screenshot.wgsl

// This vertex shader will create a triangle that will cover the entire screen
// with minimal effort, avoiding the need for a vertex buffer etc.
@vertex
fn vs_main(@builtin(vertex_index) in_vertex_index: u32) -> @builtin(position) vec4<f32> {
    let x = f32((in_vertex_index & 1u) << 2u);
    let y = f32((in_vertex_index & 2u) << 1u);
    return vec4<f32>(x - 1.0, y - 1.0, 0.0, 1.0);
}

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

@fragment
fn fs_main(@builtin(position) pos: vec4<f32>) -> @location(0) vec4<f32> {
    let coords = floor(pos.xy);
    return textureLoad(t, vec2<i32>(coords), 0i);
}