Constant SHADER_SOURCE 

pub const SHADER_SOURCE: &str = r#"
// Dear ImGui WGSL Shader
// Vertex and fragment shaders for rendering Dear ImGui draw data

struct VertexInput {
    @location(0) position: vec2<f32>,
    @location(1) uv: vec2<f32>,
    @location(2) color: vec4<f32>,
}

struct VertexOutput {
    @builtin(position) position: vec4<f32>,
    @location(0) color: vec4<f32>,
    @location(1) uv: vec2<f32>,
}

struct Uniforms {
    mvp: mat4x4<f32>,
    gamma: f32,
}

@group(0) @binding(0)
var<uniform> uniforms: Uniforms;

@group(0) @binding(1)
var u_sampler: sampler;

@group(1) @binding(0)
var u_texture: texture_2d<f32>;

@vertex
fn vs_main(in: VertexInput) -> VertexOutput {
    var out: VertexOutput;
    out.position = uniforms.mvp * vec4<f32>(in.position, 0.0, 1.0);
    out.color = in.color;
    out.uv = in.uv;
    return out;
}

@fragment
fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    let color = in.color * textureSample(u_texture, u_sampler, in.uv);
    // Apply gamma curve if uniforms.gamma != 1.0. With gamma=1.0 this is a no-op.
    let corrected = pow(color.rgb, vec3<f32>(uniforms.gamma));
    return vec4<f32>(corrected, color.a);
}
"#;

WGSL shader source

This includes both vertex and fragment shaders with optional gamma correction, similar in spirit to imgui_impl_wgpu.cpp