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use crate::{
CoreSchedule, CoreSet, IntoSystemAppConfig, IntoSystemAppConfigs, Plugin, PluginGroup,
StartupSet, SystemAppConfig,
};
pub use bevy_derive::AppLabel;
use bevy_ecs::{
prelude::*,
schedule::{
apply_state_transition, common_conditions::run_once as run_once_condition,
run_enter_schedule, BoxedScheduleLabel, IntoSystemConfig, IntoSystemSetConfigs,
ScheduleLabel,
},
};
use bevy_utils::{tracing::debug, HashMap, HashSet};
use std::{
fmt::Debug,
panic::{catch_unwind, resume_unwind, AssertUnwindSafe},
};
#[cfg(feature = "trace")]
use bevy_utils::tracing::info_span;
bevy_utils::define_label!(
/// A strongly-typed class of labels used to identify an [`App`].
AppLabel,
/// A strongly-typed identifier for an [`AppLabel`].
AppLabelId,
);
/// The [`Resource`] that stores the [`App`]'s [`TypeRegistry`](bevy_reflect::TypeRegistry).
#[cfg(feature = "bevy_reflect")]
#[derive(Resource, Clone, bevy_derive::Deref, bevy_derive::DerefMut, Default)]
pub struct AppTypeRegistry(pub bevy_reflect::TypeRegistryArc);
pub(crate) enum AppError {
DuplicatePlugin { plugin_name: String },
}
#[allow(clippy::needless_doctest_main)]
/// A container of app logic and data.
///
/// Bundles together the necessary elements like [`World`] and [`Schedule`] to create
/// an ECS-based application. It also stores a pointer to a [runner function](Self::set_runner).
/// The runner is responsible for managing the application's event loop and applying the
/// [`Schedule`] to the [`World`] to drive application logic.
///
/// # Examples
///
/// Here is a simple "Hello World" Bevy app:
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// fn main() {
/// App::new()
/// .add_system(hello_world_system)
/// .run();
/// }
///
/// fn hello_world_system() {
/// println!("hello world");
/// }
/// ```
pub struct App {
/// The main ECS [`World`] of the [`App`].
/// This stores and provides access to all the main data of the application.
/// The systems of the [`App`] will run using this [`World`].
/// If additional separate [`World`]-[`Schedule`] pairs are needed, you can use [`sub_app`](App::insert_sub_app)s.
pub world: World,
/// The [runner function](Self::set_runner) is primarily responsible for managing
/// the application's event loop and advancing the [`Schedule`].
/// Typically, it is not configured manually, but set by one of Bevy's built-in plugins.
/// See `bevy::winit::WinitPlugin` and [`ScheduleRunnerPlugin`](crate::schedule_runner::ScheduleRunnerPlugin).
pub runner: Box<dyn Fn(App) + Send>, // Send bound is required to make App Send
/// The schedule that systems are added to by default.
///
/// This is initially set to [`CoreSchedule::Main`].
pub default_schedule_label: BoxedScheduleLabel,
/// The schedule that controls the outer loop of schedule execution.
///
/// This is initially set to [`CoreSchedule::Outer`].
pub outer_schedule_label: BoxedScheduleLabel,
sub_apps: HashMap<AppLabelId, SubApp>,
plugin_registry: Vec<Box<dyn Plugin>>,
plugin_name_added: HashSet<String>,
/// A private counter to prevent incorrect calls to `App::run()` from `Plugin::build()`
building_plugin_depth: usize,
}
impl Debug for App {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "App {{ sub_apps: ")?;
f.debug_map()
.entries(self.sub_apps.iter().map(|(k, v)| (k, v)))
.finish()?;
write!(f, "}}")
}
}
/// A [`SubApp`] contains its own [`Schedule`] and [`World`] separate from the main [`App`].
/// This is useful for situations where data and data processing should be kept completely separate
/// from the main application. The primary use of this feature in bevy is to enable pipelined rendering.
