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Re: Coordinate system stuff

From: Cameron McCormack <cam@mcc.id.au>
Date: Thu, 4 Sep 2008 14:51:15 +1000
To: public-svg-wg@w3.org
Message-ID: <20080904045115.GE3118@arc.mcc.id.au>

Cameron McCormack:
> Second, the definition of “current transformation matrix” in the intro
> chapter says:
> 
>   The current transformation matrix defines the mapping from the user
>   coordinate system into the viewport coordinate system.
>    — http://dev.w3.org/SVG/profiles/1.2T/publish/intro.html#TermCurrentTransformationMatrix
> 
> But in the Coordinates chapter, section 7.7.4 defines the CTM as
> including the user transform:
> 
>   This [the CTM] is the product of all coordinate system transformations
>   that apply to an element, effectively mapping the element into a
>   coordinate system that is then transformed into device units by the
>   SVG user agent. 
>   …
>   With the above definitions for U, VB, and TS, the CTM for the
>   rectangle with xml:id="elt" is:
>     CTM(elt) = U.VB(root).TS(elt)
>              = U.VB(root). Txf(g-n).[...].Txf(g-0).Txf(elt)
>    — http://dev.w3.org/SVG/profiles/1.2T/publish/coords.html#transform-ctm
> 
> Should the CTM inclue the user transform or not?

After looking at this, I think it should, since the viewport coordinate
system is affected by the user transform (currentTranslate, etc.).  So
I’m closing ACTION-2168 with no changes to the spec.

Thanks,

Cameron

-- 
Cameron McCormack ≝ http://mcc.id.au/
Received on Thursday, 4 September 2008 04:51:57 UTC

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