85448b767e
13 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Joona Aalto
|
38c3423693
|
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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Joona Aalto
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e5dc177b4b
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Rename Trigger to On (#19596)
# Objective
Currently, the observer API looks like this:
```rust
app.add_observer(|trigger: Trigger<Explode>| {
info!("Entity {} exploded!", trigger.target());
});
```
Future plans for observers also include "multi-event observers" with a
trigger that looks like this (see [Cart's
example](https://github.com/bevyengine/bevy/issues/14649#issuecomment-2960402508)):
```rust
trigger: Trigger<(
OnAdd<Pressed>,
OnRemove<Pressed>,
OnAdd<InteractionDisabled>,
OnRemove<InteractionDisabled>,
OnInsert<Hovered>,
)>,
```
In scenarios like this, there is a lot of repetition of `On`. These are
expected to be very high-traffic APIs especially in UI contexts, so
ergonomics and readability are critical.
By renaming `Trigger` to `On`, we can make these APIs read more cleanly
and get rid of the repetition:
```rust
app.add_observer(|trigger: On<Explode>| {
info!("Entity {} exploded!", trigger.target());
});
```
```rust
trigger: On<(
Add<Pressed>,
Remove<Pressed>,
Add<InteractionDisabled>,
Remove<InteractionDisabled>,
Insert<Hovered>,
)>,
```
Names like `On<Add<Pressed>>` emphasize the actual event listener nature
more than `Trigger<OnAdd<Pressed>>`, and look cleaner. This *also* frees
up the `Trigger` name if we want to use it for the observer event type,
splitting them out from buffered events (bikeshedding this is out of
scope for this PR though).
For prior art:
[`bevy_eventlistener`](https://github.com/aevyrie/bevy_eventlistener)
used
[`On`](https://docs.rs/bevy_eventlistener/latest/bevy_eventlistener/event_listener/struct.On.html)
for its event listener type. Though in our case, the observer is the
event listener, and `On` is just a type containing information about the
triggered event.
## Solution
Steal from `bevy_event_listener` by @aevyrie and use `On`.
- Rename `Trigger` to `On`
- Rename `OnAdd` to `Add`
- Rename `OnInsert` to `Insert`
- Rename `OnReplace` to `Replace`
- Rename `OnRemove` to `Remove`
- Rename `OnDespawn` to `Despawn`
## Discussion
### Naming Conflicts??
Using a name like `Add` might initially feel like a very bad idea, since
it risks conflict with `core::ops::Add`. However, I don't expect this to
be a big problem in practice.
- You rarely need to actually implement the `Add` trait, especially in
modules that would use the Bevy ECS.
- In the rare cases where you *do* get a conflict, it is very easy to
fix by just disambiguating, for example using `ops::Add`.
- The `Add` event is a struct while the `Add` trait is a trait (duh), so
the compiler error should be very obvious.
For the record, renaming `OnAdd` to `Add`, I got exactly *zero* errors
or conflicts within Bevy itself. But this is of course not entirely
representative of actual projects *using* Bevy.
You might then wonder, why not use `Added`? This would conflict with the
`Added` query filter, so it wouldn't work. Additionally, the current
naming convention for observer events does not use past tense.
### Documentation
This does make documentation slightly more awkward when referring to
`On` or its methods. Previous docs often referred to `Trigger::target`
or "sends a `Trigger`" (which is... a bit strange anyway), which would
now be `On::target` and "sends an observer `Event`".
