[pixel shader todo]
void sub2(in uniform float4 i, out float4 o)
{
    o = i;
}

void sub(float a, uniform float b, in float c, uniform in float d, out float4 o)
{
    sub2(float4(a, b, c, d), o);
}

void main(in uniform float4 a, uniform float4 b, out float4 o : sv_target)
{
    sub(a.x, b.x, 0.3, 0.4, o);
}

[test]
uniform 0 float4 0.1 0.0 0.0 0.0
uniform 4 float4 0.2 0.0 0.0 0.0
todo draw quad
probe all rgba (0.1, 0.2, 0.3, 0.4)