Function fill_impl 

pub fn fill_impl<S: Simd>(
    simd: S,
    path: impl IntoIterator<Item = PathEl>,
    affine: Affine,
    line_buf: &mut Vec<Line>,
    flatten_ctx: &mut FlattenCtx,
    cull_bbox: RectU16,
)

Flatten a filled bezier path into line segments.

See the note about open subpaths and culling on fill.