Revert "Carry time delta between tweens in a Sequence (#39)"

This reverts commit 77b56f44.

src/tweenable.rs

@@ -650,26 +650,28 @@ impl<T> Tweenable<T> for Sequence<T> {
 
     fn tick(
         &mut self,
-        mut delta: Duration,
+        delta: Duration,
         target: &mut T,
         entity: Entity,
         event_writer: &mut EventWriter<TweenCompleted>,
     ) -> TweenState {
-        self.time = (self.time + delta).min(self.duration);
-        while self.index < self.tweens.len() {
+        if self.index < self.tweens.len() {
+            let mut state = TweenState::Active;
+            self.time = (self.time + delta).min(self.duration);
             let tween = &mut self.tweens[self.index];
-            let tween_remaining = tween.duration().mul_f32(1.0 - tween.progress());
-            if let TweenState::Active = tween.tick(delta, target, entity, event_writer) {
-                return TweenState::Active;
+            let tween_state = tween.tick(delta, target, entity, event_writer);
+            if tween_state == TweenState::Completed {
+                tween.rewind();
+                self.index += 1;
+                if self.index >= self.tweens.len() {
+                    state = TweenState::Completed;
+                    self.times_completed = 1;
+                }
             }
-
-            tween.rewind();
-            delta -= tween_remaining;
-            self.index += 1;
+            state
+        } else {
+            TweenState::Completed
         }
-
-        self.times_completed = 1;
-        TweenState::Completed
     }
 
     fn times_completed(&self) -> u32 {
@@ -1263,45 +1265,6 @@ mod tests {
         }
     }
 
-    /// Test crossing tween boundaries in one tick.
-    #[test]
-    fn seq_tick_boundaries() {
-        let mut seq = Sequence::new((0..3).map(|i| {
-            Tween::new(
-                EaseMethod::Linear,
-                TweeningType::Once,
-                Duration::from_secs(1),
-                TransformPositionLens {
-                    start: Vec3::splat(i as f32),
-                    end: Vec3::splat((i + 1) as f32),
-                },
-            )
-        }));
-        let mut transform = Transform::default();
-
-        // Dummy world and event writer
-        let mut world = World::new();
-        world.insert_resource(Events::<TweenCompleted>::default());
-        let mut system_state: SystemState<EventWriter<TweenCompleted>> =
-            SystemState::new(&mut world);
-        let mut event_writer = system_state.get_mut(&mut world);
-
-        // Tick halfway through the first tween, then in one tick:
-        // - Finish the first tween
-        // - Start and finish the second tween
-        // - Start the third tween
-        for delta in [0.5, 2.0] {
-            seq.tick(
-                Duration::from_secs_f32(delta),
-                &mut transform,
-                Entity::from_raw(0),
-                &mut event_writer,
-            );
-        }
-        assert_eq!(seq.index(), 2);
-        assert!(transform.translation.abs_diff_eq(Vec3::splat(2.5), 1e-5));
-    }
-
     /// Sequence::new() and various Sequence-specific methods
     #[test]
     fn seq_iter() {