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Re: [css-flexbox] 'stretch' can shrink flex items - is this intended?

From: Alan Stearns <stearns@adobe.com>
Date: Wed, 26 Jun 2013 11:31:12 -0700
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: W3C WWW Style <www-style@w3.org>
Message-ID: <CDF080F8.2CCB7%stearns@adobe.com>
On 6/20/13 6:16 PM, "Tab Atkins Jr." <jackalmage@gmail.com> wrote:

>On Thu, Jun 20, 2013 at 6:06 PM, Alan Stearns <stearns@adobe.com> wrote:
>> I'm looking at what happens when a flex item's hypothetical cross size
>> larger than the container's definite cross size. There seems to be a bit
>> of inconsistency (though it's interoperable inconsistency between Blink
>> and Gecko, at least).
>> Consider a flex container with max-height of 100px that contains one
>> item (A) with 'height:150px' and another flex item (B) with
>> but whose hypothetical cross size from step 7 ends up at 150px. You can
>> see something similar at [2]
>> If these items are any alignment other than 'stretch' then they are
>> consistently 150px tall.
>> But if the alignment is 'stretch' then A is 150px tall and B is 100px
>> tall. The 'stretch' value causes a flex item to shrink.
>> Step 11 of section 9.4 [1] accounts for this, but is this the correct
>> result? If not, we could add an additional caveat such as, "and its
>> hypothetical cross size is smaller than the used cross size of its flex
>> line"
>Yes, it's intentional.

Could you go into the scenarios where this is useful? At least in my
testing having a child's contents overflow doesn't seem to be a better
result than allowing a child to overflow the container.

I'm asking because of the auto-height regions in a flex container case. If
the result of the regions processing model says that an auto-height region
is a particular height, then having something increase that height does
not change the named flow fragment that fits into the region. An
auto-height region either has the entire remainder of the flow, or the
content up to the next region break. Increasing the region height doesn't
change either of those fragments.

But decreasing the region height could change the fragmentation, and that
would cause us to have to re-calculate the fragmentation and heights for
the rest of the region chain. If we could guarantee that stretch does not
make flex items shrink, then this interaction could be less complicated.


Received on Wednesday, 26 June 2013 18:32:03 UTC

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