# Objective
In #13343, `WorldQuery::get_state` was constrained from `&World` as the
argument to `&Components`, but `WorldQuery::init_state` hasn't yet been
changed from `&mut World` to match.
Fixes#13358
## Solution
Create a wrapper around `&mut Components` and `&mut Storages` that can
be obtained from `&mut World` with a `component_initializer` method.
This new `ComponentInitializer` re-exposes the API on `&mut Components`
minus the `&mut Storages` parameter where it was present. For the
`&Components` API, it simply derefs to its `components` field.
## Changelog
### Added
The `World::component_initializer` method.
The `ComponentInitializer` struct that re-exposes `Components` API.
### Changed
`WorldQuery::init_state` now takes `&mut ComponentInitializer` instead
of `&mut World`.
## Migration Guide
Instead of passing `&mut World` to `WorldQuery::init_state` directly,
pass in a mutable reference to the struct returned from
`World::component_initializer`.
# Objective
While reviewing the other open hooks-related PRs, I found that the docs
on the `ComponentHooks` struct itself didn't give enough information
about how and why the feature could be used.
## Solution
1. Clean up the docs to add additional context.
2. Add a doc test demonstrating simple usage.
## Testing
The doc test passes locally.
---------
Co-authored-by: Alice Cecile <alice.i.cecil@gmail.com>
# Objective
- Fixes#12377
## Solution
Added simple `#[diagnostic::on_unimplemented(...)]` attributes to some
critical public traits providing a more approachable initial error
message. Where appropriate, a `note` is added indicating that a `derive`
macro is available.
## Examples
<details>
<summary>Examples hidden for brevity</summary>
Below is a collection of examples showing the new error messages
produced by this change. In general, messages will start with a more
Bevy-centric error message (e.g., _`MyComponent` is not a `Component`_),
and a note directing the user to an available derive macro where
appropriate.
### Missing `#[derive(Resource)]`
<details>
<summary>Example Code</summary>
```rust
use bevy::prelude::*;
struct MyResource;
fn main() {
App::new()
.insert_resource(MyResource)
.run();
}
```
</details>
<details>
<summary>Error Generated</summary>
```error
error[E0277]: `MyResource` is not a `Resource`
--> examples/app/empty.rs:7:26
|
7 | .insert_resource(MyResource)
| --------------- ^^^^^^^^^^ invalid `Resource`
| |
| required by a bound introduced by this call
|
= help: the trait `Resource` is not implemented for `MyResource`
= note: consider annotating `MyResource` with `#[derive(Resource)]`
= help: the following other types implement trait `Resource`:
AccessibilityRequested
ManageAccessibilityUpdates
bevy::bevy_a11y::Focus
DiagnosticsStore
FrameCount
bevy::prelude::State<S>
SystemInfo
bevy::prelude::Axis<T>
and 141 others
note: required by a bound in `bevy::prelude::App::insert_resource`
--> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:419:31
|
419 | pub fn insert_resource<R: Resource>(&mut self, resource: R) -> &mut Self {
| ^^^^^^^^ required by this bound in `App::insert_resource`
```
</details>
### Putting A `QueryData` in a `QueryFilter` Slot
<details>
<summary>Example Code</summary>
```rust
use bevy::prelude::*;
#[derive(Component)]
struct A;
#[derive(Component)]
struct B;
fn my_system(_query: Query<&A, &B>) {}
fn main() {
App::new()
.add_systems(Update, my_system)
.run();
}
```
</details>
<details>
<summary>Error Generated</summary>
```error
error[E0277]: `&B` is not a valid `Query` filter
--> examples/app/empty.rs:9:22
|
9 | fn my_system(_query: Query<&A, &B>) {}
| ^^^^^^^^^^^^^ invalid `Query` filter
|
= help: the trait `QueryFilter` is not implemented for `&B`
= help: the following other types implement trait `QueryFilter`:
With<T>
Without<T>
bevy::prelude::Or<()>
bevy::prelude::Or<(F0,)>
bevy::prelude::Or<(F0, F1)>
bevy::prelude::Or<(F0, F1, F2)>
bevy::prelude::Or<(F0, F1, F2, F3)>
bevy::prelude::Or<(F0, F1, F2, F3, F4)>
