bevy/crates/bevy_app/src/sub_app.rs

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Computed State & Sub States (#11426) ## Summary/Description This PR extends states to allow support for a wider variety of state types and patterns, by providing 3 distinct types of state: - Standard [`States`] can only be changed by manually setting the [`NextState<S>`] resource. These states are the baseline on which the other state types are built, and can be used on their own for many simple patterns. See the [state example](https://github.com/bevyengine/bevy/blob/latest/examples/ecs/state.rs) for a simple use case - these are the states that existed so far in Bevy. - [`SubStates`] are children of other states - they can be changed manually using [`NextState<S>`], but are removed from the [`World`] if the source states aren't in the right state. See the [sub_states example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/sub_states.rs) for a simple use case based on the derive macro, or read the trait docs for more complex scenarios. - [`ComputedStates`] are fully derived from other states - they provide a [`compute`](ComputedStates::compute) method that takes in the source states and returns their derived value. They are particularly useful for situations where a simplified view of the source states is necessary - such as having an `InAMenu` computed state derived from a source state that defines multiple distinct menus. See the [computed state example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/computed_states.rscomputed_states.rs) to see a sampling of uses for these states. # Objective This PR is another attempt at allowing Bevy to better handle complex state objects in a manner that doesn't rely on strict equality. While my previous attempts (https://github.com/bevyengine/bevy/pull/10088 and https://github.com/bevyengine/bevy/pull/9957) relied on complex matching capacities at the point of adding a system to application, this one instead relies on deterministically deriving simple states from more complex ones. As a result, it does not require any special macros, nor does it change any other interactions with the state system once you define and add your derived state. It also maintains a degree of distinction between `State` and just normal application state - your derivations have to end up being discreet pre-determined values, meaning there is less of a risk/temptation to place a significant amount of logic and data within a given state. ### Addition - Sub States closes #9942 After some conversation with Maintainers & SMEs, a significant concern was that people might attempt to use this feature as if it were sub-states, and find themselves unable to use it appropriately. Since `ComputedState` is mainly a state matching feature, while `SubStates` are more of a state mutation related feature - but one that is easy to add with the help of the machinery introduced by `ComputedState`, it was added here as well. The relevant discussion is here: https://discord.com/channels/691052431525675048/1200556329803186316 ## Solution closes #11358 The solution is to create a new type of state - one implementing `ComputedStates` - which is deterministically tied to one or more other states. Implementors write a function to transform the source states into the computed state, and it gets triggered whenever one of the source states changes. In addition, we added the `FreelyMutableState` trait , which is implemented as part of the derive macro for `States`. This allows us to limit use of `NextState<S>` to states that are actually mutable, preventing mis-use of `ComputedStates`. --- ## Changelog - Added `ComputedStates` trait - Added `FreelyMutableState` trait - Converted `NextState` resource to an Enum, with `Unchanged` and `Pending` - Added `App::add_computed_state::<S: ComputedStates>()`, to allow for easily adding derived states to an App. - Moved the `StateTransition` schedule label from `bevy_app` to `bevy_ecs` - but maintained the export in `bevy_app` for continuity. - Modified the process for updating states. Instead of just having an `apply_state_transition` system that can be added anywhere, we now have a multi-stage process that has to run within the `StateTransition` label. First, all the state changes are calculated - manual transitions rely on `apply_state_transition`, while computed transitions run their computation process before both call `internal_apply_state_transition` to apply the transition, send out the transition event, trigger dependent states, and record which exit/transition/enter schedules need to occur. Once all the states have been updated, the transition schedules are called - first the exit schedules, then transition schedules and finally enter schedules. - Added `SubStates` trait - Adjusted `apply_state_transition` to be a no-op if the `State<S>` resource doesn't exist ## Migration Guide If the user accessed the NextState resource's value directly or created them from scratch they will need to adjust to use the new enum variants: - if they created a `NextState(Some(S))` - they should now use `NextState::Pending(S)` - if they created a `NextState(None)` -they should now use `NextState::Unchanged` - if they matched on the `NextState` value, they would need to make the adjustments above If the user manually utilized `apply_state_transition`, they should instead use systems that trigger the `StateTransition` schedule. --- ## Future Work There is still some future potential work in the area, but I wanted to keep these potential features and changes separate to keep the scope here contained, and keep the core of it easy to understand and use. However, I do want to note some of these things, both as inspiration to others and an illustration of what this PR could unlock. - `NextState::Remove` - Now that the `State` related mechanisms all utilize options (#11417), it's fairly easy to add support for explicit state removal. And while `ComputedStates` can add and remove themselves, right now `FreelyMutableState`s can't be removed from within the state system. While it existed originally in this PR, it is a different question with a separate scope and usability concerns - so having it as it's own future PR seems like the best approach. This feature currently lives in a separate branch in my fork, and the differences between it and this PR can be seen here: https://github.com/lee-orr/bevy/pull/5 - `NextState::ReEnter` - this would allow you to trigger exit & entry systems for the current state type. We can potentially also add a `NextState::ReEnterRecirsive` to also re-trigger any states that depend on the current one. - More mechanisms for `State` updates - This PR would finally make states that aren't a set of exclusive Enums useful, and with that comes the question of setting state more effectively. Right now, to update a state you either need to fully create the new state, or include the `Res<Option<State<S>>>` resource in your system, clone the state, mutate it, and then use `NextState.set(my_mutated_state)` to make it the pending next state. There are a few other potential methods that could be implemented in future PRs: - Inverse Compute States - these would essentially be compute states that have an additional (manually defined) function that can be used to nudge the source states so that they result in the computed states having a given value. For example, you could use set the `IsPaused` state, and it would attempt to pause or unpause the game by modifying the `AppState` as needed. - Closure-based state modification - this would involve adding a `NextState.modify(f: impl Fn(Option<S> -> Option<S>)` method, and then you can pass in closures or function pointers to adjust the state as needed. - Message-based state modification - this would involve either creating states that can respond to specific messages, similar to Elm or Redux. These could either use the `NextState` mechanism or the Event mechanism. - ~`SubStates` - which are essentially a hybrid of computed and manual states. In the simplest (and most likely) version, they would work by having a computed element that determines whether the state should exist, and if it should has the capacity to add a new version in, but then any changes to it's content would be freely mutated.~ this feature is now part of this PR. See above. - Lastly, since states are getting more complex there might be value in moving them out of `bevy_ecs` and into their own crate, or at least out of the `schedule` module into a `states` module. #11087 As mentioned, all these future work elements are TBD and are explicitly not part of this PR - I just wanted to provide them as potential explorations for the future. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: Marcel Champagne <voiceofmarcel@gmail.com> Co-authored-by: MiniaczQ <xnetroidpl@gmail.com>
2024-05-02 19:36:23 +00:00
use crate::{App, InternedAppLabel, Plugin, Plugins, PluginsState, Startup};
use bevy_ecs::{
Optimize Event Updates (#12936) # Objective Improve performance scalability when adding new event types to a Bevy app. Currently, just using Bevy in the default configuration, all apps spend upwards of 100+us in the `First` schedule, every app tick, evaluating if it should update events or not, even if events are not being used for that particular frame, and this scales with the number of Events registered in the app. ## Solution As `Events::update` is guaranteed `O(1)` by just checking if a resource's value, swapping two Vecs, and then clearing one of them, the actual cost of running `event_update_system` is *very* cheap. The overhead of doing system dependency injection, task scheduling ,and the multithreaded executor outweighs the cost of running the system by a large margin. Create an `EventRegistry` resource that keeps a number of function pointers that update each event. Replace the per-event type `event_update_system` with a singular exclusive system uses the `EventRegistry` to update all events instead. Update `SubApp::add_event` to use `EventRegistry` instead. ## Performance This speeds reduces the cost of the `First` schedule in both many_foxes and many_cubes by over 80%. Note this is with system spans on. The majority of this is now context-switching costs from launching `time_system`, which should be mostly eliminated with #12869. ![image](https://github.com/bevyengine/bevy/assets/3137680/037624be-21a2-4dc2-a42f-9d0bfa3e9b4a) The actual `event_update_system` is usually *very* short, using only a few microseconds on average. ![image](https://github.com/bevyengine/bevy/assets/3137680/01ff1689-3595-49b6-8f09-5c44bcf903e8) --- ## Changelog TODO ## Migration Guide TODO --------- Co-authored-by: Josh Matthews <josh@joshmatthews.net> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2024-04-13 14:11:28 +00:00
