Adds full support for COLRv1 radial gradients based on the two-point conical gradient algorithm at https://skia.org/docs/dev/design/conical/
Also adds robustness to degenerate cases in gradient encoding:
* Radial where p0 == p1 && r0 == r1 renders transparent solid
* Empty stops render as transparent solid
* Single stop renders as solid
* rename resolve_simple to resolve_solid_paths_only to better capture the semantics of the function
* move duplicated buffer size computation code to separate function
* change Resolver::resolve to call resolve_solid_paths_only when encoding.patches.is_empty() is true. This is likely to be slightly faster and will ensure that the "simple" code path is actually used.
This patch implements the pad, repeat and reflect extend modes for gradient brushes. Adds a new example demonstrating the functionality.
Also fixes a few bugs:
* Clamps alpha in blend.wgsl for the `blend_compose` function. The `Plus` mode was generating `alpha > 1.0` leading to incorrect rendering.
* Small change to radial gradients in fine.wgsl to reject pixels outside the cone when the circles don't nest. This requires further work to properly extend the cone when one of the radii is not 0.
- Use the buffer sizes in src/render.rs as the current 128K is not
sufficient for even the test scenes
- Add BumpAllocators type and bump buffer size
- Support the `base_color` render option
- Use immutable type construction where possible
- Fix the path tag stream length calculation to use the offsets stored
in Layout. This both matches the current behavior in src/render.rs and
makes it so that CpuConfig's construction no longer needs the Encoding
type as an input
- Renamed CpuConfig & GpuConfig types to 'RenderConfig' and
'ConfigUniform'
This change moves the vello encoding logic to a new crate under
crates/encoding. Combined with the `vello_shaders` crate, this enables
lightweight integration of the Vello pipelines into renderers that don't
depend on wgpu (or perhaps written in languages other than Rust).
The Scene/Fragment API currently remain the vello crate.
