38c3423693
19 Commits
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38c3423693
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Event Split: Event, EntityEvent, and BufferedEvent (#19647)
# Objective Closes #19564. The current `Event` trait looks like this: ```rust pub trait Event: Send + Sync + 'static { type Traversal: Traversal<Self>; const AUTO_PROPAGATE: bool = false; fn register_component_id(world: &mut World) -> ComponentId { ... } fn component_id(world: &World) -> Option<ComponentId> { ... } } ``` The `Event` trait is used by both buffered events (`EventReader`/`EventWriter`) and observer events. If they are observer events, they can optionally be targeted at specific `Entity`s or `ComponentId`s, and can even be propagated to other entities. However, there has long been a desire to split the trait semantically for a variety of reasons, see #14843, #14272, and #16031 for discussion. Some reasons include: - It's very uncommon to use a single event type as both a buffered event and targeted observer event. They are used differently and tend to have distinct semantics. - A common footgun is using buffered events with observers or event readers with observer events, as there is no type-level error that prevents this kind of misuse. - #19440 made `Trigger::target` return an `Option<Entity>`. This *seriously* hurts ergonomics for the general case of entity observers, as you need to `.unwrap()` each time. If we could statically determine whether the event is expected to have an entity target, this would be unnecessary. There's really two main ways that we can categorize events: push vs. pull (i.e. "observer event" vs. "buffered event") and global vs. targeted: | | Push | Pull | | ------------ | --------------- | --------------------------- | | **Global** | Global observer | `EventReader`/`EventWriter` | | **Targeted** | Entity observer | - | There are many ways to approach this, each with their tradeoffs. Ultimately, we kind of want to split events both ways: - A type-level distinction between observer events and buffered events, to prevent people from using the wrong kind of event in APIs - A statically designated entity target for observer events to avoid accidentally using untargeted events for targeted APIs This PR achieves these goals by splitting event traits into `Event`, `EntityEvent`, and `BufferedEvent`, with `Event` being the shared trait implemented by all events. ## `Event`, `EntityEvent`, and `BufferedEvent` `Event` is now a very simple trait shared by all events. ```rust pub trait Event: Send + Sync + 'static { // Required for observer APIs fn register_component_id(world: &mut World) -> ComponentId { ... } fn component_id(world: &World) -> Option<ComponentId> { ... } } ``` You can call `trigger` for *any* event, and use a global observer for listening to the event. ```rust #[derive(Event)] struct Speak { message: String, } // ... app.add_observer(|trigger: On<Speak>| { println!("{}", trigger.message); }); // ... commands.trigger(Speak { message: "Y'all like these reworked events?".to_string(), }); ``` To allow an event to be targeted at entities and even propagated further, you can additionally implement the `EntityEvent` trait: ```rust pub trait EntityEvent: Event { type Traversal: Traversal<Self>; const AUTO_PROPAGATE: bool = false; } ``` This lets you call `trigger_targets`, and to use targeted observer APIs like `EntityCommands::observe`: ```rust #[derive(Event, EntityEvent)] #[entity_event(traversal = &'static ChildOf, auto_propagate)] struct Damage { amount: f32, } // ... let enemy = commands.spawn((Enemy, Health(100.0))).id(); // Spawn some armor as a child of the enemy entity. // When the armor takes damage, it will bubble the event up to the enemy. let armor_piece = commands .spawn((ArmorPiece, Health(25.0), ChildOf(enemy))) .observe(|trigger: On<Damage>, mut query: Query<&mut Health>| { // Note: `On::target` only exists because this is an `EntityEvent`. let mut health = query.get(trigger.target()).unwrap(); health.0 -= trigger.amount(); }); commands.trigger_targets(Damage { amount: 10.0 }, armor_piece); ``` > [!NOTE] > You *can* still also trigger an `EntityEvent` without targets using `trigger`. We probably *could* make this an either-or thing, but I'm not sure that's actually desirable. To allow an event to be used with the buffered API, you can implement `BufferedEvent`: ```rust pub trait BufferedEvent: Event {} ``` The event can then be used with `EventReader`/`EventWriter`: ```rust #[derive(Event, BufferedEvent)] struct Message(String); fn write_hello(mut writer: EventWriter<Message>) { writer.write(Message("I hope these examples are alright".to_string())); } fn read_messages(mut reader: EventReader<Message>) { // Process all buffered events of type `Message`. for Message(message) in reader.read() { println!