[require]
GLSL >= 1.30

[vertex shader]
#version 130
void main()
{
	gl_Position = gl_Vertex;
}

[fragment shader]
#version 130
uniform vec4 v;

void main()
{
	uint posintx = uint(gl_FragCoord.x);
	uint one = uint(1);
	gl_FragColor = v;
	if ((posintx & one) == one) {
		return;  // return for every second pixel
	}
	gl_FragColor = vec4(1.0) - v;
}

[test]
uniform vec4 v 0 1 0 1

draw rect -1 -1 2 2
probe rgb 0 0 1 0 1
probe rgb 1 0 0 1 0
probe rgb 2 0 1 0 1
probe rgb 3 0 0 1 0