event::EventRegistry,
prelude::*,
schedule::{
Computed State & Sub States (#11426) ## Summary/Description This PR extends states to allow support for a wider variety of state types and patterns, by providing 3 distinct types of state: - Standard [`States`] can only be changed by manually setting the [`NextState<S>`] resource. These states are the baseline on which the other state types are built, and can be used on their own for many simple patterns. See the [state example](https://github.com/bevyengine/bevy/blob/latest/examples/ecs/state.rs) for a simple use case - these are the states that existed so far in Bevy. - [`SubStates`] are children of other states - they can be changed manually using [`NextState<S>`], but are removed from the [`World`] if the source states aren't in the right state. See the [sub_states example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/sub_states.rs) for a simple use case based on the derive macro, or read the trait docs for more complex scenarios. - [`ComputedStates`] are fully derived from other states - they provide a [`compute`](ComputedStates::compute) method that takes in the source states and returns their derived value. They are particularly useful for situations where a simplified view of the source states is necessary - such as having an `InAMenu` computed state derived from a source state that defines multiple distinct menus. See the [computed state example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/computed_states.rscomputed_states.rs) to see a sampling of uses for these states. # Objective This PR is another attempt at allowing Bevy to better handle complex state objects in a manner that doesn't rely on strict equality. While my previous attempts (https://github.com/bevyengine/bevy/pull/10088 and https://github.com/bevyengine/bevy/pull/9957) relied on complex matching capacities at the point of adding a system to application, this one instead relies on deterministically deriving simple states from more complex ones. As a result, it does not require any special macros, nor does it change any other interactions with the state system once you define and add your derived state. It also maintains a degree of distinction between `State` and just normal application state - your derivations have to end up being discreet pre-determined values, meaning there is less of a risk/temptation to place a significant amount of logic and data within a given state. ### Addition - Sub States closes #9942 After some conversation with Maintainers & SMEs, a significant concern was that people might attempt to use this feature as if it were sub-states, and find themselves unable to use it appropriately. Since `ComputedState` is mainly a state matching feature, while `SubStates` are more of a state mutation related feature - but one that is easy to add with the help of the machinery introduced by `ComputedState`, it was added here as well. The relevant discussion is here: https://discord.com/channels/691052431525675048/1200556329803186316 ## Solution closes #11358 The solution is to create a new type of state - one implementing `ComputedStates` - which is deterministically tied to one or more other states. Implementors write a function to transform the source states into the computed state, and it gets triggered whenever one of the source states changes. In addition, we added the `FreelyMutableState` trait , which is implemented as part of the derive macro for `States`. This allows us to limit use of `NextState<S>` to states that are actually mutable, preventing mis-use of `ComputedStates`. --- ## Changelog - Added `ComputedStates` trait - Added `FreelyMutableState` trait - Converted `NextState` resource to an Enum, with `Unchanged` and `Pending` - Added `App::add_computed_state::<S: ComputedStates>()`, to allow for easily adding derived states to an App. - Moved the `StateTransition` schedule label from `bevy_app` to `bevy_ecs` - but maintained the export in `bevy_app` for continuity. - Modified the process for updating states. Instead of just having an `apply_state_transition` system that can be added anywhere, we now have a multi-stage process that has to run within the `StateTransition` label. First, all the state changes are calculated - manual transitions rely on `apply_state_transition`, while computed transitions run their computation process before both call `internal_apply_state_transition` to apply the transition, send out the transition event, trigger dependent states, and record which exit/transition/enter schedules need to occur. Once all the states have been updated, the transition schedules are called - first the exit schedules, then transition schedules and finally enter schedules. - Added `SubStates` trait - Adjusted `apply_state_transition` to be a no-op if the `State<S>` resource doesn't exist ## Migration Guide If the user accessed the NextState resource's value directly or created them from scratch they will need to adjust to use the new enum variants: - if they created a `NextState(Some(S))` - they should now use `NextState::Pending(S)` - if they created a `NextState(None)` -they should now use `NextState::Unchanged` - if they matched on the `NextState` value, they would need to make the adjustments above If the user manually utilized `apply_state_transition`, they should instead use systems that trigger the `StateTransition` schedule. --- ## Future Work There is still some future potential work in the area, but I wanted to keep these potential features and changes separate to keep the scope here contained, and keep the core of it easy to understand and use. However, I do want to note some of these things, both as inspiration to others and an illustration of what this PR could unlock. - `NextState::Remove` - Now that the `State` related mechanisms all utilize options (#11417), it's fairly easy to add support for explicit state removal. And while `ComputedStates` can add and remove themselves, right now `FreelyMutableState`s can't be removed from within the state system. While it existed originally in this PR, it is a different question with a separate scope and usability concerns - so having it as it's own future PR seems like the best approach. This feature currently lives in a separate branch in my fork, and the differences between it and this PR can be seen here: https://github.com/lee-orr/bevy/pull/5 - `NextState::ReEnter` - this would allow you to trigger exit & entry systems for the current state type. We can potentially also add a `NextState::ReEnterRecirsive` to also re-trigger any states that depend on the current one. - More mechanisms for `State` updates - This PR would finally make states that aren't a set of exclusive Enums useful, and with that comes the question of setting state more effectively. Right now, to update a state you either need to fully create the new state, or include the `Res<Option<State<S>>>` resource in your system, clone the state, mutate it, and then use `NextState.set(my_mutated_state)` to make it the pending next state. There are a few other potential methods that could be implemented in future PRs: - Inverse Compute States - these would essentially be compute states that have an additional (manually defined) function that can be used to nudge the source states so that they result in the computed states having a given value. For example, you could use set the `IsPaused` state, and it would attempt to pause or unpause the game by modifying the `AppState` as needed. - Closure-based state modification - this would involve adding a `NextState.modify(f: impl Fn(Option<S> -> Option<S>)` method, and then you can pass in closures or function pointers to adjust the state as needed. - Message-based state modification - this would involve either creating states that can respond to specific messages, similar to Elm or Redux. These could either use the `NextState` mechanism or the Event mechanism. - ~`SubStates` - which are essentially a hybrid of computed and manual states. In the simplest (and most likely) version, they would work by having a computed element that determines whether the state should exist, and if it should has the capacity to add a new version in, but then any changes to it's content would be freely mutated.~ this feature is now part of this PR. See above. - Lastly, since states are getting more complex there might be value in moving them out of `bevy_ecs` and into their own crate, or at least out of the `schedule` module into a `states` module. #11087 As mentioned, all these future work elements are TBD and are explicitly not part of this PR - I just wanted to provide them as potential explorations for the future. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: Marcel Champagne <voiceofmarcel@gmail.com> Co-authored-by: MiniaczQ <xnetroidpl@gmail.com>
2024-05-02 19:36:23 +00:00
setup_state_transitions_in_world, FreelyMutableState, InternedScheduleLabel,
ScheduleBuildSettings, ScheduleLabel,
},
system::SystemId,
};
#[cfg(feature = "trace")]
use bevy_utils::tracing::info_span;
use bevy_utils::{HashMap, HashSet};
use std::fmt::Debug;
type ExtractFn = Box<dyn Fn(&mut World, &mut World) + Send>;
/// A secondary application with its own [`World`]. These can run independently of each other.