You can see the diff in this PR to see some of the effects. I think it
should be fine though, we may just need to reword more documentation to
read better.
|
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Eagster
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064e5e48b4
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Remove entity placeholder from observers (#19440)
# Objective `Entity::PLACEHOLDER` acts as a magic number that will *probably* never really exist, but it certainly could. And, `Entity` has a niche, so the only reason to use `PLACEHOLDER` is as an alternative to `MaybeUninit` that trades safety risks for logic risks. As a result, bevy has generally advised against using `PLACEHOLDER`, but we still use if for a lot internally. This pr starts removing internal uses of it, starting from observers. ## Solution Change all trigger target related types from `Entity` to `Option<Entity>` Small migration guide to come. ## Testing CI ## Future Work This turned a lot of code from ```rust trigger.target() ``` to ```rust trigger.target().unwrap() ``` The extra panic is no worse than before; it's just earlier than panicking after passing the placeholder to something else. But this is kinda annoying. I would like to add a `TriggerMode` or something to `Event` that would restrict what kinds of targets can be used for that event. Many events like `Removed` etc, are always triggered with a target. We can make those have a way to assume Some, etc. But I wanted to save that for a future pr. |
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Tim Overbeek
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664000f848
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Improve derive(Event) and simplify macro code (#18083)
# Objective simplify some code and improve Event macro Closes https://github.com/bevyengine/bevy/issues/14336, # Showcase you can now write derive Events like so ```rust #[derive(event)] #[event(auto_propagate, traversal = MyType)] struct MyEvent; ``` |
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AlephCubed
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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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Carter Anderson
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ba5e71f53d
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Parent -> ChildOf (#17427)
Fixes #17412 ## Objective `Parent` uses the "has a X" naming convention. There is increasing sentiment that we should use the "is a X" naming convention for relationships (following #17398). This leaves `Children` as-is because there is prevailing sentiment that `Children` is clearer than `ParentOf` in many cases (especially when treating it like a collection). This renames `Parent` to `ChildOf`. This is just the implementation PR. To discuss the path forward, do so in #17412. ## Migration Guide - The `Parent` component has been renamed to `ChildOf`. |
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Carter Anderson
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21f1e3045c
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Relationships (non-fragmenting, one-to-many) (#17398)
This adds support for one-to-many non-fragmenting relationships (with planned paths for fragmenting and non-fragmenting many-to-many relationships). "Non-fragmenting" means that entities with the same relationship type, but different relationship targets, are not forced into separate tables (which would cause "table fragmentation"). Functionally, this fills a similar niche as the current Parent/Children system. The biggest differences are: 1. Relationships have simpler internals and significantly improved performance and UX. Commands and specialized APIs are no longer necessary to keep everything in sync. Just spawn entities with the relationship components you want and everything "just works". 2. Relationships are generalized. Bevy can provide additional built in relationships, and users can define their own. **REQUEST TO REVIEWERS**: _please don't leave top level comments and instead comment on specific lines of code. That way we can take advantage of threaded discussions. Also dont leave comments simply pointing out CI failures as I can read those just fine._ ## Built on top of what we have Relationships are implemented on top of the Bevy ECS features we already have: components, immutability, and hooks. This makes them immediately compatible with all of our existing (and future) APIs for querying, spawning, removing, scenes, reflection, etc. The fewer specialized APIs we need to build, maintain, and teach, the better. ## Why focus on one-to-many non-fragmenting first? 1. This allows us to improve Parent/Children relationships immediately, in a way that is reasonably uncontroversial. Switching our hierarchy to fragmenting relationships would have significant performance implications. ~~Flecs is heavily considering a switch to non-fragmenting relations after careful considerations of the performance tradeoffs.