[css-round-display] more details needed about border boundary

[frivoal]

Some comments I made in an old mail have yet to be addressed. Most of that mail has, but not all, so I'm bring back the rest here, with some phrasing tweaks to match the fact that the spec has evolved since. I am posting these multiple comments in one issues as they are related, but feel free to split them into multiple issues if that makes them easier to address.

Original mail: https://lists.w3.org/Archives/Public/www-style/2015Apr/0399.html

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I am not sure I understand how "border-boundary: parent" works. Is it to be used to fit the border inside the parent element's shape inside? If yes, I think you need to explain this better, and explicitly mention shape-inside (and probably shape-padding as well). If it means something else, could you explain what? I think using the parent's shape-inside is useful, so if that's not what your value does, then we should add one more value for that.

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You need to give more details about how border-boundary works when the border is not uniform (different border styles, width, or colors for top/right/bottom/left borders).

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You also need to define whether border-boundary is a purely visual effect, or whether it affects layout, and if so, how. I don't think it should.

You have an informative note that says:

If the value of border-boundary is parent or display, border lines of the element are actually just a visual effect. It triggers a layout for rendering in a general way, but in the above cases (border-boundary: parent|display), the layout doesn’t occur and it only draws the border lines inward from the containing block’s borders. With this situation, the borders might hide contents around the display edge.

The first and last sentence indicate that this does not affect layout. This needs to be normative text, not informative.

I do not understand the second sentence.