trackball/
slide.rs

1use nalgebra::{Point2, RealField, Vector2};
2use simba::scalar::SubsetOf;
3
4/// Slide induced by displacement on screen.
5///
6/// Implements [`Default`] and can be created with `Slide::default()`.
7///
8/// Both its methods must be invoked on matching events fired by your 3D graphics library of choice.
9#[derive(Debug, Clone, Default)]
10pub struct Slide<N: Copy + RealField> {
11	/// Caches previous cursor/finger position.
12	pos: Option<Point2<N>>,
13}
14
15impl<N: Copy + RealField> Slide<N> {
16	/// Computes slide between previous and current cursor/finger position in screen space.
17	pub fn compute(&mut self, pos: Point2<N>) -> Option<Vector2<N>> {
18		self.pos.replace(pos).map(|old| old - pos)
19	}
20	/// Discards cached previous cursor/finger position on button/finger release.
21	pub const fn discard(&mut self) {
22		self.pos = None;
23	}
24	/// Casts components to another type, e.g., between [`f32`] and [`f64`].
25	#[must_use]
26	pub fn cast<M: Copy + RealField>(self) -> Slide<M>
27	where
28		N: SubsetOf<M>,
29	{
30		Slide {
31			pos: self.pos.map(Point2::cast),
32		}
33	}
34}
trackball/slide.rs

trackball/
slide.rs
