fix: CSS custom properties not defined when a component first renders #2999
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nicholasrice
requested review from
chrisdholt,
EisenbergEffect and
janechu
as code owners
EisenbergEffect
approved these changes
Apr 24, 2020
| sheet, | ||
| ]; | ||
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| this.customPropertyTarget = (sheet.rules[0] as CSSStyleRule).style; |
nicholasrice
commented
Apr 24, 2020
packages/web-components/fast-components/src/design-system-provider/design-system-provider.ts
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chrisdholt
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Apr 24, 2020
nicholasrice
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Description
Fixes a rendering bug related to the design-system-provider where CSS custom properties have not been written by the time a component first paints.
I also organized the methods / property order and added more code comments, so apologies if this looks more complicated than it should be.
Motivation & context
This change changes the behavior of the design-system-provider to synchronously create
CSS custom properties instead of batching them asynchronously. This is being done to prevent flashes of un-styled content and un-desired transitions that result from the CSS custom property not being defined when the component using the CSS custom property first paints.
This change also introduces an optimization where it will use a
CSSStyleSheetattached viaadoptedStyleSheetsto create the custom properties when that API is available. There are significant performance benefits to this approach over using theHTMLElement.style.setPropertyAPI: https://jsbench.me/hck9d4noez/1. Inline styles will be the fallback behavior if adopted stylesheets are not supported.Issue type checklist
Is this a breaking change?
Process & policy checklist