chore: various fixes and some cleanup

src/anim.rs

@@ -0,0 +1,51 @@
+use std::time::{Duration, Instant};
+
+/// A simple linear interpolation calculation function.
+/// p = `percent_complete` in decimal form
+#[must_use]
+pub fn lerp(start: f32, end: f32, p: f32) -> f32 {
+    (1.0 - p) * start + p * end
+}
+
+/// A fast smooth interpolation calculation function.
+/// p = `percent_complete` in decimal form
+#[must_use]
+pub fn slerp(start: f32, end: f32, p: f32) -> f32 {
+    let t = smootherstep(p);
+    (1.0 - t) * start + t * end
+}
+
+/// utility function which maps a value [0, 1] -> [0, 1] using the smootherstep function
+pub fn smootherstep(t: f32) -> f32 {
+    (6.0 * t.powi(5) - 15.0 * t.powi(4) + 10.0 * t.powi(3)).clamp(0.0, 1.0)
+}
+
+#[derive(Default, Debug)]
+pub struct State {
+    pub last_change: Option<Instant>,
+}
+
+impl State {
+    pub fn changed(&mut self, dur: Duration) {
+        let t = self.t(dur, false);
+        let diff = dur.mul_f32(t.abs());
+        let now = Instant::now();
+        self.last_change = Some(now.checked_sub(diff).unwrap_or(now));
+    }
+
+    pub fn anim_done(&mut self, dur: Duration) {
+        if self
+            .last_change
+            .is_some_and(|t| Instant::now().duration_since(t) > dur)
+        {
+            self.last_change = None;
+        }
+    }
+
+    pub fn t(&self, dur: Duration, forward: bool) -> f32 {
+        let res = self.last_change.map_or(1., |t| {
+            Instant::now().duration_since(t).as_millis() as f32 / dur.as_millis() as f32
+        });
+        if forward { res } else { 1. - res }
+    }
+}