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#[cfg(feature = "bevy_reflect")]
use bevy_ecs::reflect::ReflectResource;
use bevy_ecs::system::Resource;
#[cfg(feature = "bevy_reflect")]
use bevy_reflect::{std_traits::ReflectDefault, Reflect};
use bevy_utils::Duration;
/// A generic clock resource that tracks how much it has advanced since its
/// previous update and since its creation.
///
/// Multiple instances of this resource are inserted automatically by
/// [`TimePlugin`](crate::TimePlugin):
///
/// - [`Time<Real>`](crate::real::Real) tracks real wall-clock time elapsed.
/// - [`Time<Virtual>`](crate::virt::Virtual) tracks virtual game time that may
/// be paused or scaled.
/// - [`Time<Fixed>`](crate::fixed::Fixed) tracks fixed timesteps based on
/// virtual time.
/// - [`Time`] is a generic clock that corresponds to "current" or "default"
/// time for systems. It contains [`Time<Virtual>`](crate::virt::Virtual)
/// except inside the [`FixedMain`](bevy_app::FixedMain) schedule when it
/// contains [`Time<Fixed>`](crate::fixed::Fixed).
///
/// The time elapsed since the previous time this clock was advanced is saved as
/// [`delta()`](Time::delta) and the total amount of time the clock has advanced
/// is saved as [`elapsed()`](Time::elapsed). Both are represented as exact
/// [`Duration`] values with fixed nanosecond precision. The clock does not
/// support time moving backwards, but it can be updated with [`Duration::ZERO`]
/// which will set [`delta()`](Time::delta) to zero.
///
/// These values are also available in seconds as `f32` via
/// [`delta_seconds()`](Time::delta_seconds) and
/// [`elapsed_seconds()`](Time::elapsed_seconds), and also in seconds as `f64`
/// via [`delta_seconds_f64()`](Time::delta_seconds_f64) and
/// [`elapsed_seconds_f64()`](Time::elapsed_seconds_f64).
///
/// Since [`elapsed_seconds()`](Time::elapsed_seconds) will grow constantly and
/// is `f32`, it will exhibit gradual precision loss. For applications that
/// require an `f32` value but suffer from gradual precision loss there is
/// [`elapsed_seconds_wrapped()`](Time::elapsed_seconds_wrapped) available. The
/// same wrapped value is also available as [`Duration`] and `f64` for
/// consistency. The wrap period is by default 1 hour, and can be set by
/// [`set_wrap_period()`](Time::set_wrap_period).
///
/// # Accessing clocks
///
/// By default, any systems requiring current [`delta()`](Time::delta) or
/// [`elapsed()`](Time::elapsed) should use `Res<Time>` to access the default
/// time configured for the program. By default, this refers to
/// [`Time<Virtual>`](crate::virt::Virtual) except during the
/// [`FixedMain`](bevy_app::FixedMain) schedule when it refers to
/// [`Time<Fixed>`](crate::fixed::Fixed). This ensures your system can be used
/// either in [`Update`](bevy_app::Update) or
/// [`FixedUpdate`](bevy_app::FixedUpdate) schedule depending on what is needed.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_time::prelude::*;
/// #
/// fn ambivalent_system(time: Res<Time>) {
/// println!("this how I see time: delta {:?}, elapsed {:?}", time.delta(), time.elapsed());
/// }
/// ```
///
/// If your system needs to react based on real time (wall clock time), like for
/// user interfaces, it should use `Res<Time<Real>>`. The
/// [`delta()`](Time::delta) and [`elapsed()`](Time::elapsed) values will always
/// correspond to real time and will not be affected by pause, time scaling or
/// other tweaks.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_time::prelude::*;
/// #
/// fn real_time_system(time: Res<Time<Real>>) {
/// println!("this will always be real time: delta {:?}, elapsed {:?}", time.delta(), time.elapsed());
/// }
/// ```
///
/// If your system specifically needs to access fixed timestep clock, even when
/// placed in `Update` schedule, you should use `Res<Time<Fixed>>`. The
/// [`delta()`](Time::delta) and [`elapsed()`](Time::elapsed) values will
/// correspond to the latest fixed timestep that has been run.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_time::prelude::*;
/// #
/// fn fixed_time_system(time: Res<Time<Fixed>>) {
/// println!("this will always be the last executed fixed timestep: delta {:?}, elapsed {:?}", time.delta(), time.elapsed());
/// }
/// ```
