Add support for custom timestamps in Event via EVENT_INIT_TIMESTAMP_KEY (#56304)

packages/react-native/src/private/webapis/dom/events/Event.js

@@ -21,6 +21,7 @@ import {setPlatformObject} from '../../webidl/PlatformObjects';
 import {
   COMPOSED_PATH_KEY,
   CURRENT_TARGET_KEY,
+  EVENT_INIT_TIMESTAMP_KEY,
   EVENT_PHASE_KEY,
   IN_PASSIVE_LISTENER_FLAG_KEY,
   IS_TRUSTED_KEY,
@@ -60,7 +61,7 @@ export default class Event {
   _type: string;
 
   _defaultPrevented: boolean = false;
-  _timeStamp: number = performance.now();
+  _timeStamp: number;
 
   // $FlowExpectedError[unsupported-syntax]
   [COMPOSED_PATH_KEY]: boolean = [];
@@ -109,6 +110,14 @@ export default class Event {
     this._bubbles = Boolean(options?.bubbles);
     this._cancelable = Boolean(options?.cancelable);
     this._composed = Boolean(options?.composed);
+
+    // For internal construction of events using a custom timestamp (instead of
+    // event object creation), for use cases like dispatching events from the
+    // host platform using the original timestamps.
+    // $FlowExpectedError[prop-missing]
+    const initTimestamp: number | void = options?.[EVENT_INIT_TIMESTAMP_KEY];
+    this._timeStamp =
+      initTimestamp !== undefined ? initTimestamp : performance.now();
   }
 
   get bubbles(): boolean {

packages/react-native/src/private/webapis/dom/events/__tests__/Event-itest.js

@@ -11,7 +11,10 @@
 import '@react-native/fantom/src/setUpDefaultReactNativeEnvironment';
 
 import Event from 'react-native/src/private/webapis/dom/events/Event';
-import {setInPassiveListenerFlag} from 'react-native/src/private/webapis/dom/events/internals/EventInternals';
+import {
+  setEventInitTimeStamp,
+  setInPassiveListenerFlag,
+} from 'react-native/src/private/webapis/dom/events/internals/EventInternals';
 
 describe('Event', () => {
   it('provides read-only constants for event phases', () => {
@@ -233,6 +236,23 @@ describe('Event', () => {
     expect(event.timeStamp).toBeLessThanOrEqual(upperBoundTimestamp);
   });
 
+  it('should use a custom timestamp when set via setEventInitTimeStamp', () => {
+    const customTimestamp = 12345.678;
+    const options = {};
+    setEventInitTimeStamp(options, customTimestamp);
+    const event = new Event('custom', options);
+
+    expect(event.timeStamp).toBe(customTimestamp);
+  });
+
+  it('should accept zero as a valid custom timestamp', () => {
+    const options = {};
+    setEventInitTimeStamp(options, 0);
+    const event = new Event('custom', options);
+
+    expect(event.timeStamp).toBe(0);
+  });
+
   describe('preventDefault', () => {
     let originalConsoleError;
     let consoleErrorMock;

packages/react-native/src/private/webapis/dom/events/internals/EventInternals.js

@@ -14,7 +14,7 @@
  * (only with public exports).
  */
 
-import type Event, {EventPhase} from '../Event';
+import type Event, {EventInit, EventPhase} from '../Event';
 import type EventTarget from '../EventTarget';
 
 export const COMPOSED_PATH_KEY: symbol = Symbol('composedPath');
@@ -30,6 +30,11 @@ export const STOP_IMMEDIATE_PROPAGATION_FLAG_KEY: symbol = Symbol(
 export const STOP_PROPAGATION_FLAG_KEY: symbol = Symbol('stopPropagationFlag');
 export const TARGET_KEY: symbol = Symbol('target');
 
+// For internal construction of events using a custom timestamp (instead of
+// event object creation), for use cases like dispatching events from the host
+// platform using the original timestamps.
+export const EVENT_INIT_TIMESTAMP_KEY: symbol = Symbol('eventInitTimestamp');
+
 export function getCurrentTarget(event: Event): EventTarget | null {
   // $FlowExpectedError[prop-missing]
   return event[CURRENT_TARGET_KEY];
@@ -118,3 +123,15 @@ export function setTarget(event: Event, target: EventTarget | null): void {
   // $FlowExpectedError[prop-missing]
   event[TARGET_KEY] = target;
 }
+
+export function setEventInitTimeStamp(
+  eventInit: EventInit,
+  timeStamp: number,
+): void {
+  if (typeof timeStamp !== 'number') {
+    return;
+  }
+  // $FlowExpectedError[prop-missing]
+  // $FlowExpectedError[invalid-computed-prop]
+  eventInit[EVENT_INIT_TIMESTAMP_KEY] = timeStamp;
+}