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Re: [MathML3-PR] Alignment with display="block"

From: Bruce Miller <bruce.miller@nist.gov>
Date: Thu, 02 Sep 2010 11:32:46 -0400
Message-id: <4C7FC39E.2070709@nist.gov>
To: Sam Dooley <sam@integretechpub.com>
Cc: Alex Milowski <alex@milowski.org>, "www-math@w3.org" <www-math@w3.org>
The main intent of that passage was to clarify
that the math element can act as either a block
or inline element, depending on the display attribute.
In particular, when it is inline, it should not
have extraneous whitespace added and should align
baselines.

As far as the alignment of display blocks, it is
intentionally abstract. So, the containing document
type can specify it however it likes, as Murray
suggests. In the case of html, it could default
whatever way you like, but would be appropriate
to set with CSS, as Sam suggests.

[Also speaking personally, but we're getting close
to group concensus, anyway :> ]

On 09/02/2010 11:05 AM, Sam Dooley wrote:
>
> It seems to me a user agent has leeway to supply default style rules
> that support the preference for centered/indented block math elements,
> despite the general default for other block elements, in the same way
> legacy HTML attributes are given behaviors in terms of CSS properties.
>
> I think the intent of 2.2.1 is simply to recommend that the user agent
> take the display attribute into account when it produces a rendering,
> without over-constraining what that rendering should look like.
>
> So if a user agent centers the block math elements by default, and if
> users must supply style rules to achieve other behaviors, that for me
> would be one possible conforming behavior.
>
> Sam
> [speaking personally, not for the working group]
>
>
> At 08:30 AM 9/2/2010, Alex Milowski wrote:
>> While looking into what a user agent such as WebKit should do by
>> default for when math elements have display="block", we've read
>> through Section 2.2.1 where it says:
>>
>> "Moreover, when the math element is embedded in a larger document,
>> a block math element should be treated as a block element as
>> appropriate for the document type (typically as a new vertical block),
>> whereas an inline math element should be treated as inline (typically
>> exactly as if it were a sequence of words in normal text)."
>>
>> The default user agent behavior for a block in XHTML/HTML5 is
>> to rendered a block left aligned (or writing start direction aligned).
>> As such, I would interpret the correct default behavior by a user agent
>> rendering a 'math' element with display="block" to be the same.
>>
>> There is a great preference out there for block level Mathematics
>> to be centered.  The second preference would be for it to be
>> at least indented from the normal block flow.
>>
>> Is it the intention of MathML3 for block level Mathematics to default
>> to left or writing direction start alignment?
>>
>> If so, that would require users to add additional rules to their CSS
>> to change to centered or indented block Mathematics.
>>
>> --
>> --Alex Milowski
>> "The excellence of grammar as a guide is proportional to the paucity of the
>> inflexions, i.e. to the degree of analysis effected by the language
>> considered."
>>
>> Bertrand Russell in a footnote of Principles of Mathematics
>
>
Received on Thursday, 2 September 2010 15:33:46 GMT

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