[css-backgrounds-3][css-borders-4] Fixed definition for where box shadows apply #9296
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So I was expecting the behavior to be the principal box since that's the simple choice, but I have tried a table:
<!DOCTYPE html>
<table style="outline: 3px solid cyan; box-shadow: 0 0 0 6px magenta">
<caption>Tablecaption</caption>
<tr><td>cell</td></tr>
</table>Both Firefox and Chromium apply the shadow to the table grid box, not to the principal table wrapper box.
So maybe it should be discussed whether this should change? Or say that it's the principal box unless otherwise defined by the relevant spec (https://www.w3.org/TR/CSS21/tables.html#model would imply table grid box, and seemingly https://drafts.csswg.org/css-tables/#global-style-overrides too)
I can't find it now, but I remember some discussion about defaulting properties on a table to apply to the principal wrapper box, with some exceptions that apply to the grid box. Now the default is the grid box, which seems a bit weird.
| @@ -2599,6 +2601,8 @@ Changes since the 14 February 2024 Candidate Recommendation Snapshot</h3> | |||
| (<a href="https://github.com/w3c/csswg-drafts/issues/8496">Issue 8496</a>) | |||
| <li>Fixed an error in the Computed Value line of 'background-image'. | |||
| (<a href="https://github.com/w3c/csswg-drafts/issues/8604">Issue 8604</a>) | |||
| <li>Fixed the definition for where box shadows apply. | |||
| (<a href="https://github.com/w3c/csswg-drafts/issues/9286">Issue 9286</a>) | |||
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This is in the "Changes since the 14 February 2024 Candidate Recommendation Snapshot" which doesn't exist (should be 2023 instead).
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Not sure whether @fantasai's comment was related to this, though I went ahead and fixed this obvious mistake.
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No, I was commenting on the actual spec text.
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@Loirooriol Can you drop that comment into the issue? |
css-backgrounds-3/Overview.bs
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| @@ -2504,7 +2505,8 @@ Layering, Layout, and Other Details</h4> | |||
| and the <i>inner shadows</i> of an element are drawn immediately above the background of that element | |||
| (below the borders and border image, if any). | |||
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| <p>If an element has multiple boxes, all of them get drop shadows, | |||
| <p>Drop shadows are only applied to the [=principal box=]. | |||
| If that box has multiple [=fragments=], then all of them get shadows, | |||
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This is incorrect. How box-shadow is handled on fragments depends on box-decoration-break, see https://www.w3.org/TR/css-break-4/#break-decoration
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Isn't this addressed in the next sentence?
but shadows are only drawn where borders would also be drawn;
see 'box-decoration-break'.
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No, it's not that we have multiple shadows some parts of which aren't drawn. box-decoration-break determines whether the entire box gets shadowed and then sliced or the fragments get shadowed. If you offset the shadow by more than the width of the first fragment and then blur it, for example, the first fragment won't have a shadow attached, but there will be a shadow as wide as the combined fragments, blurred as a single unit, attached to the second fragment.
css-backgrounds-3/Overview.bs
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| <p>If an element has multiple boxes, all of them get drop shadows, | ||
| <p>Drop shadows are only applied to the [=principal box=]. | ||
| If that box has multiple [=fragments=], then all of them get shadows, |
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<p>Unless otherwise specified, drop shadows are only applied to the [=principal box=].
If the affected box has multiple fragments,
the shadows are applied as specified in 'box-decoration-break'.
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I made up for that now. Sebastian |
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@Loirooriol @fantasai Can you please have another look? Sebastian |
This corrects the description for where box shadows are applied.
Fixes #9286