionCopy.getSurfaceId()];
   });
 }
 

React/Fabric/RCTScheduler.h

@@ -12,6 +12,7 @@
 #import <react/core/ComponentDescriptor.h>
 #import <react/core/LayoutConstraints.h>
 #import <react/core/LayoutContext.h>
+#import <react/mounting/MountingTransaction.h>
 #import <react/mounting/ShadowViewMutation.h>
 #import <react/uimanager/ComponentDescriptorFactory.h>
 #import <react/utils/ContextContainer.h>
@@ -25,8 +26,7 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @protocol RCTSchedulerDelegate
 
-- (void)schedulerDidFinishTransaction:(facebook::react::ShadowViewMutationList const &)mutations
-                              rootTag:(ReactTag)rootTag;
+- (void)schedulerDidFinishTransaction:(facebook::react::MountingTransaction &&)mountingTransaction;
 
 - (void)schedulerOptimisticallyCreateComponentViewWithComponentHandle:(facebook::react::ComponentHandle)componentHandle;
 

React/Fabric/RCTScheduler.mm

@@ -22,14 +22,10 @@ class SchedulerDelegateProxy : public SchedulerDelegate {
  public:
   SchedulerDelegateProxy(void *scheduler) : scheduler_(scheduler) {}
 
-  void schedulerDidFinishTransaction(
-      Tag rootTag,
-      const ShadowViewMutationList &mutations,
-      const long commitStartTime,
-      const long layoutTime) override
+  void schedulerDidFinishTransaction(MountingTransaction &&mountingTransaction) override
   {
     RCTScheduler *scheduler = (__bridge RCTScheduler *)scheduler_;
-    [scheduler.delegate schedulerDidFinishTransaction:mutations rootTag:rootTag];
+    [scheduler.delegate schedulerDidFinishTransaction:std::move(mountingTransaction)];
   }
 
   void schedulerDidRequestPreliminaryViewAllocation(SurfaceId surfaceId, const ShadowView &shadowView) override

React/Fabric/RCTSurfacePresenter.mm

@@ -309,14 +309,13 @@ using namespace facebook::react;
 
 #pragma mark - RCTSchedulerDelegate
 
-- (void)schedulerDidFinishTransaction:(facebook::react::ShadowViewMutationList const &)mutations
-                              rootTag:(ReactTag)rootTag
+- (void)schedulerDidFinishTransaction:(facebook::react::MountingTransaction &&)mountingTransaction
 {
-  RCTFabricSurface *surface = [_surfaceRegistry surfaceForRootTag:rootTag];
+  RCTFabricSurface *surface = [_surfaceRegistry surfaceForRootTag:mountingTransaction.getSurfaceId()];
 
   [surface _setStage:RCTSurfaceStagePrepared];
 
-  [_mountingManager scheduleMutations:mutations rootTag:rootTag];
+  [_mountingManager scheduleTransaction:std::move(mountingTransaction)];
 }
 
 - (void)schedulerOptimisticallyCreateComponentViewWithComponentHandle:(ComponentHandle)componentHandle

ReactAndroid/src/main/java/com/facebook/react/fabric/jsi/jni/Binding.cpp

@@ -329,11 +329,12 @@ local_ref<JMountItem::javaobject> createDeleteMountItem(
 }
 
 void Binding::schedulerDidFinishTransaction(
-    const Tag rootTag,
-    const ShadowViewMutationList& mutations,
-    const long commitStartTime,
-    const long layoutTime) {
+    MountingTransaction &&mountingTransaction) {
   SystraceSection s("FabricUIManager::schedulerDidFinishTransaction");
+
+  auto telemetry = mountingTransaction.getTelemetry();
+  auto mutations = mountingTransaction.getMutations();
+
   std::vector<local_ref<jobject>> queue;
   // Upper bound estimation of mount items to be delivered to Java side.
   int size = mutations.size() * 3 + 42;
@@ -466,8 +467,8 @@ void Binding::schedulerDidFinishTransaction(
   scheduleMountItems(
       javaUIManager_,
       batch.get(),
-      commitStartTime,
-      layoutTime,
+      telemetry.commitStartTime,
+      telemetry.layoutTime,
       finishTransactionStartTime,
       finishTransactionEndTime);
 }

ReactAndroid/src/main/java/com/facebook/react/fabric/jsi/jni/Binding.h

@@ -57,10 +57,7 @@ class Binding : public jni::HybridClass<Binding>, public SchedulerDelegate {
   void stopSurface(jint surfaceId);
 
   void schedulerDidFinishTransaction(
-      const Tag rootTag,
-      const ShadowViewMutationList& mutations,
-      const long commitStartTime,
-      const long layoutTime);
+      MountingTransaction &&mountingTransaction);
 
   void schedulerDidRequestPreliminaryViewAllocation(
       const SurfaceId surfaceId,

