🚀 [Story performance] Fix CLS caused from AMP runtime CSS showing story before amp-story.css #37990
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gmajoulet
approved these changes
Mar 31, 2022
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Hey @gmajoulet, @newmuis! These files were changed: |
1 similar comment
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Hey @gmajoulet, @newmuis! These files were changed: |
jridgewell
approved these changes
Mar 31, 2022
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There's been a regression of some unrelated unit tests that this PR caught, I'm fixing them on #37994 and then merging this PR (these unit tests are blocking this merge) |
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On origin
ampshared.cssshows the document when v0.js is installed, but in many cases this happens in a different frame thanamp-story.cssbeing installed, meaning that for a split second the layout shows with just theampshared.cssstyles and withoutamp-story.css. When this happens, the active page can change the size (especially for inline elements that take space) which causes CLS=1.TL;DR: If amp-story.css is not present, we don't want to show the story due to possible CLS. On cached docs the CSS is inlined so this won't affect anything, but on origin this prevents a flash of unstyled story.
Somewhat reverts back #37345 but shows the story earlier (CSS installation is earlier than
layoutCallbackis completed).