[cairo] [Bug 40918] Radial gradients misrendered if focus is exactly on the outer circle

Bill Spitzak spitzak at gmail.com
Sun Sep 18 14:12:39 PDT 2011

On Sep 17, 2011, at 6:28 PM, bugzilla-daemon at freedesktop.org wrote:
>> I would much prefer if the behavior of Cairo was explicitly defined  
>> in this
>> case, rather effectively left undefined.
> It is not left undefined. The behavior follows the PDF  
> specification, which is
> also consistent with PS and HTML canvas and AFAICT with SVG, too. The
> documentation should describe the behavior of gradients, but that's  
> true for
> linear gradients as well.

Having read this, I am getting some doubts that you are copying any  
kind of defined SVG spec.

I looked around and cannot find any SVG examples that do not have the  
outer color transparent. Therefore none of the examples is proving  
that the proposed fix for cairo will break anything, as they all  
always fill the union of the main circle and the cone no matter where  
the center is.

Can anybody produce actual renderings from a non-cairo SVG interpreter  
(whether or not it is known to be correct) that shows a solid-filled  
area outside the circle abruptly turning into a transparent area when  
the center crosses the border?

Also I fail to see how Cairo would be unusable for following the SVG  
spec even with this change. All that happens is that you must set the  
repeat to NONE before drawing a radial with the point outside the  
circle if you want to match the (presumed) SVG spec.

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