A quartet of images, our next goal we will take on. As promised, we will not need to create a box this time. Instead, we our going to use the primitives we already created ourselves.

Take some time and study the picture. How are the different parts related? Do any picture primitives spring to mind?

Open src/picture/mod.rs. In it you will find the quartet function. Below is it's signature repeated.

# #![allow(unused_variables)]
#fn main() {
pub fn quartet<P, Q, R, S>(nw: Rc<P>, ne: Rc<Q>, sw: Rc<R>, se: Rc<S>) -> Rc<impl Fn(&Bx) -> Rendering>
where P: Fn(&Bx) -> Rendering, Q: Fn(&Bx) -> Rendering, R: Fn(&Bx) -> Rendering, S: Fn(&Bx) -> Rendering
#}

It is hard to look at. The reason for this is that Rust treats every closure as its own type. So even though the type parameters P, Q, R and S seem to be defined the same, at compile time they could be different.

Either way, the implementation of the quartet should result in a Rendering of the arguments. They are called nw, ne, sw and se to help orient them in the quartet.

When you find the right combination of picture primitives make sure to enjoy your hard-work and use it in the geometry binary.