ReactCommon/fabric/mounting/MountingTransaction.cpp

@@ -0,0 +1,47 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "MountingTransaction.h"
+
+namespace facebook {
+namespace react {
+
+using Telemetry = MountingTransaction::Telemetry;
+using Revision = MountingTransaction::Revision;
+
+MountingTransaction::MountingTransaction(
+    SurfaceId surfaceId,
+    Revision revision,
+    ShadowViewMutationList &&mutations,
+    Telemetry telemetry)
+    : surfaceId_(surfaceId),
+      revision_(revision),
+      mutations_(std::move(mutations)),
+      telemetry_(std::move(telemetry)) {}
+
+ShadowViewMutationList const &MountingTransaction::getMutations() const & {
+  return mutations_;
+}
+
+ShadowViewMutationList MountingTransaction::getMutations() && {
+  return std::move(mutations_);
+}
+
+Telemetry const &MountingTransaction::getTelemetry() const {
+  return telemetry_;
+}
+
+SurfaceId MountingTransaction::getSurfaceId() const {
+  return surfaceId_;
+}
+
+Revision MountingTransaction::getRevision() const {
+  return revision_;
+}
+
+} // namespace react
+} // namespace facebook

ReactCommon/fabric/mounting/MountingTransaction.h

@@ -0,0 +1,95 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <react/mounting/ShadowViewMutation.h>
+
+namespace facebook {
+namespace react {
+
+/*
+ * Encapsulates all artifacts of `ShadowTree` commit, particularly list of
+ * mutations and meta-data.
+ * Movable and copyable, but moving is strongly preferred.
+ * A moved-from object of this type has unspecified value and accessing that is
+ * UB.
+ */
+class MountingTransaction final {
+ public:
+  /*
+   * Revision grows continuously starting from `1`. Value `0` represents the
+   * state before the very first transaction happens.
+   */
+  using Revision = int64_t;
+
+  /*
+   * Represent arbitrary telementry data that can be associated with the
+   * particular transaction.
+   */
+  struct Telemetry final {
+    long commitStartTime{};
+    long layoutTime{};
+  };
+
+  /*
+   * Copying a list of `ShadowViewMutation` is expensive, so the constructor
+   * accepts it as rvalue reference to discourage copying.
+   */
+  MountingTransaction(
+      SurfaceId surfaceId,
+      Revision revision,
+      ShadowViewMutationList &&mutations,
+      Telemetry telemetry);
+
+  /*
+   * Copy semantic.
+   * Copying of MountingTransaction is expensive, so copy-constructor is
+   * explicit and copy-assignment is deleted to prevent accidental copying.
+   */
+  explicit MountingTransaction(const MountingTransaction &mountingTransaction) =
+      default;
+  MountingTransaction &operator=(const MountingTransaction &other) = delete;
+
+  /*
+   * Move semantic.
+   */
+  MountingTransaction(MountingTransaction &&mountingTransaction) noexcept =
+      default;
+  MountingTransaction &operator=(MountingTransaction &&other) = default;
+
+  /*
+   * Returns a list of mutations that represent the transaction. The list can be
+   * empty (theoretically).
+   */
+  ShadowViewMutationList const &getMutations() const &;
+  ShadowViewMutationList getMutations() &&;
+
+  /*
+   * Returns telemetry associated with this transaction.
+   */
+  Telemetry const &getTelemetry() const;
+
+  /*
+   * Returns the id of the surface that the transaction belongs to.
+   */
+  SurfaceId getSurfaceId() const;
+
+  /*
+   * Returns the revision of the ShadowTree that this transaction represents.
+   */
+  Revision getRevision() const;
+
+ private:
+  SurfaceId surfaceId_;
+  Revision revision_;
+  ShadowViewMutationList mutations_;
+  Telemetry telemetry_;
+};
+
+} // namespace react
+} // namespace facebook

ReactCommon/fabric/mounting/ShadowTree.cpp

@@ -127,15 +127,14 @@ Tag ShadowTree::getSurfaceId() const {
 
 void ShadowTree::commit(
     ShadowTreeCommitTransaction transaction,
-    long commitStartTime,
-    int *revision) const {
+    long commitStartTime) const {
   SystraceSection s("ShadowTree::commit");
 
   int attempts = 0;
 
   while (true) {
     attempts++;
-    if (tryCommit(transaction, commitStartTime, revision)) {
+    if (tryCommit(transaction, commitStartTime)) {
       return;
     }
 
@@ -147,8 +146,7 @@ void ShadowTree::commit(
 
 bool ShadowTree::tryCommit(
     ShadowTreeCommitTransaction transaction,
-    long commitStartTime,
-    int *revision) const {
+    long commitStartTime) const {
   SystraceSection s("ShadowTree::tryCommit");
 
   SharedRootShadowNode oldRootShadowNode;
@@ -170,6 +168,7 @@ bool ShadowTree::tryCommit(
   layoutTime = getTime() - layoutTime;
   newRootShadowNode->sealRecursive();
 
+  int revision;
   auto mutations =
       calculateShadowViewMutations(*oldRootShadowNode, *newRootShadowNode);
 
@@ -190,13 +189,9 @@ bool ShadowTree::tryCommit(
           oldRootShadowNode->getChildren(), newRootShadowNode->getChildren());
     }
 
+    revision = revision_;
     revision_++;
 
