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Coordinate system stuff

From: Cameron McCormack <cam@mcc.id.au>
Date: Mon, 18 Aug 2008 10:42:09 +1000
To: public-svg-wg@w3.org
Message-ID: <20080818004208.GB18063@arc.mcc.id.au>

Hello WG.

Two things.

First, since apart from 7.7.5, the subsections of section 7.7 aren’t
particularly related to constrained transformations, I suggest that the
sections be reorganised thus:

  …
  7.6 Transformations that apply to an element   (or some similar title)
        7.6.1 The user transform
        7.6.2 ViewBox to viewport transformation
        7.6.3 Element transform stack
        7.6.4 The current transformation matrix
  7.7 The 'transform' attribute
        7.7.1 The TransformList value
        7.7.2 The TransformRef value
  …

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?

Thanks,

Cameron

-- 
Cameron McCormack ≝ http://mcc.id.au/
Received on Monday, 18 August 2008 00:43:05 UTC

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