and 28 others
note: required by a bound in `bevy::prelude::Query`
--> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_ecs\src\system\query.rs:349:51
|
349 | pub struct Query<'world, 'state, D: QueryData, F: QueryFilter = ()> {
| ^^^^^^^^^^^ required by this bound in `Query`
```
</details>
### Missing `#[derive(Component)]`
<details>
<summary>Example Code</summary>
```rust
use bevy::prelude::*;
struct A;
fn my_system(mut commands: Commands) {
commands.spawn(A);
}
fn main() {
App::new()
.add_systems(Startup, my_system)
.run();
}
```
</details>
<details>
<summary>Error Generated</summary>
```error
error[E0277]: `A` is not a `Bundle`
--> examples/app/empty.rs:6:20
|
6 | commands.spawn(A);
| ----- ^ invalid `Bundle`
| |
| required by a bound introduced by this call
|
= help: the trait `bevy::prelude::Component` is not implemented for `A`, which is required by `A: Bundle`
= note: consider annotating `A` with `#[derive(Component)]` or `#[derive(Bundle)]`
= help: the following other types implement trait `Bundle`:
TransformBundle
SceneBundle
DynamicSceneBundle
AudioSourceBundle<Source>
SpriteBundle
SpriteSheetBundle
Text2dBundle
MaterialMesh2dBundle<M>
and 34 others
= note: required for `A` to implement `Bundle`
note: required by a bound in `bevy::prelude::Commands::<'w, 's>::spawn`
--> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_ecs\src\system\commands\mod.rs:243:21
|
243 | pub fn spawn<T: Bundle>(&mut self, bundle: T) -> EntityCommands {
| ^^^^^^ required by this bound in `Commands::<'w, 's>::spawn`
```
</details>
### Missing `#[derive(Asset)]`
<details>
<summary>Example Code</summary>
```rust
use bevy::prelude::*;
struct A;
fn main() {
App::new()
.init_asset::<A>()
.run();
}
```
</details>
<details>
<summary>Error Generated</summary>
```error
error[E0277]: `A` is not an `Asset`
--> examples/app/empty.rs:7:23
|
7 | .init_asset::<A>()
| ---------- ^ invalid `Asset`
| |
| required by a bound introduced by this call
|
= help: the trait `Asset` is not implemented for `A`
= note: consider annotating `A` with `#[derive(Asset)]`
= help: the following other types implement trait `Asset`:
Font
AnimationGraph
DynamicScene
Scene
AudioSource
Pitch
bevy::bevy_gltf::Gltf
GltfNode
and 17 others
note: required by a bound in `init_asset`
--> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_asset\src\lib.rs:307:22
|
307 | fn init_asset<A: Asset>(&mut self) -> &mut Self;
| ^^^^^ required by this bound in `AssetApp::init_asset`
```
</details>
### Mismatched Input and Output on System Piping
<details>
<summary>Example Code</summary>
```rust
use bevy::prelude::*;
fn producer() -> u32 {
123
}
fn consumer(_: In<u16>) {}
fn main() {
App::new()
.add_systems(Update, producer.pipe(consumer))
.run();
}
```
</details>
<details>
<summary>Error Generated</summary>
```error
error[E0277]: `fn(bevy::prelude::In<u16>) {consumer}` is not a valid system with input `u32` and output `_`
--> examples/app/empty.rs:11:44
|
11 | .add_systems(Update, producer.pipe(consumer))
| ---- ^^^^^^^^ invalid system
| |
| required by a bound introduced by this call
|
= help: the trait `bevy::prelude::IntoSystem<u32, _, _>` is not implemented for fn item `fn(bevy::prelude::In<u16>) {consumer}`
= note: expecting a system which consumes `u32` and produces `_`
note: required by a bound in `pipe`
--> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_ecs\src\system\mod.rs:168:12
|
166 | fn pipe<B, Final, MarkerB>(self, system: B) -> PipeSystem<Self::System, B::System>
| ---- required by a bound in this associated function
167 | where
168 | B: IntoSystem<Out, Final, MarkerB>,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `IntoSystem::pipe`
```
</details>
### Missing Reflection
<details>
<summary>Example Code</summary>
```rust
use bevy::prelude::*;
#[derive(Component)]
struct MyComponent;
fn main() {
App::new()
.register_type::<MyComponent>()
.run();
}
```
</details>
<details>
<summary>Error Generated</summary>
```error
