Allow pseudo-element shadow node lookup in JS (#56455)

packages/react-native/ReactCommon/react/nativemodule/viewtransition/NativeViewTransition.cpp

@@ -51,4 +51,20 @@ std::optional<jsi::Object> NativeViewTransition::getViewTransitionInstance(
   return result;
 }
 
+jsi::Value NativeViewTransition::findPseudoElementShadowNodeByTag(
+    jsi::Runtime& rt,
+    double reactTag) {
+  auto& uiManager = UIManagerBinding::getBinding(rt)->getUIManager();
+  auto* viewTransitionDelegate = uiManager.getViewTransitionDelegate();
+  if (viewTransitionDelegate != nullptr) {
+    auto shadowNode = viewTransitionDelegate->findPseudoElementShadowNodeByTag(
+        static_cast<Tag>(reactTag));
+    if (shadowNode) {
+      return Bridging<std::shared_ptr<const ShadowNode>>::toJs(rt, shadowNode);
+    }
+  }
+
+  return jsi::Value::null();
+}
+
 } // namespace facebook::react

packages/react-native/ReactCommon/react/nativemodule/viewtransition/NativeViewTransition.h

@@ -26,6 +26,8 @@ class NativeViewTransition : public NativeViewTransitionCxxSpec<NativeViewTransi
 
   std::optional<jsi::Object>
   getViewTransitionInstance(jsi::Runtime &rt, const std::string &name, const std::string &pseudo);
+
+  jsi::Value findPseudoElementShadowNodeByTag(jsi::Runtime &rt, double reactTag);
 };
 
 } // namespace facebook::react

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

@@ -160,9 +160,8 @@ Scheduler::Scheduler(
 
   // Initialize ViewTransitionModule
   if (ReactNativeFeatureFlags::viewTransitionEnabled()) {
-    viewTransitionModule_ = std::make_unique<ViewTransitionModule>();
-    viewTransitionModule_->setUIManager(uiManager_.get());
-    uiManager_->setViewTransitionDelegate(viewTransitionModule_.get());
+    viewTransitionModule_ = std::make_shared<ViewTransitionModule>();
+    viewTransitionModule_->initialize(uiManager_.get(), viewTransitionModule_);
   }
 
   uiManager->registerMountHook(*eventPerformanceLogger_);

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

@@ -147,7 +147,7 @@ class Scheduler final : public UIManagerDelegate {
 
   RuntimeScheduler *runtimeScheduler_{nullptr};
 
-  std::unique_ptr<ViewTransitionModule> viewTransitionModule_;
+  std::shared_ptr<ViewTransitionModule> viewTransitionModule_;
 
   mutable std::shared_mutex onSurfaceStartCallbackMutex_;
   OnSurfaceStartCallback onSurfaceStartCallback_;

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

@@ -981,6 +981,37 @@ jsi::Value UIManagerBinding::get(
         });
   }
 
+  if (methodName == "createViewTransitionInstance") {
+    auto paramCount = 2;
+    return jsi::Function::createFromHostFunction(
+        runtime,
+        name,
+        paramCount,
+        [uiManager, methodName, paramCount](
+            jsi::Runtime& runtime,
+            const jsi::Value& /*thisValue*/,
+            const jsi::Value* arguments,
+            size_t count) -> jsi::Value {
+          validateArgumentCount(runtime, methodName, paramCount, count);
+
+          auto transitionName = arguments[0].isString()
+              ? stringFromValue(runtime, arguments[0])
+              : "";
+          auto pseudoElementTag = tagFromValue(arguments[1]);
+
+          if (!transitionName.empty()) {
+            auto* viewTransitionDelegate =
+                uiManager->getViewTransitionDelegate();
+            if (viewTransitionDelegate != nullptr) {
+              viewTransitionDelegate->createViewTransitionInstance(
+                  transitionName, pseudoElementTag);
+            }
+          }
+
+          return jsi::Value::undefined();
+        });
+  }
+
   if (methodName == "cancelViewTransitionName") {
     auto paramCount = 2;
     return jsi::Function::createFromHostFunction(

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

@@ -23,6 +23,8 @@ class UIManagerViewTransitionDelegate {
   {
   }
 
+  virtual void createViewTransitionInstance(const std::string & /*name*/, Tag /*pseudoElementTag*/) {}
+
   virtual void cancelViewTransitionName(const ShadowNode &shadowNode, const std::string &name) {}
 
   virtual void restoreViewTransitionName(const ShadowNode &shadowNode) {}
@@ -55,6 +57,16 @@ class UIManagerViewTransitionDelegate {
   {
     return std::nullopt;
   }
+
+  // Similar to UIManager::findShadowNodeByTag, but searches all direct children
+  // of the root node (where pseudo-element nodes live) rather than just the
+  // first child. Pseudo-element nodes are appended as additional children of the
+  // root node, rather than inserted into the main React tree, to avoid
+  // disrupting the user-created component tree.
+  virtual std::shared_ptr<const ShadowNode> findPseudoElementShadowNodeByTag(Tag /*tag*/) const
+  {
+    return nullptr;
+  }
 };
 
 } // namespace facebook::react