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Re: Alignment and Embellished Operators

From: Sam Dooley <sam@integretechpub.com>
Date: Fri, 09 Apr 2010 13:28:43 -0600
Message-Id: <201004091929.o39JTI4Z017563@aragorn.integretechpub.com>
To: Frédéric WANG <fred.wang@free.fr>, "www-math@w3.org" <www-math@w3.org>
Hi Frédéric,

I would want to think about this more fully, but my first impression
would be that when the over/under script is an embellished operator,
then the <mo> at its core is the element that should be horizontally
centered (or left/right aligned) with the base, not the script as a
whole, and the embellishments should position relative to core <mo>
element, just as they would if the embellished operator appeared in
any other context.

I can imagine it should be possible to add such words to the spec
as a clarification, assuming this scheme is feasible to implement,
and the existing alignment values would give the expected result.

Would you agree?  And would such an implementation give you a way
to close out this ten-year old bug?

Thanks,
Sam

At 12:23 PM 4/9/2010, Frédéric WANG wrote:
>Hi all,
>
>I would like to mention an issue about embellished operators that was reported ten years ago in Bugzilla. Consider the files given as attachment. In the XHTML page, two embellished operators are used as scripts of a <underover/>. The screenshot shows a sample rendering: the two arrows are correctly stretched to the size of the base of the <underover/>. However, the center of the children are aligned and, because of the size added by the embellishments, the arrows do not cover the base of the <underover/>. I suppose you agree that the expected rendering would be to align the arrows with the base, using some kind of automatic positioning for the scripts?
>
>Now, MathML3 introduces a new attribute "align" for munderover (and under/over), that can only takes three values: "left" | "right" | "center". In the example I give, none of these values will give the expected result. It seems to me that either a new default value "auto" should be added or say that automatic alignment of embellished operator overrides the value of the align attribute. I think the latter is better: auto would be redundant with center in all the other cases, I don't see why one would refuse to align the stretched symbol with the base and (for munderover) this will allow to apply automatic positioning to only one of the two scripts.
>
>Frédéric Wang
Received on Friday, 9 April 2010 20:07:45 GMT

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