error[E0277]: `MyComponent` does not provide type registration information
--> examples/app/empty.rs:8:26
|
8 | .register_type::<MyComponent>()
| ------------- ^^^^^^^^^^^ the trait `GetTypeRegistration` is not implemented for `MyComponent`
| |
| required by a bound introduced by this call
|
= note: consider annotating `MyComponent` with `#[derive(Reflect)]`
= help: the following other types implement trait `GetTypeRegistration`:
bool
char
isize
i8
i16
i32
i64
i128
and 443 others
note: required by a bound in `bevy::prelude::App::register_type`
--> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:619:29
|
619 | pub fn register_type<T: bevy_reflect::GetTypeRegistration>(&mut self) -> &mut Self {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `App::register_type`
```
</details>
### Missing `#[derive(States)]` Implementation
<details>
<summary>Example Code</summary>
```rust
use bevy::prelude::*;
#[derive(Debug, Clone, Copy, Default, Eq, PartialEq, Hash)]
enum AppState {
#[default]
Menu,
InGame {
paused: bool,
turbo: bool,
},
}
fn main() {
App::new()
.init_state::<AppState>()
.run();
}
```
</details>
<details>
<summary>Error Generated</summary>
```error
error[E0277]: the trait bound `AppState: FreelyMutableState` is not satisfied
--> examples/app/empty.rs:15:23
|
15 | .init_state::<AppState>()
| ---------- ^^^^^^^^ the trait `FreelyMutableState` is not implemented for `AppState`
| |
| required by a bound introduced by this call
|
= note: consider annotating `AppState` with `#[derive(States)]`
note: required by a bound in `bevy::prelude::App::init_state`
--> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:282:26
|
282 | pub fn init_state<S: FreelyMutableState + FromWorld>(&mut self) -> &mut Self {
| ^^^^^^^^^^^^^^^^^^ required by this bound in `App::init_state`
```
</details>
### Adding a `System` with Unhandled Output
<details>
<summary>Example Code</summary>
```rust
use bevy::prelude::*;
fn producer() -> u32 {
123
}
fn main() {
App::new()
.add_systems(Update, consumer)
.run();
}
```
</details>
<details>
<summary>Error Generated</summary>
```error
error[E0277]: `fn() -> u32 {producer}` does not describe a valid system configuration
--> examples/app/empty.rs:9:30
|
9 | .add_systems(Update, producer)
| ----------- ^^^^^^^^ invalid system configuration
| |
| required by a bound introduced by this call
|
= help: the trait `IntoSystem<(), (), _>` is not implemented for fn item `fn() -> u32 {producer}`, which is required by `fn() -> u32 {producer}: IntoSystemConfigs<_>`
= help: the following other types implement trait `IntoSystemConfigs<Marker>`:
<Box<(dyn bevy::prelude::System<In = (), Out = ()> + 'static)> as IntoSystemConfigs<()>>
<NodeConfigs<Box<(dyn bevy::prelude::System<In = (), Out = ()> + 'static)>> as IntoSystemConfigs<()>>
<(S0,) as IntoSystemConfigs<(SystemConfigTupleMarker, P0)>>
<(S0, S1) as IntoSystemConfigs<(SystemConfigTupleMarker, P0, P1)>>
<(S0, S1, S2) as IntoSystemConfigs<(SystemConfigTupleMarker, P0, P1, P2)>>
<(S0, S1, S2, S3) as IntoSystemConfigs<(SystemConfigTupleMarker, P0, P1, P2, P3)>>
<(S0, S1, S2, S3, S4) as IntoSystemConfigs<(SystemConfigTupleMarker, P0, P1, P2, P3, P4)>>
<(S0, S1, S2, S3, S4, S5) as IntoSystemConfigs<(SystemConfigTupleMarker, P0, P1, P2, P3, P4, P5)>>
and 14 others
= note: required for `fn() -> u32 {producer}` to implement `IntoSystemConfigs<_>`
note: required by a bound in `bevy::prelude::App::add_systems`
--> C:\Users\Zac\Documents\GitHub\bevy\crates\bevy_app\src\app.rs:342:23
|
339 | pub fn add_systems<M>(
| ----------- required by a bound in this associated function
...
342 | systems: impl IntoSystemConfigs<M>,
| ^^^^^^^^^^^^^^^^^^^^ required by this bound in `App::add_systems`
```
</details>
</details>
## Testing
CI passed locally.
## Migration Guide
Upgrade to version 1.78 (or higher) of Rust.
## Future Work
- Currently, hints are not supported in this diagnostic. Ideally,
suggestions like _"consider using ..."_ would be in a hint rather than a
note, but that is the best option for now.