("{message}"); } } ``` In summary: - Need a basic event you can trigger and observe? Derive `Event`! - Need the event to be targeted at an entity? Derive `EntityEvent`! - Need the event to be buffered and support the `EventReader`/`EventWriter` API? Derive `BufferedEvent`! ## Alternatives I'll now cover some of the alternative approaches I have considered and briefly explored. I made this section collapsible since it ended up being quite long :P <details> <summary>Expand this to see alternatives</summary> ### 1. Unified `Event` Trait One option is not to have *three* separate traits (`Event`, `EntityEvent`, `BufferedEvent`), and to instead just use associated constants on `Event` to determine whether an event supports targeting and buffering or not: ```rust pub trait Event: Send + Sync + 'static { type Traversal: Traversal<Self>; const AUTO_PROPAGATE: bool = false; const TARGETED: bool = false; const BUFFERED: bool = false; fn register_component_id(world: &mut World) -> ComponentId { ... } fn component_id(world: &World) -> Option<ComponentId> { ... } } ``` Methods can then use bounds like `where E: Event<TARGETED = true>` or `where E: Event<BUFFERED = true>` to limit APIs to specific kinds of events. This would keep everything under one `Event` trait, but I don't think it's necessarily a good idea. It makes APIs harder to read, and docs can't easily refer to specific types of events. You can also create weird invariants: what if you specify `TARGETED = false`, but have `Traversal` and/or `AUTO_PROPAGATE` enabled? ### 2. `Event` and `Trigger` Another option is to only split the traits between buffered events and observer events, since that is the main thing people have been asking for, and they have the largest API difference. If we did this, I think we would need to make the terms *clearly* separate. We can't really use `Event` and `BufferedEvent` as the names, since it would be strange that `BufferedEvent` doesn't implement `Event`. Something like `ObserverEvent` and `BufferedEvent` could work, but it'd be more verbose. For this approach, I would instead keep `Event` for the current `EventReader`/`EventWriter` API, and call the observer event a `Trigger`, since the "trigger" terminology is already used in the observer context within Bevy (both as a noun and a verb). This is also what a long [bikeshed on Discord](https://discord.com/channels/691052431525675048/749335865876021248/1298057661878898791) seemed to land on at the end of last year. ```rust // For `EventReader`/`EventWriter` pub trait Event: Send + Sync + 'static {} // For observers pub trait Trigger: Send + Sync + 'static { type Traversal: Traversal<Self>; const AUTO_PROPAGATE: bool = false; const TARGETED: bool = false; fn register_component_id(world: &mut World) -> ComponentId { ... } fn component_id(world: &World) -> Option<ComponentId> { ... } } ``` The problem is that "event" is just a really good term for something that "happens". Observers are rapidly becoming the more prominent API, so it'd be weird to give them the `Trigger` name and leave the good `Event` name for the less common API. So, even though a split like this seems neat on the surface, I think it ultimately wouldn't really work. We want to keep the `Event` name for observer events, and there is no good alternative for the buffered variant. (`Message` was suggested, but saying stuff like "sends a collision message" is weird.) ### 3. `GlobalEvent` + `TargetedEvent` What if instead of focusing on the buffered vs. observed split, we *only* make a distinction between global and targeted events? ```rust // A shared event trait to allow global observers to work pub trait Event: Send + Sync + 'static { fn register_component_id(world: &mut World) -> ComponentId { ... } fn component_id(world: &World) -> Option<ComponentId> { ... } } // For buffered