Re: [csswg-drafts] [css-borders-4] Interaction of single-path `border-shape` with non-uniform `border-width` (#11662)

Sorry for the late reply!

@noamr The approach generally sounds reasonable. Though it's not totally clear to me yet how all of that plays together. Following are some inline comments:

How does that interact with the border shape?

> * Border width+color are chosen from the first non-zero border (with style different than `none`) in the order of TRBL
> * If only one shape is given, the selected border width is used to expand the shape into two shapes like a stroke of that width.

What happened to @smfr's / @fantasai's idea of using the four border triangles? Those could be used to influence both.

> * If only one shape is given, the selected border width is used to expand the shape into two shapes like a stroke of that width.
> * `half-border-box` is used as the default `geometry-box`. It is exactly in the middle between the padding and border box.

It is still unclear to me why we need a `half-border-box` value. The `<geometry-box>` is only used for percentages used within the shape, right?

Related to that, the spec currently doesn't define how the border shape is actually drawn when a border width is set. I assume it is meant to expand half-inwards and half-outwards from the given shape in regard of the border width, right?

> * The way border styles are rendered is not spec'ed at the moment, as they are not spec'ed for normal (box) borders as well.

While it's not spec'ed _how_ they are rendered, I think we should still specify that they have to be respected. Otherwise we're not future proof, i.e. authors won't be able to know if a UA applies border styles when a border shape is set or not. (Unless we introduce an `@supports` feature keyword as resolved on in https://github.com/w3c/csswg-drafts/issues/3559#issuecomment-1885332213.)

Sebastian

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Received on Wednesday, 1 October 2025 10:20:07 UTC