///
/// These are useful for situations where certain processes (e.g. a render thread) need to be kept
/// separate from the main application.
///
/// # Example
///
/// ```
/// # use bevy_app::{App, AppLabel, SubApp, Main};
/// # 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;
///
/// // Create an app with a certain resource.
/// let mut app = App::new();
/// app.insert_resource(Val(10));
///
/// // Create a sub-app with the same resource and a single schedule.
/// let mut sub_app = SubApp::new();
/// sub_app.insert_resource(Val(100));
///
/// // Setup an extract function to copy the resource's value in the main world.
/// sub_app.set_extract(|main_world, sub_world| {
/// sub_world.resource_mut::<Val>().0 = main_world.resource::<Val>().0;
/// });
///
/// // Schedule a system that will verify extraction is working.
/// sub_app.add_systems(Main, |counter: Res<Val>| {
/// // The value will be copied during extraction, so we should see 10 instead of 100.
/// assert_eq!(counter.0, 10);
/// });
///
/// // Add the sub-app to the main app.
/// app.insert_sub_app(ExampleApp, sub_app);
///
/// // Update the application once (using the default runner).
/// app.run();
/// ```
pub struct SubApp {
/// The data of this application.
world: World,
/// List of plugins that have been added.
pub(crate) plugin_registry: Vec<Box<dyn Plugin>>,
/// The names of plugins that have been added to this app. (used to track duplicates and
/// already-registered plugins)
pub(crate) plugin_names: HashSet<String>,
/// Panics if an update is attempted while plugins are building.
pub(crate) plugin_build_depth: usize,
pub(crate) plugins_state: PluginsState,
/// The schedule that will be run by [`update`](Self::update).
pub update_schedule: Option<InternedScheduleLabel>,
/// A function that gives mutable access to two app worlds. This is primarily
/// intended for copying data from the main world to secondary worlds.
extract: Option<ExtractFn>,
}
impl Debug for SubApp {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "SubApp")
}
}
impl Default for SubApp {
fn default() -> Self {
let mut world = World::new();
world.init_resource::<Schedules>();
Self {
world,
plugin_registry: Vec::default(),
plugin_names: HashSet::default(),
plugin_build_depth: 0,
plugins_state: PluginsState::Adding,
update_schedule: None,
extract: None,
}
}
}
impl SubApp {
/// Returns a default, empty [`SubApp`].
pub fn new() -> Self {
Self::default()
}
/// This method is a workaround. Each [`SubApp`] can have its own plugins, but [`Plugin`]
/// works on an [`App`] as a whole.
fn run_as_app<F>(&mut self, f: F)
where
F: FnOnce(&mut App),
{
let mut app = App::empty();
std::mem::swap(self, &mut app.sub_apps.main);
f(&mut app);
std::mem::swap(self, &mut app.sub_apps.main);
}
/// Returns a reference to the [`World`].
pub fn world(&self) -> &World {
&self.world
}
/// Returns a mutable reference to the [`World`].
pub fn world_mut(&mut self) -> &mut World {
&mut self.world
}
/// Runs the default schedule.
pub fn update(&mut self) {
if self.is_building_plugins() {
panic!("SubApp::update() was called while a plugin was building.");
}
if let Some(label) = self.update_schedule {
self.world.run_schedule(label);
}
self.world.clear_trackers();
}
/// Extracts data from `world` into the app's world using the registered extract method.
///
/// **Note:** There is no default extract method. Calling `extract` does nothing if
/// [`set_extract`](Self::set_extract) has not been called.
pub fn extract(&mut self, world: &mut World) {
if let Some(f) = self.extract.as_mut() {
f(world, &mut self.world);
}
}
/// Sets the method that will be called by [`extract`](Self::extract).
///
/// The first argument is the `World` to extract data from, the second argument is the app `World`.
pub fn set_extract<F>(&mut self, extract: F) -> &mut Self
where
F: Fn(&mut World, &mut World) + Send + 'static,
{
self.extract = Some(Box::new(extract));
self
}
/// See [`App::insert_resource`].
pub fn insert_resource<R: Resource>(&mut self, resource: R) -> &mut Self {
self.world.insert_resource(resource);
self
}
/// See [`App::init_resource`].
pub fn init_resource<R: Resource + FromWorld>(&mut self) -> &mut Self {
self.world.init_resource::<R>();
self
}
/// See [`App::add_systems`].
pub fn add_systems<M>(
&mut self,
schedule: impl ScheduleLabel,
systems: impl IntoSystemConfigs<M>,
) -> &mut Self {
let label = schedule.intern();
let mut schedules = self.world.resource_mut::<Schedules>();
if let Some(schedule) = schedules.get_mut(label) {
schedule.add_systems(systems);
} else {
let mut new_schedule = Schedule::new(label);
new_schedule.add_systems(systems);
schedules.insert(new_schedule);
}
self
}
/// See [`App::register_system`].
pub fn register_system<I: 'static, O: 'static, M, S: IntoSystem<I, O, M> + 'static>(
&mut self,
system: S,
) -> SystemId<I, O> {
self.world.register_system(system)
}
/// See [`App::configure_sets`].
#[track_caller]
pub fn configure_sets(
&mut self,
schedule: impl ScheduleLabel,
sets: impl IntoSystemSetConfigs,
) -> &mut Self {
let label = schedule.intern();
let mut schedules = self.world.resource_mut::<Schedules>();
if let Some(schedule) = schedules.get_mut(label) {
schedule.configure_sets(sets);
} else {
let mut new_schedule = Schedule::new(label);
new_schedule.configure_sets(sets);
schedules.insert(new_schedule);
}
self
}
/// See [`App::add_schedule`].
pub fn add_schedule(&mut self, schedule: Schedule) -> &mut Self {
let mut schedules = self.world.resource_mut::<Schedules>();
schedules.insert(schedule);
self
}
/// See [`App::init_schedule`].
pub fn init_schedule(&mut self, label: impl ScheduleLabel) -> &mut Self {
let label = label.intern();
let mut schedules = self.world.resource_mut::<Schedules>();
if !schedules.contains(label) {
schedules.insert(Schedule::new(label));
}
self
}
/// See [`App::get_schedule`].
