Chrome has overflow issues with some position-area values

[jakearchibald]

Summary

position-area in Chrome has a fundamental bug where the content of the element overflows the viewport, obscuring content. It's important to work around this.

Test results and supporting details

https://issues.chromium.org/issues/438334710

[jakearchibald]

@bfgeek @tabatkins given that this bug impacts most usage of this feature, it seems reasonable to mark it as partial_implementation.

[caugner]

@ddbeck Do you have any concerns with marking those position-area values as partially implemented in Chrome that allow unexpected overflows? The behavior is specified in the note in this section.

Alternatives considered were marking position-area altogether as partial (which doesn't seem to be justified), or introducing a behavioral subfeature (which wouldn't align with the proposed guidelines).

[ddbeck]

Not an expert in this feature, but this seems like a reasonable partial to me. I didn't count these up—do they apply to every single-value use of the property or some but not all values as single values? If it's only specific values, then I like that it's specifically targeted to the affected values and not the property in general.

I have a couple of suggestions for the notes—which I hope you'll consider despite the implied hassle of applying them to all of the notes—but I'll mark approved anyway.

[github-actions]

Tip: Review these changes grouped by change (recommended for most PRs), or grouped by feature (for large PRs).

[jakearchibald]

@ddbeck

do they apply to every single-value use of the property or some but not all values as single values? If it's only specific values, then I like that it's specifically targeted to the affected values and not the property in general.

Yeah, it's only specific single values. Although e.g top span-all will also trigger the issue. I'll update the notes for this.

[jakearchibald]

I'm happy for this to land when others are.