Add PressabilityPerformanceEventEmitter

Summary:
Add PressabilityPerformanceEventEmitter which allows product code / infrastructure to subscribe to touch-related performance events.

Changelog: [Added][JS] Product/infra can subscribe to Pressability touch events for telemetry purposes

Reviewed By: fkgozali

Differential Revision: D27034835

fbshipit-source-id: e62811f641994b9eadb5cdd7391e806b6cce479a

Libraries/Pressability/Pressability.js

@@ -18,6 +18,8 @@ import type {
  PressEvent,
  MouseEvent,
 } from '../Types/CoreEventTypes';
+import PressabilityPerformanceEventEmitter from './PressabilityPerformanceEventEmitter.js';
+import {type PressabilityTouchSignal as TouchSignal} from './PressabilityTypes.js';
 import Platform from '../Utilities/Platform';
 import UIManager from '../ReactNative/UIManager';
 import type {HostComponent} from '../Renderer/shims/ReactNativeTypes';
@@ -174,15 +176,6 @@ type TouchState =
  | 'RESPONDER_ACTIVE_LONG_PRESS_OUT'
  | 'ERROR';
 
-type TouchSignal =
- | 'DELAY'
- | 'RESPONDER_GRANT'
- | 'RESPONDER_RELEASE'
- | 'RESPONDER_TERMINATED'
- | 'ENTER_PRESS_RECT'
- | 'LEAVE_PRESS_RECT'
- | 'LONG_PRESS_DETECTED';
-
 const Transitions = Object.freeze({
  NOT_RESPONDER: {
  DELAY: 'ERROR',
@@ -630,6 +623,13 @@ export default class Pressability {
  : '<<host component>>',
  );
  if (prevState !== nextState) {
+ PressabilityPerformanceEventEmitter.emitEvent(() => {
+ return {
+ signal,
+ touchDelayMs: Date.now() - event.nativeEvent.timestamp,
+ };
+ });
+
  this._performTransitionSideEffects(prevState, nextState, signal, event);
  this._touchState = nextState;
  }

Libraries/Pressability/PressabilityPerformanceEventEmitter.js

@@ -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.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import {type PressabilityTouchSignal as TouchSignal} from './PressabilityTypes.js';
+
+export type PressabilityPerformanceEvent = $ReadOnly<{|
+ signal: TouchSignal,
+ touchDelayMs: number,
+|}>;
+export type PressabilityPerformanceEventListener = PressabilityPerformanceEvent => void;
+
+class PressabilityPerformanceEventEmitter {
+ _listeners: Array<PressabilityPerformanceEventListener> = [];
+
+ constructor() {}
+
+ addListener(listener: PressabilityPerformanceEventListener): void {
+ this._listeners.push(listener);
+ }
+
+ removeListener(listener: PressabilityPerformanceEventListener): void {
+ const index = this._listeners.indexOf(listener);
+ if (index > -1) {
+ this._listeners.splice(index, 1);
+ }
+ }
+
+ emitEvent(constructEvent: () => PressabilityPerformanceEvent): void {
+ if (this._listeners.length === 0) {
+ return;
+ }
+
+ const event = constructEvent();
+ this._listeners.forEach(listener => listener(event));
+ }
+}
+
+const PressabilityPerformanceEventEmitterSingleton: PressabilityPerformanceEventEmitter = new PressabilityPerformanceEventEmitter();
+
+export default PressabilityPerformanceEventEmitterSingleton;

Libraries/Pressability/PressabilityTypes.js

@@ -0,0 +1,18 @@
+/**
+ * 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.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+export type PressabilityTouchSignal =
+ | 'DELAY'
+ | 'RESPONDER_GRANT'
+ | 'RESPONDER_RELEASE'
+ | 'RESPONDER_TERMINATED'
+ | 'ENTER_PRESS_RECT'
+ | 'LEAVE_PRESS_RECT'
+ | 'LONG_PRESS_DETECTED';