///
/// Finally, if your system specifically needs to know the current virtual game
/// time, even if placed inside [`FixedUpdate`](bevy_app::FixedUpdate), for
/// example to know if the game is [`was_paused()`](Time::was_paused) or to use
/// [`effective_speed()`](Time::effective_speed), you can use
/// `Res<Time<Virtual>>`. However, if the system is placed in
/// [`FixedUpdate`](bevy_app::FixedUpdate), extra care must be used because your
/// system might be run multiple times with the same [`delta()`](Time::delta)
/// and [`elapsed()`](Time::elapsed) values as the virtual game time has not
/// changed between the iterations.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_time::prelude::*;
/// #
/// fn fixed_time_system(time: Res<Time<Virtual>>) {
/// println!("this will be virtual time for this update: delta {:?}, elapsed {:?}", time.delta(), time.elapsed());
/// println!("also the relative speed of the game is now {}", time.effective_speed());
/// }
/// ```
///
/// If you need to change the settings for any of the clocks, for example to
/// [`pause()`](Time::pause) the game, you should use `ResMut<Time<Virtual>>`.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_time::prelude::*;
/// #
/// #[derive(Event)]
/// struct PauseEvent(bool);
///
/// fn pause_system(mut time: ResMut<Time<Virtual>>, mut events: EventReader<PauseEvent>) {
/// for ev in events.read() {
/// if ev.0 {
/// time.pause();
/// } else {
/// time.unpause();
/// }
/// }
/// }
/// ```
///
/// # Adding custom clocks
///
/// New custom clocks can be created by creating your own struct as a context
/// and passing it to [`new_with()`](Time::new_with). These clocks can be
/// inserted as resources as normal and then accessed by systems. You can use
/// the [`advance_by()`](Time::advance_by) or [`advance_to()`](Time::advance_to)
/// methods to move the clock forwards based on your own logic.
///
/// If you want to add methods for your time instance and they require access to
/// both your context and the generic time part, it's probably simplest to add a
/// custom trait for them and implement it for `Time<Custom>`.
///
/// Your context struct will need to implement the [`Default`] trait because
/// [`Time`] structures support reflection. It also makes initialization trivial
/// by being able to call `app.init_resource::<Time<Custom>>()`.
///
/// You can also replace the "generic" `Time` clock resource if the "default"
/// time for your game should not be the default virtual time provided. You can
/// get a "generic" snapshot of your clock by calling `as_generic()` and then
/// overwrite the [`Time`] resource with it. The default systems added by
/// [`TimePlugin`](crate::TimePlugin) will overwrite the [`Time`] clock during
/// [`First`](bevy_app::First) and [`FixedUpdate`](bevy_app::FixedUpdate)
/// schedules.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_time::prelude::*;
/// # use bevy_utils::Instant;
/// #
/// #[derive(Debug)]
/// struct Custom {
/// last_external_time: Instant,
/// }
///
/// impl Default for Custom {
/// fn default() -> Self {
/// Self {
/// last_external_time: Instant::now(),
/// }
/// }
/// }
///
/// trait CustomTime {
/// fn update_from_external(&mut self, instant: Instant);
/// }
///
/// impl CustomTime for Time<Custom> {
/// fn update_from_external(&mut self, instant: Instant) {
/// let delta = instant - self.context().last_external_time;
/// self.advance_by(delta);
/// self.context_mut().last_external_time = instant;
/// }
/// }
/// ```
#[derive(Resource, Debug, Copy, Clone)]
#[cfg_attr(feature = "bevy_reflect", derive(Reflect), reflect(Resource, Default))]
pub struct Time<T: Default = ()> {
context: T,
wrap_period: Duration,
delta: Duration,
delta_seconds: f32,
delta_seconds_f64: f64,
elapsed: Duration,
elapsed_seconds: f32,
elapsed_seconds_f64: f64,
elapsed_wrapped: Duration,
elapsed_seconds_wrapped: f32,
elapsed_seconds_wrapped_f64: f64,
}
impl<T: Default> Time<T> {
const DEFAULT_WRAP_PERIOD: Duration = Duration::from_secs(3600); // 1 hour
/// Create a new clock from context with [`Self::delta`] and [`Self::elapsed`] starting from
/// zero.
pub fn new_with(context: T) -> Self {
Self {
context,
..Default::default()
}
}
/// Advance this clock by adding a `delta` duration to it.
