Refactor event pipeline to accept typed event payloads (#38276)

Summary:
Pull Request resolved: #38276

Changelog: [Internal] Refactor Fabric event pipeline to accept typed event payloads

As a first step towards my project of managing the Pointer Capture API by intercepting events in UIManagerBinding I need infrastructure to be able to safely & efficently read the properties of the event payload which is what this diff lays the ground work of addressing.

Currently the events are passed from the EventEmitter all the way to UIManagerBinding with only a ValueFactory (std::function lambda) which is called to produce the jsi::Value. My diff introduces a new virtual base class, EventPayload, which provides the same functionality but in a member function, asJSIValue. To ease the transition to this new paradigm I also introduce the first concrete subclass of EventPayload: ValueFactoryEventPayload — which simply stores and calls a ValueFactory so that we can incrementally migrate to typed events (or frankly, continue to be used for events that we don't *need* to be typed, as the only real use-case in the beginning will be for Pointer Events).

This diff notably does not change any behavior and should behave the exact same way it did before — it is in later diffs where I will begin applying this to the pointer events.

Differential Revision: D47299631

fbshipit-source-id: a97e5c2c3397cda83cf151d98324c8c1534ffc5b

Author: vincentriemer

packages/react-native/ReactCommon/react/renderer/core/EventEmitter.cpp

@@ -84,7 +84,7 @@ void EventEmitter::dispatchEvent(
   eventDispatcher->dispatchEvent(
       RawEvent(
           normalizeEventType(std::move(type)),
-          payloadFactory,
+          std::make_unique<ValueFactoryEventPayload>(payloadFactory),
           eventTarget_,
           category),
       priority);
@@ -102,7 +102,7 @@ void EventEmitter::dispatchUniqueEvent(
 
   eventDispatcher->dispatchUniqueEvent(RawEvent(
       normalizeEventType(std::move(type)),
-      payloadFactory,
+      std::make_unique<ValueFactoryEventPayload>(payloadFactory),
       eventTarget_,
       RawEvent::Category::Continuous));
 }

packages/react-native/ReactCommon/react/renderer/core/EventEmitter.h

@@ -12,9 +12,11 @@
 
 #include <folly/dynamic.h>
 #include <react/renderer/core/EventDispatcher.h>
+#include <react/renderer/core/EventPayload.h>
 #include <react/renderer/core/EventPriority.h>
 #include <react/renderer/core/EventTarget.h>
 #include <react/renderer/core/ReactPrimitives.h>
+#include <react/renderer/core/ValueFactoryEventPayload.h>
 
 namespace facebook::react {
 

packages/react-native/ReactCommon/react/renderer/core/EventPayload.h

@@ -0,0 +1,29 @@
+/*
+ * 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 <jsi/jsi.h>
+
+namespace facebook::react {
+
+/**
+ * Abstract base class for all event payload types.
+ */
+struct EventPayload {
+  virtual ~EventPayload() = default;
+
+  EventPayload() = default;
+  EventPayload(const EventPayload &) = default;
+  EventPayload &operator=(const EventPayload &) = default;
+  EventPayload(EventPayload &&) = default;
+  EventPayload &operator=(EventPayload &&) = default;
+
+  virtual jsi::Value asJSIValue(jsi::Runtime &runtime) const = 0;
+};
+
+} // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/core/EventPipe.h

@@ -11,6 +11,7 @@
 #include <string>
 
 #include <jsi/jsi.h>
+#include <react/renderer/core/EventPayload.h>
 #include <react/renderer/core/EventTarget.h>
 #include <react/renderer/core/ReactEventPriority.h>
 #include <react/renderer/core/ValueFactory.h>
@@ -22,6 +23,6 @@ using EventPipe = std::function<void(
     const EventTarget *eventTarget,
     const std::string &type,
     ReactEventPriority priority,
-    const ValueFactory &payloadFactory)>;
+    const EventPayload &payload)>;
 
 } // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/core/EventQueueProcessor.cpp

@@ -53,12 +53,17 @@ void EventQueueProcessor::flushEvents(
       eventLogger->onEventDispatch(event.loggingTag);
     }
 
