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Re: Proposal: Nesting SVG Graphics Elements

From: Steve Schafer <steve@fenestra.com>
Date: Thu, 29 Nov 2012 19:42:40 -0500
To: SVG public list <www-svg@w3.org>
Message-ID: <1svfb8lv6akisq6qp7mfkpn0apog4klr0p@4ax.com>
On Thu, 29 Nov 2012 14:52:53 -0500, you wrote:

>Hi, SVG WG-
>
>I have a proposal that may make SVG2 easier to understand and use for 
>people already familiar with the HTML+CSS world.
>
>The basic idea is to allow rendering elements to also serve as container 
>elements, with child rendering elements also rendered. (This is 
>currently not very clearly specified in SVG1.1.)
>
>Currently, to associate 2 rendering elements, you have to use a group, 
>like this:
>
>   <g id="g1">
>     <rect id="r1" x="5" y="10" width="70" height="40" fill="yellow" 
>stroke="red" />
>     <text id="t1" x="15" y="35" font-size="12" fill="crimson">Some 
>label</text>
>   </g>
>
>This can be problematic for positioning the elements relative to one 
>other, and to moving the whole unit (yes, you can use a transform, but 
>for drag-n-drop, you have to know what to grab and drag).
>
>We could allow authors to do this by simply nesting the text element, 
>which would render on top of the rect (using the same Painter's Model), 
>and could be positioned relative to the new established coordinate space 
>of the parent shape:
>
>   <rect id="r2" x="5" y="10" width="70" height="40" fill="yellow" 
>stroke="red">
>     <text id="t2" x="50%" y="50%" font-size="12" fill="crimson">Some 
>label</text>
>   </rect>
>
>This also carries the benefit of being more accessible and semantic. 
>After talking to several designers, I think it matches the conceptual 
>model of containment and presentation from HTML and CSS (though it is 
>distinctly different in some ways, since SVG merges the content and 
>presentation modes).
>
>The nesting relationship wouldn't have to be one of "visual containment" 
>like in the label example... it can be a simple one-directional 
>constraint system, which is not hard to deal with:
>
>   <g id="g3">
>     <rect id="r3" x="100" y="10" width="40" height="40"/>
>     <circle id="c3" cx="170" cy="30" r="20"/>
>   </g>
>
>Would be visually equivalent to:
>
>   <rect id="r4" x="100" y="10" width="40" height="40">
>     <circle id="c4" cx="70" cy="20" r="20"/>
>   </rect>
>
>And when r4 is moved, c4 keeps the same relationship relative to it.
>
>We would need to sort out many detail, but I think this is doable fairly 
>simply, and has a low risk of backwards incompatibility.
>
>This also solves some problems that I see coming up in SVG2 and Connectors.
>
>I'd like discuss this briefly in the telcon, before I develop it further.

It seems to me that you're trying to embed what is more properly handled
as SVG editor functionality into the base language. My personal
preference would be to keep the SVG representation itself as "lean and
mean" as possible, and put all of the interactive manipulation
expressiveness into a higher layer.

Steve Schafer
(interested observer)
Received on Friday, 30 November 2012 00:43:31 GMT

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