Block Editor: Fix block color contrast checker #68799
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Mamaduka
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[Type] Bug
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Size Change: +95 B (+0.01%) Total Size: 1.84 MB
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juanfra
approved these changes
Jan 21, 2025
Mamaduka
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Jan 21, 2025
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| // Combine `useLayoutEffect` and two rAF calls to ensure that values are read | ||
| // after the current paint but before the next paint. | ||
| window.requestAnimationFrame( () => | ||
| window.requestAnimationFrame( updateColors ) | ||
| ); |
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This is the actual fix. The rest is just moving code around for readability.
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It seems to me that the actual fix is removing the [ blockEl ] dependency array from the effect. Then it runs on every render, not only on blockEl change (the block's DOM element hardly ever changes), and catches all the color updates.
Running after the current paint but before the next paint is exactly what useEffect does. It runs when the rendered DOM is already painted. You shouldn't need to simulate it with layout effect + rAF.
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@jsnajdr, the component had an issue before adding blockEl as a dependency. It didn't always work, and the computed properties from blockEl were stale.
You shouldn't need to simulate it with layout effect + rAF.
I would like to avoid it as well, but this the only solution that works.
Quoting from: #59227.
React does not guarantee that useEffect will be called after the browser paints and, in fact, useEffect can be called before a paint when React is handling a user event (e.g. a click) or if a useLayoutEffect in the component tree updates state (e.g. calls setState). See facebook/react#20863 (comment).
This is probably a better summary for React 18 - facebook/react#24409 (comment).
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What?
Fixes #67035.
Alternative to #67036.
Combine
useLayoutEffectand two rAF calls to ensure that values are read after the current paint but before the next paint.Why?
The solution is similar to #59227, which also needs to read computed styles from the block element.
Testing Instructions
Testing Instructions for Keyboard
Same.