1 files changed, 40 insertions, 0 deletions
diff --git a/src/input/scroll_tracker.rs b/src/input/scroll_tracker.rs
new file mode 100644
index 00000000..fc48ef06
--- /dev/null
+++ b/src/input/scroll_tracker.rs
@@ -0,0 +1,40 @@
+pub struct ScrollTracker {
+    tick: f64,
+    last: f64,
+    acc: f64,
+}
+
+impl ScrollTracker {
+    #[allow(clippy::new_without_default)]
+    pub fn new(tick: i8) -> Self {
+        Self {
+            tick: f64::from(tick),
+            last: 0.,
+            acc: 0.,
+        }
+    }
+
+    pub fn accumulate(&mut self, amount: f64) -> i8 {
+        let changed_direction = (self.last > 0. && amount < 0.) || (self.last < 0. && amount > 0.);
+        if changed_direction {
+            self.acc = 0.
+        }
+
+        self.last = amount;
+        self.acc += amount;
+
+        let mut ticks = 0;
+        if self.acc.abs() >= self.tick {
+            let clamped = self.acc.clamp(-127. * self.tick, 127. * self.tick);
+            ticks = (clamped as i16 / self.tick as i16) as i8;
+            self.acc %= self.tick;
+        }
+
+        ticks
+    }
+
+    pub fn reset(&mut self) {
+        self.last = 0.;
+        self.acc = 0.;
+    }
+}