diff --git a/egui/src/input_state/touch_state.rs b/egui/src/input_state/touch_state.rs
index 41d1a590..e6437063 100644
--- a/egui/src/input_state/touch_state.rs
+++ b/egui/src/input_state/touch_state.rs
@@ -1,11 +1,10 @@
-use std::{
-    collections::BTreeMap,
-    f32::consts::{PI, TAU},
-    fmt::Debug,
-};
+use std::{collections::BTreeMap, fmt::Debug};
 
-use crate::{data::input::TouchDeviceId, Event, RawInput, TouchId, TouchPhase};
-use epaint::emath::{Pos2, Vec2};
+use crate::{
+    data::input::TouchDeviceId,
+    emath::{normalized_angle, Pos2, Vec2},
+    Event, RawInput, TouchId, TouchPhase,
+};
 
 /// All you probably need to know about a multi-touch gesture.
 pub struct MultiTouchInfo {
@@ -196,7 +195,7 @@ impl TouchState {
                 num_touches: self.active_touches.len(),
                 zoom_delta,
                 zoom_delta_2d: zoom_delta2,
-                rotation_delta: normalized_angle(state.current.heading, state_previous.heading),
+                rotation_delta: normalized_angle(state.current.heading - state_previous.heading),
                 translation_delta: state.current.avg_pos - state_previous.avg_pos,
                 force: state.current.avg_force,
             }
@@ -294,27 +293,6 @@ impl Debug for TouchState {
     }
 }
 
-/// Calculate difference between two directions, such that the absolute value of the result is
-/// minimized.
-fn normalized_angle(current_direction: f32, previous_direction: f32) -> f32 {
-    let mut angle = current_direction - previous_direction;
-    angle %= TAU;
-    if angle > PI {
-        angle -= TAU;
-    } else if angle < -PI {
-        angle += TAU;
-    }
-    angle
-}
-
-#[test]
-fn normalizing_angle_from_350_to_0_yields_10() {
-    assert!(
-        (normalized_angle(0_f32.to_radians(), 350_f32.to_radians()) - 10_f32.to_radians()).abs()
-            <= 5. * f32::EPSILON // many conversions (=divisions) involved => high error rate
-    );
-}
-
 #[derive(Clone, Debug)]
 enum PinchType {
     Horizontal,
diff --git a/emath/src/lib.rs b/emath/src/lib.rs
index 040d5f92..c29e048e 100644
--- a/emath/src/lib.rs
+++ b/emath/src/lib.rs
@@ -331,3 +331,36 @@ impl_num_ext!(f64);
 impl_num_ext!(usize);
 impl_num_ext!(Vec2);
 impl_num_ext!(Pos2);
+
+// ----------------------------------------------------------------------------
+
+/// Wrap angle to `[-PI, PI]` range.
+pub fn normalized_angle(mut angle: f32) -> f32 {
+    use std::f32::consts::{PI, TAU};
+    angle %= TAU;
+    if angle > PI {
+        angle -= TAU;
+    } else if angle < -PI {
+        angle += TAU;
+    }
+    angle
+}
+
+#[test]
+fn test_normalized_angle() {
+    macro_rules! almost_eq {
+        ($left:expr, $right:expr) => {
+            let left = $left;
+            let right = $right;
+            assert!((left - right).abs() < 1e-6, "{} != {}", left, right);
+        };
+    }
+
+    use std::f32::consts::TAU;
+    almost_eq!(normalized_angle(-3.0 * TAU), 0.0);
+    almost_eq!(normalized_angle(-2.3 * TAU), -0.3 * TAU);
+    almost_eq!(normalized_angle(-TAU), 0.0);
+    almost_eq!(normalized_angle(0.0), 0.0);
+    almost_eq!(normalized_angle(TAU), 0.0);
+    almost_eq!(normalized_angle(2.7 * TAU), -0.3 * TAU);
+}