Hi Morten -
Appreciate the response. I spent some time looking at
https://github.com/search?q=%22instanceof+CSSGroupingRule%22+language%3AJavaScript&type=code&l=JavaScript
as well as "instanceof CSSRule" earlier, but didn't see anything
immediately worrying (granted, it's hard to predict perfectly how the
tooling-related scripts might handle sites in the wild that might ship
the problematic patterns).
LGTM1 to ship.
On 5/9/24 6:16 AM, Morten Stenshorne wrote:
On Wed, 8 May 2024 at 17:18, Mike Taylor <miketa...@chromium.org> wrote:
On 5/8/24 3:37 AM, Morten Stenshorne wrote:
Interoperability and Compatibility
Low risk. The one possible issue is if an author uses "instanceof
CSSGroupingRule" or "instanceof CSSRule" with a page rule object
and makes incorrect assumptions based on that. However, given
that this is already shipping in Firefox (and also that in
Firefox, even CSSStyleRule inherits from CSSGroupingRule, as the
spec says - whereas Blink still doesn't), the risk should be very
low.
I agree the risk is likely very low, or contained to just a few
sites/applications - have you done any investigation to try to
find any problematic code examples that you mention (via GitHub
search or HTTPArchive)?
There's a use counter -
https://chromestatus.com/metrics/feature/timeline/popularity/4862 -
for CSSPageRule, but I'm not sure how useful it is, since it will
count as long as someone e.g. iterates over the rules in a style sheet
and there happens to be an @page rule in there. The use is currently
at 0.07, but the number isn't that useful, apart from being an
absolute worst-case number.
Here's a constructed problematic case if CSSPageRule suddenly inherits
from CSSGroupingRule:
```
<style>
@media screen {
div {
color: hotpink;
}
}
@page {
margin: 1in;
@top-center {
content: "Header";
}
}
</style>
<script>
for (const rule of document.styleSheets[0].cssRules) {
if (rule instanceof CSSGroupingRule) {
// Aha! You're a media rule! (d'oh!)
// ...
}
}
</script>
```
How likely is that, though?
/Gecko/: Shipped/Shipping
(https://bugzilla.mozilla.org/show_bug.cgi?id=1868215)
Noting that the patch should ship to Firefox release channel (126)
in about a week, per https://whattrainisitnow.com/calendar/.
Ah, right. Pretty recent change.
On that note, earlier (some time in 2023), Firefox changed
CSSStyleRule to inherit from CSSGroupingRule -
https://github.com/w3c/csswg-drafts/issues/8940#issuecomment-1747351690
That sounds like a much riskyisher change, but allegedly it went just
fine.
/WebKit/: No signal
Can we request a signal? Or do we have any other indications about
their intentions here?
Done. https://github.com/WebKit/standards-positions/issues/346
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