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use crate::{App, Plugin};
use bevy_ecs::{
schedule::{ExecutorKind, InternedScheduleLabel, Schedule, ScheduleLabel},
system::{Local, Resource},
world::{Mut, World},
};
/// The schedule that contains the app logic that is evaluated each tick of [`App::update()`].
///
/// By default, it will run the following schedules in the given order:
///
/// On the first run of the schedule (and only on the first run), it will run:
/// * [`PreStartup`]
/// * [`Startup`]
/// * [`PostStartup`]
///
/// Then it will run:
/// * [`First`]
/// * [`PreUpdate`]
/// * [`StateTransition`](bevy_state::transition::StateTransition)
/// * [`RunFixedMainLoop`]
/// * This will run [`FixedMain`] zero to many times, based on how much time has elapsed.
/// * [`Update`]
/// * [`PostUpdate`]
/// * [`Last`]
///
/// # Rendering
///
/// Note rendering is not executed in the main schedule by default.
/// Instead, rendering is performed in a separate [`SubApp`]
/// which exchanges data with the main app in between the main schedule runs.
///
/// See [`RenderPlugin`] and [`PipelinedRenderingPlugin`] for more details.
///
/// [`RenderPlugin`]: https://docs.rs/bevy/latest/bevy/render/struct.RenderPlugin.html
/// [`PipelinedRenderingPlugin`]: https://docs.rs/bevy/latest/bevy/render/pipelined_rendering/struct.PipelinedRenderingPlugin.html
/// [`SubApp`]: crate::SubApp
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct Main;
/// The schedule that runs before [`Startup`].
///
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct PreStartup;
/// The schedule that runs once when the app starts.
///
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct Startup;
/// The schedule that runs once after [`Startup`].
///
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct PostStartup;
/// Runs first in the schedule.
///
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct First;
/// The schedule that contains logic that must run before [`Update`]. For example, a system that reads raw keyboard
/// input OS events into an `Events` resource. This enables systems in [`Update`] to consume the events from the `Events`
/// resource without actually knowing about (or taking a direct scheduler dependency on) the "os-level keyboard event system".
///
/// [`PreUpdate`] exists to do "engine/plugin preparation work" that ensures the APIs consumed in [`Update`] are "ready".
/// [`PreUpdate`] abstracts out "pre work implementation details".
///
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct PreUpdate;
/// Runs the [`FixedMain`] schedule in a loop according until all relevant elapsed time has been "consumed".
///
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct RunFixedMainLoop;
/// Runs first in the [`FixedMain`] schedule.
///
/// See the [`FixedMain`] schedule for details on how fixed updates work.
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct FixedFirst;
/// The schedule that contains logic that must run before [`FixedUpdate`].
///
/// See the [`FixedMain`] schedule for details on how fixed updates work.
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct FixedPreUpdate;
/// The schedule that contains most gameplay logic.
///
/// See the [`FixedMain`] schedule for details on how fixed updates work.
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct FixedUpdate;
/// The schedule that runs after the [`FixedUpdate`] schedule, for reacting
/// to changes made in the main update logic.
///
/// See the [`FixedMain`] schedule for details on how fixed updates work.
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct FixedPostUpdate;
/// The schedule that runs last in [`FixedMain`]
///
/// See the [`FixedMain`] schedule for details on how fixed updates work.
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct FixedLast;
/// The schedule that contains systems which only run after a fixed period of time has elapsed.
///
/// The exclusive `run_fixed_main_schedule` system runs this schedule.
/// This is run by the [`RunFixedMainLoop`] schedule.
///
/// Frequency of execution is configured by inserting `Time<Fixed>` resource, 64 Hz by default.
/// See [this example](https://github.com/bevyengine/bevy/blob/latest/examples/time/time.rs).
///
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct FixedMain;
/// The schedule that contains app logic. Ideally containing anything that must run once per
/// render frame, such as UI.
///
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct Update;
/// The schedule that contains scene spawning.
///
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct SpawnScene;
/// The schedule that contains logic that must run after [`Update`]. For example, synchronizing "local transforms" in a hierarchy
/// to "global" absolute transforms. This enables the [`PostUpdate`] transform-sync system to react to "local transform" changes in
/// [`Update`] without the [`Update`] systems needing to know about (or add scheduler dependencies for) the "global transform sync system".
///
/// [`PostUpdate`] exists to do "engine/plugin response work" to things that happened in [`Update`].
/// [`PostUpdate`] abstracts out "implementation details" from users defining systems in [`Update`].
///
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct PostUpdate;
/// Runs last in the schedule.
///
/// See the [`Main`] schedule for some details about how schedules are run.
#[derive(ScheduleLabel, Clone, Debug, PartialEq, Eq, Hash)]
pub struct Last;
/// Defines the schedules to be run for the [`Main`] schedule, including
/// their order.
