Re: [svg2] radialGradient @fr constraints

Hi David,
You mean the condition displayed in figure 8 here, right?

The discussion and rationale for that addition can be found here:

[[ Summary of the issue: when the focal point is on the circle edge, with  
repeat, then the distance between the first and last stop for the  
repeating colors is 0 and the (SVG1.1) spec. does not define what should  
happen. ]]

On Wed, 29 Aug 2012 12:32:01 +0200, David Dailey  
<> wrote:

> Fwiw, the example at  
> (that is now many years old and appears in more than one book) is  
> rendered in ways that I consider proper in only Chrome and ASV. Opera  
> makes it too grainy; Safari doesn't reflect gradients; FF refuses to  
> differentiate between fx and cx (and even crashed for me thrice this  
> morning while running it for a while!); IE9 doesn't reflect the  
> gradients beyond the horizon (and they seem to have dropped animation  
> from the graphical web).
> HTML had the opportunity, in 2007, to have canvas follow SVG's syntax  
> for radial gradients. Some people even advised as much. Reversing the  
> role of leadership here would seem silly. Apple, despite, its recent  
> victories in the wars*, should not have so unilateral a role in defining  
> graphics for the web.
> Regards
> David
> *There was a reason the policy of mutually assured destruction worked.
> -----Original Message-----
> From: Erik Dahlstrom []
> Sent: Wednesday, August 29, 2012 4:33 AM
> To:
> Subject: [svg2] radialGradient @fr constraints
> 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?
> 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>.
> 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?
> 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.
> [1]
> --
> Erik Dahlstrom, Core Technology Developer, Opera Software Co-Chair, W3C  
> SVG Working Group Personal blog:

Erik Dahlstrom, Core Technology Developer, Opera Software
Co-Chair, W3C SVG Working Group
Personal blog:

Received on Wednesday, 29 August 2012 11:51:21 UTC