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Re: [css3-writing-modes] implementation costs for logical properties

From: fantasai <fantasai.lists@inkedblade.net>
Date: Tue, 26 Oct 2010 09:40:27 -0700
Message-ID: <4CC7047B.2030402@inkedblade.net>
To: Håkon Wium Lie <howcome@opera.com>
CC: koba Mobile2 <koba@antenna.co.jp>, John Daggett <jdaggett@mozilla.com>, www-style@w3.org
On 10/26/2010 01:21 AM, Håkon Wium Lie wrote:
> Also sprach fantasai:
>   >  That said, the performance and memory considerations for logical
>   >  properties are not as bad as they seem at first glance. Since
>   >  you can compute the logical-physical equivalence at cascade time,
>   >  you only need to store one set of data per element (physical or
>   >  logical, depending on your layout architecture). So the extra
>   >  memory load is almost nothing.
> In the formatting process, you need to remember ~35 new properties for
> every element, right? You can only let go of these when you know the
> computed value of 'writing-mode' for that element.

Which you can figure out while cascading. Basically you need to
cascade 'writing-mode' and 'direction' to get their computed values
first, then cascade the other properties and store their values.

> And what about the
> DOM, are you saying that the DOM will not offer any information about
> logical properties after formatting has been done? So, if
> 'writing-mode' changes through the DOM, logical properties don't
> apply?

The computed value of the logical properties is equal to the computed
value of the physical properties, so yes, you would need DOM access,
but it would primarily be a translation layer, not a storage layer.

Received on Tuesday, 26 October 2010 18:20:15 UTC

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