///
/// # Example
///
/// ```rust
/// # use bevy_app::{App, AppLabel, SubApp, CoreSchedule};
/// # use bevy_ecs::prelude::*;
/// # use bevy_ecs::schedule::ScheduleLabel;
///
/// #[derive(Resource, Default)]
/// struct Val(pub i32);
///
/// #[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, AppLabel)]
/// struct ExampleApp;
///
/// let mut app = App::new();
///
/// // initialize the main app with a value of 0;
/// app.insert_resource(Val(10));
///
/// // create a app with a resource and a single schedule
/// let mut sub_app = App::empty();
/// // add an outer schedule that runs the main schedule
/// sub_app.add_simple_outer_schedule();
/// sub_app.insert_resource(Val(100));
///
/// // initialize main schedule
/// sub_app.init_schedule(CoreSchedule::Main);
/// sub_app.add_system(|counter: Res<Val>| {
/// // since we assigned the value from the main world in extract
/// // we see that value instead of 100
/// assert_eq!(counter.0, 10);
/// });
///
/// // add the sub_app to the app
/// app.insert_sub_app(ExampleApp, SubApp::new(sub_app, |main_world, sub_app| {
/// // extract the value from the main app to the sub app
/// sub_app.world.resource_mut::<Val>().0 = main_world.resource::<Val>().0;
/// }));
///
/// // This will run the schedules once, since we're using the default runner
/// app.run();
/// ```
pub struct SubApp {
/// The [`SubApp`]'s instance of [`App`]
pub app: App,
/// A function that allows access to both the [`SubApp`] [`World`] and the main [`App`]. This is
/// useful for moving data between the sub app and the main app.
extract: Box<dyn Fn(&mut World, &mut App) + Send>,
}
impl SubApp {
/// Creates a new [`SubApp`].
///
/// The provided function `extract` is normally called by the [`update`](App::update) method.
/// After extract is called, the [`Schedule`] of the sub app is run. The [`World`]
/// parameter represents the main app world, while the [`App`] parameter is just a mutable
/// reference to the `SubApp` itself.
pub fn new(app: App, extract: impl Fn(&mut World, &mut App) + Send + 'static) -> Self {
Self {
app,
extract: Box::new(extract),
}
}
/// Runs the `SubApp`'s default schedule.
pub fn run(&mut self) {
self.app
.world
.run_schedule_ref(&*self.app.outer_schedule_label);
self.app.world.clear_trackers();
}
/// Extracts data from main world to this sub-app.
pub fn extract(&mut self, main_world: &mut World) {
(self.extract)(main_world, &mut self.app);
}
}
impl Debug for SubApp {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "SubApp {{ app: ")?;
f.debug_map()
.entries(self.app.sub_apps.iter().map(|(k, v)| (k, v)))
.finish()?;
write!(f, "}}")
}
}
impl Default for App {
fn default() -> Self {
let mut app = App::empty();
#[cfg(feature = "bevy_reflect")]
app.init_resource::<AppTypeRegistry>();
app.add_default_schedules();
app.add_event::<AppExit>();
#[cfg(feature = "bevy_ci_testing")]
{
crate::ci_testing::setup_app(&mut app);
}
app
}
}
impl App {
/// Creates a new [`App`] with some default structure to enable core engine features.
/// This is the preferred constructor for most use cases.
///
/// This calls [`App::add_default_schedules`].
pub fn new() -> App {
App::default()
}
/// Creates a new empty [`App`] with minimal default configuration.
///
/// This constructor should be used if you wish to provide custom scheduling, exit handling, cleanup, etc.
pub fn empty() -> App {
let mut world = World::new();
world.init_resource::<Schedules>();
Self {
world,
runner: Box::new(run_once),
sub_apps: HashMap::default(),
plugin_registry: Vec::default(),
plugin_name_added: Default::default(),
default_schedule_label: Box::new(CoreSchedule::Main),
outer_schedule_label: Box::new(CoreSchedule::Outer),
building_plugin_depth: 0,
}
}
/// Advances the execution of the [`Schedule`] by one cycle.
///
/// This method also updates sub apps.
/// See [`insert_sub_app`](Self::insert_sub_app) for more details.
///
/// The schedule run by this method is determined by the [`outer_schedule_label`](App) field.
/// In normal usage, this is [`CoreSchedule::Outer`], which will run [`CoreSchedule::Startup`]
/// the first time the app is run, then [`CoreSchedule::Main`] on every call of this method.
///
/// # Panics
///
/// The active schedule of the app must be set before this method is called.
pub fn update(&mut self) {
{
#[cfg(feature = "trace")]
let _bevy_frame_update_span = info_span!("main app").entered();
self.world.run_schedule_ref(&*self.outer_schedule_label);
}
for (_label, sub_app) in self.sub_apps.iter_mut() {
#[cfg(feature = "trace")]
let _sub_app_span = info_span!("sub app", name = ?_label).entered();
sub_app.extract(&mut self.world);
sub_app.run();
}
self.world.clear_trackers();
}
/// Starts the application by calling the app's [runner function](Self::set_runner).
