rlvgl_widgets/motion/
direction.rs

1// SPDX-License-Identifier: MIT
2//! Cardinal direction enum shared by motion widgets.
3//!
4//! Motion components such as [`crate::motion::crawl::TextCrawl`] scroll
5//! along one of four cardinal directions. The enum lives alongside the
6//! other motion infrastructure so all variants consume the same
7//! vocabulary.
8
9/// One of four cardinal scroll directions.
10///
11/// Combined with a [`crate::motion::MotionRate`], a [`Direction`]
12/// fully specifies how the visible window slides over a jumbo
13/// background buffer: the rate supplies the **speed**, the direction
14/// supplies the **axis** and **sign**.
15#[derive(Copy, Clone, Debug, PartialEq, Eq)]
16pub enum Direction {
17    /// Content scrolls upward (Star Wars crawl default).
18    Up,
19    /// Content scrolls downward.
20    Down,
21    /// Content scrolls to the left (news ticker default).
22    Left,
23    /// Content scrolls to the right.
24    Right,
25}
26
27impl Direction {
28    /// Returns `true` if this direction is vertical (`Up` or `Down`).
29    #[inline]
30    pub const fn is_vertical(self) -> bool {
31        matches!(self, Direction::Up | Direction::Down)
32    }
33
34    /// Returns `true` if this direction is horizontal (`Left` or `Right`).
35    #[inline]
36    pub const fn is_horizontal(self) -> bool {
37        matches!(self, Direction::Left | Direction::Right)
38    }
39
40    /// Sign of the scroll offset along the scroll axis.
41    ///
42    /// `+1` when the scroll accumulator should *grow* per frame
43    /// ([`Direction::Down`] / [`Direction::Right`]) and `-1` when it
44    /// should shrink ([`Direction::Up`] / [`Direction::Left`]).
45    #[inline]
46    pub const fn sign(self) -> i32 {
47        match self {
48            Direction::Down | Direction::Right => 1,
49            Direction::Up | Direction::Left => -1,
50        }
51    }
52}
53
54#[cfg(test)]
55mod tests {
56    use super::*;
57
58    #[test]
59    fn vertical_directions() {
60        assert!(Direction::Up.is_vertical());
61        assert!(Direction::Down.is_vertical());
62        assert!(!Direction::Left.is_vertical());
63        assert!(!Direction::Right.is_vertical());
64    }
65
66    #[test]
67    fn horizontal_directions() {
68        assert!(Direction::Left.is_horizontal());
69        assert!(Direction::Right.is_horizontal());
70        assert!(!Direction::Up.is_horizontal());
71        assert!(!Direction::Down.is_horizontal());
72    }
73
74    #[test]
75    fn signs() {
76        assert_eq!(Direction::Up.sign(), -1);
77        assert_eq!(Direction::Down.sign(), 1);
78        assert_eq!(Direction::Left.sign(), -1);
79        assert_eq!(Direction::Right.sign(), 1);
80    }
81}
rlvgl_widgets/motion/direction.rs

rlvgl_widgets/motion/
direction.rs
