From d631c94bc658d7d4b79d31a3b47a106f82c95ccd Mon Sep 17 00:00:00 2001
From: Paul Kim <paulkim1@meta.com>
Date: Sat, 19 Sep 2026 11:08:44 -0700
Subject: [PATCH] Include the native event timestamp in onHWKeyEvent on Android
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Summary:
`onHWKeyEvent` tells JS which key was pressed but not when it was pressed, so a listener can only time a press from the moment the device event reaches the JavaScript thread. That delivery is asynchronous, so any latency measured from JS silently excludes the native-to-JS hop — and excludes more of it the busier the JS thread is, which is exactly when the interaction is slowest.

Add the originating `KeyEvent.getEventTime()` to the event payload. It is `SystemClock.uptimeMillis()`, the same `CLOCK_MONOTONIC` base that `performance.now()` reads in JS, so a listener can subtract the two directly with no clock conversion. The field is omitted for the focus and blur events, which have no originating hardware event.

Additive and behaviour-preserving: no existing payload key changes, and nothing in the framework reads the new one.

## Changelog

Changelog: [Android][Added] - Add `eventTime` to the `onHWKeyEvent` device event payload

Reviewed By: rozele

Differential Revision: D120451212
---
 .../react/ReactAndroidHWInputDeviceHelper.kt       | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactAndroidHWInputDeviceHelper.kt b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactAndroidHWInputDeviceHelper.kt
index 42e01e8304c2..b8508835a425 100644
--- a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactAndroidHWInputDeviceHelper.kt
+++ b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactAndroidHWInputDeviceHelper.kt
@@ -29,7 +29,13 @@ internal class ReactAndroidHWInputDeviceHelper {
         (eventKeyAction == KeyEvent.ACTION_UP || eventKeyAction == KeyEvent.ACTION_DOWN) &&
             KEY_EVENTS_ACTIONS.containsKey(eventKeyCode)
     ) {
-      dispatchEvent(context, KEY_EVENTS_ACTIONS[eventKeyCode], lastFocusedViewId, eventKeyAction)
+      dispatchEvent(
+          context,
+          KEY_EVENTS_ACTIONS[eventKeyCode],
+          lastFocusedViewId,
+          eventKeyAction,
+          ev.eventTime,
+      )
     }
   }
 
@@ -58,11 +64,15 @@ internal class ReactAndroidHWInputDeviceHelper {
       eventType: String?,
       targetViewId: Int,
       eventKeyAction: Int = -1,
+      eventTime: Long = NO_EVENT_TIME,
   ) {
     val event: WritableMap =
         WritableNativeMap().apply {
           putString("eventType", eventType)
           putInt("eventKeyAction", eventKeyAction)
+          if (eventTime != NO_EVENT_TIME) {
+            putDouble("eventTime", eventTime.toDouble())
+          }
           if (targetViewId != View.NO_ID) {
             putInt("tag", targetViewId)
           }
@@ -71,6 +81,8 @@ internal class ReactAndroidHWInputDeviceHelper {
   }
 
   private companion object {
+    private const val NO_EVENT_TIME: Long = -1
+
     /**
      * Contains a mapping between handled KeyEvents and the corresponding navigation event that
      * should be fired when the KeyEvent is received.