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

From: Simon Sapin <simon.sapin@kozea.fr>
Date: Fri, 19 Oct 2012 22:26:14 +0200
Message-ID: <5081B766.6000800@kozea.fr>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: Leif Arne Storset <lstorset@opera.com>, WWW Style <www-style@w3.org>
Le 19/10/2012 21:46, Tab Atkins Jr. a écrit :
> On Fri, Oct 19, 2012 at 9:00 AM, Simon Sapin<simon.sapin@kozea.fr>  wrote:
>> >I think that the only sane way to handle viewport-percentage units in paged
>> >media is to treat them like other layout-based percentages: keep the
>> >percentage in the computed value and only convert it to an absolute unit in
>> >used values.
>> >
>> >This should not change the layout, even if these computed values end up
>> >being inherited: the initial containing block is still the same. It might be
>> >visible in the CSSOM, but I’m not sure.
>> >
>> >Spec-wise however, this is in contradiction with the "Computed value" line
>> >of every property that accept <length>.
> No, this doesn't work.  It*will*  change the layout, because the page
> size*is*  the initial containing block for the contents on that page.
>
> It seems clear that this is a trivial circular dependency, and we
> should resolve it in the standard way, which is just having them
> compute to 'auto' or similar.

Sorry, I should have made two separate threads. There are two separate 
issues:

First, cycles: viewport units in <length> are based on the initial 
containing block which is based on the page size which is defined by 
properties that use length. We need one way or another to resolve those.

Second issue: if an element is fragmented over multiple pages, the page 
size may vary. However the computed value for eg. 'margin-left: 3vw' is 
supposed to be absolute. Does that mean that the element has *multiple* 
sets of computed values, one for each page?

-- 
Simon Sapin
Received on Friday, 19 October 2012 20:26:50 GMT

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