- System chaining and other `all_tuples!(...)`-based traits have bad
error messages due to the slightly different error message format.
---------
Co-authored-by: Jamie Ridding <Themayu@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: BD103 <59022059+BD103@users.noreply.github.com>
# 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.
The actual `event_update_system` is usually *very* short, using only a
few microseconds on average.
---
## Changelog
TODO
## Migration Guide
TODO
---------
Co-authored-by: Josh Matthews <josh@joshmatthews.net>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
When doing a final pass for #3362, it appeared that `ComponentStorage`
as a trait, the two types implementing it, and the associated type on
`Component` aren't really necessary anymore. This likely was due to an
earlier constraint on the use of consts in traits, but that definitely
doesn't seem to be a problem in Rust 1.76.
## Solution
Remove them.
---
## Changelog
Changed: `Component::Storage` has been replaced with
`Component::STORAGE_TYPE` as a const.
Removed: `bevy::ecs::component::ComponentStorage` trait
Removed: `bevy::ecs::component::TableStorage` struct
Removed: `bevy::ecs::component::SparseSetStorage` struct
## Migration Guide
If you were manually implementing `Component` instead of using the
derive macro, replace the associated `Storage` associated type with the
`STORAGE_TYPE` const:
```rust
// in Bevy 0.13
impl Component for MyComponent {
type Storage = TableStorage;
}
// in Bevy 0.14
impl Component for MyComponent {
const STORAGE_TYPE: StorageType = StorageType::Table;
}
```
Component is no longer object safe. If you were relying on `&dyn
Component`, `Box<dyn Component>`, etc. please [file an issue
](https://github.com/bevyengine/bevy/issues) to get [this
change](https://github.com/bevyengine/bevy/pull/12311) reverted.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Fix mismatch between the `Component` trait method and the `World`
method.
## Solution
- Replace init_component_info with register_component_hooks.
# Objective
- Provide a reliable and performant mechanism to allows users to keep
components synchronized with external sources: closing/opening sockets,
updating indexes, debugging etc.
- Implement a generic mechanism to provide mutable access to the world
without allowing structural changes; this will not only be used here but
is a foundational piece for observers, which are key for a performant
implementation of relations.
## Solution
- Implement a new type `DeferredWorld` (naming is not important,
`StaticWorld` is also suitable) that wraps a world pointer and prevents
user code from making any structural changes to the ECS; spawning
entities, creating components, initializing resources etc.
- Add component lifecycle hooks `on_add`, `on_insert` and `on_remove`
that can be assigned callbacks in user code.
---
## Changelog
- Add new `DeferredWorld` type.
- Add new world methods: `register_component::<T>` and
`register_component_with_descriptor`. These differ from `init_component`
in that they provide mutable access to the created `ComponentInfo` but
will panic if the component is already in any archetypes. These
restrictions serve two purposes:
1. Prevent users from defining hooks for components that may already
have associated hooks provided in another plugin. (a use case better
served by observers)
2. Ensure that when an `Archetype` is created it gets the appropriate
flags to early-out when triggering hooks.
- Add methods to `ComponentInfo`: `on_add`, `on_insert` and `on_remove`
to be used to register hooks of the form `fn(DeferredWorld, Entity,
ComponentId)`
- Modify `BundleInserter`, `BundleSpawner` and `EntityWorldMut` to
trigger component hooks when appropriate.
- Add bit flags to `Archetype` indicating whether or not any contained
components have each type of hook, this can be expanded for other flags
as needed.
- Add `component_hooks` example to illustrate usage. Try it out! It's
fun to mash keys.
## Safety
The changes to component insertion, removal and deletion involve a large
amount of unsafe code and it's fair for that to raise some concern. I
have attempted to document it as clearly as possible and have confirmed
that all the hooks examples are accepted by `cargo miri` as not causing
any undefined behavior. The largest issue is in ensuring there are no
outstanding references when passing a `DeferredWorld` to the hooks which
requires some use of raw pointers (as was already happening to some
degree in those places) and I have taken some time to ensure that is the
case but feel free to let me know if I've missed anything.
## Performance
These changes come with a small but measurable performance cost of
between 1-5% on `add_remove` benchmarks and between 1-3% on `insert`
benchmarks. One consideration to be made is the existence of the current
`RemovedComponents` which is on average more costly than the addition of
`on_remove` hooks due to the early-out, however hooks doesn't completely
remove the need for `RemovedComponents` as there is a chance you want to
respond to the removal of a component that already has an `on_remove`
hook defined in another plugin, so I have not removed it here. I do
intend to deprecate it with the introduction of observers in a follow up
PR.