+    if (event.eventPayload == nullptr) {
+      // Something has gone terribly wrong
+      continue;
+    }
+
     eventPipe_(
         runtime,
         event.eventTarget.get(),
         event.type,
         reactPriority,
-        event.payloadFactory);
+        *event.eventPayload);
 
     if (eventLogger != nullptr) {
       eventLogger->onEventEnd(event.loggingTag);

packages/react-native/ReactCommon/react/renderer/core/RawEvent.cpp

@@ -11,11 +11,11 @@ namespace facebook::react {
 
 RawEvent::RawEvent(
     std::string type,
-    ValueFactory payloadFactory,
+    std::unique_ptr<EventPayload> eventPayload,
     SharedEventTarget eventTarget,
     Category category)
     : type(std::move(type)),
-      payloadFactory(std::move(payloadFactory)),
+      eventPayload(std::move(eventPayload)),
       eventTarget(std::move(eventTarget)),
       category(category) {}
 

packages/react-native/ReactCommon/react/renderer/core/RawEvent.h

@@ -11,8 +11,8 @@
 #include <string>
 
 #include <react/renderer/core/EventLogger.h>
+#include <react/renderer/core/EventPayload.h>
 #include <react/renderer/core/EventTarget.h>
-#include <react/renderer/core/ValueFactory.h>
 
 namespace facebook::react {
 
@@ -60,12 +60,12 @@ struct RawEvent {
 
   RawEvent(
       std::string type,
-      ValueFactory payloadFactory,
+      std::unique_ptr<EventPayload> eventPayload,
       SharedEventTarget eventTarget,
       Category category = Category::Unspecified);
 
   std::string type;
-  ValueFactory payloadFactory;
+  std::unique_ptr<EventPayload> eventPayload;
   SharedEventTarget eventTarget;
   Category category;
   EventTag loggingTag{0};

packages/react-native/ReactCommon/react/renderer/core/ValueFactoryEventPayload.cpp

@@ -0,0 +1,19 @@
+/*
+ * 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 "ValueFactoryEventPayload.h"
+
+namespace facebook::react {
+
+ValueFactoryEventPayload::ValueFactoryEventPayload(ValueFactory factory)
+    : valueFactory_(std::move(factory)) {}
+
+jsi::Value ValueFactoryEventPayload::asJSIValue(jsi::Runtime &runtime) const {
+  return valueFactory_(runtime);
+}
+
+} // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/core/ValueFactoryEventPayload.h

@@ -0,0 +1,24 @@
+/*
+ * 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/core/EventPayload.h>
+#include <react/renderer/core/ValueFactory.h>
+
+namespace facebook::react {
+
+class ValueFactoryEventPayload : public EventPayload {
+ public:
+  explicit ValueFactoryEventPayload(ValueFactory factory);
+  jsi::Value asJSIValue(jsi::Runtime &runtime) const override;
+
+ private:
+  ValueFactory valueFactory_;
+};
+
+} // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/core/tests/EventQueueProcessorTest.cpp

@@ -41,15 +41,15 @@ class EventQueueProcessorTest : public testing::Test {
   std::unique_ptr<EventQueueProcessor> eventProcessor_;
   std::vector<std::string> eventTypes_;
   std::vector<ReactEventPriority> eventPriorities_;
-  ValueFactory dummyValueFactory_;
+  std::unique_ptr<EventPayload> dummyEventPayload_;
 };
 
 TEST_F(EventQueueProcessorTest, singleUnspecifiedEvent) {
   eventProcessor_->flushEvents(
       *runtime_,
       {RawEvent(
           "my type",
-          dummyValueFactory_,
+          dummyEventPayload_,
           nullptr,
           RawEvent::Category::Unspecified)});
 
@@ -63,22 +63,22 @@ TEST_F(EventQueueProcessorTest, continuousEvent) {
       *runtime_,
       {RawEvent(
            "touchStart",
-           dummyValueFactory_,
+           dummyEventPayload_,
            nullptr,
            RawEvent::Category::ContinuousStart),
        RawEvent(
            "touchMove",
-           dummyValueFactory_,
+           dummyEventPayload_,
            nullptr,
            RawEvent::Category::Unspecified),
        RawEvent(
            "touchEnd",
-           dummyValueFactory_,
+           dummyEventPayload_,
            nullptr,
            RawEvent::Category::ContinuousEnd),
        RawEvent(
            "custom event",
-           dummyValueFactory_,
+           dummyEventPayload_,
            nullptr,
            RawEvent::Category::Unspecified)});
 
@@ -103,7 +103,7 @@ TEST_F(EventQueueProcessorTest, alwaysContinuousEvent) {
       {
           RawEvent(
               "onScroll",
-              dummyValueFactory_,
+              dummyEventPayload_,
               nullptr,
               RawEvent::Category::Continuous),
       });
@@ -120,7 +120,7 @@ TEST_F(EventQueueProcessorTest, alwaysDiscreteEvent) {
       {
           RawEvent(
               "onChange",
-              dummyValueFactory_,
+              dummyEventPayload_,
               nullptr,
               RawEvent::Category::Discrete),
       });