events and non-targeted observer events pub trait GlobalEvent: Event {} // For targeted observer events pub trait TargetedEvent: Event { type Traversal: Traversal<Self>; const AUTO_PROPAGATE: bool = false; } ``` This is actually the first approach I implemented, and it has the neat characteristic that you can only use non-targeted APIs like `trigger` with a `GlobalEvent` and targeted APIs like `trigger_targets` with a `TargetedEvent`. You have full control over whether the entity should or should not have a target, as they are fully distinct at the type-level. However, there's a few problems: - There is no type-level indication of whether a `GlobalEvent` supports buffered events or just non-targeted observer events - An `Event` on its own does literally nothing, it's just a shared trait required to make global observers accept both non-targeted and targeted events - If an event is both a `GlobalEvent` and `TargetedEvent`, global observers again have ambiguity on whether an event has a target or not, undermining some of the benefits - The names are not ideal ### 4. `Event` and `EntityEvent` We can fix some of the problems of Alternative 3 by accepting that targeted events can also be used in non-targeted contexts, and simply having the `Event` and `EntityEvent` traits: ```rust // For buffered events and non-targeted observer events pub trait Event: Send + Sync + 'static { fn register_component_id(world: &mut World) -> ComponentId { ... } fn component_id(world: &World) -> Option<ComponentId> { ... } } // For targeted observer events pub trait EntityEvent: Event { type Traversal: Traversal<Self>; const AUTO_PROPAGATE: bool = false; } ``` This is essentially identical to this PR, just without a dedicated `BufferedEvent`. The remaining major "problem" is that there is still zero type-level indication of whether an `Event` event *actually* supports the buffered API. This leads us to the solution proposed in this PR, using `Event`, `EntityEvent`, and `BufferedEvent`. </details> ## Conclusion The `Event` + `EntityEvent` + `BufferedEvent` split proposed in this PR aims to solve all the common problems with Bevy's current event model while keeping the "weirdness" factor minimal. It splits in terms of both the push vs. pull *and* global vs. targeted aspects, while maintaining a shared concept for an "event". ### Why I Like This - The term "event" remains as a single concept for all the different kinds of events in Bevy. - Despite all event types being "events", they use fundamentally different APIs. Instead of assuming that you can use an event type with any pattern (when only one is typically supported), you explicitly opt in to each one with dedicated traits. - Using separate traits for each type of event helps with documentation and clearer function signatures. - I can safely make assumptions on expected usage. - If I see that an event is an `EntityEvent`, I can assume that I can use `observe` on it and get targeted events. - If I see that an event is a `BufferedEvent`, I can assume that I can use `EventReader` to read events. - If I see both `EntityEvent` and `BufferedEvent`, I can assume that both APIs are supported. In summary: This allows for a unified concept for events, while limiting the different ways to use them with opt-in traits. No more guess-work involved when using APIs. ### Problems? - Because `BufferedEvent` implements `Event` (for more consistent semantics etc.), you can still use all buffered events for non-targeted observers. I think this is fine/good. The important part is that if you see that an event implements `BufferedEvent`, you know that the `EventReader`/`EventWriter` API should be supported. Whether it *also* supports other APIs is secondary. - I currently only support `trigger_targets` for an `EntityEvent`. However, you can technically target components too, without targeting any entities. I consider that such a niche and advanced use case that it's not a huge problem to only support it for `EntityEvent`s, but we could also split `trigger_targets` into `trigger_entities` and `trigger_components` if we wanted to (or implement components as entities :P). - You can still trigger an `EntityEvent` *without* targets. I consider this correct, since `Event` implements the non-targeted behavior, and it'd be weird if implementing another trait *removed* behavior. However, it does mean that global observers for entity events can technically return `Entity::PLACEHOLDER` again (since I got rid of the `Option<Entity>` added in #19440 for ergonomics). I think that's enough of an edge case that it's not a huge problem, but it is worth keeping in mind. - ~~Deriving both `EntityEvent` and `BufferedEvent` for the same type currently duplicates the `Event` implementation, so you instead need to manually implement one of them.