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Add text paint time accuracy fix to LCP changelog

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Bug: 1047684
Change-Id: I8492f76a74a66a525490cf5de4ea4cbe9daf0844
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3277075
Reviewed-by: Annie Sullivan <sullivan@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#940938}
This commit is contained in:
Nicolás Peña Moreno
2021-11-11 22:05:36 +00:00
committed by Chromium LUCI CQ
parent e0dc7653d0
commit 969818b14d
2 changed files with 25 additions and 0 deletions
docs/speed/metrics_changelog
2021_11_lcp.mdlcp.md

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# Largest Contentful Paint Bug Fixes in M98
## Bug Fixes in Chrome 98
In Chrome 98, a bug fix was made to the Chrome implementation. Previously, we
would wait for one visual update at a time and record the paint times of all
pending text nodes upon receiving the timestamp for the visual update. This
could cause certain text nodes that had just been detected to be considered
displayed even though they're not. Instead, we keep track of the objects which
are painted on each animation frame and set their timestamps to the visual
update corresponding to that animation frame. This is already how it works for
image objects, so this change only impacts text paint times, making them more
accurate. [Source code for this
change](https://chromium-review.googlesource.com/c/chromium/src/+/3265727).
## How does this affect a site's metrics?
A website whose LCP is text may see their LCP values increase due to the more
accurate paint times being used.
## When were users affected?
Chrome 98 is currently scheduled to be released the week of February 1, 2022.

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This is a list of changes to [Largest Contentful Paint](https://web.dev/lcp).
* Chrome 98
* Metric bug fix: [Text paints are more accurate](2021_11_lcp.md)
* Chrome 96
* Metric bug fix: [Largest Contentful Paint uses the page viewport](2021_09_lcp.md)
* Chrome 88