in src/ras.rs [368:381]
fn quad_to(&mut self, x1: f32, y1: f32, x: f32, y: f32) {
let to = AbPoint {
x: x * self.factor - self.x_min,
y: self.y_max - y * self.factor,
};
let c = AbPoint {
x: x1 * self.factor - self.x_min,
y: self.y_max - y1 * self.factor,
};
if let Some(prev) = self.prev.take() {
self.ras.draw_quad(prev, c, to);
}
self.prev = Some(to);
}