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RE: [css3-text-layout] New editor's draft - margin-before/after/start/end etc.

From: Håkon Wium Lie <howcome@opera.com>
Date: Fri, 28 May 2010 16:26:35 +0200
Message-ID: <19455.53915.652465.451678@gargle.gargle.HOWL>
To: Sylvain Galineau <sylvaing@microsoft.com>
Cc: "www-style@w3.org" <www-style@w3.org>
Also sprach Sylvain Galineau:

 > According to CSS2.1 : "If there are two values, the top and bottom margins
 > are set to the first value and the right and left margins are set to the second."
 > 
 > So you're effectively saying that margin: 20px 10px would result in the application
 > of logical margins based on the writing-mode and/or :lang() but if the author writes:
 > 
 > p:lang(ja) {
 >       writing-mode: tb-rl;
 > 	margin-top:20px;
 > 	margin-bottom:20px;
 > 	margin-left: 10px;
 > 	margin-right: 10px;
 > }
 > 
 > ...which per CSS2.1 is equivalent, then the margin values would be set physically instead ?

There are only physical values in my examples. This code:

  p { margin: 10px 20px }
  p:lang(ja) {
    writing-mode: tb-rl;
    margin: 20px 10px;
  }

illustrates how you can achieve automatic switching of values (as in,
"I'd like 10px margins before and after, and 20px margins at the start
and end") without introducing new properties/values.

So, I'm saying that the problem has a solution today.

Now, as it has been pointed out, the problem with this approach is
that a UA that doesn't support 'writing-mode: tb-rl' will still put
the margins in their physical location. Often, this will be what the
author intended, but sometimes not. One possible solution for this
could be:

@supports tb-rl {
  p {
    writing-mode: tb-rl;
    margin: 20px 10px;
  }
}

The @supports is a new construct. We should be careful when
introducing new constructs. But I'd much rather have this new
construct than 30 new properties. Here's a similar proposal:

   http://chriseppstein.github.com/blog/2009/10/19/css-unsupported-directive/

-h&kon
              Håkon Wium Lie                          CTO °þe®ª
howcome@opera.com                  http://people.opera.com/howcome
Received on Friday, 28 May 2010 14:27:25 GMT

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