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Re: Accents in the operator dictionary

From: Frédéric WANG <fred.wang@free.fr>
Date: Sat, 24 Apr 2010 23:19:18 +0200
Message-ID: <4BD36056.7020802@free.fr>
To: www-math@w3.org
Yes, Mozilla should probably set direction:horizontal on this operator. 
I don't know what is this infix operator "_" so I can not say whether it 
should also be stretchy by default. However, even with this change, the 
infix and postfix forms are supposed to be displayed differently in 
munderover/mover/munder, since the latter has an "accent" property:

http://www.w3.org/TR/MathML3/chapter3.html#id.3.4.5.2 (see how is 
computed the default value of accent)

My idea was to assume that the user wants the form with an "accent" 
property when he uses an operator as the child of an 
munderover/mover/munder other than the base. I was thinking there is a 
relationship between accent and postfix, but it may not be true. Hence a 
better rule is to give a higher priority to the forms with a "accent" 
property when trying to determine the form of an operator (again, used 
as the child of an munderover/mover/munder other than the base). But 
still, this would require to change the spec to give flexibility on the 
heuristic rules to determine the form of an operator.
> Yes, the spec gives implementations flexibility in operator
> dictionary entries but less flexibility in when to use them.
>
> Implementations do however have responsibility (even if not
> flexibility) to decide in which directions an operator gets
> stretched.
>
> "It is up to the renderer to know in which directions it is
> reasonable to stretch a character"
> http://monet.nag.co.uk/~dpc/draft-spec/chapter3.html#presm.op.stretch
>
> Would it be reasonable to make infix operator "_" default stretchy
> and stretch by default in all horizontal stretching situations but
> never in vertical stretching situations?
>
> Certainly with "_", vertical stretching is not reasonable.  I
> don't know whether there are any characters that would normally
> stretch horizontally as accents (default stretchy) but only
> vertically when there is explicit stretchy="true" (default not
> stretchy).
>    

-- 
Frédéric Wang.
www.maths-informatique-jeux.com <http://www.maths-informatique-jeux.com>
www.maths-informatique-jeux.com/international 
<http://www.maths-informatique-jeux.com/international>
Received on Saturday, 24 April 2010 21:16:52 GMT

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