pub fn shadow_quad(
rect: (f32, f32, f32, f32),
radius: f32,
blur: f32,
rgba: [u8; 4],
) -> ((f32, f32, f32, f32), Vec<u8>)Expand description
DrawShadow → SHADOW quad: Gaussian-approximate drop shadow of the
rounded rect. params: (corner_radius, sigma, 0, 0). Sigma maps from the
CPU path’s box-blur blur parameter: three box passes of width b
approximate a Gaussian with σ ≈ b/2 — tuned against the real
build_shadow_mask output in the A/B demo, not derived on paper.