react / react/react-native

[android] [ios] [web] `measure` returns incorrect values of `View` if its parent `View` is `scale`d using `transform` style

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描述

Description

If use measure method to calculate x, y, width, height, pageX, pageY values of View it will return incorrect values in case if parent View has styles:

transform: [
  {
    scale: 2,
  },
],

in this case width, height, pageX, pageY values from measure callback will be doubled compared to real ones.

Specs

  • It is wrong due docs as transform style prop doesnt change layout, transform is used to change appearance only:

    Transforms are style properties that will help you modify the appearance and position of your components using 2D or 3D transformations. However, once you apply transforms, the layouts remain the same around the transformed component

  • It is inconsistent with react-native-web where transform doesnt affect width, height, pageX, pageY values
  • It is inconsistent with response of onLayout callback which will return width, height NOT scaled

Problem

There are 3 different behaviors:

  • react-native-web returns real sizes
  • onLayout returns real sizes
  • measure returns size SCALED due to its parent transform style
Steps to reproduce

See example

React Native Version

0.81.5

Affected Platforms

Runtime - Android,
Runtime - iOS,
Runtime - Web

Output of npx @react-native-community/cli info
See example
Stacktrace or Logs
See example console logs on Android (or iOS)
MANDATORY Reproducer

https://snack.expo.dev/@sepu/rn-measure-bug-w-transform

Screenshots and Videos

web console logs (3rd and 4th parameters are the same) which is ok:

>>>>> useLayoutEffect measure x, y, width, height, pageX, pageY 134 351 71 39 134 351
onLayoutHandler layout.x, layout.y, layout.width, layout.height 134 351 71 39

Android / iOS console logs (3rd and 4th parameters for measure are 2x bigger than from onLayout):

>>>>> useLayoutEffect measure x, y, width, height, pageX, pageY 176 456 148 78 139 437
onLayoutHandler layout.x, layout.y, layout.width, layout.height 176 456 74 39

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  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

从必需的 Snack reproducer 开始,在 Android、iOS 和 web 上比较 measure 与 onLayout。追踪 reproducer 所展示的平台特定测量行为;完成的标准是 measure 报告的值与未缩放的布局以及现有的 web 和 onLayout 结果一致。

由索引模型根据 Issue 内容生成。

评估

技术栈
javascript, react-native
领域
mobile-dev
Issue 类型
缺陷
难度
4/5
预计耗时
3-5 天
活跃度
冷清
描述清晰度
基本清楚
新手友好度
50/100

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