## Discussion Questions
- Currently `DeferredWorld` implements `Deref` to `&World` which makes
sense conceptually, however it does cause some issues with rust-analyzer
providing autocomplete for `&mut World` references which is annoying.
There are alternative implementations that may address this but involve
more code churn so I have attempted them here. The other alternative is
to not implement `Deref` at all but that leads to a large amount of API
duplication.
- `DeferredWorld`, `StaticWorld`, something else?
- In adding support for hooks to `EntityWorldMut` I encountered some
unfortunate difficulties with my desired API. If commands are flushed
after each call i.e. `world.spawn() // flush commands .insert(A) //
flush commands` the entity may be despawned while `EntityWorldMut` still
exists which is invalid. An alternative was then to add
`self.world.flush_commands()` to the drop implementation for
`EntityWorldMut` but that runs into other problems for implementing
functions like `into_unsafe_entity_cell`. For now I have implemented a
`.flush()` which will flush the commands and consume `EntityWorldMut` or
users can manually run `world.flush_commands()` after using
`EntityWorldMut`.
- In order to allowing querying on a deferred world we need
implementations of `WorldQuery` to not break our guarantees of no
structural changes through their `UnsafeWorldCell`. All our
implementations do this, but there isn't currently any safety
documentation specifying what is or isn't allowed for an implementation,
just for the caller, (they also shouldn't be aliasing components they
didn't specify access for etc.) is that something we should start doing?
(see 10752)
Please check out the example `component_hooks` or the tests in
`bundle.rs` for usage examples. I will continue to expand this
description as I go.
See #10839 for a more ergonomic API built on top of this one that isn't
subject to the same restrictions and supports `SystemParam` dependency
injection.
# Objective
- Part of #11590
- Fix `unsafe_op_in_unsafe_fn` for trivial cases in bevy_ecs
## Solution
Fix `unsafe_op_in_unsafe_fn` in bevy_ecs for trivial cases, i.e., add an
`unsafe` block when the safety comment already exists or add a comment
like "The invariants are uphold by the caller".
---------
Co-authored-by: James Liu <contact@jamessliu.com>
Use `TypeIdMap<T>` instead of `HashMap<TypeId, T>`
- ~~`TypeIdMap` was in `bevy_ecs`. I've kept it there because of
#11478~~
- ~~I haven't swapped `bevy_reflect` over because it doesn't depend on
`bevy_ecs`, but I'd also be happy with moving `TypeIdMap` to
`bevy_utils` and then adding a dependency to that~~
- ~~this is a slight change in the public API of
`DrawFunctionsInternal`, does this need to go in the changelog?~~
## Changelog
- moved `TypeIdMap` to `bevy_utils`
- changed `DrawFunctionsInternal::indices` to `TypeIdMap`
## Migration Guide
- `TypeIdMap` now lives in `bevy_utils`
- `DrawFunctionsInternal::indices` now uses a `TypeIdMap`.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Deriving `Reflect` for some public ChangeDetection/Tick structs in
bevy_ecs
---------
Co-authored-by: Charles Bournhonesque <cbournhonesque@snapchat.com>
# Objective
There are a lot of doctests that are `ignore`d for no documented reason.
And that should be fixed.
## Solution
I searched the bevy repo with the regex ` ```[a-z,]*ignore ` in order to
find all `ignore`d doctests. For each one of the `ignore`d doctests, I
did the following steps:
1. Attempt to remove the `ignored` attribute while still passing the
test. I did this by adding hidden dummy structs and imports.
2. If step 1 doesn't work, attempt to replace the `ignored` attribute
with the `no_run` attribute while still passing the test.
3. If step 2 doesn't work, keep the `ignored` attribute but add
documentation for why the `ignored` attribute was added.
---------
Co-authored-by: François <mockersf@gmail.com>
# Objective
- Shorten paths by removing unnecessary prefixes
## Solution
- Remove the prefixes from many paths which do not need them. Finding
the paths was done automatically using built-in refactoring tools in
Jetbrains RustRover.
# Objective
- Updates for rust 1.73
## Solution
- new doc check for `redundant_explicit_links`
- updated to text for compile fail tests
---
## Changelog
- updates for rust 1.73
# Objective
Occasionally, it is useful to pull `ComponentInfo` or
`ComponentDescriptor` out of the `Components` collection so that they
can be inspected without borrowing the whole `World`.