~~ Changed to always requiring `Event` to be derived. ## Related Work There are plans to implement multi-event support for observers, especially for UI contexts. [Cart's example](https://github.com/bevyengine/bevy/issues/14649#issuecomment-2960402508) API looked like this: ```rust // Truncated for brevity trigger: Trigger<( OnAdd<Pressed>, OnRemove<Pressed>, OnAdd<InteractionDisabled>, OnRemove<InteractionDisabled>, OnInsert<Hovered>, )>, ``` I believe this shouldn't be in conflict with this PR. If anything, this PR might *help* achieve the multi-event pattern for entity observers with fewer footguns: by statically enforcing that all of these events are `EntityEvent`s in the context of `EntityCommands::observe`, we can avoid misuse or weird cases where *some* events inside the trigger are targeted while others are not. |
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7b1c9f192e
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Adopt consistent FooSystems naming convention for system sets (#18900)
# Objective Fixes a part of #14274. Bevy has an incredibly inconsistent naming convention for its system sets, both internally and across the ecosystem. <img alt="System sets in Bevy" src="https://github.com/user-attachments/assets/d16e2027-793f-4ba4-9cc9-e780b14a5a1b" width="450" /> *Names of public system set types in Bevy* Most Bevy types use a naming of `FooSystem` or just `Foo`, but there are also a few `FooSystems` and `FooSet` types. In ecosystem crates on the other hand, `FooSet` is perhaps the most commonly used name in general. Conventions being so wildly inconsistent can make it harder for users to pick names for their own types, to search for system sets on docs.rs, or to even discern which types *are* system sets. To reign in the inconsistency a bit and help unify the ecosystem, it would be good to establish a common recommended naming convention for system sets in Bevy itself, similar to how plugins are commonly suffixed with `Plugin` (ex: `TimePlugin`). By adopting a consistent naming convention in first-party Bevy, we can softly nudge ecosystem crates to follow suit (for types where it makes sense to do so). Choosing a naming convention is also relevant now, as the [`bevy_cli` recently adopted lints](https://github.com/TheBevyFlock/bevy_cli/pull/345) to enforce naming for plugins and system sets, and the recommended naming used for system sets is still a bit open. ## Which Name To Use? Now the contentious part: what naming convention should we actually adopt? This was discussed on the Bevy Discord at the end of last year, starting [here](<https://discord.com/channels/691052431525675048/692572690833473578/1310659954683936789>). `FooSet` and `FooSystems` were the clear favorites, with `FooSet` very narrowly winning an unofficial poll. However, it seems to me like the consensus was broadly moving towards `FooSystems` at the end and after the poll, with Cart ([source](https://discord.com/channels/691052431525675048/692572690833473578/1311140204974706708)) and later Alice ([source](https://discord.com/channels/691052431525675048/692572690833473578/1311092530732859533)) and also me being in favor of it. Let's do a quick pros and cons list! Of course these are just what I thought of, so take it with a grain of salt. `FooSet`: - Pro: Nice and short! - Pro: Used by many ecosystem crates. - Pro: The `Set` suffix comes directly from the trait name `SystemSet`. - Pro: Pairs nicely with existing APIs like `in_set` and `configure_sets`. - Con: `Set` by itself doesn't actually indicate that it's related to systems *at all*, apart from the implemented trait. A set of what? - Con: Is `FooSet` a set of `Foo`s or a system set related to `Foo`? Ex: `ContactSet`, `MeshSet`, `EnemySet`... `FooSystems`: - Pro: Very clearly indicates that the type represents a collection of systems. The actual core