///
/// Finalizes the [`App`] configuration. For general usage, see the example on the item
/// level documentation.
///
/// # `run()` might not return
///
/// Calls to [`App::run()`] might never return.
///
/// In simple and *headless* applications, one can expect that execution will
/// proceed, normally, after calling [`run()`](App::run()) but this is not the case for
/// windowed applications.
///
/// Windowed apps are typically driven by an *event loop* or *message loop* and
/// some window-manager APIs expect programs to terminate when their primary
/// window is closed and that event loop terminates – behaviour of processes that
/// do not is often platform dependent or undocumented.
///
/// By default, *Bevy* uses the `winit` crate for window creation. See
/// [`WinitSettings::return_from_run`](https://docs.rs/bevy/latest/bevy/winit/struct.WinitSettings.html#structfield.return_from_run)
/// for further discussion of this topic and for a mechanism to require that [`App::run()`]
/// *does* return – albeit one that carries its own caveats and disclaimers.
///
/// # Panics
///
/// Panics if called from `Plugin::build()`, because it would prevent other plugins to properly build.
pub fn run(&mut self) {
#[cfg(feature = "trace")]
let _bevy_app_run_span = info_span!("bevy_app").entered();
let mut app = std::mem::replace(self, App::empty());
if app.building_plugin_depth > 0 {
panic!("App::run() was called from within Plugin::build(), which is not allowed.");
}
Self::setup(&mut app);
let runner = std::mem::replace(&mut app.runner, Box::new(run_once));
(runner)(app);
}
/// Run [`Plugin::setup`] for each plugin. This is usually called by [`App::run`], but can
/// be useful for situations where you want to use [`App::update`].
pub fn setup(&mut self) {
// temporarily remove the plugin registry to run each plugin's setup function on app.
let plugin_registry = std::mem::take(&mut self.plugin_registry);
for plugin in &plugin_registry {
plugin.setup(self);
}
self.plugin_registry = plugin_registry;
}
/// Adds [`State<S>`] and [`NextState<S>`] resources, [`OnEnter`] and [`OnExit`] schedules
/// for each state variant, an instance of [`apply_state_transition::<S>`] in
/// [`CoreSet::StateTransitions`] so that transitions happen before [`CoreSet::Update`] and
/// a instance of [`run_enter_schedule::<S>`] in [`CoreSet::StateTransitions`] with a
/// [`run_once`](`run_once_condition`) condition to run the on enter schedule of the
/// initial state.
///
/// This also adds an [`OnUpdate`] system set for each state variant,
/// which runs during [`CoreSet::Update`] after the transitions are applied.
/// These system sets only run if the [`State<S>`] resource matches the respective state variant.
///
/// If you would like to control how other systems run based on the current state,
/// you can emulate this behavior using the [`in_state`] [`Condition`](bevy_ecs::schedule::Condition).
///
/// Note that you can also apply state transitions at other points in the schedule
/// by adding the [`apply_state_transition`] system manually.
pub fn add_state<S: States>(&mut self) -> &mut Self {
self.init_resource::<State<S>>();
self.init_resource::<NextState<S>>();
let mut schedules = self.world.resource_mut::<Schedules>();
let Some(default_schedule) = schedules.get_mut(&*self.default_schedule_label) else {
let schedule_label = &self.default_schedule_label;
panic!("Default schedule {schedule_label:?} does not exist.")
};
default_schedule.add_systems(
(
run_enter_schedule::<S>.run_if(run_once_condition()),
apply_state_transition::<S>,
)
.chain()
.in_base_set(CoreSet::StateTransitions),
);
for variant in S::variants() {
default_schedule.configure_set(
OnUpdate(variant.clone())
.in_base_set(CoreSet::Update)
.run_if(in_state(variant)),
);
}
// These are different for loops to avoid conflicting access to self
for variant in S::variants() {
self.add_schedule(OnEnter(variant.clone()), Schedule::new());
self.add_schedule(OnExit(variant), Schedule::new());
}
self
}
/// Adds a system to the default system set and schedule of the app's [`Schedules`].