///
/// The added duration will be returned by [`Self::delta`] and
/// [`Self::elapsed`] will be increased by the duration. Adding
/// [`Duration::ZERO`] is allowed and will set [`Self::delta`] to zero.
pub fn advance_by(&mut self, delta: Duration) {
self.delta = delta;
self.delta_seconds = self.delta.as_secs_f32();
self.delta_seconds_f64 = self.delta.as_secs_f64();
self.elapsed += delta;
self.elapsed_seconds = self.elapsed.as_secs_f32();
self.elapsed_seconds_f64 = self.elapsed.as_secs_f64();
self.elapsed_wrapped = duration_rem(self.elapsed, self.wrap_period);
self.elapsed_seconds_wrapped = self.elapsed_wrapped.as_secs_f32();
self.elapsed_seconds_wrapped_f64 = self.elapsed_wrapped.as_secs_f64();
}
/// Advance this clock to a specific `elapsed` time.
///
/// [`Self::delta()`] will return the amount of time the clock was advanced
/// and [`Self::elapsed()`] will be the `elapsed` value passed in. Cannot be
/// used to move time backwards.
///
/// # Panics
///
/// Panics if `elapsed` is less than `Self::elapsed()`.
pub fn advance_to(&mut self, elapsed: Duration) {
assert!(
elapsed >= self.elapsed,
"tried to move time backwards to an earlier elapsed moment"
);
self.advance_by(elapsed - self.elapsed);
}
/// Returns the modulus used to calculate [`elapsed_wrapped`](#method.elapsed_wrapped).
///
/// **Note:** The default modulus is one hour.
#[inline]
pub fn wrap_period(&self) -> Duration {
self.wrap_period
}
/// Sets the modulus used to calculate [`elapsed_wrapped`](#method.elapsed_wrapped).
///
/// **Note:** This will not take effect until the next update.
///
/// # Panics
///
/// Panics if `wrap_period` is a zero-length duration.
#[inline]
pub fn set_wrap_period(&mut self, wrap_period: Duration) {
assert!(!wrap_period.is_zero(), "division by zero");
self.wrap_period = wrap_period;
}
/// Returns how much time has advanced since the last [`update`](#method.update), as a
/// [`Duration`].
#[inline]
pub fn delta(&self) -> Duration {
self.delta
}
/// Returns how much time has advanced since the last [`update`](#method.update), as [`f32`]
/// seconds.
#[inline]
pub fn delta_seconds(&self) -> f32 {
self.delta_seconds
}
/// Returns how much time has advanced since the last [`update`](#method.update), as [`f64`]
/// seconds.
#[inline]
pub fn delta_seconds_f64(&self) -> f64 {
self.delta_seconds_f64
}
/// Returns how much time has advanced since [`startup`](#method.startup), as [`Duration`].
#[inline]
pub fn elapsed(&self) -> Duration {
self.elapsed
}
/// Returns how much time has advanced since [`startup`](#method.startup), as [`f32`] seconds.
///
/// **Note:** This is a monotonically increasing value. Its precision will degrade over time.
/// If you need an `f32` but that precision loss is unacceptable,
/// use [`elapsed_seconds_wrapped`](#method.elapsed_seconds_wrapped).
#[inline]
pub fn elapsed_seconds(&self) -> f32 {
self.elapsed_seconds
}
/// Returns how much time has advanced since [`startup`](#method.startup), as [`f64`] seconds.
#[inline]
pub fn elapsed_seconds_f64(&self) -> f64 {
self.elapsed_seconds_f64
}
/// Returns how much time has advanced since [`startup`](#method.startup) modulo
/// the [`wrap_period`](#method.wrap_period), as [`Duration`].
#[inline]
pub fn elapsed_wrapped(&self) -> Duration {
self.elapsed_wrapped
}
/// Returns how much time has advanced since [`startup`](#method.startup) modulo
/// the [`wrap_period`](#method.wrap_period), as [`f32`] seconds.
