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[Bug 15937] Clarify that units in the matrices are CSS pixels

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Date: Sun, 29 Apr 2012 06:45:05 +0000
To: public-css-bugzilla@w3.org
Message-Id: <E1SONsX-00031w-EU@jessica.w3.org>
https://www.w3.org/Bugs/Public/show_bug.cgi?id=15937

--- Comment #5 from Aryeh Gregor <ayg@aryeh.name> 2012-04-29 06:45:04 UTC ---
The units for matrix() and matrix3d() aren't all pixels.  For matrix(), the
first four entries are unitless and the last two are in pixels.  For
matrix3d(), entries 0-2, 4-6, 8-10, and 15 (0-indexed) are unitless; entries
12-14 have units of pixels; and entries 3, 7, and 11 have units of 1/pixels. 
I.e.,

 [ #    #    #   px]
 [ #    #    #   px]
 [ #    #    #   px]
 [1/px 1/px 1/px # ]

where # is a unitless number.

I don't think we need to say this explicitly.  Instead, we should say how the
matrices are used to transform coordinates, and make it clear that the input
and output coordinates are in pixels.  The units of the matrix entries will
follow from that without having to introduce confusing and unhelpful stuff like
1/px explicitly.

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Received on Sunday, 29 April 2012 06:45:08 GMT

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