///
/// Refer to the [system module documentation](bevy_ecs::system) to see how a system
/// can be defined.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # fn my_system() {}
/// # let mut app = App::new();
/// #
/// app.add_system(my_system);
/// ```
pub fn add_system<M>(&mut self, system: impl IntoSystemAppConfig<M>) -> &mut Self {
let mut schedules = self.world.resource_mut::<Schedules>();
let SystemAppConfig { system, schedule } = system.into_app_config();
if let Some(schedule_label) = schedule {
if let Some(schedule) = schedules.get_mut(&*schedule_label) {
schedule.add_system(system);
} else {
panic!("Schedule {schedule_label:?} does not exist.")
}
} else if let Some(default_schedule) = schedules.get_mut(&*self.default_schedule_label) {
default_schedule.add_system(system);
} else {
let schedule_label = &self.default_schedule_label;
panic!("Default schedule {schedule_label:?} does not exist.")
}
self
}
/// Adds a system to the default system set and schedule of the app's [`Schedules`].
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # let mut app = App::new();
/// # fn system_a() {}
/// # fn system_b() {}
/// # fn system_c() {}
/// #
/// app.add_systems((system_a, system_b, system_c));
/// ```
pub fn add_systems<M>(&mut self, systems: impl IntoSystemAppConfigs<M>) -> &mut Self {
let mut schedules = self.world.resource_mut::<Schedules>();
match systems.into_app_configs().0 {
crate::InnerConfigs::Blanket { systems, schedule } => {
let schedule = if let Some(label) = schedule {
schedules
.get_mut(&*label)
.unwrap_or_else(|| panic!("Schedule '{label:?}' does not exist."))
} else {
let label = &*self.default_schedule_label;
schedules
.get_mut(label)
.unwrap_or_else(|| panic!("Default schedule '{label:?}' does not exist."))
};
schedule.add_systems(systems);
}
crate::InnerConfigs::Granular(systems) => {
for system in systems {
self.add_system(system);
}
}
}
self
}
/// Adds a system to [`CoreSchedule::Startup`].
///
/// These systems will run exactly once, at the start of the [`App`]'s lifecycle.
/// To add a system that runs every frame, see [`add_system`](Self::add_system).
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// fn my_startup_system(_commands: Commands) {
/// println!("My startup system");
/// }
///
/// App::new()
/// .add_startup_system(my_startup_system);
/// ```
pub fn add_startup_system<M>(&mut self, system: impl IntoSystemConfig<M>) -> &mut Self {
self.add_system(system.in_schedule(CoreSchedule::Startup))
}
/// Adds a collection of systems to [`CoreSchedule::Startup`].
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # let mut app = App::new();
/// # fn startup_system_a() {}
/// # fn startup_system_b() {}
/// # fn startup_system_c() {}
/// #
/// app.add_startup_systems((
/// startup_system_a,
/// startup_system_b,
/// startup_system_c,
/// ));
/// ```
pub fn add_startup_systems<M>(&mut self, systems: impl IntoSystemConfigs<M>) -> &mut Self {
self.add_systems(systems.into_configs().in_schedule(CoreSchedule::Startup))
}
/// Configures a system set in the default schedule, adding the set if it does not exist.
pub fn configure_set(&mut self, set: impl IntoSystemSetConfig) -> &mut Self {
self.world
.resource_mut::<Schedules>()
.get_mut(&*self.default_schedule_label)
.unwrap()
.configure_set(set);
self
}
/// Configures a collection of system sets in the default schedule, adding any sets that do not exist.
pub fn configure_sets(&mut self, sets: impl IntoSystemSetConfigs) -> &mut Self {
self.world
.resource_mut::<Schedules>()
.get_mut(&*self.default_schedule_label)
.unwrap()
.configure_sets(sets);
self
}
/// Adds standardized schedules and labels to an [`App`].
///
/// Adding these schedules is necessary to make almost all core engine features work.
/// This is typically done implicitly by calling `App::default`, which is in turn called by
/// [`App::new`].
