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Re: [CSS-transforms] rotate(<angle>[, <translation-value>, <translation-value>])

From: L. David Baron <dbaron@dbaron.org>
Date: Wed, 15 Feb 2012 14:43:59 -0800
To: Dirk Schulze <dschulze@adobe.com>
Cc: Rik Cabanier <cabanier@gmail.com>, www-style list <www-style@w3.org>
Message-ID: <20120215224359.GA23597@pickering.dbaron.org>
On Wednesday 2012-02-15 12:27 -0800, Dirk Schulze wrote:
> I tried to describe the benefits for CSS[2] but more necessary the
> requirements for SVG [3]. This is the last blocking issue for
> compliance between CSS Transforms and SVG Transforms for
> transformation functions. That is the reason why I think it is
> necessary to leave it in. Like I wrote before, it doesn't break
> existing content. These are just two more optional arguments, and
> it is easy to implement. It is already done for the SVG
> implementation on all browser anyway. So SVG authors would expect
> that it works on CSS as well, beside that if it is not supported
> we would break existing SVG content. And for SVG a rotate with
> three arguments is used a lot!

My main concern here is that adding additional requirements on
implementations might add additional barriers to unprefixing.

In particular, the working group this morning did not achieve
consensus on the idea that we might make any exceptions to the rules
on dropping prefixes.  This means that we have to follow the rules
stated in http://www.w3.org/TR/2011/NOTE-css-2010-20110512/#testing
(that's the current version of http://www.w3.org/TR/CSS/#testing ):

  # To establish and maintain the interoperability of CSS across
  # implementations, the CSS Working Group requests that
  # non-experimental CSS renderers submit an implementation report
  # (and, if necessary, the testcases used for that implementation
  # report) to the W3C before releasing an unprefixed implementation
  # of any CSS features. Testcases submitted to W3C are subject to
  # review and correction by the CSS Working Group. 

While this doesn't explicitly say anything about whether the
implementation is required to *pass* the tests per that
implementation report, I suspect it might be interpreted that way.
(It's a new requirement since the last unprefixing has happened.)

So from a spec advancement perspective I'd be ok with this change
only if either (1) the spec explicitly says that implementations are
not required to support the additional 2 arguments in order to
unprefix their implementations of the transform property (though
they'd still be required to do so to fully conform to the
specification) or (2) /TR/CSS/ is clarified in such a way that this
isn't an issue.


That said, I also find the additional parameters confusing, but I
suppose if SVG has them we're probably stuck with them, and I don't
plan to object on those grounds since I'm not particularly an expert
in the area.  (I'd note, however, that they're not at all analogous
to the extra parameters to rotate3d(), which describe what axis to
rotate about, not where the center of the rotation is.)

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Wednesday, 15 February 2012 22:44:28 GMT

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