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Re: [CSS21] Single viewport

From: Ian Hickson <ian@hixie.ch>
Date: Sun, 28 Aug 2005 20:46:08 +0000 (UTC)
To: Chris Lilley <chris@w3.org>
Cc: www-style@w3.org
Message-ID: <Pine.LNX.4.62.0508282039570.27381@dhalsim.dreamhost.com>

On Thu, 25 Aug 2005, Chris Lilley wrote:
> 
> In 9.1.1
> 
>   There is at most one viewport per canvas, but user agents may render
>   to more than one canvas (i.e., provide different views of the same
>   document).
>   http://www.w3.org/TR/2005/WD-CSS21-20050613/visuren.html#viewport
>
> Its not clear whether this conflicts with SVG or not. Maybe if [you] 
> said that CSS establishes only a single viewport, it would not then 
> appear to conflict with graphical systems where multiple viewports are 
> common.

Multiple viewports on a single canvas in CSS is impossible; for example 
fixed positioned elements would need to be in multiple places at once in 
such a scenario, and boxes whose size depended on the viewport would have 
multiple sizes simultaneously (note that the ICB dimensions typically 
depend on the width, and sometimes height, of the viewport, so this is 
pretty much a ubiquitous situation).

Could you expand on which graphical systems allow multiple viewports to 
exist on a single canvas? (It is clear that multiple canvases may exist 
for a single document, each with its own viewport, of course.)

Also, since this statement is specifically about CSS (it's in a CSS spec, 
for one, and deep inside the internals of the rendering model at that), it 
is unclear why you believe that the CSS specification should explicitly 
state that it is talking about CSS here.

Further clarifications from the SVG working group as to the reasoning 
behind this request would be greatly appreciated and would allow us to 
expedite our resolution of this issue.

Thanks in advance,
-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Sunday, 28 August 2005 20:46:16 GMT

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