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[css-flexbox] clarify whether collapsed flex items influence the flex container's intrinsic main size #5985
Description
The "flex container intrinsic main sizes" spec-text (section 9.9.1) doesn't currently say anything special about excluding or special handling for collapsed flex items. It probably should.
I think they are intended to have zero contribution to the container's main size, based on a side-comment in the "Collapsed Items" section, section 4.4 -- that section says: "...collapsing or uncollapsing items may change the flex container’s main size", but never says precisely how. (That section does say that these items turn into zero-main-size "struts", but that happens after the container's intrinsic sizing.)
Probably https://drafts.csswg.org/css-flexbox-1/#intrinsic-main-sizes step 1 needs:
s/For each flex item/For each flex item (excluding collapsed flex items)/
...or something along those lines.
Activity
dholbert commentedon Feb 12, 2021
actually, step 3 is the most important step to adjust:
add each item’s flex base size to the product of [...]. We need to define things such that this added quantity ends up at 0, for collapsed flex items (or simply exclude collapsed flex items from the "add each item's..." operation here.)dholbert commentedon Feb 12, 2021
I filed https://bugzilla.mozilla.org/show_bug.cgi?id=1692366 on fixing this in Firefox/Gecko (to exclude collapsed items from the container's main-axis intrinsic sizing)
[css-flexbox-1] Exclude collapsed items from intrinsic main size comp…
fantasai commentedon Jun 9, 2021
@dholbert Edits checked in, let us know if we missed anything?
Agenda+ to verify with the CSSWG.
dholbert commentedon Jun 16, 2021
The edits look good to me. Thanks!
css-meeting-bot commentedon Jun 16, 2021
The CSS Working Group just discussed
Flexbox, and agreed to the following:RESOLVED: Accept editsThe full IRC log of that discussion
<fantasai> Topic: Flexbox<TabAtkins> github: https://github.com//issues/5985
<fantasai> github: https://github.com//issues/5985
<fantasai> TabAtkins: just got approval from dholbert so probably easy
<chrishtr> I need to follow up some more on issue 5896, let's cover it another time.
<fantasai> TabAtkins: dholbert noticed that collaped flex items aren't explicitly excluded from intrinsic size calculation
<fantasai> TabAtkins: so we updated to explicitly skip those items
<fantasai> commits are https://github.com/w3c/csswg-drafts/commit/60ffc4058780d832d880a076fe02788f0cc6e8a7
<fantasai> TabAtkins: We made the fix, just wanted WG confirmation it's OK
<cbiesinger> I haven't read the text but your description sounds good
<fantasai> astearns: proposal to accept?
<fantasai> RESOLVED: Accept edits
tabatkins commentedon Sep 10, 2021
Implicitly tested by https://github.com/web-platform-tests/wpt/blob/master/css/css-flexbox/flexbox-collapsed-item-horiz-001.html