#![version="110"]

#[varying] static zed: Vec2;
#[uniform] static prev_frame: Sampler2D;
#[uniform] static _p_scale: f32;

fn complex_to_tex(p: Vec2) -> Vec2 {
    (0.5/_p_scale)*p + Vec2(0.5, 0.5)
}

fn complex_mul(a: Vec2, b: Vec2) -> Vec2 {
    Vec2(a.x*b.x - a.y*b.y, a.x*b.y + a.y*b.x);
}

fn in_bounds(p: Vec2) -> bool {
    macro_rules! check {
        ($i:ident) => ((p.$i >= -_p_scale) && (p.$i <= _p_scale))
    }

    check!(p.x) && check!(p.y)
}

#[uniform] static param: Vec2;

fn main() {
    let color: Vec3;
    let oldpoint: Vec2 = complex_mul(zed, zed) + 1.6*param;

    if in_bounds(oldpoint) {
        let oldcoord: Vec2 = complex_to_tex(oldpoint);
        color = 1.8*texture2D(prev_frame, oldcoord).brg;
    } else {
        color = Vec3(1.0, 0.0, 0.0);
    }

    gl_FragColor = Vec4(color, 1.0);
}