[cairo] Path Gradients

[Bill Spitzak]

Behdad Esfahbod wrote:
> On Thu, 2008-01-03 at 22:28 -0500, Bill Spitzak wrote:
>> In truth this only looks useful to make the same results that Cairo does 
>> with radial gradients. Shapes that are not round are pretty useless due 
>> to Mach banding (this is the starburst rays you see). However I can 
>> certainly see that this is a more convienent way to specify a radial 
>> gradient.
> 
> Another interesting feature of the path gradients in the links is that
> one can also have color stop along the path (that is, along the circle),
> not only from the center to the path.

You are right, some of the examples show that. The center point was a 
fixed color, but gradiated in straight lines to a different color at 
each control point, with that end color interpolated between them.

It was unclear what happens with multiple-step gradients, which some of 
the examples show. Does it only change the last step, or is there an api 
to change all the steps?

I found it interesting that all the "real" examples did not use this 
feature and kept a constant color. It may indicate that emulation of 
this is not necessary.

I am still very interested in any explanation why the path needs to be 
specified twice and what happens if the two paths are different.