[require]
GLSL >= 1.10

[vertex shader]
void main()
{
	gl_Position = gl_Vertex;
	gl_Position.w = 2.0;
}

[fragment shader]
void main()
{
	gl_FragColor = vec4(1.0, gl_FragCoord.w, 1.0, 0.0);
}

[test]
draw rect -1 -1 2 2
relative probe rgb (0.5, 0.5) (1.0, 0.5, 1.0)