bevy/crates/bevy_ecs/src/schedule/condition.rs

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use std::borrow::Cow;
use crate::system::{CombinatorSystem, Combine, IntoSystem, ReadOnlySystem, System};
pub type BoxedCondition = Box<dyn ReadOnlySystem<In = (), Out = bool>>;
/// A system that determines if one or more scheduled systems should run.
///
/// Implemented for functions and closures that convert into [`System<In=(), Out=bool>`](crate::system::System)
/// with [read-only](crate::system::ReadOnlySystemParam) parameters.
pub trait Condition<Marker>: sealed::Condition<Marker> {
/// Returns a new run condition that only returns `true`
/// if both this one and the passed `and_then` return `true`.
///
/// The returned run condition is short-circuiting, meaning
/// `and_then` will only be invoked if `self` returns `true`.
///
/// # Examples
///
/// ```should_panic
/// use bevy_ecs::prelude::*;
///
/// #[derive(Resource, PartialEq)]
/// struct R(u32);
///
/// # let mut app = Schedule::new();
/// # let mut world = World::new();
/// # fn my_system() {}
/// app.add_system(
/// // The `resource_equals` run condition will panic since we don't initialize `R`,
/// // just like if we used `Res<R>` in a system.
/// my_system.run_if(resource_equals(R(0))),
/// );
/// # app.run(&mut world);
/// ```
///
/// Use `.and_then()` to avoid checking the condition.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # #[derive(Resource, PartialEq)]
/// # struct R(u32);
/// # let mut app = Schedule::new();
/// # let mut world = World::new();
/// # fn my_system() {}
/// app.add_system(
/// // `resource_equals` will only get run if the resource `R` exists.
/// my_system.run_if(resource_exists::<R>().and_then(resource_equals(R(0)))),
/// );
/// # app.run(&mut world);
/// ```
///
/// Note that in this case, it's better to just use the run condition [`resource_exists_and_equals`].
///
/// [`resource_exists_and_equals`]: common_conditions::resource_exists_and_equals
fn and_then<M, C: Condition<M>>(self, and_then: C) -> AndThen<Self::System, C::System> {
let a = IntoSystem::into_system(self);
let b = IntoSystem::into_system(and_then);
let name = format!("{} && {}", a.name(), b.name());
CombinatorSystem::new(a, b, Cow::Owned(name))
}
/// Returns a new run condition that returns `true`
/// if either this one or the passed `or_else` return `true`.
///
/// The returned run condition is short-circuiting, meaning
/// `or_else` will only be invoked if `self` returns `false`.
///
/// # Examples
///
/// ```
/// use bevy_ecs::prelude::*;
///
/// #[derive(Resource, PartialEq)]
/// struct A(u32);
///
/// #[derive(Resource, PartialEq)]
/// struct B(u32);
///
/// # let mut app = Schedule::new();
/// # let mut world = World::new();
/// # #[derive(Resource)] struct C(bool);
/// # fn my_system(mut c: ResMut<C>) { c.0 = true; }
/// app.add_system(
/// // Only run the system if either `A` or `B` exist.
/// my_system.run_if(resource_exists::<A>().or_else(resource_exists::<B>())),
/// );
/// #
/// # world.insert_resource(C(false));
/// # app.run(&mut world);
/// # assert!(!world.resource::<C>().0);
/// #
/// # world.insert_resource(A(0));
/// # app.run(&mut world);
/// # assert!(world.resource::<C>().0);
/// #
/// # world.remove_resource::<A>();
/// # world.insert_resource(B(0));
/// # world.insert_resource(C(false));
/// # app.run(&mut world);
/// # assert!(world.resource::<C>().0);
/// ```
fn or_else<M, C: Condition<M>>(self, or_else: C) -> OrElse<Self::System, C::System> {
let a = IntoSystem::into_system(self);
let b = IntoSystem::into_system(or_else);
let name = format!("{} || {}", a.name(), b.name());
CombinatorSystem::new(a, b, Cow::Owned(name))
}
}
impl<Marker, F> Condition<Marker> for F where F: sealed::Condition<Marker> {}
mod sealed {
use crate::system::{IntoSystem, ReadOnlySystem};
pub trait Condition<Marker>:
IntoSystem<(), bool, Marker, System = Self::ReadOnlySystem>
{
// This associated type is necessary to let the compiler
// know that `Self::System` is `ReadOnlySystem`.