///
/// The schedules added are defined in the [`CoreSchedule`] enum,
/// and have a starting configuration defined by:
///
/// - [`CoreSchedule::Outer`]: uses [`CoreSchedule::outer_schedule`]
/// - [`CoreSchedule::Startup`]: uses [`StartupSet::base_schedule`]
/// - [`CoreSchedule::Main`]: uses [`CoreSet::base_schedule`]
/// - [`CoreSchedule::FixedUpdate`]: no starting configuration
///
/// # Examples
///
/// ```
/// use bevy_app::App;
/// use bevy_ecs::schedule::Schedules;
///
/// let app = App::empty()
/// .init_resource::<Schedules>()
/// .add_default_schedules()
/// .update();
/// ```
pub fn add_default_schedules(&mut self) -> &mut Self {
self.add_schedule(CoreSchedule::Outer, CoreSchedule::outer_schedule());
self.add_schedule(CoreSchedule::Startup, StartupSet::base_schedule());
self.add_schedule(CoreSchedule::Main, CoreSet::base_schedule());
self.init_schedule(CoreSchedule::FixedUpdate);
self
}
/// adds a single threaded outer schedule to the [`App`] that just runs the main schedule
pub fn add_simple_outer_schedule(&mut self) -> &mut Self {
fn run_main_schedule(world: &mut World) {
world.run_schedule(CoreSchedule::Main);
}
self.edit_schedule(CoreSchedule::Outer, |schedule| {
schedule.set_executor_kind(bevy_ecs::schedule::ExecutorKind::SingleThreaded);
schedule.add_system(run_main_schedule);
});
self
}
/// Setup the application to manage events of type `T`.
///
/// This is done by adding a [`Resource`] of type [`Events::<T>`],
/// and inserting an [`update_system`](Events::update_system) into [`CoreSet::First`].
///
/// See [`Events`] for defining events.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # struct MyEvent;
/// # let mut app = App::new();
/// #
/// app.add_event::<MyEvent>();
/// ```
pub fn add_event<T>(&mut self) -> &mut Self
where
T: Event,
{
if !self.world.contains_resource::<Events<T>>() {
self.init_resource::<Events<T>>()
.add_system(Events::<T>::update_system.in_base_set(CoreSet::First));
}
self
}
/// Inserts a [`Resource`] to the current [`App`] and overwrites any [`Resource`] previously added of the same type.
///
/// A [`Resource`] in Bevy represents globally unique data. [`Resource`]s must be added to Bevy apps
/// before using them. This happens with [`insert_resource`](Self::insert_resource).
///
/// See [`init_resource`](Self::init_resource) for [`Resource`]s that implement [`Default`] or [`FromWorld`].
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// #[derive(Resource)]
/// struct MyCounter {
/// counter: usize,
/// }
///
/// App::new()
/// .insert_resource(MyCounter { counter: 0 });
/// ```
pub fn insert_resource<R: Resource>(&mut self, resource: R) -> &mut Self {
self.world.insert_resource(resource);
self
}
/// Inserts a non-send resource to the app.
///
/// You usually want to use [`insert_resource`](Self::insert_resource),
/// but there are some special cases when a resource cannot be sent across threads.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// struct MyCounter {
/// counter: usize,
/// }
///
/// App::new()
/// .insert_non_send_resource(MyCounter { counter: 0 });
/// ```
pub fn insert_non_send_resource<R: 'static>(&mut self, resource: R) -> &mut Self {
self.world.insert_non_send_resource(resource);
self
}
/// Initialize a [`Resource`] with standard starting values by adding it to the [`World`].
///
/// If the [`Resource`] already exists, nothing happens.
///
/// The [`Resource`] must implement the [`FromWorld`] trait.
/// If the [`Default`] trait is implemented, the [`FromWorld`] trait will use
/// the [`Default::default`] method to initialize the [`Resource`].
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// #[derive(Resource)]
/// struct MyCounter {
/// counter: usize,
/// }
///
/// impl Default for MyCounter {
/// fn default() -> MyCounter {
/// MyCounter {
/// counter: 100
/// }
/// }
/// }
///
/// App::new()
/// .init_resource::<MyCounter>();
/// ```
pub fn init_resource<R: Resource + FromWorld>(&mut self) -> &mut Self {
self.world.init_resource::<R>();
self
}
/// Initialize a non-send [`Resource`] with standard starting values by adding it to the [`World`].
///
/// The [`Resource`] must implement the [`FromWorld`] trait.
/// If the [`Default`] trait is implemented, the [`FromWorld`] trait will use
/// the [`Default::default`] method to initialize the [`Resource`].
pub fn init_non_send_resource<R: 'static + FromWorld>(&mut self) -> &mut Self {
self.world.init_non_send_resource::<R>();
self
}
/// Sets the function that will be called when the app is run.
///
/// The runner function `run_fn` is called only once by [`App::run`]. If the
/// presence of a main loop in the app is desired, it is the responsibility of the runner
/// function to provide it.
///
/// The runner function is usually not set manually, but by Bevy integrated plugins
/// (e.g. `WinitPlugin`).