pub fn get_schedule(&self, label: impl ScheduleLabel) -> Option<&Schedule> {
let schedules = self.world.get_resource::<Schedules>()?;
schedules.get(label)
}
/// See [`App::get_schedule_mut`].
pub fn get_schedule_mut(&mut self, label: impl ScheduleLabel) -> Option<&mut Schedule> {
let schedules = self.world.get_resource_mut::<Schedules>()?;
// We must call `.into_inner` here because the borrow checker only understands reborrows
// using ordinary references, not our `Mut` smart pointers.
schedules.into_inner().get_mut(label)
}
/// See [`App::edit_schedule`].
pub fn edit_schedule(
&mut self,
label: impl ScheduleLabel,
mut f: impl FnMut(&mut Schedule),
) -> &mut Self {
let label = label.intern();
let mut schedules = self.world.resource_mut::<Schedules>();
if !schedules.contains(label) {
schedules.insert(Schedule::new(label));
}
let schedule = schedules.get_mut(label).unwrap();
f(schedule);
self
}
/// See [`App::configure_schedules`].
pub fn configure_schedules(
&mut self,
schedule_build_settings: ScheduleBuildSettings,
) -> &mut Self {
self.world_mut()
.resource_mut::<Schedules>()
.configure_schedules(schedule_build_settings);
self
}
/// See [`App::allow_ambiguous_component`].
pub fn allow_ambiguous_component<T: Component>(&mut self) -> &mut Self {
self.world_mut().allow_ambiguous_component::<T>();
self
}
/// See [`App::allow_ambiguous_resource`].
pub fn allow_ambiguous_resource<T: Resource>(&mut self) -> &mut Self {
self.world_mut().allow_ambiguous_resource::<T>();
self
}
/// See [`App::ignore_ambiguity`].
#[track_caller]
pub fn ignore_ambiguity<M1, M2, S1, S2>(
&mut self,
schedule: impl ScheduleLabel,
a: S1,
b: S2,
) -> &mut Self
where
S1: IntoSystemSet<M1>,
S2: IntoSystemSet<M2>,
{
let schedule = schedule.intern();
let mut schedules = self.world.resource_mut::<Schedules>();
if let Some(schedule) = schedules.get_mut(schedule) {
let schedule: &mut Schedule = schedule;
schedule.ignore_ambiguity(a, b);
} else {
let mut new_schedule = Schedule::new(schedule);
new_schedule.ignore_ambiguity(a, b);
schedules.insert(new_schedule);
}
self
}
/// See [`App::init_state`].
Computed State & Sub States (#11426) ## Summary/Description This PR extends states to allow support for a wider variety of state types and patterns, by providing 3 distinct types of state: - Standard [`States`] can only be changed by manually setting the [`NextState<S>`] resource. These states are the baseline on which the other state types are built, and can be used on their own for many simple patterns. See the [state example](https://github.com/bevyengine/bevy/blob/latest/examples/ecs/state.rs) for a simple use case - these are the states that existed so far in Bevy. - [`SubStates`] are children of other states - they can be changed manually using [`NextState<S>`], but are removed from the [`World`] if the source states aren't in the right state. See the [sub_states example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/sub_states.rs) for a simple use case based on the derive macro, or read the trait docs for more complex scenarios. - [`ComputedStates`] are fully derived from other states - they provide a [`compute`](ComputedStates::compute) method that takes in the source states and returns their derived value. They are particularly useful for situations where a simplified view of the source states is necessary - such as having an `InAMenu` computed state derived from a source state that defines multiple distinct menus. See the [computed state example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/computed_states.rscomputed_states.rs) to see a sampling of uses for these states. # Objective This PR is another attempt at allowing Bevy to better handle complex state objects in a manner that doesn't rely on strict equality. While my previous attempts (https://github.com/bevyengine/bevy/pull/10088 and https://github.com/bevyengine/bevy/pull/9957) relied on complex matching capacities at the point of adding a system to application, this one instead relies on deterministically deriving simple states from more complex ones. As a result, it does not require any special macros, nor does it change any other interactions with the state system once you define and add your derived state. It also maintains a degree of distinction between `State` and just normal application state - your derivations have to end up being discreet pre-determined values, meaning there is less of a risk/temptation to place a significant amount of logic and data within a given state. ### Addition - Sub States closes #9942 After some conversation with Maintainers & SMEs, a significant concern was that people might attempt to use this feature as if it were sub-states, and find themselves unable to use it appropriately. Since `ComputedState` is mainly a state matching feature, while `SubStates` are more of a state mutation related feature - but one that is easy to add with the help of the machinery introduced by `ComputedState`, it was added here as well. The relevant discussion is here: https://discord.com/channels/691052431525675048/1200556329803186316 ## Solution closes #11358 The solution is to create a new type of state - one implementing `ComputedStates` - which is deterministically tied to one or more other states. Implementors write a function to transform the source states into the computed state, and it gets triggered whenever one of the source states changes. In addition, we added the `FreelyMutableState` trait , which is implemented as part of the derive macro for `States`. This allows us to limit use of `NextState<S>` to states that are actually mutable, preventing mis-use of `ComputedStates`. --- ## Changelog - Added `ComputedStates` trait - Added `FreelyMutableState` trait - Converted `NextState` resource to an Enum, with `Unchanged` and `Pending` - Added `App::add_computed_state::<S: ComputedStates>()`, to allow for easily adding derived states to an App. - Moved the `StateTransition` schedule label from `bevy_app` to `bevy_ecs` - but maintained the export in `bevy_app` for continuity. - Modified the process for updating states. Instead of just having an `apply_state_transition` system that can be added anywhere, we now have a multi-stage process that has to run within the `StateTransition` label. First, all the state changes are calculated - manual transitions rely on `apply_state_transition`, while computed transitions run their computation process before both call `internal_apply_state_transition` to apply the transition, send out the transition event, trigger dependent states, and record which exit/transition/enter schedules need to occur. Once all the states have been updated, the transition schedules are called - first the exit schedules, then transition schedules and finally enter schedules. - Added `SubStates` trait - Adjusted `apply_state_transition` to be a no-op if the `State<S>` resource doesn't exist ## Migration Guide If the user accessed the NextState resource's value directly or created them from scratch they will need to adjust to use the new enum variants: - if they created a `NextState(Some(S))` - they should now use `NextState::Pending(S)` - if they created a `NextState(None)` -they should now use `NextState::Unchanged` - if they matched on the `NextState` value, they would need to make the adjustments above If the user manually utilized `apply_state_transition`, they should instead use systems that trigger the `StateTransition` schedule. --- ## Future Work There is still some future potential work in the area, but I wanted to keep these potential features and changes separate to keep the scope here contained, and keep the core of it easy to understand and use. However, I do want to note some of these things, both as inspiration to others and an illustration of what this PR could unlock. - `NextState::Remove` - Now that the `State` related mechanisms all utilize options (#11417), it's fairly easy to add support for explicit state removal. And while `ComputedStates` can add and remove themselves, right now `FreelyMutableState`s can't be removed from within the state system. While it existed originally in this PR, it is a different question with a separate scope and usability concerns - so having it as it's own future PR seems like the best approach. This feature currently lives in a separate branch in my fork, and the differences between it and this PR can be seen here: https://github.com/lee-orr/bevy/pull/5 - `NextState::ReEnter` - this would allow you to trigger exit & entry systems for the current state type. We can potentially also add a `NextState::ReEnterRecirsive` to also re-trigger any states that depend on the current one. - More mechanisms for `State` updates - This PR would finally make states that aren't a set of exclusive Enums useful, and with that comes the question of setting state more effectively. Right now, to update a state you either need to fully create the new state, or include the `Res<Option<State<S>>>` resource in your system, clone the state, mutate it, and then use `NextState.set(my_mutated_state)` to make it the pending next state. There are a few other potential methods that could be implemented in future PRs: - Inverse Compute States - these would essentially be compute states that have an additional (manually defined) function that can be used to nudge the source states so that they result in the computed states having a given value. For example, you could use set the `IsPaused` state, and it would attempt to pause or unpause the game by modifying the `AppState` as needed. - Closure-based state modification - this would involve adding a `NextState.modify(f: impl Fn(Option<S> -> Option<S>)` method, and then you can pass in closures or function pointers to adjust the state as needed. - Message-based state modification - this would involve either creating states that can respond to specific messages, similar to Elm or Redux. These could either use the `NextState` mechanism or the Event mechanism. - ~`SubStates` - which are essentially a hybrid of computed and manual states. In the simplest (and most likely) version, they would work by having a computed element that determines whether the state should exist, and if it should has the capacity to add a new version in, but then any changes to it's content would be freely mutated.~ this feature is now part of this PR. See above. - Lastly, since states are getting more complex there might be value in moving them out of `bevy_ecs` and into their own crate, or at least out of the `schedule` module into a `states` module. #11087 As mentioned, all these future work elements are TBD and are explicitly not part of this PR - I just wanted to provide them as potential explorations for the future. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: Marcel Champagne <voiceofmarcel@gmail.com> Co-authored-by: MiniaczQ <xnetroidpl@gmail.com>
