diagrams/diagrams-cairo — pull request #37 by jeffreyrosenbluth (2013-11-16 02:18:30+00:00)
Title: Gradient

SVG and Cairo have built in support for different types of radial gradients.
SVG allows the specification of a focal point in addition to a center and radius from which the gradient eminates.
Cairo allows the specification of a torus on which the gradient lives.

The easiest way to understand the difference is to look at: http://www.w3.org/TR/SVG/pservers.html#RadialGradients

and

cairo_pattern_create_radial () in: http://cairographics.org/manual/cairo-cairo-pattern-t.html