- From: Emilio Cobos Álvarez <notifications@github.com>
- Date: Thu, 22 Apr 2021 12:10:16 -0700
- To: WICG/webcomponents <webcomponents@noreply.github.com>
- Cc: Subscribed <subscribed@noreply.github.com>
- Message-ID: <WICG/webcomponents/issues/909/825114042@github.com>
> I ran a quick benchmark and, in Chrome at least, there doesn't seem to be a big perf difference between injecting the same stylesheet into multiple shadow roots versus just having a single <style> tag in the <head> (using light DOM). So it seems viable perf-wise.
Chrome's style system looks very different from Firefox's / Safari's, fwiw. Chrome collects invalidations globally, not per shadow root.
So we discussed some of this today, and there are different use-cases. From what I understand, the most common one (from @justinfagnani / @bkardell) was ability to import "global" stylesheets into the shadow root automatically. A proposal could be something like:
```js
host.attachShadow({ importGlobalStyles: true }) // Or such
```
Combined with something like `<style global>` or `<link rel=stylesheet global>` or whatever.
In which order / with which priority / etc these sheets would apply seems a bit TBD and probably requires CSSWG discussion. It looks sorta like a "page UA sheet" of sorts, but I don't know if we want it to behave similarly to how UA sheets behave (`!important` in UA sheets can't be overridden by the page for example, in this case it wouldn't be overridable by the web component author for example), or maybe it'd be easier to just treat them as "earlier in source order" or such.
But then there was another use-case from @gregwhitworth which (if I understood correctly) would additionally allow descendant selectors on those stylesheets to pierce through, `querySelectorAll` to break the shadow DOM boundary, etc. I think that'd be much more challenging to implement.
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Received on Thursday, 22 April 2021 19:10:30 UTC