## Solution
Make `ComponentInfo` and `ComponentDescriptor` `Clone`, so that
reflection-heavy code can store them in a side table.
---
## Changelog
- Implement `Clone` for `ComponentInfo` and `ComponentDescriptor`
# Objective
- When reading API docs and seeing a reference to `ComponentId`, it
isn't immediately clear how to get one from your `Component`. It could
be made to be more clear.
## Solution
- Improve cross-linking of docs about `ComponentId`
# Objective
- Remove need to call `.get()` on two ticks to compare them for
equality.
## Solution
- Derive `Eq` and `PartialEq`.
---
## Changelog
> `Tick` now implements `Eq` and `PartialEq`
# Objective
`ComponentIdFor` is a type that gives you access to a component's
`ComponentId` in a system. It is currently awkward to use, since it must
be wrapped in a `Local<>` to be used.
## Solution
Make `ComponentIdFor` a proper SystemParam.
---
## Changelog
- Refactored the type `ComponentIdFor` in order to simplify how it is
used.
## Migration Guide
The type `ComponentIdFor<T>` now implements `SystemParam` instead of
`FromWorld` -- this means it should be used as the parameter for a
system directly instead of being used in a `Local`.
```rust
// Before:
fn my_system(
component_id: Local<ComponentIdFor<MyComponent>>,
) {
let component_id = **component_id;
}
// After:
fn my_system(
component_id: ComponentIdFor<MyComponent>,
) {
let component_id = component_id.get();
}
```
# Objective
EntityRef::get_change_ticks mentions that ComponentTicks is useful to
create change detection for your own runtime.
However, ComponentTicks doesn't even expose enough data to create
something that implements DetectChanges. Specifically, we need to be
able to extract the last change tick.
## Solution
We add a method to get the last change tick. We also add a method to get
the added tick.
## Changelog
- Add `last_changed_tick` and `added_tick` to `ComponentTicks`
# Objective
Title.
---------
Co-authored-by: François <mockersf@gmail.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: James Liu <contact@jamessliu.com>
# Objective
Upon closer inspection, there are a few functions in the ECS that are
not being inlined, even with the highest optimizations and LTO enabled:
- Almost all
[WorldQuery::init_fetch](9fd5f20e25/results/query_get.s (L57))
calls. Affects `Query::get` calls in hot loops. In particular, the
`WorldQuery` implementation for `()` is used *everywhere* as the default
filter and is effectively a no-op.
-
[Entities::get](9fd5f20e25/results/query_get.s (L39)).
Affects `Query::get`, `World::get`, and any component insertion or
removal.
-
[Entities::set](9fd5f20e25/results/entity_remove.s (L2487)).
Affects any component insertion or removal.
-
[Tick::new](9fd5f20e25/results/entity_insert.s (L1368)).
I've only seen this in component insertion and spawning.
- ArchetypeRow::new
- BlobVec::set_len
Almost all of these have trivial or even empty implementations or have
significant opportunity to be optimized into surrounding code when
inlined with LTO enabled.
## Solution
Inline them
Fixes issue mentioned in PR #8285.
_Note: By mistake, this is currently dependent on #8285_
# Objective
Ensure consistency in the spelling of the documentation.
Exceptions:
`crates/bevy_mikktspace/src/generated.rs` - Has not been changed from
licence to license as it is part of a licensing agreement.
Maybe for further consistency,
https://github.com/bevyengine/bevy-website should also be given a look.
## Solution
### Changed the spelling of the current words (UK/CN/AU -> US) :
cancelled -> canceled (Breaking API changes in #8285)
behaviour -> behavior (Breaking API changes in #8285)
neighbour -> neighbor
grey -> gray
recognise -> recognize
centre -> center
metres -> meters
colour -> color
### ~~Update [`engine_style_guide.md`]~~ Moved to #8324
---
## Changelog
Changed UK spellings in documentation to US
## Migration Guide
Non-breaking changes*
\* If merged after #8285
…able like Table. Rename clear to clear_entities to clarify that metadata keeps, only value cleared
# Objective
- Provide some inspectability for SparseSets.
## Solution
- `Tables` has these three methods, len, is_empty and iter too. Add these methods to `SparseSets`, so user can print the shape of storage.
---
## Changelog
> This section is optional. If this was a trivial fix, or has no externally-visible impact, you can delete this section.
- Add `len`, `is_empty`, `iter` methods on SparseSets.