~~ _(Correction from @SanderMertens: Flecs is implementing non-fragmenting storage specialized for asset hierarchies, where asset hierarchies are many instances of small trees that have a well defined structure)_ 2. Adding generalized one-to-many relationships is currently a priority for the [Next Generation Scene / UI effort](https://github.com/bevyengine/bevy/discussions/14437). Specifically, we're interested in building reactions and observers on top. ## The changes This PR does the following: 1. Adds a generic one-to-many Relationship system 3. Ports the existing Parent/Children system to Relationships, which now lives in `bevy_ecs::hierarchy`. The old `bevy_hierarchy` crate has been removed. 4. Adds on_despawn component hooks 5. Relationships can opt-in to "despawn descendants" behavior, meaning that the entire relationship hierarchy is despawned when `entity.despawn()` is called. The built in Parent/Children hierarchies enable this behavior, and `entity.despawn_recursive()` has been removed. 6. `world.spawn` now applies commands after spawning. This ensures that relationship bookkeeping happens immediately and removes the need to manually flush. This is in line with the equivalent behaviors recently added to the other APIs (ex: insert). 7. Removes the ValidParentCheckPlugin (system-driven / poll based) in favor of a `validate_parent_has_component` hook. ## Using Relationships The `Relationship` trait looks like this: ```rust pub trait Relationship: Component + Sized { type RelationshipSources: RelationshipSources<Relationship = Self>; fn get(&self) -> Entity; fn from(entity: Entity) -> Self; } ``` A relationship is a component that: 1. Is a simple wrapper over a "target" Entity. 2. Has a corresponding `RelationshipSources` component, which is a simple wrapper over a collection of entities. Every "target entity" targeted by a "source entity" with a `Relationship` has a `RelationshipSources` component, which contains every "source entity" that targets it. For example, the `Parent` component (as it currently exists in Bevy) is the `Relationship` component and the entity containing the Parent is the "source entity". The entity _inside_ the `Parent(Entity)` component is the "target entity". And that target entity has a `Children` component (which implements `RelationshipSources`). In practice, the Parent/Children relationship looks like this: ```rust #[derive(Relationship)] #[relationship(relationship_sources = Children)] pub struct Parent(pub Entity); #[derive(RelationshipSources)] #[relationship_sources(relationship = Parent)] pub struct Children(Vec<Entity>); ``` The Relationship and RelationshipSources derives automatically implement Component with the relevant configuration (namely, the hooks necessary to keep everything in sync). The most direct way to add relationships is to spawn entities with relationship components: ```rust let a = world.spawn_empty().id(); let b = world.spawn(Parent(a)).id(); assert_eq!(world.entity(a).get::<Children>().unwrap(), &[b]); ``` There are also convenience APIs for spawning more than one entity with the same relationship: ```rust world.spawn_empty().with_related::<Children>(|s| { s.spawn_empty(); s.spawn_empty(); }) ``` The existing `with_children` API is now a simpler wrapper over `with_related`. This makes this change largely non-breaking for existing spawn patterns. ```rust world.spawn_empty().with_children(|s| { s.spawn_empty(); s.spawn_empty(); }) ``` There are also other relationship APIs, such as `add_related` and `despawn_related`. ## Automatic recursive despawn via the new on_despawn hook `RelationshipSources` can opt-in to "despawn descendants" behavior, which will despawn all related entities in the relationship hierarchy: ```rust #[derive(RelationshipSources)] #[relationship_sources(relationship = Parent, despawn_descendants)] pub struct Children(Vec<Entity>); ``` This means that `entity.despawn_recursive()` is no longer required. Instead, just use `entity.despawn()` and the relevant related entities will also be despawned. To despawn an entity _without_ despawning its parent/child descendants, you should remove the `Children` component first, which will also remove the related `Parent` components: ```rust entity .remove::<Children>() .despawn() ``` This builds on the on_despawn hook introduced in this PR, which is fired when an entity is despawned (before other hooks). ## Relationships are the source of truth `Relationship` is the _single_ source of truth component. `RelationshipSources` is merely a reflection of what all the `Relationship` components say. By embracing this, we are able to significantly improve the performance of the system as a whole. We can rely on component lifecycles to protect us against duplicates, rather than needing to scan at runtime to ensure entities don't already exist (which results in quadratic runtime). A single source of truth gives us constant-time inserts. This does mean that we cannot directly spawn populated `Children` components (or directly add or remove entities from those components). I personally think this is a