[ResizeObserver 2/3] Layout event emitter

packages/react-native/ReactCommon/react/renderer/mounting/ShadowTree.cpp

@@ -11,7 +11,6 @@
 #include <jsinspector-modern/tracing/PerformanceTracerSection.h>
 #include <react/debug/react_native_assert.h>
 #include <react/renderer/components/root/RootComponentDescriptor.h>
-#include <react/renderer/components/view/ViewShadowNode.h>
 #include <react/renderer/core/LayoutContext.h>
 #include <react/renderer/core/LayoutPrimitives.h>
 #include <react/renderer/mounting/ShadowTreeRevision.h>
@@ -463,7 +462,8 @@ CommitStatus ShadowTree::tryCommit(
     }
   }
 
-  emitLayoutEvents(affectedLayoutableNodes);
+  delegate_.shadowTreeDidCommit(
+      *this, newRevision.rootShadowNode, affectedLayoutableNodes);
 
   if (isReactBranch) {
     scheduleReactRevisionPromotion();
@@ -634,25 +634,6 @@ void ShadowTree::commitEmptyTree() const {
       {/* default commit options */});
 }
 
-void ShadowTree::emitLayoutEvents(
-    std::vector<const LayoutableShadowNode*>& affectedLayoutableNodes) const {
-  TraceSection s(
-      "ShadowTree::emitLayoutEvents",
-      "affectedLayoutableNodes",
-      affectedLayoutableNodes.size());
-
-  for (const auto* layoutableNode : affectedLayoutableNodes) {
-    if (auto viewProps =
-            dynamic_cast<const ViewProps*>(layoutableNode->getProps().get())) {
-      if (viewProps->onLayout) {
-        static_cast<const BaseViewEventEmitter&>(
-            *layoutableNode->getEventEmitter())
-            .onLayout(layoutableNode->getLayoutMetrics());
-      }
-    }
-  }
-}
-
 void ShadowTree::notifyDelegatesOfUpdates() const {
   delegate_.shadowTreeDidFinishTransaction(mountingCoordinator_, true);
 }

packages/react-native/ReactCommon/react/renderer/mounting/ShadowTree.h

@@ -161,8 +161,6 @@ class ShadowTree final {
 
   void mount(ShadowTreeRevision revision, bool mountSynchronously) const;
 
-  void emitLayoutEvents(std::vector<const LayoutableShadowNode *> &affectedLayoutableNodes) const;
-
   void scheduleReactRevisionPromotion() const;
 
   const SurfaceId surfaceId_;

packages/react-native/ReactCommon/react/renderer/mounting/ShadowTreeDelegate.h

@@ -11,6 +11,7 @@
 
 namespace facebook::react {
 
+class LayoutableShadowNode;
 class ShadowTree;
 struct ShadowTreeCommitOptions;
 
@@ -49,6 +50,16 @@ class ShadowTreeDelegate {
    */
   virtual void shadowTreeDidPromoteReactRevision(const ShadowTree &shadowTree) const = 0;
 
+  /*
+   * Called right after a Shadow Tree commits a new tree, reporting the nodes
+   * whose layout changed in this commit.
+   */
+  virtual void shadowTreeDidCommit(
+      const ShadowTree& shadowTree,
+      const RootShadowNode::Shared& rootShadowNode,
+      const std::vector<const LayoutableShadowNode*>& affectedLayoutableNodes)
+      const noexcept {}
+
   virtual ~ShadowTreeDelegate() noexcept = default;
 };
 

packages/react-native/ReactCommon/react/renderer/scheduler/Scheduler.cpp

@@ -20,6 +20,7 @@
 #include <react/renderer/mounting/MountingOverrideDelegate.h>
 #include <react/renderer/mounting/ShadowViewMutation.h>
 #include <react/renderer/runtimescheduler/RuntimeScheduler.h>
+#include <react/renderer/uimanager/LayoutEventEmitter.h>
 #include <react/renderer/uimanager/UIManager.h>
 #include <react/renderer/uimanager/UIManagerBinding.h>
 #include <mutex>
@@ -148,6 +149,11 @@ Scheduler::Scheduler(
 