#[derive(Resource, Debug)]
pub struct MainScheduleOrder {
/// The labels to run for the main phase of the [`Main`] schedule (in the order they will be run).
pub labels: Vec<InternedScheduleLabel>,
/// The labels to run for the startup phase of the [`Main`] schedule (in the order they will be run).
pub startup_labels: Vec<InternedScheduleLabel>,
}
impl Default for MainScheduleOrder {
fn default() -> Self {
Self {
labels: vec![
First.intern(),
PreUpdate.intern(),
RunFixedMainLoop.intern(),
Update.intern(),
SpawnScene.intern(),
PostUpdate.intern(),
Last.intern(),
],
startup_labels: vec![PreStartup.intern(), Startup.intern(), PostStartup.intern()],
}
}
}
impl MainScheduleOrder {
/// Adds the given `schedule` after the `after` schedule in the main list of schedules.
pub fn insert_after(&mut self, after: impl ScheduleLabel, schedule: impl ScheduleLabel) {
let index = self
.labels
.iter()
.position(|current| (**current).eq(&after))
.unwrap_or_else(|| panic!("Expected {after:?} to exist"));
self.labels.insert(index + 1, schedule.intern());
}
/// Adds the given `schedule` before the `before` schedule in the main list of schedules.
pub fn insert_before(&mut self, before: impl ScheduleLabel, schedule: impl ScheduleLabel) {
let index = self
.labels
.iter()
.position(|current| (**current).eq(&before))
.unwrap_or_else(|| panic!("Expected {before:?} to exist"));
self.labels.insert(index, schedule.intern());
}
/// Adds the given `schedule` after the `after` schedule in the list of startup schedules.
pub fn insert_startup_after(
&mut self,
after: impl ScheduleLabel,
schedule: impl ScheduleLabel,
) {
let index = self
.startup_labels
.iter()
.position(|current| (**current).eq(&after))
.unwrap_or_else(|| panic!("Expected {after:?} to exist"));
self.startup_labels.insert(index + 1, schedule.intern());
}
/// Adds the given `schedule` before the `before` schedule in the list of startup schedules.
pub fn insert_startup_before(
&mut self,
before: impl ScheduleLabel,
schedule: impl ScheduleLabel,
) {
let index = self
.startup_labels
.iter()
.position(|current| (**current).eq(&before))
.unwrap_or_else(|| panic!("Expected {before:?} to exist"));
self.startup_labels.insert(index, schedule.intern());
}
}
impl Main {
/// A system that runs the "main schedule"
pub fn run_main(world: &mut World, mut run_at_least_once: Local<bool>) {
if !*run_at_least_once {
world.resource_scope(|world, order: Mut<MainScheduleOrder>| {
for &label in &order.startup_labels {
let _ = world.try_run_schedule(label);
}
});
*run_at_least_once = true;
}
world.resource_scope(|world, order: Mut<MainScheduleOrder>| {
for &label in &order.labels {
let _ = world.try_run_schedule(label);
}
});
}
}
/// Initializes the [`Main`] schedule, sub schedules, and resources for a given [`App`].
pub struct MainSchedulePlugin;
impl Plugin for MainSchedulePlugin {
fn build(&self, app: &mut App) {
// simple "facilitator" schedules benefit from simpler single threaded scheduling
let mut main_schedule = Schedule::new(Main);
main_schedule.set_executor_kind(ExecutorKind::SingleThreaded);
let mut fixed_main_schedule = Schedule::new(FixedMain);
fixed_main_schedule.set_executor_kind(ExecutorKind::SingleThreaded);
let mut fixed_main_loop_schedule = Schedule::new(RunFixedMainLoop);
fixed_main_loop_schedule.set_executor_kind(ExecutorKind::SingleThreaded);
app.add_schedule(main_schedule)
.add_schedule(fixed_main_schedule)
.add_schedule(fixed_main_loop_schedule)
.init_resource::<MainScheduleOrder>()
.init_resource::<FixedMainScheduleOrder>()
.add_systems(Main, Main::run_main)
.add_systems(FixedMain, FixedMain::run_fixed_main);
#[cfg(feature = "bevy_debug_stepping")]
{
use bevy_ecs::schedule::{IntoSystemConfigs, Stepping};
app.add_systems(Main, Stepping::begin_frame.before(Main::run_main));
}
}
}
/// Defines the schedules to be run for the [`FixedMain`] schedule, including
/// their order.
#[derive(Resource, Debug)]
pub struct FixedMainScheduleOrder {
/// The labels to run for the [`FixedMain`] schedule (in the order they will be run).
pub labels: Vec<InternedScheduleLabel>,
}
impl Default for FixedMainScheduleOrder {
fn default() -> Self {
Self {
labels: vec![
FixedFirst.intern(),
FixedPreUpdate.intern(),
FixedUpdate.intern(),
FixedPostUpdate.intern(),
FixedLast.intern(),
],
}
}
}
impl FixedMainScheduleOrder {
/// Adds the given `schedule` after the `after` schedule
pub fn insert_after(&mut self, after: impl ScheduleLabel, schedule: impl ScheduleLabel) {
let index = self
.labels
.iter()
.position(|current| (**current).eq(&after))
.unwrap_or_else(|| panic!("Expected {after:?} to exist"));
self.labels.insert(index + 1, schedule.intern());
}
/// Adds the given `schedule` before the `before` schedule
pub fn insert_before(&mut self, before: impl ScheduleLabel, schedule: impl ScheduleLabel) {
let index = self
.labels
.iter()
.position(|current| (**current).eq(&before))
.unwrap_or_else(|| panic!("Expected {before:?} to exist"));
self.labels.insert(index, schedule.intern());
}
}
impl FixedMain {
/// A system that runs the fixed timestep's "main schedule"
pub fn run_fixed_main(world: &mut World) {
world.resource_scope(|world, order: Mut<FixedMainScheduleOrder>| {
for &label in &order.labels {
let _ = world.try_run_schedule(label);
}
});
}
}