A Go-like language for shaders

shader.go

package main

type VertexIn struct {
	Vertex     vec2
	Tex        vec2
	TexRegion  vec4
	ColorScale vec4
}

type VertexOut struct {
	Tex        vec2
	TexRegion  vec4
	ColorScale vec4
}

// Vertex is a vertex shader.
//
// The first argument is attribute values, and the second is a uniform value.
func Vertex(in VertexIn, viewportSize vec2) (pos vec4, out VertexOut) {
	projectionMatrix := mat4(
		2.0/viewportSize.x, 0, 0, -1,
		0, -2.0/viewportSize.y, 0, 1,
		0, 0, 1, 0,
		0, 0, 0, 1,
	)
	pos := projectionMatrix * vec4(in.Vertex, 0, 1)

	vo := VertexOutput{
		Tex:        in.TexRegion,
		TexRegion:  in.TexRegion,
		ColorScale: in.ColorScale,
	}
	return pos, vo
}

// Fragment is a fragment shader.
//
// The third and following arguments are uniform values.
func Fragment(vertexPos vec4, out VertexOut, texture sampler2d, sourceSize vec2, colorMatrixBody vec4, colorMatrixTransition vec4, scale float) vec4 {
	pos := out.Tex
	var color vec4
	if out.TexRegion[0] <= pos.x && out.TexRegion[1] <= pos.y &&
		pos.x < out.TexRegion[2] && pos.y < out.TexRegion[3] {
		color = at(texture, pos) // Better name?
	}

	color.rgb /= color.a + (1.0 - sign(color.a))
	color = (colorMatrixBody * color) + colorMatrixTranslation
	color *= out.ColorScale
	color.rgb *= color.a

	return color
}