concept, system(s), is in the name. - Pro: Parallels nicely with `FooPlugins` for plugin groups. - Pro: Low risk of conflicts with other names or misunderstandings about what the type is. - Pro: In most cases, reads *very* nicely and clearly. Ex: `PhysicsSystems` and `AnimationSystems` as opposed to `PhysicsSet` and `AnimationSet`. - Pro: Easy to search for on docs.rs. - Con: Usually results in longer names. - Con: Not yet as widely used. Really the big problem with `FooSet` is that it doesn't actually describe what it is. It describes what *kind of thing* it is (a set of something), but not *what it is a set of*, unless you know the type or check its docs or implemented traits. `FooSystems` on the other hand is much more self-descriptive in this regard, at the cost of being a bit longer to type. Ultimately, in some ways it comes down to preference and how you think of system sets. Personally, I was originally in favor of `FooSet`, but have been increasingly on the side of `FooSystems`, especially after seeing what the new names would actually look like in Avian and now Bevy. I prefer it because it usually reads better, is much more clearly related to groups of systems than `FooSet`, and overall *feels* more correct and natural to me in the long term. For these reasons, and because Alice and Cart also seemed to share a preference for it when it was previously being discussed, I propose that we adopt a `FooSystems` naming convention where applicable. ## Solution Rename Bevy's system set types to use a consistent `FooSet` naming where applicable. - `AccessibilitySystem` → `AccessibilitySystems` - `GizmoRenderSystem` → `GizmoRenderSystems` - `PickSet` → `PickingSystems` - `RunFixedMainLoopSystem` → `RunFixedMainLoopSystems` - `TransformSystem` → `TransformSystems` - `RemoteSet` → `RemoteSystems` - `RenderSet` → `RenderSystems` - `SpriteSystem` → `SpriteSystems` - `StateTransitionSteps` → `StateTransitionSystems` - `RenderUiSystem` → `RenderUiSystems` - `UiSystem` → `UiSystems` - `Animation` → `AnimationSystems` - `AssetEvents` → `AssetEventSystems` - `TrackAssets` → `AssetTrackingSystems` - `UpdateGizmoMeshes` → `GizmoMeshSystems` - `InputSystem` → `InputSystems` - `InputFocusSet` → `InputFocusSystems` - `ExtractMaterialsSet` → `MaterialExtractionSystems` - `ExtractMeshesSet` → `MeshExtractionSystems` - `RumbleSystem` → `RumbleSystems` - `CameraUpdateSystem` → `CameraUpdateSystems` - `ExtractAssetsSet` → `AssetExtractionSystems` - `Update2dText` → `Text2dUpdateSystems` - `TimeSystem` → `TimeSystems` - `AudioPlaySet` → `AudioPlaybackSystems` - `SendEvents` → `EventSenderSystems` - `EventUpdates` → `EventUpdateSystems` A lot of the names got slightly longer, but they are also a lot more consistent, and in my opinion the majority of them read much better. For a few of the names I took the liberty of rewording things a bit; definitely open to any further naming improvements. There are still also cases where the `FooSystems` naming doesn't really make sense, and those I left alone. This primarily includes system sets like `Interned<dyn SystemSet>`, `EnterSchedules<S>`, `ExitSchedules<S>`, or `TransitionSchedules<S>`, where the type has some special purpose and semantics. ## Todo - [x] Should I keep all the old names as deprecated type aliases? I can do this, but to avoid wasting work I'd prefer to first reach consensus on whether these renames are even desired. - [x] Migration guide - [x] Release notes |
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d82c359a5a
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Add Default for all schedule labels (#18731)
# Objective In `bevy_enhanced_input`, I'm trying to associate `Actions` with a schedule. I can do this via an associated type on a trait, but there's no way to construct the associated label except by requiring a `Default` implementation. However, Bevy labels don't implement `Default`. ## Solution Add `Default` to all built-in labels. I think it should be useful in general. |
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d20f8553bf
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Fix misleading documentation of Main schedule (#18579)
