[require]
shader model >= 3.0

[pixel shader]
float4 main(float4 pos : sv_position) : sv_target
{
    // Shader models < 4 don't add 0.5 to sv_position, so this adjustment is required to get the
    // same outputs.
    pos.x = floor(pos.x) + 0.5;
    pos.y = floor(pos.y) + 0.5;

    pos /= 10.0;
    float nonlinear = pos.x * pos.y - pos.x * (pos.x + 0.5);
    float4 res = fwidth(nonlinear);

    // Each device may use either the coarse or the fine derivate, so use quantization.
    return round(30 * res);
}

[test]
todo(sm<4 | glsl | msl) draw quad
probe (10, 10) rgba (8.0, 8.0, 8.0, 8.0)
probe (11, 10) rgba (8.0, 8.0, 8.0, 8.0)
probe (12, 10) rgba (10.0, 10.0, 10.0, 10.0)
probe (16, 16) rgba (12.0, 12.0, 12.0, 12.0)
probe (150, 150) rgba (92.0, 92.0, 92.0, 92.0)