1struct Transform {
2    scale: vec2<f32>,
3    translation: vec2<f32>,
4}
5
6struct VertexInput {
7    @location(0) position: vec2<f32>,
8    @location(1) uv: vec2<f32>,
9    @location(2) color: vec4<f32>,
10}
11
12struct VertexOutput {
13    @builtin(position) position: vec4<f32>,
14    @location(0) color: vec4<f32>,
15    @location(1) uv: vec2<f32>,
16}
17
18@group(0) @binding(0) var<uniform> transform: Transform;
19
20#ifdef BINDLESS
21@group(1) @binding(0) var image_texture: binding_array<texture_2d<f32>>;
22@group(1) @binding(1) var image_sampler: binding_array<sampler>;
23
24// Fix for DX12 backend in wgpu which appears to only support struct immediates
25// wgpu::backend::wgpu_core: Shader translation error for stage ShaderStages(FRAGMENT): HLSL: Unimplemented("immediate 'offset' has non-struct type; tracked by: https://github.com/gfx-rs/wgpu/issues/5683")
26struct BindlessOffset {
27    offset: u32,
28};
29var<immediate> offset: BindlessOffset;
30
31#else //BINDLESS
32@group(1) @binding(0) var image_texture: texture_2d<f32>;
33@group(1) @binding(1) var image_sampler: sampler;
34#endif // BINDLESS
35
36// 0-1 linear  from  0-1 sRGB gamma.
37fn linear_from_gamma_rgb(srgb: vec3<f32>) -> vec3<f32> {
38    let cutoff = srgb < vec3<f32>(0.04045);
39    let lower = srgb / vec3<f32>(12.92);
40    let higher = pow((srgb + vec3<f32>(0.055)) / vec3<f32>(1.055), vec3<f32>(2.4));
41    return select(higher, lower, cutoff);
42}
43
44// 0-1 sRGB gamma  from  0-1 linear.
45fn gamma_from_linear_rgb(rgb: vec3<f32>) -> vec3<f32> {
46    let cutoff = rgb < vec3<f32>(0.0031308);
47    let lower = rgb * vec3<f32>(12.92);
48    let higher = vec3<f32>(1.055) * pow(rgb, vec3<f32>(1.0 / 2.4)) - vec3<f32>(0.055);
49    return select(higher, lower, cutoff);
50}
51
52// 0-1 sRGBA gamma  from  0-1 linear.
53fn gamma_from_linear_rgba(linear_rgba: vec4<f32>) -> vec4<f32> {
54    return vec4<f32>(gamma_from_linear_rgb(linear_rgba.rgb), linear_rgba.a);
55}
56
57@vertex
58fn vs_main(in: VertexInput) -> VertexOutput {
59    let position = in.position * transform.scale + transform.translation;
60    // Not sure why Egui does vertex color interpolation in sRGB but here we do it the same way as well.
61    return VertexOutput(vec4<f32>(position, 0.0, 1.0), in.color, in.uv);
62}
63
64@fragment
65fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
66    #ifdef BINDLESS
67    let image_texture = image_texture[offset.offset];
68    let image_sampler = image_sampler[offset.offset];
69    #endif
70
71    // Quoting the Egui's glsl shader:
72    // "We multiply the colors in gamma space, because that's the only way to get text to look right."
73    let texture_color_linear = textureSample(image_texture, image_sampler, in.uv);
74    let texture_color_gamma = gamma_from_linear_rgba(texture_color_linear);
75    let color_gamma = texture_color_gamma * in.color;
76
77    return vec4<f32>(linear_from_gamma_rgb(color_gamma.rgb), color_gamma.a);
78}