Add GamepadAxis2DEvent::direction

Author: fwcd

lighthouse-protocol/src/input/gamepad_axis_2d_event.rs

@@ -1,6 +1,6 @@
 use serde::{Deserialize, Serialize};
 
-use crate::Vec2;
+use crate::{Direction, Vec2};
 
 /// A 2D axis event on a gamepad.
 #[derive(Debug, Serialize, Deserialize, PartialEq, Clone)]
@@ -11,3 +11,52 @@ pub struct GamepadAxis2DEvent {
     /// The value of the axis (each component is between -1.0 and 1.0, modeled after the Web Gamepad API).
     pub value: Vec2<f64>,
 }
+
+impl GamepadAxis2DEvent {
+    /// The approximate direction (outside of a small deadzone).
+    pub fn direction(&self) -> Option<Direction> {
+        let deadzone_radius: f64 = 0.1;
+        if self.value.length() < deadzone_radius {
+            return None;
+        }
+
+        // See https://www.desmos.com/calculator/472pdoxzqa for visualization
+        // Note that the y-axis is flipped here, per computer graphics conventions,
+        // hence the sign flip (-y instead of y).
+        let Vec2 { x, y } = self.value;
+        let left_or_up = x < -y;
+        let right_or_up = -x < -y;
+        Some(
+            match (left_or_up, right_or_up) {
+                (true, true) => Direction::Up,
+                (true, false) => Direction::Left,
+                (false, true) => Direction::Right,
+                (false, false) => Direction::Down, 
+            }
+        )
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{Direction, Vec2, Zero};
+
+    use super::GamepadAxis2DEvent;
+
+    #[test]
+    fn directions() {
+        assert_eq!(event(Vec2::UP).direction(), Some(Direction::Up));
+        assert_eq!(event(Vec2::DOWN).direction(), Some(Direction::Down));
+        assert_eq!(event(Vec2::LEFT).direction(), Some(Direction::Left));
+        assert_eq!(event(Vec2::RIGHT).direction(), Some(Direction::Right));
+        assert_eq!(event(Vec2::ZERO).direction(), None);
+        assert_eq!(event(Vec2::new(-0.05, 0.05)).direction(), None); // within deadzone
+    }
+
+    fn event(value: Vec2<f64>) -> GamepadAxis2DEvent {
+        GamepadAxis2DEvent {
+            index: 0,
+            value,
+        }
+    }
+}