type ReadOnlySystem: ReadOnlySystem<In = (), Out = bool>;
}
impl<Marker, F> Condition<Marker> for F
where
F: IntoSystem<(), bool, Marker>,
F::System: ReadOnlySystem,
{
type ReadOnlySystem = F::System;
}
}
Migrate engine to Schedule v3 (#7267) Huge thanks to @maniwani, @devil-ira, @hymm, @cart, @superdump and @jakobhellermann for the help with this PR. # Objective - Followup #6587. - Minimal integration for the Stageless Scheduling RFC: https://github.com/bevyengine/rfcs/pull/45 ## Solution - [x] Remove old scheduling module - [x] Migrate new methods to no longer use extension methods - [x] Fix compiler errors - [x] Fix benchmarks - [x] Fix examples - [x] Fix docs - [x] Fix tests ## Changelog ### Added - a large number of methods on `App` to work with schedules ergonomically - the `CoreSchedule` enum - `App::add_extract_system` via the `RenderingAppExtension` trait extension method - the private `prepare_view_uniforms` system now has a public system set for scheduling purposes, called `ViewSet::PrepareUniforms` ### Removed - stages, and all code that mentions stages - states have been dramatically simplified, and no longer use a stack - `RunCriteriaLabel` - `AsSystemLabel` trait - `on_hierarchy_reports_enabled` run criteria (now just uses an ad hoc resource checking run condition) - systems in `RenderSet/Stage::Extract` no longer warn when they do not read data from the main world - `RunCriteriaLabel` - `transform_propagate_system_set`: this was a nonstandard pattern that didn't actually provide enough control. The systems are already `pub`: the docs have been updated to ensure that the third-party usage is clear. ### Changed - `System::default_labels` is now `System::default_system_sets`. - `App::add_default_labels` is now `App::add_default_sets` - `CoreStage` and `StartupStage` enums are now `CoreSet` and `StartupSet` - `App::add_system_set` was renamed to `App::add_systems` - The `StartupSchedule` label is now defined as part of the `CoreSchedules` enum - `.label(SystemLabel)` is now referred to as `.in_set(SystemSet)` - `SystemLabel` trait was replaced by `SystemSet` - `SystemTypeIdLabel<T>` was replaced by `SystemSetType<T>` - The `ReportHierarchyIssue` resource now has a public constructor (`new`), and implements `PartialEq` - Fixed time steps now use a schedule (`CoreSchedule::FixedTimeStep`) rather than a run criteria. - Adding rendering extraction systems now panics rather than silently failing if no subapp with the `RenderApp` label is found. - the `calculate_bounds` system, with the `CalculateBounds` label, is now in `CoreSet::Update`, rather than in `CoreSet::PostUpdate` before commands are applied. - `SceneSpawnerSystem` now runs under `CoreSet::Update`, rather than `CoreStage::PreUpdate.at_end()`. - `bevy_pbr::add_clusters` is no longer an exclusive system - the top level `bevy_ecs::schedule` module was replaced with `bevy_ecs::scheduling` - `tick_global_task_pools_on_main_thread` is no longer run as an exclusive system. Instead, it has been replaced by `tick_global_task_pools`, which uses a `NonSend` resource to force running on the main thread. ## Migration Guide - Calls to `.label(MyLabel)` should be replaced with `.in_set(MySet)` - Stages have been removed. Replace these with system sets, and then add command flushes using the `apply_system_buffers` exclusive system where needed. - The `CoreStage`, `StartupStage, `RenderStage` and `AssetStage` enums have been replaced with `CoreSet`, `StartupSet, `RenderSet` and `AssetSet`. The same scheduling guarantees have been preserved. - Systems are no longer added to `CoreSet::Update` by default. Add systems manually if this behavior is needed, although you should consider adding your game logic systems to `CoreSchedule::FixedTimestep` instead for more reliable framerate-independent behavior. - Similarly, startup systems are no longer part of `StartupSet::Startup` by default. In most cases, this won't matter to you. - For example, `add_system_to_stage(CoreStage::PostUpdate, my_system)` should be replaced with - `add_system(my_system.in_set(CoreSet::PostUpdate)` - When testing systems or otherwise running them in a headless fashion, simply construct and run a schedule using `Schedule::new()` and `World::run_schedule` rather than constructing stages - Run criteria have been renamed to run conditions. These can now be combined with each other and with states. - Looping run criteria and state stacks have been removed. Use an exclusive system that runs a schedule if you need this level of control over system control flow. - For app-level control flow over which schedules get run when (such as for rollback networking), create your own schedule and insert it under the `CoreSchedule::Outer` label. - Fixed timesteps are now evaluated in a schedule, rather than controlled via run