Bug 237236 – Fix typo in StyleSharingResolver

• Component: CSS
• Status: RESOLVED FIXED

[Tim Nguyen (:ntim)]

https://webkit-search.igalia.com/webkit/rev/d9fb961816b603d071c05f5fbc2754c061adabaa/Source/WebCore/style/StyleSharingResolver.cpp#300-301

```
    if (element.matchesInvalidPseudoClass() != element.matchesValidPseudoClass())
        return false;
```

This essentially is `if (true) return false` in most cases.

This typo was introduced in bug 153768, before that it was:

```
    if (element->matchesInvalidPseudoClass() != state.element()->matchesValidPseudoClass())
        return false;
```

That version was introduced in bug 138769, which I also doubt is correct, since it says if both elements are invalid, then do not share.

I think the version that we want is:

```
    if (candidateElement.matchesInvalidPseudoClass() != element.matchesInvalidPseudoClass())
        return false;
```

which is sort of redundant with `if (candidateElement.matchesValidPseudoClass() != element.matchesValidPseudoClass())` above, so maybe this should just be an ASSERT checking that valid is the exact opposite of invalid.

[Tim Nguyen (:ntim)]

Created attachment 453372 [details]
Patch

[Antti Koivisto]

Comment on attachment 453372 [details]
Patch

test would be nice

[Antti Koivisto]

Comment on attachment 453372 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=453372&action=review

> Source/WebCore/ChangeLog:9
> +        The typo was introduced in bug 153768 and bug 138769. This essentially disables
> +        style sharing completely for many elements which isn't great.

I think it only really affected form controls.

[Antti Koivisto]

Another option would be to disable it more robustly as it is probably not a super valuable optimization. I'd like to eliminate style sharing completely at some point as it doesn't work well with things like :has() and container queries.

[Tim Nguyen (:ntim)]

Created attachment 453386 [details]
Patch

[Tim Nguyen (:ntim)]

Created attachment 453412 [details]
Patch

[Tim Nguyen (:ntim)]

Created attachment 453416 [details]
Patch

[Darin Adler]

Comment on attachment 453416 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=453416&action=review

> Source/WebCore/ChangeLog:3
> +        Explicitely disable style sharing for form controls

Spelling error here "Explicitly".

> Source/WebCore/ChangeLog:6
> +        Reviewed by Antti Koivisto.

If this is already reviewed, then I guess I won’t. Antti does seem like the best reviewer for a style sharing change.

[Tim Nguyen (:ntim)]

Created attachment 453438 [details]
Patch

[Tim Nguyen (:ntim)]

Created attachment 453441 [details]
[fast-cq] Patch

[EWS]

Committed r290640 (247913@main): <https://commits.webkit.org/247913@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 453441 [details].

[Radar WebKit Bug Importer]

<rdar://problem/89611152>