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[CSS21] Issue 120 (again)

From: Bert Bos <bert@w3.org>
Date: Wed, 6 Oct 2010 18:57:18 +0200
To: W3C style mailing list <www-style@w3.org>
Message-Id: <201010061857.19132.bert@w3.org>
http://wiki.csswg.org/spec/css2.1#issue-120

The WG agreed to the definitions from Fantasai's message[1]. However, 
while looking at issue 142, I noticed that one of the changes in that 
message didn't just replace a long phrase with a shorter one, it 
actually introduced a change.

Bullet 2 in section 10.1 defines the "containing block" for certain 
kinds of elements. It used to say:

    [...] the containing block is formed by the content edge of the
    nearest block-level, table cell or inline-block ancestor box.

Now it uses the newly defined term "block container box" and says:

    [...] the containing block is formed by the content edge of the
    nearest block container ancestor box.

(Issue 142 is about moving and explaining that word "ancestor", but that 
is not relevant now.) When checking issue 120, we all apparently 
overlooked that this misses the case of the ancestor being a table. A 
table is a block-level element, so under the old definition, the 
content edge of the table is the containing block. But under the new 
definition, the table is ignored, and instead an ancestor of the table 
provides the containing block. That is because the definition of "block 
container box" says:

    Except for table boxes, which are described in a later chapter, and
    replaced elements, a block-level box is also a block container box.
    A block container box either contains only block-level boxes or
    establishes an inline formatting context and thus contains only
    inline-level boxes.

Which implies that a table box is not a "block container box."

I think bullet 2 of 10.1 should be amended so that a table establish a 
containing block again.

(I'm not suggesting concrete text yet, because issue 142 may change the 
text, too.)

[1] http://lists.w3.org/Archives/Public/www-style/2010Aug/0399.html



Bert
-- 
  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/people/bos                               W3C/ERCIM
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
Received on Wednesday, 6 October 2010 16:58:14 GMT

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