-    // Returning last revision if requested.
-    if (revision) {
-      *revision = revision_;
-    }
-
 #ifdef RN_SHADOW_TREE_INTROSPECTION
     stubViewTree_.mutate(mutations);
     auto stubViewTree = stubViewTreeFromShadowNode(*rootShadowNode_);
@@ -219,7 +214,11 @@ bool ShadowTree::tryCommit(
 
   if (delegate_) {
     delegate_->shadowTreeDidCommit(
-        *this, mutations, commitStartTime, layoutTime);
+        *this,
+        {surfaceId_,
+         revision,
+         std::move(mutations),
+         {commitStartTime, layoutTime}});
   }
 
   return true;

ReactCommon/fabric/mounting/ShadowTree.h

@@ -55,22 +55,16 @@ class ShadowTree final {
    * Performs commit calling `transaction` function with a `oldRootShadowNode`
    * and expecting a `newRootShadowNode` as a return value.
    * The `transaction` function can abort commit returning `nullptr`.
-   * If a `revision` pointer is not null, the method will store there a
-   * contiguous revision number of the successfully performed transaction.
    * Returns `true` if the operation finished successfully.
    */
-  bool tryCommit(
-      ShadowTreeCommitTransaction transaction,
-      long commitStartTime,
-      int *revision = nullptr) const;
+  bool tryCommit(ShadowTreeCommitTransaction transaction, long commitStartTime)
+      const;
 
   /*
    * Calls `tryCommit` in a loop until it finishes successfully.
    */
-  void commit(
-      ShadowTreeCommitTransaction transaction,
-      long commitStartTime,
-      int *revision = nullptr) const;
+  void commit(ShadowTreeCommitTransaction transaction, long commitStartTime)
+      const;
 
 #pragma mark - Delegate
 

ReactCommon/fabric/mounting/ShadowTreeDelegate.h

@@ -5,7 +5,7 @@
 
 #pragma once
 
-#include <react/mounting/ShadowViewMutation.h>
+#include <react/mounting/MountingTransaction.h>
 
 namespace facebook {
 namespace react {
@@ -22,9 +22,7 @@ class ShadowTreeDelegate {
    */
   virtual void shadowTreeDidCommit(
       const ShadowTree &shadowTree,
-      const ShadowViewMutationList &mutations,
-      long commitStartTime,
-      long layoutTime) const = 0;
+      MountingTransaction &&transaction) const = 0;
 
   virtual ~ShadowTreeDelegate() noexcept = default;
 };

ReactCommon/fabric/mounting/ShadowView.h

@@ -23,6 +23,7 @@ namespace react {
 struct ShadowView final {
   ShadowView() = default;
   ShadowView(const ShadowView &shadowView) = default;
+  ShadowView(ShadowView &&shadowView) noexcept = default;
 
   ~ShadowView(){};
 
@@ -32,6 +33,7 @@ struct ShadowView final {
   explicit ShadowView(const ShadowNode &shadowNode);
 
   ShadowView &operator=(const ShadowView &other) = default;
+  ShadowView &operator=(ShadowView &&other) = default;
 
   bool operator==(const ShadowView &rhs) const;
   bool operator!=(const ShadowView &rhs) const;

ReactCommon/fabric/uimanager/Scheduler.cpp

@@ -242,14 +242,11 @@ SchedulerDelegate *Scheduler::getDelegate() const {
 
 void Scheduler::shadowTreeDidCommit(
     const ShadowTree &shadowTree,
-    const ShadowViewMutationList &mutations,
-    long commitStartTime,
-    long layoutTime) const {
+    MountingTransaction &&transaction) const {
   SystraceSection s("Scheduler::shadowTreeDidCommit");
 
   if (delegate_) {
-    delegate_->schedulerDidFinishTransaction(
-        shadowTree.getSurfaceId(), mutations, commitStartTime, layoutTime);
+    delegate_->schedulerDidFinishTransaction(std::move(transaction));
   }
 }
 

ReactCommon/fabric/uimanager/Scheduler.h

@@ -93,9 +93,7 @@ class Scheduler final : public UIManagerDelegate, public ShadowTreeDelegate {
 
   void shadowTreeDidCommit(
       const ShadowTree &shadowTree,
-      const ShadowViewMutationList &mutations,
-      long commitStartTime,
-      long layoutTime) const override;
+      MountingTransaction &&transaction) const override;
 
  private:
   SchedulerDelegate *delegate_;

ReactCommon/fabric/uimanager/SchedulerDelegate.h

@@ -9,6 +9,7 @@
 
 #include <react/core/ReactPrimitives.h>
 #include <react/core/ShadowNode.h>
+#include <react/mounting/MountingTransaction.h>
 #include <react/mounting/ShadowViewMutation.h>
 
 namespace facebook {
@@ -25,10 +26,7 @@ class SchedulerDelegate {
    * to construct a new one.
    */
   virtual void schedulerDidFinishTransaction(
-      Tag rootTag,
-      ShadowViewMutationList const &mutations,
-      const long commitStartTime,
-      const long layoutTime) = 0;
+      MountingTransaction &&mountingTransaction) = 0;
 
   /*
    * Called right after a new ShadowNode was created.