   delegate_ = delegate;
   commitHooks_ = schedulerToolbox.commitHooks;
+
+  // Layout events (`onLayout`) are emitted as a standalone consumer of the
+  // `shadowTreeDidCommit` commit hook.
+  commitHooks_.push_back(std::make_shared<LayoutEventEmitter>());
+
   uiManager_ = uiManager;
 
   for (auto& commitHook : commitHooks_) {

packages/react-native/ReactCommon/react/renderer/uimanager/LayoutEventEmitter.cpp

@@ -0,0 +1,38 @@
+/*
+ * 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.
+ */
+
+#include "LayoutEventEmitter.h"
+
+#include <cxxreact/TraceSection.h>
+#include <react/renderer/components/view/ViewShadowNode.h>
+#include <react/renderer/core/LayoutableShadowNode.h>
+
+namespace facebook::react {
+
+void LayoutEventEmitter::shadowTreeDidCommit(
+    const ShadowTree& /*shadowTree*/,
+    const RootShadowNode::Shared& /*rootShadowNode*/,
+    const std::vector<const LayoutableShadowNode*>&
+        affectedLayoutableNodes) noexcept {
+  TraceSection s(
+      "LayoutEventEmitter::shadowTreeDidCommit",
+      "affectedLayoutableNodes",
+      affectedLayoutableNodes.size());
+
+  for (const auto* layoutableNode : affectedLayoutableNodes) {
+    if (auto viewProps =
+            dynamic_cast<const ViewProps*>(layoutableNode->getProps().get())) {
+      if (viewProps->onLayout) {
+        static_cast<const BaseViewEventEmitter&>(
+            *layoutableNode->getEventEmitter())
+            .onLayout(layoutableNode->getLayoutMetrics());
+      }
+    }
+  }
+}
+
+} // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/uimanager/LayoutEventEmitter.h

@@ -0,0 +1,32 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+#include <react/renderer/uimanager/UIManagerCommitHook.h>
+
+namespace facebook::react {
+
+/*
+ * Emits layout events (`onLayout`) for the nodes whose layout changed in
+ * each commit, using the `shadowTreeDidCommit` commit hook as the source of
+ * layout changes (this logic used to be implemented directly in
+ * `ShadowTree`).
+ */
+class LayoutEventEmitter final : public UIManagerCommitHook {
+ public:
+  void commitHookWasRegistered(const UIManager& uiManager) noexcept override {}
+  void commitHookWasUnregistered(const UIManager& uiManager) noexcept override {}
+
+  void shadowTreeDidCommit(
+      const ShadowTree& shadowTree,
+      const RootShadowNode::Shared& rootShadowNode,
+      const std::vector<const LayoutableShadowNode*>&
+          affectedLayoutableNodes) noexcept override;
+};
+
+} // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/uimanager/UIManager.cpp

@@ -670,6 +670,21 @@ void UIManager::shadowTreeDidPromoteReactRevision(
   }
 }
 
+void UIManager::shadowTreeDidCommit(
+    const ShadowTree& shadowTree,
+    const RootShadowNode::Shared& rootShadowNode,
+    const std::vector<const LayoutableShadowNode*>& affectedLayoutableNodes)
+    const noexcept {
+  TraceSection s("UIManager::shadowTreeDidCommit");
+
+  std::shared_lock lock(commitHookMutex_);
+
+  for (auto* commitHook : commitHooks_) {
+    commitHook->shadowTreeDidCommit(
+        shadowTree, rootShadowNode, affectedLayoutableNodes);
+  }
+}
+
 void UIManager::reportMount(SurfaceId surfaceId) const {
   TraceSection s("UIManager::reportMount");
 

packages/react-native/ReactCommon/react/renderer/uimanager/UIManager.h

@@ -146,6 +146,12 @@ class UIManager final : public ShadowTreeDelegate {
 
   void shadowTreeDidPromoteReactRevision(const ShadowTree &shadowTree) const override;
 
