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perf(Banner): Optimize CSS :has() selectors for better INP #7324

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perf(Banner): Optimize CSS :has() selectors for better INP #7324

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1a01f56
perf(Banner): Optimize CSS :has() selectors for better INP
mattcosta7 Dec 15, 2025
154df2b
Merge branch 'main' into perf/banner-has-selector
mattcosta7 Dec 19, 2025
101f69e
Merge branch 'main' into perf/banner-has-selector
mattcosta7 Dec 30, 2025
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8 changes: 8 additions & 0 deletions .changeset/perf-banner-has-selector.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
---
'@primer/react': patch
---

perf(Banner): Optimize CSS :has() selectors for better INP

- Scope `:has(.BannerActions)` selectors to shallow path `> * >` for O(1) lookup
- Scope `:has(.BannerActionsContainer)` to direct child with `>` combinator
12 changes: 8 additions & 4 deletions packages/react/src/Banner/Banner.module.css
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Original file line number Diff line number Diff line change
Expand Up @@ -119,7 +119,8 @@
margin-block: var(--base-size-8);
}

.Banner[data-title-hidden]:not(:has(.BannerActions)) .BannerContent {
/* PERFORMANCE: BannerActions is inside BannerContainer, use shallow path > * > for O(1) lookup */
.Banner[data-title-hidden]:not(:has(> * > .BannerActions)) .BannerContent {
margin-block: var(--base-size-6);
}

Expand Down Expand Up @@ -152,8 +153,9 @@
fill: var(--banner-icon-fgColor);
}

/* PERFORMANCE: BannerActions is inside BannerContainer, use shallow path > * > for O(1) lookup */
/* stylelint-disable-next-line selector-max-specificity */
.Banner[data-title-hidden]:not(:has(.BannerActions)) .BannerIcon svg {
.Banner[data-title-hidden]:not(:has(> * > .BannerActions)) .BannerIcon svg {
height: var(--base-size-16);
}

Expand All @@ -166,7 +168,8 @@
margin-inline-start: var(--base-size-4);
}

:where(.Banner):has(.BannerActions) .BannerDismiss {
/* PERFORMANCE: BannerActions is inside BannerContainer, use shallow path > * > for O(1) lookup */
:where(.Banner):has(> * > .BannerActions) .BannerDismiss {
margin-block: var(--base-size-2);
}

Expand Down Expand Up @@ -211,7 +214,8 @@
display: grid;
}

.BannerContainer:has(.BannerActionsContainer) {
/* PERFORMANCE: BannerActionsContainer is direct child of BannerContainer, scope with > for O(1) lookup */
.BannerContainer:has(> .BannerActionsContainer) {
grid-template-rows: auto auto;
}

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