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Re: [csswg-drafts] [css-overflow] Clarify what rect clips the root element with overflow:hidden on mobile environments with dynamic toolbar (#5646)

From: CSS Meeting Bot via GitHub <sysbot+gh@w3.org>
Date: Thu, 29 Jul 2021 22:20:28 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-889498713-1627597227-sysbot+gh@w3.org>
The CSS Working Group just discussed `clipping the root element on mobile`, and agreed to the following:

* `RESOLVED: Accept the Note above.`

<details><summary>The full IRC log of that discussion</summary>
&lt;fantasai> topic: clipping the root element on mobile<br>
&lt;fantasai> github: https://github.com/w3c/csswg-drafts/issues/5646<br>
&lt;TabAtkins> ScribeNick: TabAtkins<br>
&lt;fantasai> https://hiikezoe.github.io/overflow-clip-on-root.html<br>
&lt;TabAtkins> fantasai: there's a testcase which makes this clearer...<br>
&lt;TabAtkins> fantasai: on mobile when we ahve dynamic toolbars there's a small and large viewport<br>
&lt;TabAtkins> fantasai: the ICB, the size of the document when it's height:100%, si the small viewport size<br>
&lt;TabAtkins> fantasai: But when the content retracts you see more than that<br>
&lt;TabAtkins> fantasai: This isn't interesting for long scrollable docs<br>
&lt;TabAtkins> fantasai: But if it's overflow:hidden and you're expecting a clipped rectangle equal to the ICB (so stuff outside the rect isn't visible), but it is indeed visible in these cases<br>
&lt;TabAtkins> fantasai: If you load it in a mobile browser, there's a red bar below the ICB. can't see it in desktop browsers, but it's visible in all mobiles when the UI retracts<br>
&lt;Rossen_> q?<br>
&lt;TabAtkins> fantasai: So since we have compat, do we need to spec this?<br>
&lt;TabAtkins> fantasai: Or do we have concerns?<br>
&lt;TabAtkins> florian: I think it's weird, but it's interoperable<br>
&lt;TabAtkins> fantasai: And I also can't think of a better idea<br>
&lt;TabAtkins> fantasai: I suppose you coudl clip the content but extend the canvas area...?<br>
&lt;TabAtkins> Rossen_: Thoughts?<br>
&lt;TabAtkins> TabAtkins: Since we don't ahve a better idea, and it's interop already, suggest we go for it<br>
&lt;TabAtkins> Rossen_: proposed resolution?<br>
&lt;TabAtkins> proposed resolution: the ICB is the small viewport, but the viewport clip rectangle is the large viewport<br>
&lt;TabAtkins> Rossen_: So if I have position:fixed with bottom:0, and I zoom out, will it stick to the viewport or not?<br>
&lt;TabAtkins> flackr: in impls it does<br>
&lt;TabAtkins> flackr: But it sounds like that would disagree with the spec<br>
&lt;TabAtkins> emilio: Can we resolve on aligning to the interoperable bits?<br>
&lt;TabAtkins> emilio: And figure out exactly what those bits are?<br>
&lt;TabAtkins> florian: That's what we tried to do; seems we failed to consider zooming<br>
&lt;TabAtkins> Rossen_: Yeah that's where ICB and visual vs layout viewports make the most difference<br>
&lt;TabAtkins> Rossen_: given decent interop, i suggest diving into details and documenting the status quo better, rather than resolving now<br>
&lt;TabAtkins> florian: so if we just talk about the clipping of overflow:hidden using the large viewport - is that incompatible with reality?<br>
&lt;TabAtkins> Rossen_: It woudl be inconsistent with what I said about position:sticky to the bottom<br>
&lt;TabAtkins> Rossen_: spec'll stick it to the ICB bottom, if I zoom it *currently* sticks to the screen bottom<br>
&lt;TabAtkins> fantasai: Florian's just talking about the clip rectangle, not the poisition of anything<br>
&lt;TabAtkins> fantasai: Issue here is that if you ahve overflow:hidden on the root, it might still not clip everything on the screen<br>
&lt;TabAtkins> florian: I think what I'm hearing is we might ahve the right answer, but more research is needed<br>
&lt;TabAtkins> Rossen_: I think something must be missing, happy to be wrong<br>
&lt;TabAtkins> florian: We should take the time to get our terminology exactly right<br>
&lt;TabAtkins> smfr: I'd appreciate more time to look at this to understand iOS<br>
&lt;TabAtkins> fantasai: We also don't have a spec that describes visual vs layout viewport, and small vs large viewport, and what's tied to what<br>
&lt;TabAtkins> fantasai: like is bottom:0 and top:100% the same? dunno<br>
&lt;TabAtkins> Rossen_: And when you add zoom and transforms, might end up with clipping, or sticking to the wrong thing, both are unexpected<br>
&lt;TabAtkins> fantasai: What we can say for this specific issue is that overflow:hidden on the root might not necessarily clip to the ICB rect<br>
&lt;TabAtkins> TabAtkins: That sounds like a Note, not normative text.<br>
&lt;TabAtkins> Rossen_: so what's th enote?<br>
&lt;TabAtkins> fantasai: proposed note: overflow:hidden on the root might not clip everything outside the ICB if the ICB is smaller than the viewport, which can happen on mobile<br>
&lt;TabAtkins> Rossen_: objections?<br>
&lt;TabAtkins> RESOLVED: Accept the Note above.<br>

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Received on Thursday, 29 July 2021 22:20:30 UTC

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