# Objective Fixes #18562. ## Solution - Specified that `StateTransition` is actually run before `PreStartup`. - Specified consequences of this and how to actually run systems before any game logic regardless of state. - Updated docs of `StateTransition` to reflect that it is run before `PreStartup` in addition to being run after `PreUpdate`. ## Testing - `cargo doc` - `cargo test --doc` |
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ecccd57417
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Generic system config (#17962)
# Objective Prevents duplicate implementation between IntoSystemConfigs and IntoSystemSetConfigs using a generic, adds a NodeType trait for more config flexibility (opening the door to implement https://github.com/bevyengine/bevy/issues/14195?). ## Solution Followed writeup by @ItsDoot: https://hackmd.io/@doot/rJeefFHc1x Removes IntoSystemConfigs and IntoSystemSetConfigs, instead using IntoNodeConfigs with generics. ## Testing Pending --- ## Showcase N/A ## Migration Guide SystemSetConfigs -> NodeConfigs<InternedSystemSet> SystemConfigs -> NodeConfigs<ScheduleSystem> IntoSystemSetConfigs -> IntoNodeConfigs<InternedSystemSet, M> IntoSystemConfigs -> IntoNodeConfigs<ScheduleSystem, M> --------- Co-authored-by: Christian Hughes <9044780+ItsDoot@users.noreply.github.com> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |
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5f86668bbb
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Renamed EventWriter::send methods to write. (#17977)
Fixes #17856. ## Migration Guide - `EventWriter::send` has been renamed to `EventWriter::write`. - `EventWriter::send_batch` has been renamed to `EventWriter::write_batch`. - `EventWriter::send_default` has been renamed to `EventWriter::write_default`. --------- Co-authored-by: François Mockers <mockersf@gmail.com> |
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c6147e57f4
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Make StateTransitionSteps public (#16612)
# Objective - Fixes #16594 ## Solution - `StateTransitionSteps` was made public ## Testing - _Did you test these changes? If so, how?_ I am now able to import it and use it. --- ## Showcase - Users can now write their own state scoped resources ```rust fn init_state_scoped_resource<R: Resource + FromWorld>( &mut self, state: impl States, ) -> &mut Self { use bevy::state::state::StateTransitionSteps; // this PR in action self.add_systems( StateTransition, ( clear_state_scoped_resource_impl::<_, R>(state.clone()) .in_set(StateTransitionSteps::ExitSchedules), // and here init_state_scoped_resource_impl::<_, R>(state) .in_set(StateTransitionSteps::EnterSchedules), // here too ), ); self } ``` |
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30d84519a2
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Use en-us locale for typos (#16037)
# Objective Bevy seems to want to standardize on "American English" spellings. Not sure if this is laid out anywhere in writing, but see also #15947. While perusing the docs for `typos`, I noticed that it has a `locale` config option and tried it out. ## Solution Switch to `en-us` locale in the `typos` config and run `typos -w` ## Migration Guide The following methods or fields have been renamed from `*dependants*` to `*dependents*`. - `ProcessorAssetInfo::dependants` - `ProcessorAssetInfos::add_dependant` - `ProcessorAssetInfos::non_existent_dependants` - `AssetInfo::dependants_waiting_on_load` - `AssetInfo::dependants_waiting_on_recursive_dep_load` - `AssetInfos::loader_dependants` - `AssetInfos::remove_dependants_and_labels` |
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b4071ca370
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Add World::get_resource_or_init as an alternative to World::get_resource_or_insert_with (#15758)
# Objective
If a `Resource` implements `FromWorld` or `Default`, it's nicer to be
able to write:
```rust
let foo = world.get_resource_or_init::<Foo>();
```
Rather than:
```rust
let foo = world.get_resource_or_insert_with(Foo::default);
```
The latter is also not possible if a type implements `FromWorld` only,
and not `Default`.
## Solution
Added:
```rust
impl World {
pub fn get_resource_or_init<R: Resource + FromWorld>(&mut self) -> Mut<'_, R>;
}
```
Turns out all current in-engine uses of `get_resource_or_insert_with`
are exactly the above, so they've also been replaced.
## Testing
- Added a doc-test.
- Also added a doc-test for `World::get_resource_or_insert_with`.