worthwhile tradeoff, both because it makes the performance much better _and_ because it means theres exactly one way to do things (which is a philosophy we try to employ for Bevy APIs). As an aside: treating both sides of the relationship as "equivalent source of truth relations" does enable building simple and flexible many-to-many relationships. But this introduces an _inherent_ need to scan (or hash) to protect against duplicates. [`evergreen_relations`](https://github.com/EvergreenNest/evergreen_relations) has a very nice implementation of the "symmetrical many-to-many" approach. Unfortunately I think the performance issues inherent to that approach make it a poor choice for Bevy's default relationship system. ## Followup Work * Discuss renaming `Parent` to `ChildOf`. I refrained from doing that in this PR to keep the diff reasonable, but I'm personally biased toward this change (and using that naming pattern generally for relationships). * [Improved spawning ergonomics](https://github.com/bevyengine/bevy/discussions/16920) * Consider adding relationship observers/triggers for "relationship targets" whenever a source is added or removed. This would replace the current "hierarchy events" system, which is unused upstream but may have existing users downstream. I think triggers are the better fit for this than a buffered event queue, and would prefer not to add that back. * Fragmenting relations: My current idea hinges on the introduction of "value components" (aka: components whose type _and_ value determines their ComponentId, via something like Hashing / PartialEq). By labeling a Relationship component such as `ChildOf(Entity)` as a "value component", `ChildOf(e1)` and `ChildOf(e2)` would be considered "different components". This makes the transition between fragmenting and non-fragmenting a single flag, and everything else continues to work as expected. * Many-to-many support * Non-fragmenting: We can expand Relationship to be a list of entities instead of a single entity. I have largely already written the code for this. * Fragmenting: With the "value component" impl mentioned above, we get many-to-many support "for free", as it would allow inserting multiple copies of a Relationship component with different target entities. Fixes #3742 (If this PR is merged, I think we should open more targeted followup issues for the work above, with a fresh tracking issue free of the large amount of less-directed historical context) Fixes #17301 Fixes #12235 Fixes #15299 Fixes #15308 ## Migration Guide * Replace `ChildBuilder` with `ChildSpawnerCommands`. * Replace calls to `.set_parent(parent_id)` with `.insert(Parent(parent_id))`. * Replace calls to `.replace_children()` with `.remove::<Children>()` followed by `.add_children()`. Note that you'll need to manually despawn any children that are not carried over. * Replace calls to `.despawn_recursive()` with `.despawn()`. * Replace calls to `.despawn_descendants()` with `.despawn_related::<Children>()`. * If you have any calls to `.despawn()` which depend on the children being preserved, you'll need to remove the `Children` component first. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |
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Aevyrie
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61b98ec80f
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Rename trigger.entity() to trigger.target() (#16716)
# Objective - A `Trigger` has multiple associated `Entity`s - the entity observing the event, and the entity that was targeted by the event. - The field `entity: Entity` encodes no semantic information about what the entity is used for, you can already tell that it's an `Entity` by the type signature! ## Solution - Rename `trigger.entity()` to `trigger.target()` --- ## Changelog - `Trigger`s are associated with multiple entities. `Trigger::entity()` has been renamed to `Trigger::target()` to reflect the semantics of the entity being returned. ## Migration Guide - Rename `Trigger::entity()` to `Trigger::target()`. - Rename `ObserverTrigger::entity` to `ObserverTrigger::target` |
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Christian Hughes
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219b5930f1
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Rename App/World::observe to add_observer, EntityWorldMut::observe_entity to observe. (#15754)
# Objective - Closes #15752 Calling the functions `App::observe` and `World::observe` doesn't make sense because you're not "observing" the `App` or `World`, you're adding an observer that listens for an event that occurs *within* the `World`. We should rename them to better fit this. ## Solution Renames: - `App::observe` -> `App::add_observer` - `World::observe` -> `World::add_observer` - `Commands::observe` -> `Commands::add_observer` - `EntityWorldMut::observe_entity` -> `EntityWorldMut::observe` (Note this isn't a breaking change as the original rename was introduced earlier this cycle.) ## Testing Reusing current tests. |
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Benjamin Brienen
