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Re: [MathML3-last-call] add a notion of "natural" direction for operators to prevent weird stretching

From: Neil Soiffer <Neils@dessci.com>
Date: Thu, 19 Nov 2009 17:42:31 -0800
Message-ID: <d98bce170911191742q212364crb86e52308361450d@mail.gmail.com>
To: www-math@w3.org
 Frédéric,

My apologies for this late reply.  In reviewing last call comments, it
appears that no one ever responded to your comment.

The WG discussed your ideas and agreed with you that the text could use some
clarification that stretchy="true" does not require stretching a character
in all possible directions.  The new language is:

"There is no provision in MathML for specifying in which direction
(horizontal or vertical) to stretch a specific character or operator;
rather, when stretchy="true" it should be stretched in each direction
for which stretching is possible and reasonable for that character.
It is up to the renderer to know in which directions it is reasonable to
stretch a character, if it can stretch the character."


/w3ccvs/WWW/Math/Group/spec/xml/presentation-markup.xml,v  <--
presentation-markup.xml
new revision: 1.306; previous revision: 1.305


We would appreciate a response by Monday as to whether this change is
satisfactory to you -- we need to record all responses so that we can submit
documentation to request moving to a Candidate Recommendation phase.

Thanks,

Neil Soiffer
Senior Scientist
Design Science, Inc.
www.dessci.com
~ Makers of MathType, MathFlow, MathPlayer, MathDaisy, Equation Editor ~


In section 3.2.5.8 "Stretching of operators, fences and accents", it is
> written that an operator should be stretched in each possible direction:
>
> "There is no provision in MathML for specifying in which direction
> (horizontal or vertical) to stretch a specific character or operator;
> rather, when stretchy="true" it should be stretched in each direction
> for which stretching is possible. It is up to the renderer to know in
> which directions it is able to stretch each character."
>
> Currently, it seems that the stretching directions that one would
> expect for an operator are only determined by the technical constraints
> imposed to the renderer. Nevertheless, this overlooks the fact that
> renderer could use techniques to make possible stretching in both
> direction, for any single character. For instance, some graphics library
> allow "scale transform" (as defined in chapter 7 of SVG rec) that can be
> used for this purpose. In that case, some weird stretching could happen
> such that a vertical arrows stretched horizontally.
>
> Hence I suggest to add a notion of "natural" direction that will be
> used when an operator needs to be stretched (with either a default or
> explicit stretchy=true). For instance the working draft already suggests
> "vertical" direction for most fences, "horizontal" direction for some
> accents, and both directions for diagonal arrows. Apart from the
> examples given in the working draft, it would of course be up to the
> renderer to determine what direction is "natural" for a given operator.
> For example, an integral symbol is likely to be defined as "naturally"
> vertical.
>
Received on Friday, 20 November 2009 01:43:05 GMT

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