New arch, RTL touchable having wrong coordinates
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- C++
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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
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the mandatory reproducer and compare Fabric behavior for measureInWindow, measure, UIManager.measure, TouchableOpacity, and Pressable under RTL on a 3D Touch iOS device. Trace the renderer-level coordinate and hit-testing paths involved in those entry points, then verify that measurements are physically valid and touchables respond normally in the reproducer.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- ios, react-native
- Domain
- mobile
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100