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// #
/// fn my_runner(mut app: App) {
/// loop {
/// println!("In main loop");
/// app.update();
/// }
/// }
///
/// App::new()
/// .set_runner(my_runner);
/// ```
pub fn set_runner(&mut self, run_fn: impl Fn(App) + 'static + Send) -> &mut Self {
self.runner = Box::new(run_fn);
self
}
/// Adds a single [`Plugin`].
///
/// One of Bevy's core principles is modularity. All Bevy engine features are implemented
/// as [`Plugin`]s. This includes internal features like the renderer.
///
/// Bevy also provides a few sets of default [`Plugin`]s. See [`add_plugins`](Self::add_plugins).
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// #
/// # // Dummies created to avoid using `bevy_log`,
/// # // which pulls in too many dependencies and breaks rust-analyzer
/// # pub mod bevy_log {
/// # use bevy_app::prelude::*;
/// # #[derive(Default)]
/// # pub struct LogPlugin;
/// # impl Plugin for LogPlugin{
/// # fn build(&self, app: &mut App) {}
/// # }
/// # }
/// App::new().add_plugin(bevy_log::LogPlugin::default());
/// ```
///
/// # Panics
///
/// Panics if the plugin was already added to the application.
pub fn add_plugin<T>(&mut self, plugin: T) -> &mut Self
where
T: Plugin,
{
match self.add_boxed_plugin(Box::new(plugin)) {
Ok(app) => app,
Err(AppError::DuplicatePlugin { plugin_name }) => panic!(
"Error adding plugin {plugin_name}: : plugin was already added in application"
),
}
}
/// Boxed variant of `add_plugin`, can be used from a [`PluginGroup`]
pub(crate) fn add_boxed_plugin(
&mut self,
plugin: Box<dyn Plugin>,
) -> Result<&mut Self, AppError> {
debug!("added plugin: {}", plugin.name());
if plugin.is_unique() && !self.plugin_name_added.insert(plugin.name().to_string()) {
Err(AppError::DuplicatePlugin {
plugin_name: plugin.name().to_string(),
})?;
}
self.building_plugin_depth += 1;
let result = catch_unwind(AssertUnwindSafe(|| plugin.build(self)));
self.building_plugin_depth -= 1;
if let Err(payload) = result {
resume_unwind(payload);
}
self.plugin_registry.push(plugin);
Ok(self)
}
/// Checks if a [`Plugin`] has already been added.
///
/// This can be used by plugins to check if a plugin they depend upon has already been
/// added.
pub fn is_plugin_added<T>(&self) -> bool
where
T: Plugin,
{
self.plugin_registry
.iter()
.any(|p| p.downcast_ref::<T>().is_some())
}
/// Returns a vector of references to any plugins of type `T` that have been added.
///
/// This can be used to read the settings of any already added plugins.
/// This vector will be length zero if no plugins of that type have been added.
/// If multiple copies of the same plugin are added to the [`App`], they will be listed in insertion order in this vector.
///
/// ```rust
/// # use bevy_app::prelude::*;
/// # #[derive(Default)]
/// # struct ImagePlugin {
/// # default_sampler: bool,
/// # }
/// # impl Plugin for ImagePlugin {
/// # fn build(&self, app: &mut App) {}
/// # }
/// # let mut app = App::new();
/// # app.add_plugin(ImagePlugin::default());
/// let default_sampler = app.get_added_plugins::<ImagePlugin>()[0].default_sampler;
/// ```
pub fn get_added_plugins<T>(&self) -> Vec<&T>
where
T: Plugin,
{
self.plugin_registry
.iter()
.filter_map(|p| p.downcast_ref())
.collect()
}
/// Adds a group of [`Plugin`]s.
///
/// [`Plugin`]s can be grouped into a set by using a [`PluginGroup`].
///
/// There are built-in [`PluginGroup`]s that provide core engine functionality.
/// The [`PluginGroup`]s available by default are `DefaultPlugins` and `MinimalPlugins`.
///
/// To customize the plugins in the group (reorder, disable a plugin, add a new plugin
/// before / after another plugin), call [`build()`](PluginGroup::build) on the group,
/// which will convert it to a [`PluginGroupBuilder`](crate::PluginGroupBuilder).