+  void shadowTreeDidCommit(
+      const ShadowTree& shadowTree,
+      const RootShadowNode::Shared& rootShadowNode,
+      const std::vector<const LayoutableShadowNode*>& affectedLayoutableNodes)
+      const noexcept override;
+
   std::shared_ptr<ShadowNode> createNode(
       Tag tag,
       const std::string &componentName,

packages/react-native/ReactCommon/react/renderer/uimanager/UIManagerCommitHook.h

@@ -11,6 +11,7 @@
 
 namespace facebook::react {
 
+class LayoutableShadowNode;
 class ShadowTree;
 struct ShadowTreeCommitOptions;
 class UIManager;
@@ -54,6 +55,16 @@ class UIManagerCommitHook {
     return newRootShadowNode;
   }
 
+  /*
+   * Called right after a `ShadowTree` commits a new tree.
+   * The semantic of the method corresponds to a method of the same name
+   * from `ShadowTreeDelegate`.
+   */
+  virtual void shadowTreeDidCommit(
+      const ShadowTree& /*shadowTree*/,
+      const RootShadowNode::Shared& /*rootShadowNode*/,
+      const std::vector<const LayoutableShadowNode*>& /*affectedLayoutableNodes*/) noexcept {}
+
   virtual ~UIManagerCommitHook() noexcept = default;
 };
 

scripts/cxx-api/api-snapshots/ReactAndroidDebugCxx.api

@@ -3165,6 +3165,12 @@ class facebook::react::LayoutAnimationStatusDelegate {
 class facebook::react::LayoutConformanceShadowNode : public facebook::react::ConcreteShadowNode<facebook::react::LayoutConformanceShadowNodeComponentName, facebook::react::YogaLayoutableShadowNode, facebook::react::LayoutConformanceProps> {
 }
 
+class facebook::react::LayoutEventEmitter : public facebook::react::UIManagerCommitHook {
+  public virtual void commitHookWasRegistered(const facebook::react::UIManager& uiManager) noexcept override;
+  public virtual void commitHookWasUnregistered(const facebook::react::UIManager& uiManager) noexcept override;
+  public virtual void shadowTreeDidCommit(const facebook::react::ShadowTree& shadowTree, const facebook::react::RootShadowNode::Shared& rootShadowNode, const std::vector<const facebook::react::LayoutableShadowNode*>& affectedLayoutableNodes) noexcept override;
+}
+
 class facebook::react::LayoutableShadowNode : public facebook::react::ShadowNode {
   public LayoutableShadowNode(const facebook::react::ShadowNode& sourceShadowNode, const facebook::react::ShadowNodeFragment& fragment);
   public LayoutableShadowNode(const facebook::react::ShadowNodeFragment& fragment, const facebook::react::ShadowNodeFamily::Shared& family, facebook::react::ShadowNodeTraits traits);
@@ -4751,6 +4757,7 @@ class facebook::react::ShadowTree {
 
