struct Instance {
	position: vec2<f32>,
	scale:    vec2<f32>,
	uv:       vec4<f32>,
}

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

@group(0) @binding(0) var<storage, read> instances: array<Instance>;

@group(1) @binding(0) var tex_sampler: sampler;
@group(1) @binding(1) var font_tex:    texture_2d<f32>;

@vertex
fn vs_main(
	@builtin(vertex_index)   in_vertex_index:   u32,
	@builtin(instance_index) in_instance_index: u32,
) -> VertexOutput {
	let uv = vec2<f32>(f32((in_vertex_index << 1) & 2), f32(in_vertex_index & 2)) / 2.0;
	let instance = instances[in_instance_index];

	var out: VertexOutput;
	out.position = vec4<f32>(instance.position + (uv - 0.5) * instance.scale * 2.0, 0.0, 1.0);
	out.uv = instance.uv.xy + vec2<f32>(uv.x, 1.0 - uv.y) * instance.uv.zw;

	return out;
}

@fragment
fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
	return vec4<f32>(1.0, 1.0, 1.0, textureSample(font_tex, tex_sampler, in.uv).r);
}