///
/// ## Examples
/// ```
/// # use bevy_app::{prelude::*, PluginGroupBuilder, NoopPluginGroup as MinimalPlugins};
/// #
/// App::new()
/// .add_plugins(MinimalPlugins);
/// ```
///
/// # Panics
///
/// Panics if one of the plugin in the group was already added to the application.
pub fn add_plugins<T: PluginGroup>(&mut self, group: T) -> &mut Self {
let builder = group.build();
builder.finish(self);
self
}
/// Registers the type `T` in the [`TypeRegistry`](bevy_reflect::TypeRegistry) resource,
/// adding reflect data as specified in the [`Reflect`](bevy_reflect::Reflect) derive:
/// ```rust,ignore
/// #[derive(Reflect)]
/// #[reflect(Component, Serialize, Deserialize)] // will register ReflectComponent, ReflectSerialize, ReflectDeserialize
/// ```
///
/// See [`bevy_reflect::TypeRegistry::register`].
#[cfg(feature = "bevy_reflect")]
pub fn register_type<T: bevy_reflect::GetTypeRegistration>(&mut self) -> &mut Self {
let registry = self.world.resource_mut::<AppTypeRegistry>();
registry.write().register::<T>();
self
}
/// Adds the type data `D` to type `T` in the [`TypeRegistry`](bevy_reflect::TypeRegistry) resource.
///
/// Most of the time [`App::register_type`] can be used instead to register a type you derived [`Reflect`](bevy_reflect::Reflect) for.
/// However, in cases where you want to add a piece of type data that was not included in the list of `#[reflect(...)]` type data in the derive,
/// or where the type is generic and cannot register e.g. `ReflectSerialize` unconditionally without knowing the specific type parameters,
/// this method can be used to insert additional type data.
///
/// # Example
/// ```rust
/// use bevy_app::App;
/// use bevy_reflect::{ReflectSerialize, ReflectDeserialize};
///
/// App::new()
/// .register_type::<Option<String>>()
/// .register_type_data::<Option<String>, ReflectSerialize>()
/// .register_type_data::<Option<String>, ReflectDeserialize>();
/// ```
///
/// See [`bevy_reflect::TypeRegistry::register_type_data`].
#[cfg(feature = "bevy_reflect")]
pub fn register_type_data<
T: bevy_reflect::Reflect + 'static,
D: bevy_reflect::TypeData + bevy_reflect::FromType<T>,
>(
&mut self,
) -> &mut Self {
let registry = self.world.resource_mut::<AppTypeRegistry>();
registry.write().register_type_data::<T, D>();
self
}
/// Retrieves a `SubApp` stored inside this [`App`].
///
/// # Panics
///
/// Panics if the `SubApp` doesn't exist.
pub fn sub_app_mut(&mut self, label: impl AppLabel) -> &mut App {
match self.get_sub_app_mut(label) {
Ok(app) => app,
Err(label) => panic!("Sub-App with label '{:?}' does not exist", label.as_str()),
}
}
/// Retrieves a `SubApp` inside this [`App`] with the given label, if it exists. Otherwise returns
/// an [`Err`] containing the given label.
pub fn get_sub_app_mut(&mut self, label: impl AppLabel) -> Result<&mut App, AppLabelId> {
let label = label.as_label();
self.sub_apps
.get_mut(&label)
.map(|sub_app| &mut sub_app.app)
.ok_or(label)
}
/// Retrieves a `SubApp` stored inside this [`App`].
///
/// # Panics
///
/// Panics if the `SubApp` doesn't exist.
pub fn sub_app(&self, label: impl AppLabel) -> &App {
match self.get_sub_app(label) {
Ok(app) => app,
Err(label) => panic!("Sub-App with label '{:?}' does not exist", label.as_str()),
}
}
/// Inserts an existing sub app into the app
pub fn insert_sub_app(&mut self, label: impl AppLabel, sub_app: SubApp) {
self.sub_apps.insert(label.as_label(), sub_app);
}
/// Removes a sub app from the app. Returns [`None`] if the label doesn't exist.
pub fn remove_sub_app(&mut self, label: impl AppLabel) -> Option<SubApp> {
self.sub_apps.remove(&label.as_label())
}
/// Retrieves a `SubApp` inside this [`App`] with the given label, if it exists. Otherwise returns
/// an [`Err`] containing the given label.
pub fn get_sub_app(&self, label: impl AppLabel) -> Result<&App, impl AppLabel> {
self.sub_apps
.get(&label.as_label())
.map(|sub_app| &sub_app.app)
.ok_or(label)
}
/// Adds a new `schedule` to the [`App`] under the provided `label`.
