[Scheduler] Get current time from performance.now in non-DOM environments #19532
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emilisb
changed the title
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| @@ -16,10 +16,24 @@ export let requestPaint; | |||
| export let getCurrentTime; | |||
| export let forceFrameRate; | |||
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| const isWindowUndefined = typeof window === 'undefined'; | |||
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| const performance = isWindowUndefined ? global.performance : window.performance; | |||
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Why is this needed? Why not just use performance as a global in the first place?
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This is based on a comment in the previous code.
// Capture local references to native APIs, in case a polyfill overrides them.
const performance = window.performance;
const Date = window.Date;
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I wonder if all environments that don't have window are guaranteed to have global, or not. We don't already use global in this file yet.
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For example what if this code is loaded in a worker. Would it crash?
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I would feel better about refactoring to read globals directly from the global scope (without a qualifier) and aliasing them. Kind of like it was before 3f2cafe.
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Good thinking. I refactored the code. I had to refactor the browser test too, window is not considered as global under test environment.
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Makes sense. Thanks. |
Summary
Scheduler makes an assumption that
performance.nowdoes not exist in a non-DOM environment. React Native is such environment, however, latest RN versions do have support forperformance.now(facebook/react-native@232517a).This PR changes
getCurrentTimeimplementation to useperformance.nowif it is defined, and fallback toDate.nowif the function is missing.This change is required for React Profiler API to work properly in React Native. Without this change, the Profiler in RN uses
Datewhich is not so precise.Test Plan
schedulerand tested the change in a React Native project. Profiler API now takes time fromperformance.nowand the precision is greatly improved.