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Re: ISSUE: current user space and <svg>

From: Jon Ferraiolo <jon.ferraiolo@adobe.com>
Date: Tue, 11 Jan 2005 00:15:13 -0800
To: Jonathan Watt <jonathan.watt@strath.ac.uk>, www-svg@w3.org
Message-id: <>
The key thing is that there are often two "current user coordinate systems" 
for a given element - the one before you process 'transform' or 'viewBox' 
and the one after you process the transformations associated with these 

Section 7.4 of the SVG 1.1 spec 
(http://www.w3.org/TR/SVG11/coords.html#EstablishingANewUserSpace) includes 
the following snippet in the first paragraph:

The <file://coords.html#TransformAttribute>transform and 
<file://coords.html#ViewBoxAttribute>viewBox attributes transform user 
space coordinates and lengths on sibling attributes on the given element 
(see <file://coords.html#TransformAttributeEffectOnSiblingAttributes>effect 
of the transform attribute on sibling attributes and 
<file://coords.html#ViewBoxAttributeEffectOnSiblingAttributes>effect of the 
viewBox attribute on sibling attributes) and all of its descendants.

and further on in the same section (if you follow the link to "effect of 
the transform attribute on sibling attributes):
The transform attribute is applied to an element before processing any 
other coordinate or length values supplied for that element. In the element

<rect x="10" y="10" width="20" height="20" transform="scale(2)"/>

the x, y, width and height values are processed after the current 
coordinate system has been scaled uniformly by a factor of 2 by the 
transform attribute

However, I agree that it makes sense to add some additional clarifications 
to the SVG spec.


At 09:19 AM 1/10/2005, Jonathan Watt wrote:

>What is the "current user coordinate system" for an element defined as 
>(with emphesis on *current*, *user* and *element*)? Is it correct to say 
>that it's the coordinate system refered to by the element's "coordinate" 
>attributes (such as 'x' and 'y')?
>I'm specifically interested to know what the *current* user coordinate 
>system is for an 'svg' element. Is it the user coordinate system that the 
>element exists in (the one established by the 'svg' element's parent, and 
>to which it's "coordinate" attributes refer to)? Or is it the user space 
>it itself establishes via it's viewBox attribute?
>I don't believe this can be clearly answered from the contents of the specs.
Received on Tuesday, 11 January 2005 12:41:16 UTC

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