2024-05-02 19:36:23 +00:00
pub fn init_state<S: FreelyMutableState + FromWorld>(&mut self) -> &mut Self {
if !self.world.contains_resource::<State<S>>() {
Computed State & Sub States (#11426) ## Summary/Description This PR extends states to allow support for a wider variety of state types and patterns, by providing 3 distinct types of state: - Standard [`States`] can only be changed by manually setting the [`NextState<S>`] resource. These states are the baseline on which the other state types are built, and can be used on their own for many simple patterns. See the [state example](https://github.com/bevyengine/bevy/blob/latest/examples/ecs/state.rs) for a simple use case - these are the states that existed so far in Bevy. - [`SubStates`] are children of other states - they can be changed manually using [`NextState<S>`], but are removed from the [`World`] if the source states aren't in the right state. See the [sub_states example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/sub_states.rs) for a simple use case based on the derive macro, or read the trait docs for more complex scenarios. - [`ComputedStates`] are fully derived from other states - they provide a [`compute`](ComputedStates::compute) method that takes in the source states and returns their derived value. They are particularly useful for situations where a simplified view of the source states is necessary - such as having an `InAMenu` computed state derived from a source state that defines multiple distinct menus. See the [computed state example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/computed_states.rscomputed_states.rs) to see a sampling of uses for these states. # Objective This PR is another attempt at allowing Bevy to better handle complex state objects in a manner that doesn't rely on strict equality. While my previous attempts (https://github.com/bevyengine/bevy/pull/10088 and https://github.com/bevyengine/bevy/pull/9957) relied on complex matching capacities at the point of adding a system to application, this one instead relies on deterministically deriving simple states from more complex ones. As a result, it does not require any special macros, nor does it change any other interactions with the state system once you define and add your derived state. It also maintains a degree of distinction between `State` and just normal application state - your derivations have to end up being discreet pre-determined values, meaning there is less of a risk/temptation to place a significant amount of logic and data within a given state. ### Addition - Sub States closes #9942 After some conversation with Maintainers & SMEs, a significant concern was that people might attempt to use this feature as if it were sub-states, and find themselves unable to use it appropriately. Since `ComputedState` is mainly a state matching feature, while `SubStates` are more of a state mutation related feature - but one that is easy to add with the help of the machinery introduced by `ComputedState`, it was added here as well. The relevant discussion is here: https://discord.com/channels/691052431525675048/1200556329803186316 ## Solution closes #11358 The solution is to create a new type of state - one implementing `ComputedStates` - which is deterministically tied to one or more other states. Implementors write a function to transform the source states into the computed state, and it gets triggered whenever one of the source states changes. In addition, we added the `FreelyMutableState` trait , which is implemented as part of the derive macro for `States`. This allows us to limit use of `NextState<S>` to states that are actually mutable, preventing mis-use of `ComputedStates`. --- ## Changelog - Added `ComputedStates` trait - Added `FreelyMutableState` trait - Converted `NextState` resource to an Enum, with `Unchanged` and `Pending` - Added `App::add_computed_state::<S: ComputedStates>()`, to allow for easily adding derived states to an App. - Moved the `StateTransition` schedule label from `bevy_app` to `bevy_ecs` - but maintained the export in `bevy_app` for continuity. - Modified the process for updating states. Instead of just having an `apply_state_transition` system that can be added anywhere, we now have a multi-stage process that has to run within the `StateTransition` label. First, all the state changes are calculated - manual transitions rely on `apply_state_transition`, while computed transitions run their computation process before both call `internal_apply_state_transition` to apply the transition, send out the transition event, trigger dependent states, and record which exit/transition/enter schedules need to occur. Once all the states have been updated, the transition schedules are called - first the exit schedules, then transition schedules and finally enter schedules. - Added `SubStates` trait - Adjusted `apply_state_transition` to be a no-op if the `State<S>` resource doesn't exist ## Migration Guide If the user accessed the NextState resource's value directly or created them from scratch they will need to adjust to use the new enum variants: - if they created a `NextState(Some(S))` - they should now use `NextState::Pending(S)` - if they created a `NextState(None)` -they should now use `NextState::Unchanged` - if they matched on the `NextState` value, they would need to make the adjustments above If the user manually utilized `apply_state_transition`, they should instead use systems that trigger the `StateTransition` schedule. --- ## Future Work There is still some future potential work in the area, but I wanted to keep these potential features and changes separate to keep the scope here contained, and keep the core of it easy to understand and use. However, I do want to note some of these things, both as inspiration to others and an illustration of what this PR could unlock. - `NextState::Remove` - Now that the `State` related mechanisms all utilize options (#11417), it's fairly easy to add support for explicit state removal. And while `ComputedStates` can add and remove themselves, right now `FreelyMutableState`s can't be removed from within the state system. While it existed originally in this PR, it is a different question with a separate scope and usability concerns - so having it as it's own future PR seems like the best approach. This feature currently lives in a separate branch in my fork, and the differences between it and this PR can be seen here: https://github.com/lee-orr/bevy/pull/5 - `NextState::ReEnter` - this would allow you to trigger exit & entry systems for the current state type. We can potentially also add a `NextState::ReEnterRecirsive` to also re-trigger any states that depend on the current one. - More mechanisms for `State` updates - This PR would finally make states that aren't a set of exclusive Enums useful, and with that comes the question of setting state more effectively. Right now, to update a state you either need to fully create the new state, or include the `Res<Option<State<S>>>` resource in your system, clone the state, mutate it, and then use `NextState.set(my_mutated_state)` to make it the pending next state. There are a few other potential methods that could be implemented in future PRs: - Inverse Compute States - these would essentially be compute states that have an additional (manually defined) function that can be used to nudge the source states so that they result in the computed states having a given value. For example, you could use set the `IsPaused` state, and it would attempt to pause or unpause the game by modifying the `AppState` as needed. - Closure-based state modification - this would involve adding a `NextState.modify(f: impl Fn(Option<S> -> Option<S>)` method, and then you can pass in closures or function pointers to adjust the state as needed. - Message-based state modification - this would involve either creating states that can respond to specific messages, similar to Elm or Redux. These could either use the `NextState` mechanism or the Event mechanism. - ~`SubStates` - which are essentially a hybrid of computed and manual states. In the simplest (and most likely) version, they would work by having a computed element that determines whether the state should exist, and if it should has the capacity to add a new version in, but then any changes to it's content would be freely mutated.~ this feature is now part of this PR. See above. - Lastly, since states are getting more complex there might be value in moving them out of `bevy_ecs` and into their own crate, or at least out of the `schedule` module into a `states` module. #11087 As mentioned, all these future work elements are TBD and are explicitly not part of this PR - I just wanted to provide them as potential explorations for the future. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: Marcel Champagne <voiceofmarcel@gmail.com> Co-authored-by: MiniaczQ <xnetroidpl@gmail.com>
