W3C home > Mailing lists > Public > www-svg@w3.org > May 2012

Re: computed values of properties

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Wed, 23 May 2012 00:12:41 -0700
Message-ID: <CAAWBYDAgLQxkxikxYh66Y8x5WhQjA=0DMZTHRrrH_5BOGT7RZw@mail.gmail.com>
To: Cameron McCormack <cam@mcc.id.au>
Cc: Erik Dahlstrom <ed@opera.com>, SVG public list <www-svg@w3.org>
On Tue, May 22, 2012 at 6:18 PM, Cameron McCormack <cam@mcc.id.au> wrote:
> 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.

Easier: say something like "as specified, but with URLs made absolute
and <color>s computed".

> 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.)

The clamping should definitely occur at computed-value time.  It
doesn't require any layout computations.

> 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

Yes, all lengths should be made absolute as part of computation.

Received on Wednesday, 23 May 2012 07:13:54 UTC

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