react / react/react-native

onTextLayout incorrectly returns multiple lines for text that renders in a single line

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还没有人认领这个 Issue。

Issue: Author Provided Repro Needs: React Native Team Attention
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描述

Description

onTextLayout is returning incorrect lines data for simple single-line text.
In previous React Native versions (tested on Expo 52 with react-native 0.79), the lines array matched the actual number of rendered lines. After the latest update (RN 0.81), some texts that clearly render in one line are reported as two lines.

This breaks logic that depends on overflow detection (e.g., switching between normal text and marquee scrolling). Because onTextLayout now gives false positives, it’s impossible to reliably detect when text exceeds one line.

Steps to reproduce

The bug is present in Expo template when created with npx create-expo-app@latest.

  1. Install the dependencies npm install
  2. Open the app in Expo Go application
  3. See the log in terminal. You should see the text is rendered in one line, but onTextLayout gives an array with 2 items.
React Native Version

0.81.5

Affected Platforms

Runtime - Android

Output of npx @react-native-community/cli info
System:
  OS: macOS 26.1
  CPU: (11) arm64 Apple M3 Pro
  Memory: 286.83 MB / 18.00 GB
  Shell:
    version: 3.2.57
    path: /bin/sh
Binaries:
  Node:
    version: 22.12.0
    path: /Users/smhd/.nvm/versions/node/v22.12.0/bin/node
  Yarn: Not Found
  npm:
    version: 10.9.0
    path: /Users/smhd/.nvm/versions/node/v22.12.0/bin/npm
  Watchman:
    version: 2024.12.02.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods: Not Found
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.2
      - iOS 18.2
      - macOS 15.2
      - tvOS 18.2
      - visionOS 2.2
      - watchOS 11.2
  Android SDK: Not Found
IDEs:
  Android Studio: 2025.1 AI-251.26094.121.2513.14007798
  Xcode:
    version: 16.2/16C5032a
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.14
    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: 0.81.5
    wanted: 0.81.5
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: Not found
  newArchEnabled: Not found
iOS:
  hermesEnabled: Not found
  newArchEnabled: Not found

info React Native v0.82.1 is now available (your project is running on v0.81.5).
info Changelog: https://github.com/facebook/react-native/releases/tag/v0.82.1
info Diff: https://react-native-community.github.io/upgrade-helper/?from=0.81.5&to=0.82.1
info For more info, check out "https://reactnative.dev/docs/upgrading?os=macos".
Stacktrace or Logs
No stacktrace available. Not related in this case.
MANDATORY Reproducer

https://github.com/SMhdAsadi/onTextLayout-issue-rn81

Screenshots and Videos

This is the first page of a new Expo project in default template:

Image

The title "Welcome!" is rendered in one line, but is reported to be in two lines in onTextLayout prop.

贡献指南

打开贡献指南

从这里开始

  1. 先读完整个 Issue,再读项目的贡献指南。
  2. 在 Issue 下留言说明你要接手 —— 这能避免两个人做同样的事。
  3. Fork 仓库,在一个分支上完成修改。
  4. 提交 Pull Request,并在描述里引用这个 Issue 编号。

调研方向

使用 Expo 模板在 Android 上运行 https://github.com/SMhdAsadi/onTextLayout-issue-rn81 中的必需 reproducer,并检查单行 “Welcome!” 文本的 onTextLayout 输出。跟踪生成 lines array 的 React Native Android 文本布局路径。当在一行上渲染的文本报告一行且不会中断溢出检测时,即表示完成。

由索引模型根据 Issue 内容生成。

评估

技术栈
android, react-native
领域
mobile-dev
Issue 类型
缺陷
难度
3/5
预计耗时
1-2 天
活跃度
冷清
描述清晰度
基本清楚
新手友好度
55/100

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