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Re: Coordinate spaces in SVG and CSS

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Fri, 30 Apr 2010 17:15:35 -0700
Message-ID: <x2gdd0fbad1004301715q66a3798dlde089717198ba934@mail.gmail.com>
To: fantasai <fantasai.lists@inkedblade.net>
Cc: public-fx@w3.org
On Tue, Apr 27, 2010 at 4:53 PM, fantasai <fantasai.lists@inkedblade.net> wrote:
> Here's a rough draft of a terminology rewrite that might help.
> You'll need to add "object view box".
> <h2 id="sizing-objects">Sizing Images and Replaced Content</h2>
> <p>Images and replaced content in CSS can offer many types of sizing
> information to CSS, or none at all. This section defines generically
> the size negotiation model between the image or replaced content
> object and the CSS layout algorithms. First, the following terms are
> defined:</p>
> <dl>
>  <dt><dfn>intrinsic dimensions</dfn></dt>
>  <dd>The intrinsic dimensions are defined are the object's preferred,
>    natural size or aspect ratio, if any. There can be an <dfn>intrinsic
>    height</dfn> and <dfn>intrinsic width</dfn>, defining a definite
>    rectangle. (Most bitmap images fall into this category.) There can
>    be an <dfn>intrinsic aspect ratio</dfn> defining the relation of the
>    width to the height, but no definite size. (SVG images designed to
>    scale may fall into this category.) There can be just an intrinsic
>    height or width. Or there can be no intrinsic dimensions at all,
>    implying that the object has no preferred size or aspect ratio.
>    (Embedded documents are often assumed to have no intrinsic size.)
>    If an object (such as an icon) has multiple sizes, then the largest
>    size is used. If it has multiple aspect ratios of that size (or of
>    no size), then the aspect ratio closest to the aspect ratio of the
>    default image sizing area is use <span class="issue">This is pretty
>    arbitrary</span>.</dd>
>  <dt><dfn>specified size</dfn></dt>
>  <dd>The specified size of an object is given by CSS. The specified
>    size can be a definite width and height, a set of constraints, or
>    a combination thereof.
>  <dt><dfn>CSS view box</dfn></dt>
>  <dd>The CSS view box is the result of transforming the intrinsic
>    dimensions into a concrete size using the specified size and the
>    layout rules in CSS.  A CSS view box always has a definite height
>    and width.</dd>
>  <dt><dfn>default object sizing area</dfn></dt>
>  <dd>The default object sizing area is a rectangle with a definite
>    height and width that is used to resolve the CSS View box when
>    dimensions are missing from both the specified dimensions and
>    the intrinsic dimensions.</dd>
> </dl>
> I outlined the negotiation model here (bottom):
>  http://lists.w3.org/Archives/Public/www-style/2010Feb/0164.html
> What we probably want is to merge that with what you have in the
> draft.

That did indeed help.  I've committed a new revision of Images based
on this feedback, and which should, I think, be technically correct
with the interactions between the various properties and dimensions.
I'm still defining sizing explicitly, because I think it's somewhat
non-obvious how things are supposed to act in several cases, but I
think I'm taking in the right information and producing the right
outputs now.


Received on Saturday, 1 May 2010 00:16:27 UTC

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