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Re: computed values of properties

From: Cameron McCormack <cam@mcc.id.au>
Date: Wed, 23 May 2012 11:18:36 +1000
Message-ID: <4FBC3AEC.7070305@mcc.id.au>
To: Erik Dahlstrom <ed@opera.com>
CC: SVG public list <www-svg@w3.org>
OK, here are some differences that might be worth discussing.


In SVG Tiny 1.2, the Computed Value line for fill says:

   "none", system paint, specified <color> value or absolute IRI

What I have currently written for SVG 2 is:

   If a <color> value is part of the specified value, then it is
   computed as per the 'color' property.  For anything else the
   computed value is as specified.

I do need to add something about the absolutisation of the IRI.  But 
what about the <color> part?  Are you OK with keeping that in?  It's 
probably good to be consistent with other CSS properties that take <color>s.


In Tiny, fill-rule says:

   Specified value, except inherit

(We can forget about the "except inherit" bit, since CSS already handles 
that for us.)  I've currently got:

   as specified, but clamped to the range [0, 1]

Here's a test:

   http://people.mozilla.org/~cmccormack/tests/fill-opacity-computed.svg

The text shows what getComputedStyle returns for an element with 
fill-opacity="-1" on it.  (Yes that's the used value, not computed, but 
still might be interesting.)  Since CSS Transitions work on computed 
values, I used those to see transitioning from -1 to 1 looks like. 
Gecko seems to do the clamping as part of the computed value 
computation, as both rectangles transition the same, from 0 to 1. 
WebKit seems to clamp later than computed value and used value time, so 
the transition actually runs from -1 to 1.  (The transitions aren't 
working for me in Opera.)


In Tiny and currently in SVG 2, stroke-dasharray and stroke-dashoffset's 
computed value is "as specified".  But it seems common in CSS properties 
to compute lengths to absolute values.  I've asked about that here:

   http://lists.w3.org/Archives/Public/www-style/2012May/0818.html
Received on Wednesday, 23 May 2012 01:19:30 GMT

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