Re: [csswg-drafts] [css-backgrounds-3][css-borders-4] The shape of box-shadow should be a circle for a box with border-radius:50% and big spread (#7103)

> The last case in your image shows the problem: the inner element only has a negligible 1px border radius for the bottom right corner, while the shadow has a big radius. So that doesn't seem continuous at all.

This is the big deal that underlies a lot of the discussion. We've got two conflicting pressures:

* people use box-shadow with spread to do "outlines" a lot (basically strokes), and they expect sharp corners (0px border-radius) to stay sharp when they do so, but the exact roundness of rounded corners is a lot more flexible
* CSS should, as much as realistically possible, not expose rounding behavior. Having "exactly 0" and "very slightly > 0" act meaningfully different is something we try hard to avoid.

This is why the cubic adjustment is used - it keeps *very small* corners very small, converging to staying sharp at exactly 0, while letting reasonably-sized corners grow.

Keeping sharp corners sharp is indeed not what a "real" shadow does, tho.

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Received on Tuesday, 26 August 2025 21:33:03 UTC