///
/// # Warning
/// This method will overwrite any existing schedule at that label.
/// To avoid this behavior, use the `init_schedule` method instead.
pub fn add_schedule(&mut self, label: impl ScheduleLabel, schedule: Schedule) -> &mut Self {
let mut schedules = self.world.resource_mut::<Schedules>();
schedules.insert(label, schedule);
self
}
/// Initializes a new empty `schedule` to the [`App`] under the provided `label` if it does not exists.
///
/// See [`App::add_schedule`] to pass in a pre-constructed schedule.
pub fn init_schedule(&mut self, label: impl ScheduleLabel) -> &mut Self {
let mut schedules = self.world.resource_mut::<Schedules>();
if !schedules.contains(&label) {
schedules.insert(label, Schedule::new());
}
self
}
/// Gets read-only access to the [`Schedule`] with the provided `label` if it exists.
pub fn get_schedule(&self, label: impl ScheduleLabel) -> Option<&Schedule> {
let schedules = self.world.get_resource::<Schedules>()?;
schedules.get(&label)
}
/// Gets read-write access to a [`Schedule`] with the provided `label` if it exists.
pub fn get_schedule_mut(&mut self, label: impl ScheduleLabel) -> Option<&mut Schedule> {
let schedules = self.world.get_resource_mut::<Schedules>()?;
// We need to call .into_inner here to satisfy the borrow checker:
// it can reason about reborrows using ordinary references but not the `Mut` smart pointer.
schedules.into_inner().get_mut(&label)
}
/// Applies the function to the [`Schedule`] associated with `label`.
///
/// **Note:** This will create the schedule if it does not already exist.
pub fn edit_schedule(
&mut self,
label: impl ScheduleLabel,
mut f: impl FnMut(&mut Schedule),
) -> &mut Self {
let mut schedules = self.world.resource_mut::<Schedules>();
if schedules.get(&label).is_none() {
schedules.insert(label.dyn_clone(), Schedule::new());
}
let schedule = schedules.get_mut(&label).unwrap();
// Call the function f, passing in the schedule retrieved
f(schedule);
self
}
}
fn run_once(mut app: App) {
app.update();
}
/// An event that indicates the [`App`] should exit. This will fully exit the app process at the
/// start of the next tick of the schedule.
///
/// You can also use this event to detect that an exit was requested. In order to receive it, systems
/// subscribing to this event should run after it was emitted and before the schedule of the same
/// frame is over. This is important since [`App::run()`] might never return.
///
/// If you don't require access to other components or resources, consider implementing the [`Drop`]
/// trait on components/resources for code that runs on exit. That saves you from worrying about
/// system schedule ordering, and is idiomatic Rust.
#[derive(Debug, Clone, Default)]
pub struct AppExit;
#[cfg(test)]
mod tests {
use crate::{App, Plugin};
struct PluginA;
impl Plugin for PluginA {
fn build(&self, _app: &mut crate::App) {}
}
struct PluginB;
impl Plugin for PluginB {
fn build(&self, _app: &mut crate::App) {}
}
struct PluginC<T>(T);
impl<T: Send + Sync + 'static> Plugin for PluginC<T> {
fn build(&self, _app: &mut crate::App) {}
}
struct PluginD;
impl Plugin for PluginD {
fn build(&self, _app: &mut crate::App) {}
fn is_unique(&self) -> bool {
false
}
}
#[test]
fn can_add_two_plugins() {
App::new().add_plugin(PluginA).add_plugin(PluginB);
}
#[test]
#[should_panic]
fn cant_add_twice_the_same_plugin() {
App::new().add_plugin(PluginA).add_plugin(PluginA);
}
#[test]
fn can_add_twice_the_same_plugin_with_different_type_param() {
App::new().add_plugin(PluginC(0)).add_plugin(PluginC(true));
}
#[test]
fn can_add_twice_the_same_plugin_not_unique() {
App::new().add_plugin(PluginD).add_plugin(PluginD);
}
#[test]
#[should_panic]
fn cant_call_app_run_from_plugin_build() {
struct PluginRun;
struct InnerPlugin;
impl Plugin for InnerPlugin {
fn build(&self, _: &mut crate::App) {}
}
impl Plugin for PluginRun {
fn build(&self, app: &mut crate::App) {
app.add_plugin(InnerPlugin).run();
}
}
App::new().add_plugin(PluginRun);
}
}