 class facebook::react::ShadowTreeDelegate {
   public virtual facebook::react::RootShadowNode::Unshared shadowTreeWillCommit(const facebook::react::ShadowTree& shadowTree, const facebook::react::RootShadowNode::Shared& oldRootShadowNode, const facebook::react::RootShadowNode::Unshared& newRootShadowNode, const facebook::react::ShadowTreeCommitOptions& commitOptions) const = 0;
+  public virtual void shadowTreeDidCommit(const facebook::react::ShadowTree& shadowTree, const facebook::react::RootShadowNode::Shared& rootShadowNode, const std::vector<const facebook::react::LayoutableShadowNode*>& affectedLayoutableNodes) const noexcept;
   public virtual void shadowTreeDidFinishReactCommit(const facebook::react::ShadowTree& shadowTree) const = 0;
   public virtual void shadowTreeDidFinishTransaction(std::shared_ptr<const facebook::react::MountingCoordinator> mountingCoordinator, bool mountSynchronously) const = 0;
   public virtual void shadowTreeDidPromoteReactRevision(const facebook::react::ShadowTree& shadowTree) const = 0;
@@ -5260,6 +5267,7 @@ class facebook::react::UIManager : public facebook::react::ShadowTreeDelegate {
   public std::shared_ptr<facebook::react::ShadowNode> cloneNode(const facebook::react::ShadowNode& shadowNode, const std::shared_ptr<const std::vector<std::shared_ptr<const facebook::react::ShadowNode>>>& children, facebook::react::RawProps rawProps) const;
   public std::shared_ptr<facebook::react::ShadowNode> createNode(facebook::react::Tag tag, const std::string& componentName, facebook::react::SurfaceId surfaceId, facebook::react::RawProps props, facebook::react::InstanceHandle::Shared instanceHandle) const;
   public virtual facebook::react::RootShadowNode::Unshared shadowTreeWillCommit(const facebook::react::ShadowTree& shadowTree, const facebook::react::RootShadowNode::Shared& oldRootShadowNode, const facebook::react::RootShadowNode::Unshared& newRootShadowNode, const facebook::react::ShadowTree::CommitOptions& commitOptions) const override;
+  public virtual void shadowTreeDidCommit(const facebook::react::ShadowTree& shadowTree, const facebook::react::RootShadowNode::Shared& rootShadowNode, const std::vector<const facebook::react::LayoutableShadowNode*>& affectedLayoutableNodes) const noexcept override;
   public virtual void shadowTreeDidFinishReactCommit(const facebook::react::ShadowTree& shadowTree) const override;
   public virtual void shadowTreeDidFinishTransaction(std::shared_ptr<const facebook::react::MountingCoordinator> mountingCoordinator, bool mountSynchronously) const override;
   public virtual void shadowTreeDidPromoteReactRevision(const facebook::react::ShadowTree& shadowTree) const override;
@@ -5331,6 +5339,7 @@ class facebook::react::UIManagerCommitHook {
   public virtual facebook::react::RootShadowNode::Unshared shadowTreeWillCommit(const facebook::react::ShadowTree&, const facebook::react::RootShadowNode::Shared&, const facebook::react::RootShadowNode::Unshared& newRootShadowNode) noexcept;
   public virtual void commitHookWasRegistered(const facebook::react::UIManager& uiManager) noexcept = 0;
   public virtual void commitHookWasUnregistered(const facebook::react::UIManager& uiManager) noexcept = 0;
+  public virtual void shadowTreeDidCommit(const facebook::react::ShadowTree&, const facebook::react::RootShadowNode::Shared&, const std::vector<const facebook::react::LayoutableShadowNode*>&) noexcept;
   public virtual ~UIManagerCommitHook() noexcept = default;
 }
 

scripts/cxx-api/api-snapshots/ReactAndroidNewarchCxx.api

@@ -3074,6 +3074,12 @@ class facebook::react::LayoutAnimationStatusDelegate {
 class facebook::react::LayoutConformanceShadowNode : public facebook::react::ConcreteShadowNode<facebook::react::LayoutConformanceShadowNodeComponentName, facebook::react::YogaLayoutableShadowNode, facebook::react::LayoutConformanceProps> {
 }
 
+class facebook::react::LayoutEventEmitter : public facebook::react::UIManagerCommitHook {
+  public virtual void commitHookWasRegistered(const facebook::react::UIManager& uiManager) noexcept override;
+  public virtual void commitHookWasUnregistered(const facebook::react::UIManager& uiManager) noexcept override;
+  public virtual void shadowTreeDidCommit(const facebook::react::ShadowTree& shadowTree, const facebook::react::RootShadowNode::Shared& rootShadowNode, const std::vector<const facebook::react::LayoutableShadowNode*>& affectedLayoutableNodes) noexcept override;
+}
+
 class facebook::react::LayoutableShadowNode : public facebook::react::ShadowNode {
   public LayoutableShadowNode(const facebook::react::ShadowNode& sourceShadowNode, const facebook::react::ShadowNodeFragment& fragment);
   public LayoutableShadowNode(const facebook::react::ShadowNodeFragment& fragment, const facebook::react::ShadowNodeFamily::Shared& family, facebook::react::ShadowNodeTraits traits);
@@ -4562,6 +4568,7 @@ class facebook::react::ShadowTree {
 
