[require]
GLSL >= 1.10

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

[fragment shader]
uniform vec4 color;
void main()
{
	gl_FragColor = ((vec4(0.5, 0.0, 0.0, 0.0) + color) -
			vec4(1.0, 0.0, 0.0, 0.0));
}

[test]
uniform vec4 color 0.5 1.0 0.0 0.0
draw rect -1 -1 2 2
probe all rgba 0.0 1.0 0.0 0.0