Support full `SkTwoPointConicalGradient`

[wmedrano]

Would it be possible to add start radius to the two point conical gradient? I'm rasterizing NotoColorEmoji and noticed a few emojis require this feature.

From src/shaders/radial_gradient.rs

/// A radial gradient shader.
///
/// This is not `SkRadialGradient` like in Skia, but rather `SkTwoPointConicalGradient`
/// without the start radius.
#[derive(Clone, PartialEq, Debug)]
pub struct RadialGradient {

I'm currently prototyping support by looking at skia as a reference.

[wmedrano]

Related: #1

[RazrFalcon]

Only if someone would send a patch.

[LaurenzV]

You could also try using vello_cpu, which supports two-point conical gradients and has built-in rendering support for COLR emojis.

[wmedrano]

I may consider vello_cpu in the future, but I'd like to stay on tiny skia for this project.

[wmedrano]

@RazrFalcon I did my best attempt at a straight port in #164

It still needs testing, but any feedback would be appreciated. Specifically, I introduced a new ConicalGradient::new so that:

• Its really easy to review my change by cross referencing against Skia
• Avoid changing RadialGradient::new API.

What do you think of (in the future) aligning the RadialGradient::new API with Skia? Specifically, it would remove c1 and users would have to migrate to ConicalGradient::new https://source.chromium.org/chromium/chromium/src/+/main:third_party/skia/src/shaders/gradients/SkRadialGradient.cpp;l=42;drc=075316994c97ee86961b369bb2bff246aaa9d6c4

[wmedrano]

This is checked in! @LaurenzV can you do a major 0.12.0 release due to breaking changes?

Thank you 🙏🏽