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Re: [css3-images] rtl/ltr annotation

From: Kang-Hao (Kenny) Lu <kennyluck@csail.mit.edu>
Date: Sun, 11 Mar 2012 04:34:38 +0800
Message-ID: <4F5BBADE.1060909@csail.mit.edu>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: Andrew Fedoniouk <news@terrainformatica.com>, WWW Style <www-style@w3.org>
(12/03/11 4:16), Tab Atkins Jr. wrote:
> On Sat, Mar 10, 2012 at 11:57 AM, Andrew Fedoniouk
> <news@terrainformatica.com> wrote:
>> Reference: http://dev.w3.org/csswg/css3-images/#image-notation
>>
>> Am I correct in my assumptions that two cases below are functional equivalents?
>>
>> 1.  el { background: image(a.png ltr, b.png rtl); }
>>
>> 2.  el:dir(ltr) { background: url(a.png); }
>>     el:dir(rtl) { background: url(b.png); }
>>
>> In other words, these ltr/rtl annotators are sensors of what actually?
> 
> They aren't sensors at all.  They *declare* the image to be ltr or
> rtl.  Then, if it finds itself in an element with opposite
> directionality, it's flipped in the inline direction.  So no, your two
> cases are definitely not equivalent.
> 
> All of this is described pretty clearly in the spec.  The entire
> description is a single short paragraph.

which I'll include here

  # Along with each ‘<image-decl>’, the author may specify a
  # directionality, similar to adding a dir attribute to an element in
  # HTML. The ‘image()’ function takes on the directionality of the
  # used ‘<image-decl>’, if any. If a directional image is used on or
  # in an element with opposite direction, the image must be flipped in
  # the inline direction (as if it was transformed by, e.g.,scaleX(-1),
  # if the inline direction is the X axis).


Regarding this, I don't think there is a use case for specifying
different modes (non-flipping, ltr, rtl) for different images in the
fallback chain. The fact that the syntax allows this seems to indicate
that this syntax is suboptimal, although I don't have better suggestion
at the moment.

By the way, this paragraph draws analogy with @dir in HTML which might
be the reason of this confusion because in HTML @dir defaults to ltr (in
some sense) while the default is "non-flipping" here.


Cheers,
Kenny
Received on Saturday, 10 March 2012 20:35:07 GMT

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