criteria. The `run_fixed_timestep` system runs this schedule between `CoreSet::First` and `CoreSet::PreUpdate` by default. - Command flush points introduced by `AssetStage` have been removed. If you were relying on these, add them back manually. - Adding extract systems is now typically done directly on the main app. Make sure the `RenderingAppExtension` trait is in scope, then call `app.add_extract_system(my_system)`. - the `calculate_bounds` system, with the `CalculateBounds` label, is now in `CoreSet::Update`, rather than in `CoreSet::PostUpdate` before commands are applied. You may need to order your movement systems to occur before this system in order to avoid system order ambiguities in culling behavior. - the `RenderLabel` `AppLabel` was renamed to `RenderApp` for clarity - `App::add_state` now takes 0 arguments: the starting state is set based on the `Default` impl. - Instead of creating `SystemSet` containers for systems that run in stages, simply use `.on_enter::<State::Variant>()` or its `on_exit` or `on_update` siblings. - `SystemLabel` derives should be replaced with `SystemSet`. You will also need to add the `Debug`, `PartialEq`, `Eq`, and `Hash` traits to satisfy the new trait bounds. - `with_run_criteria` has been renamed to `run_if`. Run criteria have been renamed to run conditions for clarity, and should now simply return a bool. - States have been dramatically simplified: there is no longer a "state stack". To queue a transition to the next state, call `NextState::set` ## TODO - [x] remove dead methods on App and World - [x] add `App::add_system_to_schedule` and `App::add_systems_to_schedule` - [x] avoid adding the default system set at inappropriate times - [x] remove any accidental cycles in the default plugins schedule - [x] migrate benchmarks - [x] expose explicit labels for the built-in command flush points - [x] migrate engine code - [x] remove all mentions of stages from the docs - [x] verify docs for States - [x] fix uses of exclusive systems that use .end / .at_start / .before_commands - [x] migrate RenderStage and AssetStage - [x] migrate examples - [x] ensure that transform propagation is exported in a sufficiently public way (the systems are already pub) - [x] ensure that on_enter schedules are run at least once before the main app - [x] re-enable opt-in to execution order ambiguities - [x] revert change to `update_bounds` to ensure it runs in `PostUpdate` - [x] test all examples - [x] unbreak directional lights - [x] unbreak shadows (see 3d_scene, 3d_shape, lighting, transparaency_3d examples) - [x] game menu example shows loading screen and menu simultaneously - [x] display settings menu is a blank screen - [x] `without_winit` example panics - [x] ensure all tests pass - [x] SubApp doc test fails - [x] runs_spawn_local tasks fails - [x] [Fix panic_when_hierachy_cycle test hanging](https://github.com/alice-i-cecile/bevy/pull/120) ## Points of Difficulty and Controversy **Reviewers, please give feedback on these and look closely** 1. Default sets, from the RFC, have been removed. These added a tremendous amount of implicit complexity and result in hard to debug scheduling errors. They're going to be tackled in the form of "base sets" by @cart in a followup. 2. The outer schedule controls which schedule is run when `App::update` is called. 3. I implemented `Label for `Box<dyn Label>` for our label types. This enables us to store schedule labels in concrete form, and then later run them. I ran into the same set of problems when working with one-shot systems. We've previously investigated this pattern in depth, and it does not appear to lead to extra indirection with nested boxes. 4. `SubApp::update` simply runs the default schedule once. This sucks, but this whole API is incomplete and this was the minimal changeset. 5. `time_system` and `tick_global_task_pools_on_main_thread` no longer use exclusive systems to attempt to force scheduling order 6. Implemetnation strategy for fixed timesteps 7. `AssetStage` was migrated to `AssetSet` without reintroducing command flush points. These did not appear to be used, and it's nice to remove these bottlenecks. 8. Migration of `bevy_render/lib.rs` and pipelined rendering. The logic here is unusually tricky, as we have complex scheduling requirements. ## Future Work (ideally before 0.10) - Rename schedule_v3 module to schedule or scheduling - Add a derive macro to states, and likely a `EnumIter` trait of some form - Figure out what exactly to do with the "systems added should basically work by default" problem - Improve ergonomics for working with fixed timesteps and states - Polish FixedTime API to match Time - Rebase and merge #7415 - Resolve all internal ambiguities (blocked on better tools, especially #7442) - Add "base sets" to replace the removed default sets.
