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[csswg-drafts] [css-flexbox][css-grid] Spec doesn't say whether "overflow: [non-visible]" on flex/grid container triggers a different baseline (as it does for inline-block)

From: Daniel Holbert via GitHub <sysbot+gh@w3.org>
Date: Tue, 10 Jul 2018 16:50:32 +0000
To: public-css-archive@w3.org
Message-ID: <issues.opened-339925587-1531241430-sysbot+gh@w3.org>
dholbert has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-flexbox][css-grid] Spec doesn't say whether "overflow: [non-visible]" on flex/grid container triggers a different baseline (as it does for inline-block) ==
In the CSS2 spec section about baselines of inline-blocks, there's a special case for `overflow:[non-visible]` (i.e. scrollable) inline-blocks, for which "the baseline is the bottom margin edge".[1]

The flexbox/grid specs don't have any such special case, so I'm left wondering whether they should implicitly behave like inline-blocks in this respect. The flexbox/grid specs do have *some* text about baselines of scrollable things[2], but I don't think it helps here -- if I'm understanding correctly, that text is about flex/grid items (it's about **the box contributing a baseline** to the flex/grid container, and cases where **that box** is scrollable).

Browsers disagree on this baseline-determination right now, so we don't have interoperability on this point (testcase: https://jsfiddle.net/06wxgroy/ ). Firefox uses the margin-bottom as the baseline (consistent with `display:inline-block` behavior), whereas Chrome, Edge, and Safari do not.

Could the spec editors or CSSWG weigh in on this and update the spec to clarify what the expected behavior is?

[1] https://drafts.csswg.org/css2/visudet.html#leading *"The baseline of an 'inline-block' is ..., unless it has either no in-flow line boxes or if its 'overflow' property has a computed value other than 'visible', in which case the baseline is the bottom margin edge."*
[2] https://drafts.csswg.org/css-flexbox-1/#flex-baselines *"When calculating the baseline according to the above rules, if the box contributing a baseline has an overflow value that allows scrolling, the box must be treated as being in its initial scroll position for the purpose of determining its baseline."*

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/2902 using your GitHub account
Received on Tuesday, 10 July 2018 16:50:36 UTC

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