2024-05-02 19:36:23 +00:00
setup_state_transitions_in_world(&mut self.world, Some(Startup.intern()));
self.init_resource::<State<S>>()
.init_resource::<NextState<S>>()
Computed State & Sub States (#11426) ## Summary/Description This PR extends states to allow support for a wider variety of state types and patterns, by providing 3 distinct types of state: - Standard [`States`] can only be changed by manually setting the [`NextState<S>`] resource. These states are the baseline on which the other state types are built, and can be used on their own for many simple patterns. See the [state example](https://github.com/bevyengine/bevy/blob/latest/examples/ecs/state.rs) for a simple use case - these are the states that existed so far in Bevy. - [`SubStates`] are children of other states - they can be changed manually using [`NextState<S>`], but are removed from the [`World`] if the source states aren't in the right state. See the [sub_states example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/sub_states.rs) for a simple use case based on the derive macro, or read the trait docs for more complex scenarios. - [`ComputedStates`] are fully derived from other states - they provide a [`compute`](ComputedStates::compute) method that takes in the source states and returns their derived value. They are particularly useful for situations where a simplified view of the source states is necessary - such as having an `InAMenu` computed state derived from a source state that defines multiple distinct menus. See the [computed state example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/computed_states.rscomputed_states.rs) to see a sampling of uses for these states. # Objective This PR is another attempt at allowing Bevy to better handle complex state objects in a manner that doesn't rely on strict equality. While my previous attempts (https://github.com/bevyengine/bevy/pull/10088 and https://github.com/bevyengine/bevy/pull/9957) relied on complex matching capacities at the point of adding a system to application, this one instead relies on deterministically deriving simple states from more complex ones. As a result, it does not require any special macros, nor does it change any other interactions with the state system once you define and add your derived state. It also maintains a degree of distinction between `State` and just normal application state - your derivations have to end up being discreet pre-determined values, meaning there is less of a risk/temptation to place a significant amount of logic and data within a given state. ### Addition - Sub States closes #9942 After some conversation with Maintainers & SMEs, a significant concern was that people might attempt to use this feature as if it were sub-states, and find themselves unable to use it appropriately. Since `ComputedState` is mainly a state matching feature, while `SubStates` are more of a state mutation related feature - but one that is easy to add with the help of the machinery introduced by `ComputedState`, it was added here as well. The relevant discussion is here: https://discord.com/channels/691052431525675048/1200556329803186316 ## Solution closes #11358 The solution is to create a new type of state - one implementing `ComputedStates` - which is deterministically tied to one or more other states. Implementors write a function to transform the source states into the computed state, and it gets triggered whenever one of the source states changes. In addition, we added the `FreelyMutableState` trait , which is implemented as part of the derive macro for `States`. This allows us to limit use of `NextState<S>` to states that are actually mutable, preventing mis-use of `ComputedStates`. --- ## Changelog - Added `ComputedStates` trait - Added `FreelyMutableState` trait - Converted `NextState` resource to an Enum, with `Unchanged` and `Pending` - Added `App::add_computed_state::<S: ComputedStates>()`, to allow for easily adding derived states to an App. - Moved the `StateTransition` schedule label from `bevy_app` to `bevy_ecs` - but maintained the export in `bevy_app` for continuity. - Modified the process for updating states. Instead of just having an `apply_state_transition` system that can be added anywhere, we now have a multi-stage process that has to run within the `StateTransition` label. First, all the state changes are calculated - manual transitions rely on `apply_state_transition`, while computed transitions run their computation process before both call `internal_apply_state_transition` to apply the transition, send out the transition event, trigger dependent states, and record which exit/transition/enter schedules need to occur. Once all the states have been updated, the transition schedules are called - first the exit schedules, then transition schedules and finally enter schedules. - Added `SubStates` trait - Adjusted `apply_state_transition` to be a no-op if the `State<S>` resource doesn't exist ## Migration Guide If the user accessed the NextState resource's value directly or created them from scratch they will need to adjust to use the new enum variants: - if they created a `NextState(Some(S))` - they should now use `NextState::Pending(S)` - if they created a `NextState(None)` -they should now use `NextState::Unchanged` - if they matched on the `NextState` value, they would need to make the adjustments above If the user manually utilized `apply_state_transition`, they should instead use systems that trigger the `StateTransition` schedule. --- ## Future Work There is still some future potential work in the area, but I wanted to keep these potential features and changes separate to keep the scope here contained, and keep the core of it easy to understand and use. However, I do want to note some of these things, both as inspiration to others and an illustration of what this PR could unlock. - `NextState::Remove` - Now that the `State` related mechanisms all utilize options (#11417), it's fairly easy to add support for explicit state removal. And while `ComputedStates` can add and remove themselves, right now `FreelyMutableState`s can't be removed from within the state system. While it existed originally in this PR, it is a different question with a separate scope and usability concerns - so having it as it's own future PR seems like the best approach. This feature currently lives in a separate branch in my fork, and the differences between it and this PR can be seen here: https://github.com/lee-orr/bevy/pull/5 - `NextState::ReEnter` - this would allow you to trigger exit & entry systems for the current state type. We can potentially also add a `NextState::ReEnterRecirsive` to also re-trigger any states that depend on the current one. - More mechanisms for `State` updates - This PR would finally make states that aren't a set of exclusive Enums useful, and with that comes the question of setting state more effectively. Right now, to update a state you either need to fully create the new state, or include the `Res<Option<State<S>>>` resource in your system, clone the state, mutate it, and then use `NextState.set(my_mutated_state)` to make it the pending next state. There are a few other potential methods that could be implemented in future PRs: - Inverse Compute States - these would essentially be compute states that have an additional (manually defined) function that can be used to nudge the source states so that they result in the computed states having a given value. For example, you could use set the `IsPaused` state, and it would attempt to pause or unpause the game by modifying the `AppState` as needed. - Closure-based state modification - this would involve adding a `NextState.modify(f: impl Fn(Option<S> -> Option<S>)` method, and then you can pass in closures or function pointers to adjust the state as needed. - Message-based state modification - this would involve either creating states that can respond to specific messages, similar to Elm or Redux. These could either use the `NextState` mechanism or the Event mechanism. - ~`SubStates` - which are essentially a hybrid of computed and manual states. In the simplest (and most likely) version, they would work by having a computed element that determines whether the state should exist, and if it should has the capacity to add a new version in, but then any changes to it's content would be freely mutated.~ this feature is now part of this PR. See above. - Lastly, since states are getting more complex there might be value in moving them out of `bevy_ecs` and into their own crate, or at least out of the `schedule` module into a `states` module. #11087 As mentioned, all these future work elements are TBD and are explicitly not part of this PR - I just wanted to provide them as potential explorations for the future. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: Marcel Champagne <voiceofmarcel@gmail.com> Co-authored-by: MiniaczQ <xnetroidpl@gmail.com>
2024-05-02 19:36:23 +00:00
.add_event::<StateTransitionEvent<S>>();
let schedule = self.get_schedule_mut(StateTransition).unwrap();
S::register_state(schedule);
}
self
}
/// See [`App::insert_state`].
