react / react/react-native

New arch, RTL touchable having wrong coordinates

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Description

Description

Description
In the New Architecture (Fabric) on iOS, Right-to-Left (RTL) mode causes a fundamental breakdown in coordinate calculations on devices with 3D Touch hardware (iPhone 6s through iPhone XS Max).

The bug manifests in two ways:

Impossible Measurements: measureInWindow, measure, and UIManager.measure return coordinates that are physically impossible (e.g., -440pt or 975pt on a 375pt wide screen).
Broken Hit-Testing: Core components like TouchableOpacity and Pressable become unresponsive or require dozens of taps to trigger, likely because the renderer believes the touch is landing outside the component's calculated bounds.
Key Technical Finding: This is a Renderer-level bug. It persists regardless of whether you use a Core ScrollView or a react-native-gesture-handler ScrollView. However, using react-native-gesture-handler for the buttons (Pressables) serves as a workaround for the hit-testing issue because RNGH handles touches outside of the standard renderer's coordinate logic.

Steps to reproduce

Steps to Reproduce
Enable the New Architecture (newArchEnabled: true).
Run the application on a 3D Touch-enabled device (e.g., iPhone XS).
Switch the app to RTL mode (I18nManager.forceRTL(true)) and reload.
Place an element inside a horizontal ScrollView at a significant offset (e.g., end of a 800pt wide container).
Attempt to tap the element and measure its position using ref.current.measureInWindow.

React Native Version

0.82.1

Affected Platforms

Runtime - iOS

Output of npx @react-native-community/cli info
npx @react-native-community/cli info
info Fetching system and libraries information...
System:
  OS: macOS 26.2
  CPU: (10) arm64 Apple M4
  Memory: 167.22 MB / 16.00 GB
  Shell:
    version: 4.3.3
    path: /opt/homebrew/bin/fish
Binaries:
  Node:
    version: 25.2.1
    path: /Users/abdullah.mzaien/.local/share/mise/installs/node/25.2.1/bin/node
  Yarn:
    version: 1.22.22
    path: /Users/abdullah.mzaien/.local/share/mise/installs/yarn/1.22.22/bin/yarn
  npm:
    version: 11.6.2
    path: /Users/abdullah.mzaien/.local/share/mise/installs/node/25.2.1/bin/npm
  Watchman: Not Found
Managers:
  CocoaPods:
    version: 1.16.2
    path: /opt/homebrew/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.2
      - iOS 26.2
      - macOS 26.2
      - tvOS 26.2
      - visionOS 26.2
      - watchOS 26.2
  Android SDK: Not Found
IDEs:
  Android Studio: 2025.2 AI-252.27397.103.2522.14617522
  Xcode:
    version: 26.2/17C52
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.17
    path: /usr/bin/javac
  Ruby:
    version: 2.6.10
    path: /usr/bin/ruby
npmPackages:
  "@react-native-community/cli": Not Found
  react:
    installed: 19.1.0
    wanted: 19.1.0
  react-native:
    installed: 0.81.4
    wanted: 0.81.4
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: Not found
  newArchEnabled: Not found
iOS:
  hermesEnabled: Not found
  newArchEnabled: Not found
Stacktrace or Logs
RTL Measurement Failure (ScrollView Content):
📐 ========== MEASURING: Scroll Item ==========
 LOG  📱 Screen Width: 375
 LOG  🌍 RTL Mode: true
 LOG  📱 Platform: ios
 LOG  1️⃣ measureInWindow: {"height": 45, "x": -440, "y": 474}  <-- IMPOSSIBLE
 LOG  2️⃣ measure: {"pageX": -440, "relativeX": 20}           <-- IMPOSSIBLE
 LOG  3️⃣ UIManager.measure: {"pageX": -440, "x": 20}         <-- IMPOSSIBLE


Touch Event Discrepancy (Hit-testing failure):

 LOG  👆 [TouchableOpacity] CoreRN Touch: pageX=98, derivedX=67, force=0.00
 // Note: Touch registered at pageX=98, but the target was measured at x=-440.
MANDATORY Reproducer

https://github.com/mzaien/rtl-measurment-bug-repro

Screenshots and Videos

https://github.com/user-attachments/assets/1b2940aa-5c2d-4d58-a34b-28e34e9190b9

Guide de contribution

Ouvrir le guide de contribution

Par où commencer

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  2. Signalez en commentaire que vous la prenez — cela évite que deux personnes fassent le même travail.
  3. Forkez le dépôt et travaillez sur une branche.
  4. Ouvrez une pull request qui référence le numéro de l'issue.

Piste de recherche

Commencez par le reproducer obligatoire et comparez le comportement de Fabric pour measureInWindow, measure, UIManager.measure, TouchableOpacity et Pressable sous RTL sur un appareil iOS avec 3D Touch. Suivez les chemins de coordonnées et de hit-testing au niveau du renderer impliqués par ces points d’entrée, puis vérifiez que les mesures sont physiquement valides et que les touchables réagissent normalement dans le reproducer.

Rédigé par le modèle d'indexation à partir du texte de l'issue.

Évaluation

Stack technique
ios, react-native
Domaine
mobile
Type d'issue
Bug
Difficulté
4/5
Temps estimé
3-5 jours
Activité
Calme
Clarté
Plutôt claire
Accessibilité débutants
45/100

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