[cairo] Radial Patterns Repeat Radially

[Andrea Canciani]

On Thu, Mar 12, 2015 at 9:40 AM, Lawrence D'Oliveiro <
ldo at geek-central.gen.nz> wrote:

> I was pleased to discover that radial gradients with EXTEND_REPEAT do
> their repeating outwards from the pattern centre, not actually by
> tiling at all. This is a useful effect, but it is not made clear
> anywhere in the documentation that I can see
> <http://cairographics.org/manual/cairo-cairo-pattern-t.html>.
>

Gradients (as opposed to surface-based patterns) lack of a natural notion
of tile.
Linear gradients are quite simple and their current description might
already be sufficient to provide the intuition of their behavior.
Mesh gradients are quite complex, hence they have extensive documentation
(and even reference the PDF specification for a more complete description).
We might want to extend the documentation for linear and radial gradients
by mentioning the relevant parametrization (so that in cairo_extend_t we
can explicitly say the mathematical meaning of each setting).
Alternatively, we might mention specifically in create_linear/create_radial
what happens for each different extend setting.

Are these effective ways to explain the gradients?
Which one should be preferred?

Andrea
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