1 files changed, 176 insertions, 15 deletions

diff --git a/src/animation/clock.rs b/src/animation/clock.rs
index 3cfa727b..30f8bd45 100644
--- a/src/animation/clock.rs
+++ b/src/animation/clock.rs
@@ -1,41 +1,202 @@
-use std::cell::Cell;
+use std::cell::RefCell;
 use std::rc::Rc;
 use std::time::Duration;
 
 use crate::utils::get_monotonic_time;
 
-/// Clock that can have its time value overridden.
+/// Shareable lazy clock that can change rate.
 ///
-/// Can be cloned to share the same clock.
+/// The clock will fetch the time once and then retain it until explicitly cleared with
+/// [`Clock::clear`].
 #[derive(Debug, Default, Clone)]
 pub struct Clock {
-    time_override: Rc<Cell<Option<Duration>>>,
+    inner: Rc<RefCell<AdjustableClock>>,
+}
+
+#[derive(Debug, Default)]
+struct LazyClock {
+    time: Option<Duration>,
+}
+
+/// Clock that can adjust its rate.
+#[derive(Debug)]
+struct AdjustableClock {
+    inner: LazyClock,
+    current_time: Duration,
+    last_seen_time: Duration,
+    rate: f64,
+    complete_instantly: bool,
 }
 
 impl Clock {
-    /// Creates a new [`Clock`] with time override in place.
-    pub fn with_override(time: Duration) -> Self {
+    /// Creates a new clock with the given time.
+    pub fn with_time(time: Duration) -> Self {
+        let clock = AdjustableClock::new(LazyClock::with_time(time));
         Self {
-            time_override: Rc::new(Cell::new(Some(time))),
+            inner: Rc::new(RefCell::new(clock)),
         }
     }
 
-    /// Sets the current time override.
-    pub fn set_time_override(&mut self, time: Option<Duration>) {
-        self.time_override.set(time);
+    /// Returns the current time.
+    pub fn now(&self) -> Duration {
+        self.inner.borrow_mut().now()
     }
 
-    /// Gets the current time.
-    #[inline]
-    pub fn now(&self) -> Duration {
-        self.time_override.get().unwrap_or_else(get_monotonic_time)
+    /// Returns the underlying time not adjusted for rate change.
+    pub fn now_unadjusted(&self) -> Duration {
+        self.inner.borrow_mut().inner.now()
+    }
+
+    /// Sets the unadjusted clock time.
+    pub fn set_unadjusted(&mut self, time: Duration) {
+        self.inner.borrow_mut().inner.set(time);
+    }
+
+    /// Clears the stored time so it's re-fetched again next.
+    pub fn clear(&mut self) {
+        self.inner.borrow_mut().inner.clear();
+    }
+
+    /// Gets the clock rate.
+    pub fn rate(&self) -> f64 {
+        self.inner.borrow().rate()
+    }
+
+    /// Sets the clock rate.
+    pub fn set_rate(&mut self, rate: f64) {
+        self.inner.borrow_mut().set_rate(rate);
+    }
+
+    /// Returns whether animations should complete instantly.
+    pub fn should_complete_instantly(&self) -> bool {
+        self.inner.borrow().should_complete_instantly()
+    }
+
+    /// Sets whether animations should complete instantly.
+    pub fn set_complete_instantly(&mut self, value: bool) {
+        self.inner.borrow_mut().set_complete_instantly(value);
     }
 }
 
 impl PartialEq for Clock {
     fn eq(&self, other: &Self) -> bool {
-        Rc::ptr_eq(&self.time_override, &other.time_override)
+        Rc::ptr_eq(&self.inner, &other.inner)
     }
 }
 
 impl Eq for Clock {}
+
+impl LazyClock {
+    pub fn with_time(time: Duration) -> Self {
+        Self { time: Some(time) }
+    }
+
+    pub fn clear(&mut self) {
+        self.time = None;
+    }
+
+    pub fn set(&mut self, time: Duration) {
+        self.time = Some(time);
+    }
+
+    pub fn now(&mut self) -> Duration {
+        *self.time.get_or_insert_with(get_monotonic_time)
+    }
+}
+
+impl AdjustableClock {
+    pub fn new(mut inner: LazyClock) -> Self {
+        let time = inner.now();
+        Self {
+            inner,
+            current_time: time,
+            last_seen_time: time,
+            rate: 1.,
+            complete_instantly: false,
+        }
+    }
+
+    pub fn rate(&self) -> f64 {
+        self.rate
+    }
+
+    pub fn set_rate(&mut self, rate: f64) {
+        self.rate = rate.clamp(0., 1000.);
+    }
+
+    pub fn should_complete_instantly(&self) -> bool {
+        self.complete_instantly
+    }
+
+    pub fn set_complete_instantly(&mut self, value: bool) {
+        self.complete_instantly = value;
+    }
+
+    pub fn now(&mut self) -> Duration {
+        let time = self.inner.now();
+
+        if self.last_seen_time == time {
+            return self.current_time;
+        }
+
+        if self.last_seen_time < time {
+            let delta = time - self.last_seen_time;
+            let delta = delta.mul_f64(self.rate);
+            self.current_time = self.current_time.saturating_add(delta);
+        } else {
+            let delta = self.last_seen_time - time;
+            let delta = delta.mul_f64(self.rate);
+            self.current_time = self.current_time.saturating_sub(delta);
+        }
+
+        self.last_seen_time = time;
+        self.current_time
+    }
+}
+
+impl Default for AdjustableClock {
+    fn default() -> Self {
+        Self::new(LazyClock::default())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn frozen_clock() {
+        let mut clock = Clock::with_time(Duration::ZERO);
+        assert_eq!(clock.now(), Duration::ZERO);
+
+        clock.set_unadjusted(Duration::from_millis(100));
+        assert_eq!(clock.now(), Duration::from_millis(100));
+
+        clock.set_unadjusted(Duration::from_millis(200));
+        assert_eq!(clock.now(), Duration::from_millis(200));
+    }
+
+    #[test]
+    fn rate_change() {
+        let mut clock = Clock::with_time(Duration::ZERO);
+        clock.set_rate(0.5);
+
+        clock.set_unadjusted(Duration::from_millis(100));
+        assert_eq!(clock.now_unadjusted(), Duration::from_millis(100));
+        assert_eq!(clock.now(), Duration::from_millis(50));
+
+        clock.set_unadjusted(Duration::from_millis(200));
+        assert_eq!(clock.now_unadjusted(), Duration::from_millis(200));
+        assert_eq!(clock.now(), Duration::from_millis(100));
+
+        clock.set_unadjusted(Duration::from_millis(150));
+        assert_eq!(clock.now_unadjusted(), Duration::from_millis(150));
+        assert_eq!(clock.now(), Duration::from_millis(75));
+
+        clock.set_rate(2.0);
+
+        clock.set_unadjusted(Duration::from_millis(250));
+        assert_eq!(clock.now_unadjusted(), Duration::from_millis(250));
+        assert_eq!(clock.now(), Duration::from_millis(275));
+    }
+}