- Rename `clear` to `clear_entities` to clarify its purpose.
- Add `new_for_test` on `ComponentInfo` to make test code easy.
- Add test case covering new methods.
## Migration Guide
> This section is optional. If there are no breaking changes, you can delete this section.
- Simply adding new functionality is not a breaking change.
…u64, so hash safety is not a concern
# Objective
- While reading the code, just noticed the BundleInfo's HashMap is std::collections::HashMap, which uses a slow but safe hasher.
## Solution
- Use bevy_utils::HashMap instead
benchmark diff (I run several times in a linux box, the perf improvement is consistent, though numbers varies from time to time, I paste my last run result here):
``` bash
cargo bench -- spawn
Compiling bevy_ecs v0.9.0 (/home/lishuo/developer/pr/bevy/crates/bevy_ecs)
Compiling bevy_app v0.9.0 (/home/lishuo/developer/pr/bevy/crates/bevy_app)
Compiling benches v0.1.0 (/home/lishuo/developer/pr/bevy/benches)
Finished bench [optimized] target(s) in 1m 17s
Running benches/bevy_ecs/change_detection.rs (/home/lishuo/developer/pr/bevy/benches/target/release/deps/change_detection-86c5445d0dc34529)
Gnuplot not found, using plotters backend
Running benches/bevy_ecs/benches.rs (/home/lishuo/developer/pr/bevy/benches/target/release/deps/ecs-e49b3abe80bfd8c0)
Gnuplot not found, using plotters backend
spawn_commands/2000_entities
time: [153.94 µs 159.19 µs 164.37 µs]
change: [-14.706% -11.050% -6.9633%] (p = 0.00 < 0.05)
Performance has improved.
spawn_commands/4000_entities
time: [328.77 µs 339.11 µs 349.11 µs]
change: [-7.6331% -3.9932% +0.0487%] (p = 0.06 > 0.05)
No change in performance detected.
spawn_commands/6000_entities
time: [445.01 µs 461.29 µs 477.36 µs]
change: [-16.639% -13.358% -10.006%] (p = 0.00 < 0.05)
Performance has improved.
spawn_commands/8000_entities
time: [657.94 µs 677.71 µs 696.95 µs]
change: [-8.8708% -5.2591% -1.6847%] (p = 0.01 < 0.05)
Performance has improved.
get_or_spawn/individual time: [452.02 µs 466.70 µs 482.07 µs]
change: [-17.218% -14.041% -10.728%] (p = 0.00 < 0.05)
Performance has improved.
get_or_spawn/batched time: [291.12 µs 301.12 µs 311.31 µs]
change: [-12.281% -8.9163% -5.3660%] (p = 0.00 < 0.05)
Performance has improved.
spawn_world/1_entities time: [81.668 ns 84.284 ns 86.860 ns]
change: [-12.251% -6.7872% -1.5402%] (p = 0.02 < 0.05)
Performance has improved.
spawn_world/10_entities time: [789.78 ns 821.96 ns 851.95 ns]
change: [-19.738% -14.186% -8.0733%] (p = 0.00 < 0.05)
Performance has improved.
spawn_world/100_entities
time: [7.9906 µs 8.2449 µs 8.5013 µs]
change: [-12.417% -6.6837% -0.8766%] (p = 0.02 < 0.05)
Change within noise threshold.
spawn_world/1000_entities
time: [81.602 µs 84.161 µs 86.833 µs]
change: [-13.656% -8.6520% -3.0491%] (p = 0.00 < 0.05)
Performance has improved.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high mild
Benchmarking spawn_world/10000_entities: Warming up for 500.00 ms
Warning: Unable to complete 100 samples in 4.0s. You may wish to increase target time to 4.0s, enable flat sampling, or reduce sample count to 70.
spawn_world/10000_entities
time: [813.02 µs 839.76 µs 865.41 µs]
change: [-12.133% -6.1970% -0.2302%] (p = 0.05 < 0.05)
Change within noise threshold.
```
---
## Changelog
> This section is optional. If this was a trivial fix, or has no externally-visible impact, you can delete this section.
- use bevy_utils::HashMap for Bundles::bundle_ids
## Migration Guide
> This section is optional. If there are no breaking changes, you can delete this section.
- Not a breaking change, hashmap is internal impl.
# Objective
Clarify what the function is actually calculating.