2023-02-06 02:04:50 +00:00
pub mod common_conditions {
use super::Condition;
use crate::{
change_detection::DetectChanges,
event::{Event, EventReader},
prelude::{Component, Query, With},
schedule::{State, States},
system::{In, IntoPipeSystem, ReadOnlySystem, Res, Resource},
};
Migrate engine to Schedule v3 (#7267) Huge thanks to @maniwani, @devil-ira, @hymm, @cart, @superdump and @jakobhellermann for the help with this PR. # Objective - Followup #6587. - Minimal integration for the Stageless Scheduling RFC: https://github.com/bevyengine/rfcs/pull/45 ## Solution - [x] Remove old scheduling module - [x] Migrate new methods to no longer use extension methods - [x] Fix compiler errors - [x] Fix benchmarks - [x] Fix examples - [x] Fix docs - [x] Fix tests ## Changelog ### Added - a large number of methods on `App` to work with schedules ergonomically - the `CoreSchedule` enum - `App::add_extract_system` via the `RenderingAppExtension` trait extension method - the private `prepare_view_uniforms` system now has a public system set for scheduling purposes, called `ViewSet::PrepareUniforms` ### Removed - stages, and all code that mentions stages - states have been dramatically simplified, and no longer use a stack - `RunCriteriaLabel` - `AsSystemLabel` trait - `on_hierarchy_reports_enabled` run criteria (now just uses an ad hoc resource checking run condition) - systems in `RenderSet/Stage::Extract` no longer warn when they do not read data from the main world - `RunCriteriaLabel` - `transform_propagate_system_set`: this was a nonstandard pattern that didn't actually provide enough control. The systems are already `pub`: the docs have been updated to ensure that the third-party usage is clear. ### Changed - `System::default_labels` is now `System::default_system_sets`. - `App::add_default_labels` is now `App::add_default_sets` - `CoreStage` and `StartupStage` enums are now `CoreSet` and `StartupSet` - `App::add_system_set` was renamed to `App::add_systems` - The `StartupSchedule` label is now defined as part of the `CoreSchedules` enum - `.label(SystemLabel)` is now referred to as `.in_set(SystemSet)` - `SystemLabel` trait was replaced by `SystemSet` - `SystemTypeIdLabel<T>` was replaced by `SystemSetType<T>` - The `ReportHierarchyIssue` resource now has a public constructor (`new`), and implements `PartialEq` - Fixed time steps now use a schedule (`CoreSchedule::FixedTimeStep`) rather than a run criteria. - Adding rendering extraction systems now panics rather than silently failing if no subapp with the `RenderApp` label is found. - the `calculate_bounds` system, with the `CalculateBounds` label, is now in `CoreSet::Update`, rather than in `CoreSet::PostUpdate` before commands are applied. - `SceneSpawnerSystem` now runs under `CoreSet::Update`, rather than `CoreStage::PreUpdate.at_end()`. - `bevy_pbr::add_clusters` is no longer an exclusive system - the top level `bevy_ecs::schedule` module was replaced with `bevy_ecs::scheduling` - `tick_global_task_pools_on_main_thread` is no longer run as an exclusive system. Instead, it has been replaced by `tick_global_task_pools`, which uses a `NonSend` resource to force running on the main thread. ## Migration Guide - Calls to `.label(MyLabel)` should be replaced with `.in_set(MySet)` - Stages have been removed. Replace these with system sets, and then add command flushes using the `apply_system_buffers` exclusive system where needed. - The `CoreStage`, `StartupStage, `RenderStage` and `AssetStage` enums have been replaced with `CoreSet`, `StartupSet, `RenderSet` and `AssetSet`. The same scheduling guarantees have been preserved. - Systems are no longer added to `CoreSet::Update` by default. Add systems manually if this behavior is needed, although you should consider adding your game logic systems to `CoreSchedule::FixedTimestep` instead for more reliable framerate-independent behavior. - Similarly, startup systems are no longer part of `StartupSet::Startup` by default. In most cases, this won't matter to you. - For example, `add_system_to_stage(CoreStage::PostUpdate, my_system)` should be replaced with - `add_system(my_system.in_set(CoreSet::PostUpdate)` - When testing systems or otherwise running them in a headless fashion, simply construct and run a schedule using `Schedule::new()` and `World::run_schedule` rather than constructing stages - Run criteria have been renamed to run conditions. These can now be combined with each other and with states. - Looping run criteria and state stacks have been removed. Use an exclusive system that runs a schedule if you need this level of control over system control flow. - For app-level control flow over which schedules get run when (such as for rollback networking), create your own schedule and insert it under the `CoreSchedule::Outer` label. - Fixed timesteps are now evaluated in a