///
/// This method is intended for applications (e.g. shaders) that require an [`f32`] value but
/// suffer from the gradual precision loss of [`elapsed_seconds`](#method.elapsed_seconds).
#[inline]
pub fn elapsed_seconds_wrapped(&self) -> f32 {
self.elapsed_seconds_wrapped
}
/// Returns how much time has advanced since [`startup`](#method.startup) modulo
/// the [`wrap_period`](#method.wrap_period), as [`f64`] seconds.
#[inline]
pub fn elapsed_seconds_wrapped_f64(&self) -> f64 {
self.elapsed_seconds_wrapped_f64
}
/// Returns a reference to the context of this specific clock.
#[inline]
pub fn context(&self) -> &T {
&self.context
}
/// Returns a mutable reference to the context of this specific clock.
#[inline]
pub fn context_mut(&mut self) -> &mut T {
&mut self.context
}
/// Returns a copy of this clock as fully generic clock without context.
#[inline]
pub fn as_generic(&self) -> Time<()> {
Time {
context: (),
wrap_period: self.wrap_period,
delta: self.delta,
delta_seconds: self.delta_seconds,
delta_seconds_f64: self.delta_seconds_f64,
elapsed: self.elapsed,
elapsed_seconds: self.elapsed_seconds,
elapsed_seconds_f64: self.elapsed_seconds_f64,
elapsed_wrapped: self.elapsed_wrapped,
elapsed_seconds_wrapped: self.elapsed_seconds_wrapped,
elapsed_seconds_wrapped_f64: self.elapsed_seconds_wrapped_f64,
}
}
}
impl<T: Default> Default for Time<T> {
fn default() -> Self {
Self {
context: Default::default(),
wrap_period: Self::DEFAULT_WRAP_PERIOD,
delta: Duration::ZERO,
delta_seconds: 0.0,
delta_seconds_f64: 0.0,
elapsed: Duration::ZERO,
elapsed_seconds: 0.0,
elapsed_seconds_f64: 0.0,
elapsed_wrapped: Duration::ZERO,
elapsed_seconds_wrapped: 0.0,
elapsed_seconds_wrapped_f64: 0.0,
}
}
}
fn duration_rem(dividend: Duration, divisor: Duration) -> Duration {
// `Duration` does not have a built-in modulo operation
let quotient = (dividend.as_nanos() / divisor.as_nanos()) as u32;
dividend - (quotient * divisor)
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_initial_state() {
let time: Time = Time::default();
assert_eq!(time.wrap_period(), Time::<()>::DEFAULT_WRAP_PERIOD);
assert_eq!(time.delta(), Duration::ZERO);
assert_eq!(time.delta_seconds(), 0.0);
assert_eq!(time.delta_seconds_f64(), 0.0);
assert_eq!(time.elapsed(), Duration::ZERO);
assert_eq!(time.elapsed_seconds(), 0.0);
assert_eq!(time.elapsed_seconds_f64(), 0.0);
assert_eq!(time.elapsed_wrapped(), Duration::ZERO);
assert_eq!(time.elapsed_seconds_wrapped(), 0.0);
assert_eq!(time.elapsed_seconds_wrapped_f64(), 0.0);
}
#[test]
fn test_advance_by() {
let mut time: Time = Time::default();
time.advance_by(Duration::from_millis(250));
assert_eq!(time.delta(), Duration::from_millis(250));
assert_eq!(time.delta_seconds(), 0.25);
assert_eq!(time.delta_seconds_f64(), 0.25);
assert_eq!(time.elapsed(), Duration::from_millis(250));
assert_eq!(time.elapsed_seconds(), 0.25);
assert_eq!(time.elapsed_seconds_f64(), 0.25);
time.advance_by(Duration::from_millis(500));
assert_eq!(time.delta(), Duration::from_millis(500));
assert_eq!(time.delta_seconds(), 0.5);
assert_eq!(time.delta_seconds_f64(), 0.5);
assert_eq!(time.elapsed(), Duration::from_millis(750));
assert_eq!(time.elapsed_seconds(), 0.75);
assert_eq!(time.elapsed_seconds_f64(), 0.75);
time.advance_by(Duration::ZERO);
assert_eq!(time.delta(), Duration::ZERO);
