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Re: Possibly missing fences and accents in the MathML Operator Dictionary

From: David Carlisle <davidc@nag.co.uk>
Date: Tue, 29 Jun 2010 11:50:42 +0100
Message-ID: <4C29D002.3060302@nag.co.uk>
To: Frédéric WANG <fred.wang@free.fr>
Cc: "www-math@w3.org" <www-math@w3.org>
On 29/06/2010 10:18, Frédéric WANG wrote:
> Hi all,

Thanks for the comments, this is a personal reply, not speaking for the 
working group.
>
> The Asana Math font [http://tug.ctan.org/pkg/asana-math] contains
> various glyphs to stretch mathematical operators but some of them are
> not included in the MathML Operator Dictionary. Here is the list (I use
> the Unicode names):
>
> - LEFT SQUARE BRACKET WITH QUILL, RIGHT SQUARE BRACKET WITH QUILL, LEFT
> S-SHAPED BAG DELIMITER, RIGHT S-SHAPED BAG DELIMITER which seem to be
> stretchy fences.

Personally I'd leave this. There are a lot of characters in unicode (and 
more get added each time) the ones that look as if they might stretch, 
and the ones for which real fonts actually have stretching information 
is not something we can really track. The operator dictionary tries to 
show a basic setup and there will always need to be font and system 
specific differences. That said, if there are really only 4 missing 
fences to get full support for this font, I suppose adding those lines 
is something we should consider.

>
> - COMBINING TILDE, COMBINING OVERLINE, COMBINING BREVE, COMBINING CARON,
> COMBINING LOW LINE, COMBINING DOUBLE LOW LINE, COMBINING DOUBLE
> OVERLINE, COMBINING LEFT HARPOON ABOVE, COMBINING RIGHT HARPOON ABOVE,
> COMBINING LEFT ARROW ABOVE, COMBINING RIGHT ARROW ABOVE, COMBINING LEFT
> RIGHT ARROW ABOVE, COMBINING WIDE BRIDGE ABOVE which seem to be stretchy
> accents. Note that most of them already have a "non-combining" version
> in the dictionary and that the circumflex accent exists in both
> versions. Also, breve is not stretchy in the operator dictionary, while
> it looks like the author of Asana Math wants it to stretch.

I'd be against adding  combining characters to the operator dictionary 
(some may be there historically but I'd not want to add any more)
combing characters are designed to combine which means they should 
follow the base character directly in the unicode text run. This makes 
sense even in an XML context in things like negated operators
<mo>[base][negation slash]</mo> but for strechy fences where the 
character is the full content of the mo, the combining character is not 
appropriate. The font may want to support stretching these characters 
for non-xml uses, or if users do this anyway, but I don't think that the 
mathml spec should encourage this usage.

>
> --
> Frédéric Wang.
> Website <http://www.maths-informatique-jeux.com/> - Weblog
> <http://www.maths-informatique-jeux.com/blog/frederic/>

David

>
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Received on Tuesday, 29 June 2010 10:51:16 GMT

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