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Re: [css3-writing-modes] a third option for implementing logical properties

From: Håkon Wium Lie <howcome@opera.com>
Date: Mon, 25 Oct 2010 11:29:47 +0200
Message-ID: <19653.19979.639951.403701@gargle.gargle.HOWL>
To: David Hyatt <hyatt@apple.com>
Cc: www-style@w3.org
Also sprach David Hyatt:

 > Logical properties were trivial to implement in WebKit 

 > I still think they're the best solution that has been proposed for
 > producing a layout that can work in both the horizontal and
 > vertical directions.

Implementation cost is one metric, but no the only one. For one,
there's also a memory cost. I presume you have implemented this so that
the logical propertie cascade and inherit separately? on a per-element
basis? And cannot be resolved until you know the computed value for
'writing-mode'? If so, the memory use will be significant: ~35
property values for every element.

 > I still think they're the best solution that has been proposed for
 > producing a layout that can work in both the horizontal and
 > vertical directions.

There's also the inside/outside duality. If we want to address that
issue with a similar property-doubling approach, we need another 35 or
so properties.

And then there's the values. For example, 'float' accept 'right',
'left', 'top', 'bottom' (in GCPM). Should we duplicate these? There's
a long list of issues like these that will come up.

Rather, I think it's better to continue to use the existing property
names -- top, right, bottom, left are universal concepts with no bias.
Then we use media queries or some other syntactic construct to shield
legacy implementations. No new properties, no new syntax, and better
results: values aren't simply mirrored, but can also be set
specifically for the writing direction.

Cheers,

-h&kon
              Håkon Wium Lie                          CTO °þe®ª
howcome@opera.com                  http://people.opera.com/howcome
Received on Monday, 25 October 2010 09:30:28 GMT

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