rootvg-quad 0.2.0

Quad primitives for RootVG
Documentation 
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// The following code was copied and modified from
// https://github.com/iced-rs/iced/blob/31d1d5fecbef50fa319cabd5d4194f1e4aaefa21/wgpu/src/shader/quad.wgsl
// Iced license (MIT): https://github.com/iced-rs/iced/blob/31d1d5fecbef50fa319cabd5d4194f1e4aaefa21/LICENSE

struct Globals {
    screen_to_clip_scale: vec2<f32>,
    scale_factor: f32,
}

@group(0) @binding(0) var<uniform> globals: Globals;

fn distance_alg(
    frag_coord: vec2<f32>,
    position: vec2<f32>,
    size: vec2<f32>,
    radius: f32
) -> f32 {
    var inner_half_size: vec2<f32> = (size - vec2<f32>(radius, radius) * 2.0) / 2.0;
    var top_left: vec2<f32> = position + vec2<f32>(radius, radius);
    return rounded_box_sdf(frag_coord - top_left - inner_half_size, inner_half_size, 0.0);
}

// Given a vector from a point to the center of a rounded rectangle of the given `size` and
// border `radius`, determines the point's distance from the nearest edge of the rounded rectangle
fn rounded_box_sdf(to_center: vec2<f32>, size: vec2<f32>, radius: f32) -> f32 {
    return length(max(abs(to_center) - size + vec2<f32>(radius, radius), vec2<f32>(0.0, 0.0))) - radius;
}

// Based on the fragement position and the center of the quad, select one of the 4 radi.
// Order matches CSS border radius attribute:
// radi.x = top-left, radi.y = top-right, radi.z = bottom-right, radi.w = bottom-left
fn select_border_radius(radi: vec4<f32>, position: vec2<f32>, center: vec2<f32>) -> f32 {
    var rx = radi.x;
    var ry = radi.y;
    rx = select(radi.x, radi.y, position.x > center.x);
    ry = select(radi.w, radi.z, position.x > center.x);
    rx = select(rx, ry, position.y > center.y);
    return rx;
}

// The following code was copied from
// https://github.com/iced-rs/iced/blob/31d1d5fecbef50fa319cabd5d4194f1e4aaefa21/wgpu/src/shader/vertex.wgsl
// Iced license (MIT): https://github.com/iced-rs/iced/blob/31d1d5fecbef50fa319cabd5d4194f1e4aaefa21/LICENSE

// Compute the normalized quad coordinates based on the vertex index.
fn vertex_position(vertex_index: u32) -> vec2<f32> {
    // #: 0 1 2 3 4 5
    // x: 1 1 0 0 0 1
    // y: 1 0 0 0 1 1
    return vec2<f32>((vec2(1u, 2u) + vertex_index) % vec2(6u) < vec2(3u));
}