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Re: [CSS21] Proposal to define "Block container element"

From: Anton Prowse <prowse@moonhenge.net>
Date: Wed, 18 Jul 2012 09:55:06 +0200
Message-ID: <50066BDA.1030900@moonhenge.net>
To: www-style@w3.org
CC: fantasai <fantasai.lists@inkedblade.net>
On 18/07/2012 00:50, fantasai wrote:
> On 07/14/2012 07:12 PM, Anton Prowse wrote:
>>
>> (1) The definition of "principal block-level box" is extended to
>> "principal box" for a wider range of elements (inline block,
>> inline table and table cell in addition to block-level elements). This
>> has no effect on the rest of the spec, since the only
>> cases where the principal box is referred to is in the context of
>> block-level elements/boxes.
>>
>> (2) The term "block container element" is introduced to mean an
>> element whose principal box is a block container box, ie a
>> block, list-item, inline-block, table, inline-table or table-cell in
>> CSS21.
>
> I don't have a problem with defining these terms, however I do have
> a problem with defining "principal box" generally in 9.2.1, which
> is titled "Block-level elements and block boxes". If we're defining
> it, it should go in 9.2.

I see your point, of course; but 9.2.1 already defines "block container 
box" which is nothing to do with block-level elements or block boxes 
either, and I was trying to disrupt the spec text at little as possible.

But here's a proposal that factors the block container stuff out into 9.2:

Proposal B:

   # 9.2 Controlling box generation
   #
   # The following sections describe the types of boxes that may be
   # generated in CSS 2.1. A box's type affects, in part, its behavior
   # in the visual formatting model. The 'display' property, described
   # below, specifies a box's type.
   #
   # <ins>Each _block-level element_<link to 9.2.1>, inline block,
   # inline table and table cell generates a principal box that contains
   # descendant boxes and generated content and is also the box involved
   # in any positioning scheme. Some block-level elements may generate
   # additional boxes in addition to the principal box: 'list-item'
   # elements. These additional boxes are placed with respect to the
   # principal box.</ins>
   #
   # 9.2.1 Block-level elements and block boxes
   #
   # Block-level elements are those elements of the source document
   # that are formatted visually as blocks (e.g., paragraphs). The
   # following values of the 'display' property make an element
   # block-level: 'block', 'list-item', and 'table'.
   #
   # <del>Block-level boxes are boxes that participate in a block
   # formatting context. Each block-level element generates a principal
   # block-level box that contains descendant boxes and generated
   # content and is also the box involved in any positioning scheme.
   # Some block-level elements may generate additional boxes in
   # addition to the principal box: 'list-item' elements. These
   # additional boxes are placed with respect to the principal box.</del>
   #
   # <ins>The principal box of a block-level element is a block-level
   # box. Block-level boxes are boxes that participate in a block
   # formatting context.</ins> Except for table boxes, which are
   # described in a later chapter, and <ins>the principal box of</ins>
   # 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.  <del>Not all block container boxes are block-
   # level boxes: non-replaced inline blocks and non-replaced table
   # cells are block containers but not block-level boxes.</del> Block-
   # level boxes that are also block containers are called block boxes.
   #
   # <ins>Block container elements are elements whose principal box
   # is a block container box. The following values of the
   # 'display' property make an element a block container: 'block',
   # 'list-item', 'table', 'inline-block', 'inline-table'.  Non-replaced
   # inline blocks and non-replaced table cells are block containers but
   # are not block-level.
   #
   # The three terms "block-level box," "block container box," and
   # "block box" are sometimes abbreviated as "block" where unambiguous.

Note: the only change from Proposal A is that a paragraph has moved from 
9.2.1 to 9.2.

Note: I chose to move the bit about list items and their additional box 
to 9.2.  Whilst not strictly necessary for this proposal since that 
sentence is about block-level elements, elsewhere I propose[1] to modify 
this to mention the table box of table elements  - and I wanted to 
mention the table box of inline table elements too, but since the 
sentence was talking about block-level elements I didn't.  Moving the 
bit about additional boxes to the more neutral 9.2 makes it easy to 
update that proposal to mention inline tables at that position.


[1] http://lists.w3.org/Archives/Public/www-style/2012Jul/0414.html

Cheers,
Anton Prowse
http://dev.moonhenge.net
Received on Wednesday, 18 July 2012 07:55:41 GMT

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