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27bea6abf7
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Bubbling observers traversal should use query data (#15385)
# Objective Fixes #14331 ## Solution - Make `Traversal` a subtrait of `ReadOnlyQueryData` - Update implementations and usages ## Testing - Updated unit tests ## Migration Guide Update implementations of `Traversal`. --------- Co-authored-by: Christian Hughes <9044780+ItsDoot@users.noreply.github.com> |
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EdJoPaTo
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938d810766
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Apply unused_qualifications lint (#14828)
# Objective Fixes #14782 ## Solution Enable the lint and fix all upcoming hints (`--fix`). Also tried to figure out the false-positive (see review comment). Maybe split this PR up into multiple parts where only the last one enables the lint, so some can already be merged resulting in less many files touched / less potential for merge conflicts? Currently, there are some cases where it might be easier to read the code with the qualifier, so perhaps remove the import of it and adapt its cases? In the current stage it's just a plain adoption of the suggestions in order to have a base to discuss. ## Testing `cargo clippy` and `cargo run -p ci` are happy. |
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EdJoPaTo
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a6d233981d
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Fix ecs example thread_rng duplicate creation (#14795)
# Objective While looking through the changes #14782 will create I noticed this. ## Solution Reuse the existing thread_rng. As this is a code change I would like to not include it in a pure lint enable PR. ## Testing I did not test this change (other than the automated CI with this PR). I think it should be a fairly simple change that can be reviewed only by the code. |
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Miles Silberling-Cook
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ed2b8e0f35
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Minimal Bubbling Observers (#13991)
# Objective
Add basic bubbling to observers, modeled off `bevy_eventlistener`.
## Solution
- Introduce a new `Traversal` trait for components which point to other
entities.
- Provide a default `TraverseNone: Traversal` component which cannot be
constructed.
- Implement `Traversal` for `Parent`.
- The `Event` trait now has an associated `Traversal` which defaults to
`TraverseNone`.
- Added a field `bubbling: &mut bool` to `Trigger` which can be used to
instruct the runner to bubble the event to the entity specified by the
event's traversal type.
- Added an associated constant `SHOULD_BUBBLE` to `Event` which
configures the default bubbling state.
- Added logic to wire this all up correctly.
Introducing the new associated information directly on `Event` (instead
of a new `BubblingEvent` trait) lets us dispatch both bubbling and
non-bubbling events through the same api.
## Testing
I have added several unit tests to cover the common bugs I identified
during development. Running the unit tests should be enough to validate
correctness. The changes effect unsafe portions of the code, but should
not change any of the safety assertions.
## Changelog
Observers can now bubble up the entity hierarchy! To create a bubbling
event, change your `Derive(Event)` to something like the following:
```rust
#[derive(Component)]
struct MyEvent;
impl Event for MyEvent {
type Traverse = Parent; // This event will propagate up from child to parent.
const AUTO_PROPAGATE: bool = true; // This event will propagate by default.
}
```
You can dispatch a bubbling event using the normal
`world.trigger_targets(MyEvent, entity)`.
Halting an event mid-bubble can be done using
`trigger.propagate(false)`. Events with `AUTO_PROPAGATE = false` will
not propagate by default, but you can enable it using
`trigger.propagate(true)`.
If there are multiple observers attached to a target, they will all be
triggered by bubbling. They all share a bubbling state, which can be
accessed mutably using `trigger.propagation_mut()` (`trigger.propagate`
is just sugar for this).
You can choose to implement `Traversal` for your own types, if you want
to bubble along a different structure than provided by `bevy_hierarchy`.
Implementers must be careful never to produce loops, because this will
cause bevy to hang.
## Migration Guide
+ Manual implementations of `Event` should add associated type `Traverse
= TraverseNone` and associated constant `AUTO_PROPAGATE = false`;
+ `Trigger::new` has new field `propagation: &mut Propagation` which
provides the bubbling state.
+ `ObserverRunner` now takes the same `&mut Propagation` as a final
parameter.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Torstein Grindvik <52322338+torsteingrindvik@users.noreply.github.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
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