Computed State & Sub States (#11426) ## Summary/Description This PR extends states to allow support for a wider variety of state types and patterns, by providing 3 distinct types of state: - Standard [`States`] can only be changed by manually setting the [`NextState<S>`] resource. These states are the baseline on which the other state types are built, and can be used on their own for many simple patterns. See the [state example](https://github.com/bevyengine/bevy/blob/latest/examples/ecs/state.rs) for a simple use case - these are the states that existed so far in Bevy. - [`SubStates`] are children of other states - they can be changed manually using [`NextState<S>`], but are removed from the [`World`] if the source states aren't in the right state. See the [sub_states example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/sub_states.rs) for a simple use case based on the derive macro, or read the trait docs for more complex scenarios. - [`ComputedStates`] are fully derived from other states - they provide a [`compute`](ComputedStates::compute) method that takes in the source states and returns their derived value. They are particularly useful for situations where a simplified view of the source states is necessary - such as having an `InAMenu` computed state derived from a source state that defines multiple distinct menus. See the [computed state example](https://github.com/lee-orr/bevy/blob/derived_state/examples/ecs/computed_states.rscomputed_states.rs) to see a sampling of uses for these states. # Objective This PR is another attempt at allowing Bevy to better handle complex state objects in a manner that doesn't rely on strict equality. While my previous attempts (https://github.com/bevyengine/bevy/pull/10088 and https://github.com/bevyengine/bevy/pull/9957) relied on complex matching capacities at the point of adding a system to application, this one instead relies on deterministically deriving simple states from more complex ones. As a result, it does not require any special macros, nor does it change any other interactions with the state system once you define and add your derived state. It also maintains a degree of distinction between `State` and just normal application state - your derivations have to end up being discreet pre-determined values, meaning there is less of a risk/temptation to place a significant amount of logic and data within a given state. ### Addition - Sub States closes #9942 After some conversation with Maintainers & SMEs, a significant concern was that people might attempt to use this feature as if it were sub-states, and find themselves unable to use it appropriately. Since `ComputedState` is mainly a state matching feature, while `SubStates` are more of a state mutation related feature - but one that is easy to add with the help of the machinery introduced by `ComputedState`, it was added here as well. The relevant discussion is here: https://discord.com/channels/691052431525675048/1200556329803186316 ## Solution closes #11358 The solution is to create a new type of state - one implementing `ComputedStates` - which is deterministically tied to one or more other states. Implementors write a function to transform the source states into the computed state, and it gets triggered whenever one of the source states changes. In addition, we added the `FreelyMutableState` trait , which is implemented as part of the derive macro for `States`. This allows us to limit use of `NextState<S>` to states that are actually mutable, preventing mis-use of `ComputedStates`. --- ## Changelog - Added `ComputedStates` trait - Added `FreelyMutableState` trait - Converted `NextState` resource to an Enum, with `Unchanged` and `Pending` - Added `App::add_computed_state::<S: ComputedStates>()`, to allow for easily adding derived states to an App. - Moved the `StateTransition` schedule label from `bevy_app` to `bevy_ecs` - but maintained the export in `bevy_app` for continuity. - Modified the process for updating states. Instead of just having an `apply_state_transition` system that can be added anywhere, we now have a multi-stage process that has to run within the `StateTransition` label. First, all the state changes are calculated - manual transitions rely on `apply_state_transition`, while computed transitions run their computation process before both call `internal_apply_state_transition` to apply the transition, send out the transition event, trigger dependent states, and record which exit/transition/enter schedules need to occur. Once all the states have been updated, the transition schedules are called - first the exit schedules, then transition schedules and finally enter schedules. - Added `SubStates` trait - Adjusted `apply_state_transition` to be a no-op if the `State<S>` resource doesn't exist ## Migration Guide If the user accessed the NextState resource's value directly or created them from scratch they will need to adjust to use the new enum variants: - if they created a `NextState(Some(S))` - they should now use `NextState::Pending(S)` - if they created a `NextState(None)` -they should now use `NextState::Unchanged` - if they matched on the `NextState` value, they would need to make the adjustments above If the user manually utilized `apply_state_transition`, they should instead use systems that trigger the `StateTransition` schedule. --- ## Future Work There is still some future potential work in the area, but I wanted to keep these potential features and changes separate to keep the scope here contained, and keep the core of it easy to understand and use. However, I do want to note some of these things, both as inspiration to others and an illustration of what this PR could unlock. - `NextState::Remove` - Now that the `State` related mechanisms all utilize options (#11417), it's fairly easy to add support for explicit state removal. And while `ComputedStates` can add and remove themselves, right now `FreelyMutableState`s can't be removed from within the state system. While it existed originally in this PR, it is a different question with a separate scope and usability concerns - so having it as it's own future PR seems like the best approach. This feature currently lives in a separate branch in my fork, and the differences between it and this PR can be seen here: https://github.com/lee-orr/bevy/pull/5 - `NextState::ReEnter` - this would allow you to trigger exit & entry systems for the current state type. We can potentially also add a `NextState::ReEnterRecirsive` to also re-trigger any states that depend on the current one. - More mechanisms for `State` updates - This PR would finally make states that aren't a set of exclusive Enums useful, and with that comes the question of setting state more effectively. Right now, to update a state you either need to fully create the new state, or include the `Res<Option<State<S>>>` resource in your system, clone the state, mutate it, and then use `NextState.set(my_mutated_state)` to make it the pending next state. There are a few other potential methods that could be implemented in future PRs: - Inverse Compute States - these would essentially be compute states that have an additional (manually defined) function that can be used to nudge the source states so that they result in the computed states having a given value. For example, you could use set the `IsPaused` state, and it would attempt to pause or unpause the game by modifying the `AppState` as needed. - Closure-based state modification - this would involve adding a `NextState.modify(f: impl Fn(Option<S> -> Option<S>)` method, and then you can pass in closures or function pointers to adjust the state as needed. - Message-based state modification - this would involve either creating states that can respond to specific messages, similar to Elm or Redux. These could either use the `NextState` mechanism or the Event mechanism. - ~`SubStates` - which are essentially a hybrid of computed and manual states. In the simplest (and most likely) version, they would work by having a computed element that determines whether the state should exist, and if it should has the capacity to add a new version in, but then any changes to it's content would be freely mutated.~ this feature is now part of this PR. See above. - Lastly, since states are getting more complex there might be value in moving them out of `bevy_ecs` and into their own crate, or at least out of the `schedule` module into a `states` module. #11087 As mentioned, all these future work elements are TBD and are explicitly not part of this PR - I just wanted to provide them as potential explorations for the future. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: Marcel Champagne <voiceofmarcel@gmail.com> Co-authored-by: MiniaczQ <xnetroidpl@gmail.com>
2024-05-02 19:36:23 +00:00
pub fn insert_state<S: FreelyMutableState>(&mut self, state: S) -> &mut Self {
if !self.world.contains_resource::<State<S>>() {
setup_state_transitions_in_world(&mut self.world, Some(Startup.intern()));
self.insert_resource::<State<S>>(State::new(state))
.init_resource::<NextState<S>>()
.add_event::<StateTransitionEvent<S>>();
let schedule = self.get_schedule_mut(StateTransition).unwrap();
S::register_state(schedule);
}
self
}
/// See [`App::add_computed_state`].