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d70595b667
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Add core and alloc over std Lints (#15281)
# Objective - Fixes #6370 - Closes #6581 ## Solution - Added the following lints to the workspace: - `std_instead_of_core` - `std_instead_of_alloc` - `alloc_instead_of_core` - Used `cargo +nightly fmt` with [item level use formatting](https://rust-lang.github.io/rustfmt/?version=v1.6.0&search=#Item%5C%3A) to split all `use` statements into single items. - Used `cargo clippy --workspace --all-targets --all-features --fix --allow-dirty` to _attempt_ to resolve the new linting issues, and intervened where the lint was unable to resolve the issue automatically (usually due to needing an `extern crate alloc;` statement in a crate root). - Manually removed certain uses of `std` where negative feature gating prevented `--all-features` from finding the offending uses. - Used `cargo +nightly fmt` with [crate level use formatting](https://rust-lang.github.io/rustfmt/?version=v1.6.0&search=#Crate%5C%3A) to re-merge all `use` statements matching Bevy's previous styling. - Manually fixed cases where the `fmt` tool could not re-merge `use` statements due to conditional compilation attributes. ## Testing - Ran CI locally ## Migration Guide The MSRV is now 1.81. Please update to this version or higher. ## Notes - This is a _massive_ change to try and push through, which is why I've outlined the semi-automatic steps I used to create this PR, in case this fails and someone else tries again in the future. - Making this change has no impact on user code, but does mean Bevy contributors will be warned to use `core` and `alloc` instead of `std` where possible. - This lint is a critical first step towards investigating `no_std` options for Bevy. --------- Co-authored-by: François Mockers <francois.mockers@vleue.com> |
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bc72cedfe3
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Make initial StateTransition run before PreStartup (#14208)
# Objective - Fixes #14206 ## Solution - Run initial `StateTransition` as a startup schedule before `PreStartup`, instead of running it inside `Startup` as an exclusive system. Related discord discussion: https://discord.com/channels/691052431525675048/692572690833473578/1259543775668207678 ## Testing Reproduction now works correctly: ```rs use bevy::prelude::*; #[derive(Debug, Clone, Copy, Default, Eq, PartialEq, Hash, States)] enum AppState { #[default] Menu, InGame, } fn main() { App::new() .add_plugins(DefaultPlugins) .init_state::<AppState>() .add_systems(Startup, setup) .add_systems(OnEnter(AppState::Menu), enter_menu_state) .run(); } fn setup(mut next_state: ResMut<NextState<AppState>>) { next_state.set(AppState::Menu); } fn enter_menu_state() { println!("Entered menu state"); } ```  --- ## Changelog - Initial `StateTransition` runs before `PreStartup` instead of inside `Startup`. |
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d7080369a7
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Fix intra-doc links and make CI test them (#14076)
# Objective - Bevy currently has lot of invalid intra-doc links, let's fix them! - Also make CI test them, to avoid future regressions. - Helps with #1983 (but doesn't fix it, as there could still be explicit links to docs.rs that are broken) ## Solution - Make `cargo r -p ci -- doc-check` check fail on warnings (could also be changed to just some specific lints) - Manually fix all the warnings (note that in some cases it was unclear to me what the fix should have been, I'll try to highlight them in a self-review) |
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7ec301c48d
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fix docs around StateTransition and remove references to `apply_sta… (#13772)
The documentation for the `State` resource still referenced the use of `apply_state_transition` to manually force a state transition to occur, and the question around how to force transitions had come up a few times on discord. This is a docs-only change, that does the following: - Properly references `StateTransition` in the `MainSchedule` docs - replace the explanations for applying `NextState` with ones that explain the `StateTransition` schedule, and mentions the possibility of calling it manually - Add an example of calling `StateTransition` manually in the docs for the state transition schedule itself. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |
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6d0b7504a2
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Add more granular system sets for state transition schedule ordering (#13763)
# Objective Fixes #13711 ## Solution Introduce smaller, generic system sets for each schedule variant, which are ordered against other generic variants: - `ExitSchedules<S>` - For `OnExit` schedules, runs from leaf states to root states. - `TransitionSchedules<S>` - For `OnTransition` schedules, runs in arbitrary order. - `EnterSchedules<S>` - For `OnEnter` schedules, runs from root states to leaf states. Also unified `ApplyStateTransition<S>` schedule which works in basically the same way, just for internals. ## Testing - One test that tests schedule execution order --------- Co-authored-by: Lee-Orr <lee-orr@users.noreply.github.com> |
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49338245ea