assert_eq!(time.delta_seconds(), 0.0);
assert_eq!(time.delta_seconds_f64(), 0.0);
assert_eq!(time.elapsed(), Duration::from_millis(750));
assert_eq!(time.elapsed_seconds(), 0.75);
assert_eq!(time.elapsed_seconds_f64(), 0.75);
}
#[test]
fn test_advance_to() {
let mut time: Time = Time::default();
time.advance_to(Duration::from_millis(250));
assert_eq!(time.delta(), Duration::from_millis(250));
assert_eq!(time.delta_seconds(), 0.25);
assert_eq!(time.delta_seconds_f64(), 0.25);
assert_eq!(time.elapsed(), Duration::from_millis(250));
assert_eq!(time.elapsed_seconds(), 0.25);
assert_eq!(time.elapsed_seconds_f64(), 0.25);
time.advance_to(Duration::from_millis(750));
assert_eq!(time.delta(), Duration::from_millis(500));
assert_eq!(time.delta_seconds(), 0.5);
assert_eq!(time.delta_seconds_f64(), 0.5);
assert_eq!(time.elapsed(), Duration::from_millis(750));
assert_eq!(time.elapsed_seconds(), 0.75);
assert_eq!(time.elapsed_seconds_f64(), 0.75);
time.advance_to(Duration::from_millis(750));
assert_eq!(time.delta(), Duration::ZERO);
assert_eq!(time.delta_seconds(), 0.0);
assert_eq!(time.delta_seconds_f64(), 0.0);
assert_eq!(time.elapsed(), Duration::from_millis(750));
assert_eq!(time.elapsed_seconds(), 0.75);
assert_eq!(time.elapsed_seconds_f64(), 0.75);
}
#[test]
#[should_panic]
fn test_advance_to_backwards_panics() {
let mut time: Time = Time::default();
time.advance_to(Duration::from_millis(750));
time.advance_to(Duration::from_millis(250));
}
#[test]
fn test_wrapping() {
let mut time: Time = Time::default();
time.set_wrap_period(Duration::from_secs(3));
time.advance_by(Duration::from_secs(2));
assert_eq!(time.elapsed_wrapped(), Duration::from_secs(2));
assert_eq!(time.elapsed_seconds_wrapped(), 2.0);
assert_eq!(time.elapsed_seconds_wrapped_f64(), 2.0);
time.advance_by(Duration::from_secs(2));
assert_eq!(time.elapsed_wrapped(), Duration::from_secs(1));
assert_eq!(time.elapsed_seconds_wrapped(), 1.0);
assert_eq!(time.elapsed_seconds_wrapped_f64(), 1.0);
time.advance_by(Duration::from_secs(2));
assert_eq!(time.elapsed_wrapped(), Duration::ZERO);
assert_eq!(time.elapsed_seconds_wrapped(), 0.0);
assert_eq!(time.elapsed_seconds_wrapped_f64(), 0.0);
time.advance_by(Duration::new(3, 250_000_000));
assert_eq!(time.elapsed_wrapped(), Duration::from_millis(250));
assert_eq!(time.elapsed_seconds_wrapped(), 0.25);
assert_eq!(time.elapsed_seconds_wrapped_f64(), 0.25);
}
#[test]
fn test_wrapping_change() {
let mut time: Time = Time::default();
time.set_wrap_period(Duration::from_secs(5));
time.advance_by(Duration::from_secs(8));
assert_eq!(time.elapsed_wrapped(), Duration::from_secs(3));
assert_eq!(time.elapsed_seconds_wrapped(), 3.0);
assert_eq!(time.elapsed_seconds_wrapped_f64(), 3.0);
time.set_wrap_period(Duration::from_secs(2));
assert_eq!(time.elapsed_wrapped(), Duration::from_secs(3));
assert_eq!(time.elapsed_seconds_wrapped(), 3.0);
assert_eq!(time.elapsed_seconds_wrapped_f64(), 3.0);
time.advance_by(Duration::ZERO);
// Time will wrap to modulo duration from full `elapsed()`, not to what
// is left in `elapsed_wrapped()`. This test of values is here to ensure
// that we notice if we change that behaviour.
assert_eq!(time.elapsed_wrapped(), Duration::from_secs(0));
assert_eq!(time.elapsed_seconds_wrapped(), 0.0);
assert_eq!(time.elapsed_seconds_wrapped_f64(), 0.0);
}
}