vkrunner test that generates a checkerboard pattern

checkerboard.shader_test.glsl

[require]
fbsize 800 600

[vertex shader passthrough]

[fragment shader]
#version 450
float checkerboard(in vec2 uv)
{
    vec2 pos = floor(uv);
  	return mod(pos.x + mod(pos.y, 2.0), 2.0);
}

layout(location = 0) out vec4 out_color;
void main()
{
	vec2 uv = gl_FragCoord.xy;
	float p = checkerboard(uv);

	out_color = vec4(p, p, p, 1.0);
}

[test]
draw rect -1 -1 2 2