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struct Globals {
transform: mat4x4<f32>,
scale: f32,
}
@group(0) @binding(0) var<uniform> globals: Globals;
struct VertexInput {
@location(0) v_pos: vec2<f32>,
@location(1) pos: vec2<f32>,
@location(2) scale: vec2<f32>,
@location(3) color: vec4<f32>,
@location(4) border_color: vec4<f32>,
@location(5) border_radius: vec4<f32>,
@location(6) border_width: f32,
}
struct VertexOutput {
@builtin(position) position: vec4<f32>,
@location(0) color: vec4<f32>,
@location(1) border_color: vec4<f32>,
@location(2) pos: vec2<f32>,
@location(3) scale: vec2<f32>,
@location(4) border_radius: vec4<f32>,
@location(5) border_width: f32,
}
@vertex
fn vs_main(input: VertexInput) -> VertexOutput {
var out: VertexOutput;
var pos: vec2<f32> = input.pos * globals.scale;
var scale: vec2<f32> = input.scale * globals.scale;
var min_border_radius = min(input.scale.x, input.scale.y) * 0.5;
var border_radius: vec4<f32> = vec4<f32>(
min(input.border_radius.x, min_border_radius),
min(input.border_radius.y, min_border_radius),
min(input.border_radius.z, min_border_radius),
min(input.border_radius.w, min_border_radius)
);
var transform: mat4x4<f32> = mat4x4<f32>(
vec4<f32>(scale.x + 1.0, 0.0, 0.0, 0.0),
vec4<f32>(0.0, scale.y + 1.0, 0.0, 0.0),
vec4<f32>(0.0, 0.0, 1.0, 0.0),
vec4<f32>(pos - vec2<f32>(0.5, 0.5), 0.0, 1.0)
);
out.color = input.color;
out.border_color = input.border_color;
out.pos = pos;
out.scale = scale;
out.border_radius = border_radius * globals.scale;
out.border_width = input.border_width * globals.scale;
out.position = globals.transform * transform * vec4<f32>(input.v_pos, 0.0, 1.0);
return out;
}
fn distance_alg(
frag_coord: vec2<f32>,
position: vec2<f32>,
size: vec2<f32>,
radius: f32
) -> f32 {
var inner_size: vec2<f32> = size - vec2<f32>(radius, radius) * 2.0;
var top_left: vec2<f32> = position + vec2<f32>(radius, radius);
var bottom_right: vec2<f32> = top_left + inner_size;
var top_left_distance: vec2<f32> = top_left - frag_coord;
var bottom_right_distance: vec2<f32> = frag_coord - bottom_right;
var dist: vec2<f32> = vec2<f32>(
max(max(top_left_distance.x, bottom_right_distance.x), 0.0),
max(max(top_left_distance.y, bottom_right_distance.y), 0.0)
);
return sqrt(dist.x * dist.x + dist.y * dist.y);
}
// 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;
}
@fragment
fn fs_main(
input: VertexOutput
) -> @location(0) vec4<f32> {
var mixed_color: vec4<f32> = input.color;
var border_radius = select_border_radius(
input.border_radius,
input.position.xy,
(input.pos + input.scale * 0.5).xy
);
if (input.border_width > 0.0) {
var internal_border: f32 = max(border_radius - input.border_width, 0.0);
var internal_distance: f32 = distance_alg(
input.position.xy,
input.pos + vec2<f32>(input.border_width, input.border_width),
input.scale - vec2<f32>(input.border_width * 2.0, input.border_width * 2.0),
internal_border
);
var border_mix: f32 = smoothstep(
max(internal_border - 0.5, 0.0),
internal_border + 0.5,
internal_distance
);
mixed_color = mix(input.color, input.border_color, vec4<f32>(border_mix, border_mix, border_mix, border_mix));
}
var dist: f32 = distance_alg(
vec2<f32>(input.position.x, input.position.y),
input.pos,
input.scale,
border_radius
);
var radius_alpha: f32 = 1.0 - smoothstep(
max(border_radius - 0.5, 0.0),
border_radius + 0.5,
dist
);
return vec4<f32>(mixed_color.x, mixed_color.y, mixed_color.z, mixed_color.w * radius_alpha);
}
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