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Re: [svg2] radialGradient @fr constraints

From: Dirk Schulze <dschulze@adobe.com>
Date: Wed, 29 Aug 2012 15:30:33 -0700
To: Rik Cabanier <cabanier@gmail.com>
CC: Erik Dahlstrom <ed@opera.com>, "www-svg@w3.org" <www-svg@w3.org>
Message-ID: <EDBD7E43-11D8-47ED-851F-6337DCF4E1FA@adobe.com>

On Aug 29, 2012, at 2:13 PM, Dirk Schulze <dschulze@adobe.com> wrote:

> 
> On Aug 29, 2012, at 2:08 PM, Rik Cabanier <cabanier@gmail.com> wrote:
> 
>> 
>> 
>> On Wed, Aug 29, 2012 at 1:32 AM, Erik Dahlstrom <ed@opera.com> wrote:
>> Some issues regarding the added 'fr' attribute on radialGradient:
>> 
>> a) Should 'fr' be allowed to be negative? (this is disallowed in <canvas>). What should happen if it is?
>> 
>> yes, that should not be allowed.
>> 
>> b) Should we still keep the constraint[1] to move the focal point inside the other circle? <canvas> doesn't do this. What the spec currently defines means some kinds of conical gradients aren't possible to do with <radialGradient>.
>> 
>> No. let's remove it.
> Have you ever tried it across browsers? If not do it. You can not rely on it. Every browser does it different. See my previous response.
I have to correct this statement. All browsers worked on the behavior lately. IE 9 and 10 are the only browsers that differ  on the following test: http://canvex.lazyilluminati.com/misc/radial/examples.html But just slightly. Not a big difference. And you need to check nightly builds of browsers.

The test does not include spread mods since they are not supported by HTML Canvas.

Greetings,
Dirk

> 
> Dirk
> 
>> 
>> c) Related to b): the case where the focal point is outside the other circle, but the focal radius makes the two circles intersect, how should that be handled?
>> 
>> The gradient will render as a cone.
>> Repeat/reflect might display a bit strange, but that's probably OK
>> 
>> 
>> Proposal:
>> a) disallow negative values for 'fr', and let these cases fallback to the lacuna value '0%'.
>> b) remove the constraint and handle it the same as in <canvas>, noting that this may break some existing content. If we do this way it doesn't matter how the two circles are positioned relative to one another, so it addresses c) as well.
>> 
>> agreed
>> 
>> 
>> 
>> [1] https://svgwg.org/svg2-draft/pservers.html#RadialGradientNotes
>> -- 
>> Erik Dahlstrom, Core Technology Developer, Opera Software
>> Co-Chair, W3C SVG Working Group
>> Personal blog: http://my.opera.com/macdev_ed
>> 
>> 
> 
> 
Received on Wednesday, 29 August 2012 23:46:01 GMT

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