Re: [csswg-drafts] [css-align][css-position][css-anchor-position] Introduce "document containing block" for some purposes? (#10861)

Summary of the two options under consideration:
* Size Percentages resolve against the effective containing block, whether that's the scrollport or the scrollable area, or modified by `position-area`, or whatever. In other words `inset: 50%; size: 50%` will always fill exactly the effective containing block. [currently specced]
* Size Percentages always resolve against the original containing block / scrollport, while Inset Percentages resolve against the effective containing block. In other words, the extent of the scrollable area (vs scrollport), or CB modifications via `position-area`, have no effect on percentage sizes, which always reference the original containing block. Inset percentages continue to resolve against the effective containing block. [Tab's proposal]

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Received on Tuesday, 8 July 2025 21:16:40 UTC