schedule, rather than controlled via run criteria. The `run_fixed_timestep` system runs this schedule between `CoreSet::First` and `CoreSet::PreUpdate` by default. - Command flush points introduced by `AssetStage` have been removed. If you were relying on these, add them back manually. - Adding extract systems is now typically done directly on the main app. Make sure the `RenderingAppExtension` trait is in scope, then call `app.add_extract_system(my_system)`. - the `calculate_bounds` system, with the `CalculateBounds` label, is now in `CoreSet::Update`, rather than in `CoreSet::PostUpdate` before commands are applied. You may need to order your movement systems to occur before this system in order to avoid system order ambiguities in culling behavior. - the `RenderLabel` `AppLabel` was renamed to `RenderApp` for clarity - `App::add_state` now takes 0 arguments: the starting state is set based on the `Default` impl. - Instead of creating `SystemSet` containers for systems that run in stages, simply use `.on_enter::<State::Variant>()` or its `on_exit` or `on_update` siblings. - `SystemLabel` derives should be replaced with `SystemSet`. You will also need to add the `Debug`, `PartialEq`, `Eq`, and `Hash` traits to satisfy the new trait bounds. - `with_run_criteria` has been renamed to `run_if`. Run criteria have been renamed to run conditions for clarity, and should now simply return a bool. - States have been dramatically simplified: there is no longer a "state stack". To queue a transition to the next state, call `NextState::set` ## TODO - [x] remove dead methods on App and World - [x] add `App::add_system_to_schedule` and `App::add_systems_to_schedule` - [x] avoid adding the default system set at inappropriate times - [x] remove any accidental cycles in the default plugins schedule - [x] migrate benchmarks - [x] expose explicit labels for the built-in command flush points - [x] migrate engine code - [x] remove all mentions of stages from the docs - [x] verify docs for States - [x] fix uses of exclusive systems that use .end / .at_start / .before_commands - [x] migrate RenderStage and AssetStage - [x] migrate examples - [x] ensure that transform propagation is exported in a sufficiently public way (the systems are already pub) - [x] ensure that on_enter schedules are run at least once before the main app - [x] re-enable opt-in to execution order ambiguities - [x] revert change to `update_bounds` to ensure it runs in `PostUpdate` - [x] test all examples - [x] unbreak directional lights - [x] unbreak shadows (see 3d_scene, 3d_shape, lighting, transparaency_3d examples) - [x] game menu example shows loading screen and menu simultaneously - [x] display settings menu is a blank screen - [x] `without_winit` example panics - [x] ensure all tests pass - [x] SubApp doc test fails - [x] runs_spawn_local tasks fails - [x] [Fix panic_when_hierachy_cycle test hanging](https://github.com/alice-i-cecile/bevy/pull/120) ## Points of Difficulty and Controversy **Reviewers, please give feedback on these and look closely** 1. Default sets, from the RFC, have been removed. These added a tremendous amount of implicit complexity and result in hard to debug scheduling errors. They're going to be tackled in the form of "base sets" by @cart in a followup. 2. The outer schedule controls which schedule is run when `App::update` is called. 3. I implemented `Label for `Box<dyn Label>` for our label types. This enables us to store schedule labels in concrete form, and then later run them. I ran into the same set of problems when working with one-shot systems. We've previously investigated this pattern in depth, and it does not appear to lead to extra indirection with nested boxes. 4. `SubApp::update` simply runs the default schedule once. This sucks, but this whole API is incomplete and this was the minimal changeset. 5. `time_system` and `tick_global_task_pools_on_main_thread` no longer use exclusive systems to attempt to force scheduling order 6. Implemetnation strategy for fixed timesteps 7. `AssetStage` was migrated to `AssetSet` without reintroducing command flush points. These did not appear to be used, and it's nice to remove these bottlenecks. 8. Migration of `bevy_render/lib.rs` and pipelined rendering. The logic here is unusually tricky, as we have complex scheduling requirements. ## Future Work (ideally before 0.10) - Rename schedule_v3 module to schedule or scheduling - Add a derive macro to states, and likely a `EnumIter` trait of some form - Figure out what exactly to do with the "systems added should basically work by default" problem - Improve ergonomics for working with fixed timesteps and states - Polish FixedTime API to match Time - Rebase and merge #7415 - Resolve all internal ambiguities (blocked on better tools, especially #7442) - Add "base sets" to replace the removed default sets.
