Efficiently draw paths using piston - rust

Question

Piston's graphics library provides a function for drawing a line between two points, but nothing for more than two. How do I efficiently draw a path through many points without having to draw a line for every segment?
Let's say I have the following code:
extern crate piston_window;
use piston_window::*;
fn main() {
let mut window: PistonWindow = WindowSettings::new("Hello Piston!", [640, 480])
.exit_on_esc(true).build().unwrap();
while let Some(e) = window.next() {
window.draw_2d(&e, |c, g| {
clear([1.0; 4], g);
let points = [
[100., 100.],
[200., 200.],
[150., 350.],
//...
];
let mut prev = points[0];
for pt in points[1..].iter() {
line([0., 0., 0., 255.], 1., [
prev[0], prev[1], pt[0], pt[1]
], c.transform, g);
prev = *pt;
}
});
}
}
Is there a way to turn it into something like this?
extern crate piston_window;
use piston_window::*;
fn main() {
let mut window: PistonWindow = WindowSettings::new("Hello Piston!", [640, 480])
.exit_on_esc(true).build().unwrap();
while let Some(e) = window.next() {
window.draw_2d(&e, |c, g| {
clear([1.0; 4], g);
let points = [
[100., 100.],
[200., 200.],
[150., 350.],
//...
];
path([0., 0., 0., 255.], 1., &points, c.transform, g);
});
}
}
I was referred to the lyon library but I don't know how to use it with piston.

Answer 1

How do I efficiently draw a path through many points without having to draw a line for every segment?
I'm not hugely familiar with Piston, but I would question your assumption that line() has some overhead that makes it inefficient to call repeatedly. In the end, whether you draw lots of lines or a library function draws them they will get drawn and there shouldn't be much difference in performance.
It doesn't look like there is currently a method to draw a sequence of lines between points, but it should just be a matter of looping through them as you were already doing. Using Vec::windows is a bit nicer though, as you don't need temporary mutable variables:
pub fn path<G>(color: Color, radius: Radius, points: &[[Scalar; 2]], transform: Matrix2d, g: &mut G)
where
G: Graphics,
{
for w in points.windows(2) {
line(
color,
radius,
[w[0][0], w[0][1], w[1][0], w[1][1]],
transform,
g,
);
}
}
You might consider making a feature request or a PR to the Piston project.