 class facebook::react::ShadowTreeDelegate {
   public virtual facebook::react::RootShadowNode::Unshared shadowTreeWillCommit(const facebook::react::ShadowTree& shadowTree, const facebook::react::RootShadowNode::Shared& oldRootShadowNode, const facebook::react::RootShadowNode::Unshared& newRootShadowNode, const facebook::react::ShadowTreeCommitOptions& commitOptions) const = 0;
+  public virtual void shadowTreeDidCommit(const facebook::react::ShadowTree& shadowTree, const facebook::react::RootShadowNode::Shared& rootShadowNode, const std::vector<const facebook::react::LayoutableShadowNode*>& affectedLayoutableNodes) const noexcept;
   public virtual void shadowTreeDidFinishReactCommit(const facebook::react::ShadowTree& shadowTree) const = 0;
   public virtual void shadowTreeDidFinishTransaction(std::shared_ptr<const facebook::react::MountingCoordinator> mountingCoordinator, bool mountSynchronously) const = 0;
   public virtual void shadowTreeDidPromoteReactRevision(const facebook::react::ShadowTree& shadowTree) const = 0;
@@ -5071,6 +5078,7 @@ class facebook::react::UIManager : public facebook::react::ShadowTreeDelegate {
   public std::shared_ptr<facebook::react::ShadowNode> cloneNode(const facebook::react::ShadowNode& shadowNode, const std::shared_ptr<const std::vector<std::shared_ptr<const facebook::react::ShadowNode>>>& children, facebook::react::RawProps rawProps) const;
   public std::shared_ptr<facebook::react::ShadowNode> createNode(facebook::react::Tag tag, const std::string& componentName, facebook::react::SurfaceId surfaceId, facebook::react::RawProps props, facebook::react::InstanceHandle::Shared instanceHandle) const;
   public virtual facebook::react::RootShadowNode::Unshared shadowTreeWillCommit(const facebook::react::ShadowTree& shadowTree, const facebook::react::RootShadowNode::Shared& oldRootShadowNode, const facebook::react::RootShadowNode::Unshared& newRootShadowNode, const facebook::react::ShadowTree::CommitOptions& commitOptions) const override;
+  public virtual void shadowTreeDidCommit(const facebook::react::ShadowTree& shadowTree, const facebook::react::RootShadowNode::Shared& rootShadowNode, const std::vector<const facebook::react::LayoutableShadowNode*>& affectedLayoutableNodes) const noexcept override;
   public virtual void shadowTreeDidFinishReactCommit(const facebook::react::ShadowTree& shadowTree) const override;
   public virtual void shadowTreeDidFinishTransaction(std::shared_ptr<const facebook::react::MountingCoordinator> mountingCoordinator, bool mountSynchronously) const override;
   public virtual void shadowTreeDidPromoteReactRevision(const facebook::react::ShadowTree& shadowTree) const override;
@@ -5142,6 +5150,7 @@ class facebook::react::UIManagerCommitHook {
   public virtual facebook::react::RootShadowNode::Unshared shadowTreeWillCommit(const facebook::react::ShadowTree&, const facebook::react::RootShadowNode::Shared&, const facebook::react::RootShadowNode::Unshared& newRootShadowNode) noexcept;
   public virtual void commitHookWasRegistered(const facebook::react::UIManager& uiManager) noexcept = 0;
   public virtual void commitHookWasUnregistered(const facebook::react::UIManager& uiManager) noexcept = 0;
+  public virtual void shadowTreeDidCommit(const facebook::react::ShadowTree&, const facebook::react::RootShadowNode::Shared&, const std::vector<const facebook::react::LayoutableShadowNode*>&) noexcept;
   public virtual ~UIManagerCommitHook() noexcept = default;
 }