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fix(utils): single global stylesheet instance for performance #6320

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Merged
merged 3 commits into from
Jun 29, 2025
Merged

fix(utils): single global stylesheet instance for performance #6320

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997a8b4
fix(utils): single global stylesheet instance for performance
aeharding Jun 27, 2025
20d4046
lazy getter
aeharding Jun 28, 2025
1414c08
simplify
aeharding Jun 28, 2025
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simplify
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@aeharding
aeharding committed Jun 28, 2025
commit 1414c08e6fd1e523f50310b40f5eeae6f39367f0
31 changes: 5 additions & 26 deletions src/utils/shadow-root.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -5,31 +5,7 @@ import { CMP_FLAGS } from '@utils';
import type * as d from '../declarations';
import { createStyleSheetIfNeededAndSupported } from './style';

/**
* Create a single, shared global stylesheet for all shadow roots.
*
* This singleton avoids the performance and memory hit of
* creating a new CSSStyleSheet every time a shadow root is created.
*
* Lazy getter due to "ReferenceError: Cannot access 'globalStyles'
* before initialization" if setup is run at root level
*
* internal state:
* - undefined: not yet computed
* - null: computed and cached, but stylesheet not needed/supported
* - CSSStyleSheet: computed and cached
*
* @returns CSSStyleSheet | null
*/
const getLazyGlobalStyleSheet = (() => {
let value: CSSStyleSheet | null | undefined;

return () => {
if (value === undefined) value = createStyleSheetIfNeededAndSupported(globalStyles) ?? null;

return value;
};
})();
let globalStyleSheet: CSSStyleSheet | null | undefined;

export function createShadowRoot(this: HTMLElement, cmpMeta: d.ComponentRuntimeMeta) {
const shadowRoot = BUILD.shadowDelegatesFocus
Expand All @@ -39,6 +15,9 @@ export function createShadowRoot(this: HTMLElement, cmpMeta: d.ComponentRuntimeM
})
: this.attachShadow({ mode: 'open' });

const globalStyleSheet = getLazyGlobalStyleSheet();
// Initialize if undefined, set to CSSStyleSheet or null
if (globalStyleSheet === undefined) globalStyleSheet = createStyleSheetIfNeededAndSupported(globalStyles) ?? null;

// Use initialized global stylesheet if available
if (globalStyleSheet) shadowRoot.adoptedStyleSheets.push(globalStyleSheet);
}
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