[require]
GLSL >= 1.10

[vertex shader]
varying float y;

void main()
{
	gl_Position = gl_Vertex;
	y = gl_Vertex.y;
}

[fragment shader]
varying float y;
uniform float x;

void main()
{
	float retVal = tan(x);

	// expected result, calculated by C program
	const float tolerance = 0.001;
	const vec2 expVal = vec2(1255.765592 - tolerance,
				 1255.848311 + tolerance);

	// Top half of the window should be 0.5 gray, and the bottom half
	// should be green.
	if (y > 0.0)
		gl_FragColor = vec4(vec2(retVal / (2.0 * expVal)).xyy, 1.0);
	else
		gl_FragColor = ((retVal >= expVal.x) && (retVal <= expVal.y))
			? vec4(0.0, 1.0, 0.0, 1.0)   // green
			: vec4(1.0, 0.0, 0.0, 1.0);  // red
}

[test]
uniform float x 1.57
draw rect -1 -1 2 2
relative probe rgb (0.1, 0.6) (0.5, 0.5, 0.5)
relative probe rgb (0.1, 0.1) (0.0, 1.0, 0.0)