// vertex
const c_scale: f32 = 1.2;

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

@vertex
fn vert_main(
  @location(0) pos : vec2<f32>,
  @location(1) uv : vec2<f32>,
) -> VertexOutput {
  return VertexOutput(uv, vec4<f32>(c_scale * pos, 0.0, 1.0));
}

// fragment
@group(0) @binding(0) var u_texture : texture_2d<f32>;
@group(0) @binding(1) var u_sampler : sampler;

@fragment
fn frag_main(@location(0) uv : vec2<f32>) -> @location(0) vec4<f32> {
  let color = textureSample(u_texture, u_sampler, uv);
  if color.a == 0.0 {
    discard;
  }
  // forcing the expression here to be emitted in order to check the
  // uniformity of the control flow a bit more strongly.
  let premultiplied = color.a * color;
  return premultiplied;
}


// We need to make sure that backends are successfully handling multiple entry points for the same shader stage.
@fragment
fn fs_extra() -> @location(0) vec4<f32> {
    return vec4<f32>(0.0, 0.5, 0.0, 0.5);
}