pub fn add_computed_state<S: ComputedStates>(&mut self) -> &mut Self {
if !self
.world
.contains_resource::<Events<StateTransitionEvent<S>>>()
{
setup_state_transitions_in_world(&mut self.world, Some(Startup.intern()));
self.add_event::<StateTransitionEvent<S>>();
let schedule = self.get_schedule_mut(StateTransition).unwrap();
S::register_computed_state_systems(schedule);
}
self
}
/// See [`App::add_sub_state`].
pub fn add_sub_state<S: SubStates>(&mut self) -> &mut Self {
if !self
.world
.contains_resource::<Events<StateTransitionEvent<S>>>()
{
setup_state_transitions_in_world(&mut self.world, Some(Startup.intern()));
self.init_resource::<NextState<S>>();
self.add_event::<StateTransitionEvent<S>>();
let schedule = self.get_schedule_mut(StateTransition).unwrap();
S::register_sub_state_systems(schedule);
}
self
}
/// See [`App::add_event`].
pub fn add_event<T>(&mut self) -> &mut Self
where
T: Event,
{
if !self.world.contains_resource::<Events<T>>() {
Optimize Event Updates (#12936) # Objective Improve performance scalability when adding new event types to a Bevy app. Currently, just using Bevy in the default configuration, all apps spend upwards of 100+us in the `First` schedule, every app tick, evaluating if it should update events or not, even if events are not being used for that particular frame, and this scales with the number of Events registered in the app. ## Solution As `Events::update` is guaranteed `O(1)` by just checking if a resource's value, swapping two Vecs, and then clearing one of them, the actual cost of running `event_update_system` is *very* cheap. The overhead of doing system dependency injection, task scheduling ,and the multithreaded executor outweighs the cost of running the system by a large margin. Create an `EventRegistry` resource that keeps a number of function pointers that update each event. Replace the per-event type `event_update_system` with a singular exclusive system uses the `EventRegistry` to update all events instead. Update `SubApp::add_event` to use `EventRegistry` instead. ## Performance This speeds reduces the cost of the `First` schedule in both many_foxes and many_cubes by over 80%. Note this is with system spans on. The majority of this is now context-switching costs from launching `time_system`, which should be mostly eliminated with #12869. ![image](https://github.com/bevyengine/bevy/assets/3137680/037624be-21a2-4dc2-a42f-9d0bfa3e9b4a) The actual `event_update_system` is usually *very* short, using only a few microseconds on average. ![image](https://github.com/bevyengine/bevy/assets/3137680/01ff1689-3595-49b6-8f09-5c44bcf903e8) --- ## Changelog TODO ## Migration Guide TODO --------- Co-authored-by: Josh Matthews <josh@joshmatthews.net> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2024-04-13 14:11:28 +00:00
EventRegistry::register_event::<T>(self.world_mut());
}
self
}
/// See [`App::add_plugins`].
pub fn add_plugins<M>(&mut self, plugins: impl Plugins<M>) -> &mut Self {
self.run_as_app(|app| plugins.add_to_app(app));
self
}
/// See [`App::is_plugin_added`].
pub fn is_plugin_added<T>(&self) -> bool
where
T: Plugin,
{
self.plugin_names.contains(std::any::type_name::<T>())
}
/// See [`App::get_added_plugins`].
pub fn get_added_plugins<T>(&self) -> Vec<&T>
where
T: Plugin,
{
self.plugin_registry
.iter()
.filter_map(|p| p.downcast_ref())
.collect()
}
/// Returns `true` if there is no plugin in the middle of being built.
pub(crate) fn is_building_plugins(&self) -> bool {
self.plugin_build_depth > 0
}
/// Return the state of plugins.
#[inline]
pub fn plugins_state(&mut self) -> PluginsState {
match self.plugins_state {
PluginsState::Adding => {
let mut state = PluginsState::Ready;
let plugins = std::mem::take(&mut self.plugin_registry);
self.run_as_app(|app| {
for plugin in &plugins {
if !plugin.ready(app) {
state = PluginsState::Adding;
return;
}
}
});
self.plugin_registry = plugins;
state
}
state => state,
}
}
/// Runs [`Plugin::finish`] for each plugin.
pub fn finish(&mut self) {
let plugins = std::mem::take(&mut self.plugin_registry);
self.run_as_app(|app| {
for plugin in &plugins {
plugin.finish(app);
}
});
self.plugin_registry = plugins;
self.plugins_state = PluginsState::Finished;
}
/// Runs [`Plugin::cleanup`] for each plugin.
pub fn cleanup(&mut self) {
let plugins = std::mem::take(&mut self.plugin_registry);
self.run_as_app(|app| {
for plugin in &plugins {
plugin.cleanup(app);
}
});
self.plugin_registry = plugins;
self.plugins_state = PluginsState::Cleaned;
}
/// See [`App::register_type`].
#[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
}
/// See [`App::register_type_data`].
#[cfg(feature = "bevy_reflect")]
pub fn register_type_data<
T: bevy_reflect::Reflect + bevy_reflect::TypePath,
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
}
}
/// The collection of sub-apps that belong to an [`App`].
#[derive(Default)]
pub struct SubApps {
/// The primary sub-app that contains the "main" world.
pub main: SubApp,
/// Other, labeled sub-apps.
pub sub_apps: HashMap<InternedAppLabel, SubApp>,
}
impl SubApps {
/// Calls [`update`](SubApp::update) for the main sub-app, and then calls
/// [`extract`](SubApp::extract) and [`update`](SubApp::update) for the rest.
pub fn update(&mut self) {
#[cfg(feature = "trace")]
let _bevy_update_span = info_span!("update").entered();
{
#[cfg(feature = "trace")]
let _bevy_frame_update_span = info_span!("main app").entered();
self.main.update();
}
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.main.world);
sub_app.update();
}
self.main.world.clear_trackers();
}
/// Returns an iterator over the sub-apps (starting with the main one).
pub fn iter(&self) -> impl Iterator<Item = &SubApp> + '_ {
std::iter::once(&self.main).chain(self.sub_apps.values())
}
/// Returns a mutable iterator over the sub-apps (starting with the main one).
pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut SubApp> + '_ {
std::iter::once(&mut self.main).chain(self.sub_apps.values_mut())
}
}