2023-02-06 02:04:50 +00:00
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the first time the condition is run and false every time after
pub fn run_once() -> impl FnMut() -> bool {
let mut has_run = false;
move || {
if !has_run {
has_run = true;
true
} else {
false
}
}
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the resource exists.
pub fn resource_exists<T>() -> impl FnMut(Option<Res<T>>) -> bool
where
T: Resource,
{
move |res: Option<Res<T>>| res.is_some()
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the resource is equal to `value`.
///
/// # Panics
///
/// The condition will panic if the resource does not exist.
pub fn resource_equals<T>(value: T) -> impl FnMut(Res<T>) -> bool
where
T: Resource + PartialEq,
{
move |res: Res<T>| *res == value
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the resource exists and is equal to `value`.
///
/// The condition will return `false` if the resource does not exist.
pub fn resource_exists_and_equals<T>(value: T) -> impl FnMut(Option<Res<T>>) -> bool
where
T: Resource + PartialEq,
{
move |res: Option<Res<T>>| match res {
Some(res) => *res == value,
None => false,
}
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the resource of the given type has been added since the condition was last checked.
pub fn resource_added<T>() -> impl FnMut(Option<Res<T>>) -> bool
where
T: Resource,
{
move |res: Option<Res<T>>| match res {
Some(res) => res.is_added(),
None => false,
}
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the resource of the given type has had its value changed since the condition
/// was last checked.
///
/// The value is considered changed when it is added. The first time this condition
/// is checked after the resource was added, it will return `true`.
/// Change detection behaves like this everywhere in Bevy.
///
/// # Panics
///
/// The condition will panic if the resource does not exist.
pub fn resource_changed<T>() -> impl FnMut(Res<T>) -> bool
where
T: Resource,
{
move |res: Res<T>| res.is_changed()
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the resource of the given type has had its value changed since the condition
/// was last checked.
///
/// The value is considered changed when it is added. The first time this condition
/// is checked after the resource was added, it will return `true`.
/// Change detection behaves like this everywhere in Bevy.
///
/// This run condition does not detect when the resource is removed.
///
/// The condition will return `false` if the resource does not exist.
pub fn resource_exists_and_changed<T>() -> impl FnMut(Option<Res<T>>) -> bool
where
T: Resource,
{
move |res: Option<Res<T>>| match res {
Some(res) => res.is_changed(),
None => false,
}
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the resource of the given type has had its value changed since the condition
/// was last checked.
///
/// The value is considered changed when it is added. The first time this condition
/// is checked after the resource was added, it will return `true`.
/// Change detection behaves like this everywhere in Bevy.
///
/// This run condition also detects removal. It will return `true` if the resource
/// has been removed since the run condition was last checked.
///
/// The condition will return `false` if the resource does not exist.
pub fn resource_changed_or_removed<T>() -> impl FnMut(Option<Res<T>>) -> bool
where
T: Resource,
{
let mut existed = false;
move |res: Option<Res<T>>| {
if let Some(value) = res {
existed = true;
value.is_changed()
} else if existed {
existed = false;
true
} else {
false
}
}
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the resource of the given type has been removed since the condition was last checked.
pub fn resource_removed<T>() -> impl FnMut(Option<Res<T>>) -> bool
where
T: Resource,
{
let mut existed = false;
move |res: Option<Res<T>>| {
if res.is_some() {
existed = true;
false
} else if existed {
existed = false;
true
} else {
false
}
}
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the state machine exists.
pub fn state_exists<S: States>() -> impl FnMut(Option<Res<State<S>>>) -> bool {
move |current_state: Option<Res<State<S>>>| current_state.is_some()
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the state machine is currently in `state`.
