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Re: [css3-values][css3-page] Viewport-percentage length units in the page context.

From: Leif Arne Storset <lstorset@opera.com>
Date: Fri, 19 Oct 2012 15:33:47 +0200
To: "WWW Style" <www-style@w3.org>, "Simon Sapin" <simon.sapin@kozea.fr>
Message-ID: <op.wmfhalsntmo5g6@localhost.localdomain>
On Sat, 13 Oct 2012 13:57:11 +0200, Simon Sapin <simon.sapin@kozea.fr>  
wrote:

> Le 13/10/2012 10:55, Simon Sapin a écrit :
>> While writing this, I notice another kind of cycle. css3-page defines:
>> "The page context inherits from the root element." How about this?
>>
>>       :root { font-size: 1vw }
>>       @page { width: 200em }
>>
>> I can’t find a satisfying way to resolve this one. Any ideas?

How about disallowing the least useful of the two? In my mind, expressing  
font-size in viewport units seems least useful, and there's no precedent  
for sizing fonts relative to a box.

> It’s actually worse than I thought. With css3-page, the size of the page  
> (and thus, of the ICB) can change in across pages in the same document.  
> css3-values explicitly says that vw and friends are affected.
>
> However, the computed value of most length-based properties is supposed  
> to be absolute. For example, em-based values are made absolute at this  
> point, much earlier than layout. What about vw? Computed values apply to  
> elements, not box fragments. Should every element have a (potentially)  
> different set of computed values for every page?

Doesn't this apply to percentage lengths as well? Their computed values  
are still percentages (for relevant properties). What happens for them  
when laid out over multiple differently-sized pages?

-- 
Leif Arne Storset
Opera Software
Oslo, Norway
Received on Friday, 19 October 2012 13:34:20 GMT

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