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Re: [CSS21] margin-collapse-164 is currently invalid per section 9.5.2

From: Anton Prowse <prowse@moonhenge.net>
Date: Mon, 21 May 2012 20:10:57 +0200
Message-ID: <4FBA8531.3090006@moonhenge.net>
To: Public CSS testsuite mailing list <public-css-testsuite@w3.org>
CC: Arron Eicholz <Arron.Eicholz@microsoft.com>, "css21testsuite@gtalbot.org" <css21testsuite@gtalbot.org>, www-style mailing list <www-style@w3.org>
On 21/05/2012 19:58, Arron Eicholz wrote:
> On Sunday, May 20, 2012 6:27 AM Anton Prowse wrote:
>> On 10/02/2012 03:16, "Gérard Talbot" wrote:

>>> What is the final word on [RC6]
>>> http://test.csswg.org/suites/css2.1/20110323/html4/margin-collapse-164.htm ?
>>>
>>> As far as I can see and as far as I'm concerned,
>>> margin-collapse-164 is invalid.
>>
>> This test is now invalid.  It assumes "Behaviour 1":
>>
>> # Then the amount of clearance is set to the greater of: # 1. The
>> amount necessary to place the border edge of the block even #
>> with the bottom outer edge of the lowest float that is to be #
>> cleared. # 2. The amount necessary to place the top border edge of
>> the block #    at its hypothetical position.
>>
>> yet the spec now explicitly allows an alternative "Behaviour 2":
>>
>> # Alternatively, clearance is set exactly to the amount necessary
>> to # place the border edge of the block even with the bottom outer
>> edge # of the lowest float that is to be cleared.
>>
>
> We resolved on this a long time ago. We decided that both scenarios
> were valid that is why margin-collapse-clear-005 and 011 have two
> possible correct renderings.

Exactly.

> The problem is that margin-collapse-164 was never updated to account
> for the possibility of two different behaviors. We need to update
> margin-collpase-164 to have two possible solutions that will match
> the 2 behaviors called out in the spec and the
> margin-collpase-clear-005 and 011 cases.

Ah, you want a test case with precisely two possible pass conditions, 
rather than no test case at all.  (Do we have other complex test cases 
like that in the test suite?)

It might take a bit of cunning, but it's probably achievable!

> I believe we as a group preferred Behavior 1 (which is the current
> behavior of margin-collapse-164) but we were unwilling/unable change
> the spec to that because we would not have interoperability to pass
> the test suite and move the spec to REC. There was also an agreement
> at the Seattle F2F that we would in the next update of our browsers
> fix the margin collapse issue to pass the margin-collapse-164 case
> and match Behavior 1. As of today I only see IE10 has gone and fixed
> the issue. No other browser has fixed the margin collapse bug yet.

Interesting.  I thought this was genuinely pending a web compat review, 
not a ploy to pass REC!

Cheers,
Anton Prowse
http://dev.moonhenge.net
Received on Monday, 21 May 2012 18:11:51 GMT

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