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Generalize StateTransitionEvent<S> to allow identity transitions (#13579)
# Objective This PR addresses one of the issues from [discord state discussion](https://discord.com/channels/691052431525675048/1237949214017716356). Same-state transitions can be desirable, so there should exist a hook for them. Fixes https://github.com/bevyengine/bevy/issues/9130. ## Solution - Allow `StateTransitionEvent<S>` to contain identity transitions. - Ignore identity transitions at schedule running level (`OnExit`, `OnTransition`, `OnEnter`). - Propagate identity transitions through `SubStates` and `ComputedStates`. - Add example about registering custom transition schedules. ## Changelog - `StateTransitionEvent<S>` can be emitted with same `exited` and `entered` state. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |
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07aa9e5641
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Combine transition systems of Substates (#13626)
# Objective Prerequisite to #13579. Combine separate `Substates` transition systems to centralize transition logic and exert more control over it. ## Solution Originally the transition happened in 2 stages: - `apply_state_transition` in `ManualTransitions` handled `NextState`, - closure system in `DependentTransitions` handled parent-related changes, insertion and deletion of the substate. Now: - Both transitions are processed in a single closure system during `DependentTransitions`. - Since `Substates` no longer use `ManualTransitions`, it's been renamed to `RootTransitions`. Only root states use it. - When `Substates` state comes into existence, it will try to initialize from `NextState` and fallback to `should_exist` result. - Remove `apply_state_transition` from public API. Consequentially, removed the possibility of multiple `StateTransitionEvent`s when both transition systems fire in a single frame. ## Changelog - Renamed `ManualTransitions` to `RootTransitions`. - `Substates` will initialize their value with `NextState` if available and fallback to `should_exist` result. ## Migration Guide - `apply_state_transition` is no longer publicly available, run the `StateTransition` schedule instead. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |
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5cb4808026
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Simplify state transitions (#13616)
# Objective Prerequisite to #13579. Make state transition schedule running simpler. ## Solution - Remove `should_run_transition` which read the latest event and fake-fire an event for the startup transitions (e.g. startup `OnEnter()`). - Account for startup event, by actually emitting an event when adding states to `App`. - Replace `should_run_transition` with `last_transition`, which is a light wrapper over `EventReader::read().last()`. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |
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912f77b2fe
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Unify transition names to exited and entered (#13594)
# Objective Unifies the naming convention between `StateTransitionEvent<S>` and transition schedules. ## Migration Guide - `StateTransitionEvent<S>` and `OnTransition<S>` schedule had their fields renamed to `exited` and `entered` to match schedules. |
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42ba9dfaea
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Separate state crate (#13216)
# Objective Extracts the state mechanisms into a new crate called "bevy_state". This comes with a few goals: - state wasn't really an inherent machinery of the ecs system, and so keeping it within bevy_ecs felt forced - by mixing it in with bevy_ecs, the maintainability of our more robust state system was significantly compromised moving state into a new crate makes it easier to encapsulate as it's own feature, and easier to read and understand since it's no longer a single, massive file. ## Solution move the state-related elements from bevy_ecs to a new crate ## Testing - Did you test these changes? If so, how? all the automated tests migrated and passed, ran the pre-existing examples without changes to validate. --- ## Migration Guide Since bevy_state is now gated behind the `bevy_state` feature, projects that use state but don't use the `default-features` will need to add that feature flag. Since it is no longer part of bevy_ecs, projects that use bevy_ecs directly will need to manually pull in `bevy_state`, trigger the StateTransition schedule, and handle any of the elements that bevy_app currently sets up. --------- Co-authored-by: Kristoffer Søholm <k.soeholm@gmail.com> |