Re: [csswg-drafts] [css-overflow] Should overflow-clip-margin apply to scrollable boxes? (#10745)

The CSS Working Group just discussed `[css-overflow] Should overflow-clip-margin apply to scrollable boxes?`, and agreed to the following:

* `RESOLVED: scrollable boxes can combine content-box and a positive margin (clamped to padding box), and content-box and padding box can use negative margins. border-box ignores margin either way.`

<details><summary>The full IRC log of that discussion</summary>
&lt;TabAtkins> astearns: proposed resolution: new negative sizes to overflow-clip-margin (from 11355) also apply to scrolalble areas<br>
&lt;TabAtkins> florian: supprot with a question<br>
&lt;TabAtkins> florian: if you ahve content-box with or without negative margins, or padding box + negative margin, yes<br>
&lt;TabAtkins> florian: but if you have border-box (expands) and negative margins (reduces), do we take that into acocunt, or do we stop with just border box<br>
&lt;TabAtkins> emilio: main implication is that with classic scrollbars...<br>
&lt;TabAtkins> emilio: we dont' want to make clipping are larger than the padding box<br>
&lt;TabAtkins> emilio: because it's a scorllable box, that's core to the idea<br>
&lt;TabAtkins> emilio: so if you set border-box with a negative margin, so it's bigger than the scrollbar and shrinks partially, but in a system with bigger scrollbars it doesn't, so you get clipping in one but not the other...<br>
&lt;TabAtkins> florian: i don't think it's a very interesting case, so we could just say that if you set border-box it doesn't apply<br>
&lt;TabAtkins> TabAtkins: how do we handle today content-box + positive margin<br>
&lt;TabAtkins> florian: think it's unspecified<br>
&lt;TabAtkins> TabAtkins: we shoudl specify that it's clamped to padding box, since that seems to be our constraint<br>
&lt;oriol> q+<br>
&lt;TabAtkins> TabAtkins: so proposal: scrolalble boxes can use padding box and negative value, or content-box + any value (but clamped to padding box). border-box can't be used with negative value, because its relation to padding box is possible varyign between impls<br>
&lt;TabAtkins> oriol: i didn't fully udnerstand the reason for not allowing this with border box<br>
&lt;TabAtkins> oriol: if we allow content-box to grow to the padding, seems consistent ot allwo border box to shrink<br>
&lt;TabAtkins> TabAtkins: issue is that we always clamp scrollable down to padding box.<br>
&lt;TabAtkins> TabAtkins: you can grow content box up to that point<br>
&lt;TabAtkins> TabAtkins: if you shrink border box, it either does nothing (because it didn't shirnk enough and our clamp goes further) or it does shirnk to below padding box<br>
&lt;TabAtkins> TabAtkins: but the concern is, with varying scrollbar widths, whether you hit that point or not can be browser dependent<br>
&lt;TabAtkins> TabAtkins: which seems potentially bad for authors<br>
&lt;TabAtkins> astearns: no objections to the resolution<br>
&lt;TabAtkins> RESOLVED: scrollable boxes can combine content-box and a positive margin (clamped to padding box), and content-box and padding box can use negative margins. border-box ignores margin either way.<br>
</details>


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Received on Friday, 31 January 2025 00:00:27 UTC