///
/// # Panics
///
/// The condition will panic if the resource does not exist.
pub fn in_state<S: States>(state: S) -> impl FnMut(Res<State<S>>) -> bool {
move |current_state: Res<State<S>>| current_state.0 == state
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the state machine exists and is currently in `state`.
///
/// The condition will return `false` if the state does not exist.
pub fn state_exists_and_equals<S: States>(
state: S,
) -> impl FnMut(Option<Res<State<S>>>) -> bool {
move |current_state: Option<Res<State<S>>>| match current_state {
Some(current_state) => current_state.0 == state,
None => false,
}
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if the state machine changed state.
///
/// To do things on transitions to/from specific states, use their respective OnEnter/OnExit
/// schedules. Use this run condition if you want to detect any change, regardless of the value.
///
/// # Panics
///
/// The condition will panic if the resource does not exist.
pub fn state_changed<S: States>() -> impl FnMut(Res<State<S>>) -> bool {
move |current_state: Res<State<S>>| current_state.is_changed()
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if there are any new events of the given type since it was last called.
pub fn on_event<T: Event>() -> impl FnMut(EventReader<T>) -> bool {
// The events need to be consumed, so that there are no false positives on subsequent
// calls of the run condition. Simply checking `is_empty` would not be enough.
// PERF: note that `count` is efficient (not actually looping/iterating),
// due to Bevy having a specialized implementation for events.
move |mut reader: EventReader<T>| reader.iter().count() > 0
}
/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
/// if there are any entities with the given component type.
pub fn any_with_component<T: Component>() -> impl FnMut(Query<(), With<T>>) -> bool {
move |query: Query<(), With<T>>| !query.is_empty()
}
/// Generates a [`Condition`](super::Condition) that inverses the result of passed one.
///
/// # Examples
///
/// ```
/// use bevy_ecs::prelude::*;
/// // Building a new schedule/app...
/// let mut sched = Schedule::default();
/// sched.add_system(
/// // This system will never run.
/// my_system.run_if(not(always_true))
/// )
/// // ...
/// # ;
/// # let mut world = World::new();
/// # sched.run(&mut world);
///
/// // A condition that always returns true.
/// fn always_true() -> bool {
/// true
/// }
/// #
/// # fn my_system() { unreachable!() }
/// ```
pub fn not<Marker>(
condition: impl Condition<Marker>,
) -> impl ReadOnlySystem<In = (), Out = bool> {
condition.pipe(|In(val): In<bool>| !val)
}
}
/// Combines the outputs of two systems using the `&&` operator.
pub type AndThen<A, B> = CombinatorSystem<AndThenMarker, A, B>;
/// Combines the outputs of two systems using the `||` operator.
pub type OrElse<A, B> = CombinatorSystem<OrElseMarker, A, B>;
#[doc(hidden)]
pub struct AndThenMarker;
impl<In, A, B> Combine<A, B> for AndThenMarker
where
In: Copy,
A: System<In = In, Out = bool>,
B: System<In = In, Out = bool>,
{
type In = In;
type Out = bool;
fn combine(
input: Self::In,
a: impl FnOnce(<A as System>::In) -> <A as System>::Out,
b: impl FnOnce(<B as System>::In) -> <B as System>::Out,
) -> Self::Out {
a(input) && b(input)
}
}
#[doc(hidden)]
pub struct OrElseMarker;
impl<In, A, B> Combine<A, B> for OrElseMarker
where
In: Copy,
A: System<In = In, Out = bool>,
B: System<In = In, Out = bool>,
{
type In = In;
type Out = bool;
fn combine(
input: Self::In,
a: impl FnOnce(<A as System>::In) -> <A as System>::Out,
b: impl FnOnce(<B as System>::In) -> <B as System>::Out,
) -> Self::Out {
a(input) || b(input)
}
}