The `Tick::is_older_than` function is actually calculating whether the tick is newer than the system's `last_change_tick`, not older. As far as I can tell, the engine was using it correctly everywhere already.
## Solution
- Rename the function.
---
## Changelog
- `Tick::is_older_than` was renamed to `Tick::is_newer_than`. This is not a functional change, since that was what was always being calculated, despite the wrong name.
## Migration Guide
- Replace usages of `Tick::is_older_than` with `Tick::is_newer_than`.
Huge thanks to @maniwani, @devil-ira, @hymm, @cart, @superdump and @jakobhellermann for the help with this PR.
# Objective
- Followup #6587.
- Minimal integration for the Stageless Scheduling RFC: https://github.com/bevyengine/rfcs/pull/45
## Solution
- [x] Remove old scheduling module
- [x] Migrate new methods to no longer use extension methods
- [x] Fix compiler errors
- [x] Fix benchmarks
- [x] Fix examples
- [x] Fix docs
- [x] Fix tests
## Changelog
### Added
- a large number of methods on `App` to work with schedules ergonomically
- the `CoreSchedule` enum
- `App::add_extract_system` via the `RenderingAppExtension` trait extension method
- the private `prepare_view_uniforms` system now has a public system set for scheduling purposes, called `ViewSet::PrepareUniforms`
### Removed
- stages, and all code that mentions stages
- states have been dramatically simplified, and no longer use a stack
- `RunCriteriaLabel`
- `AsSystemLabel` trait
- `on_hierarchy_reports_enabled` run criteria (now just uses an ad hoc resource checking run condition)
- systems in `RenderSet/Stage::Extract` no longer warn when they do not read data from the main world
- `RunCriteriaLabel`
- `transform_propagate_system_set`: this was a nonstandard pattern that didn't actually provide enough control. The systems are already `pub`: the docs have been updated to ensure that the third-party usage is clear.
### Changed
- `System::default_labels` is now `System::default_system_sets`.
- `App::add_default_labels` is now `App::add_default_sets`
- `CoreStage` and `StartupStage` enums are now `CoreSet` and `StartupSet`
- `App::add_system_set` was renamed to `App::add_systems`
- The `StartupSchedule` label is now defined as part of the `CoreSchedules` enum
- `.label(SystemLabel)` is now referred to as `.in_set(SystemSet)`
- `SystemLabel` trait was replaced by `SystemSet`
- `SystemTypeIdLabel<T>` was replaced by `SystemSetType<T>`
- The `ReportHierarchyIssue` resource now has a public constructor (`new`), and implements `PartialEq`
- Fixed time steps now use a schedule (`CoreSchedule::FixedTimeStep`) rather than a run criteria.
- Adding rendering extraction systems now panics rather than silently failing if no subapp with the `RenderApp` label is found.
- the `calculate_bounds` system, with the `CalculateBounds` label, is now in `CoreSet::Update`, rather than in `CoreSet::PostUpdate` before commands are applied.
- `SceneSpawnerSystem` now runs under `CoreSet::Update`, rather than `CoreStage::PreUpdate.at_end()`.
- `bevy_pbr::add_clusters` is no longer an exclusive system
- the top level `bevy_ecs::schedule` module was replaced with `bevy_ecs::scheduling`
- `tick_global_task_pools_on_main_thread` is no longer run as an exclusive system. Instead, it has been replaced by `tick_global_task_pools`, which uses a `NonSend` resource to force running on the main thread.
## Migration Guide
- Calls to `.label(MyLabel)` should be replaced with `.in_set(MySet)`
- Stages have been removed. Replace these with system sets, and then add command flushes using the `apply_system_buffers` exclusive system where needed.
- The `CoreStage`, `StartupStage, `RenderStage` and `AssetStage` enums have been replaced with `CoreSet`, `StartupSet, `RenderSet` and `AssetSet`. The same scheduling guarantees have been preserved.
- Systems are no longer added to `CoreSet::Update` by default. Add systems manually if this behavior is needed, although you should consider adding your game logic systems to `CoreSchedule::FixedTimestep` instead for more reliable framerate-independent behavior.
- Similarly, startup systems are no longer part of `StartupSet::Startup` by default. In most cases, this won't matter to you.
- For example, `add_system_to_stage(CoreStage::PostUpdate, my_system)` should be replaced with
- `add_system(my_system.in_set(CoreSet::PostUpdate)`
- When testing systems or otherwise running them in a headless fashion, simply construct and run a schedule using `Schedule::new()` and `World::run_schedule` rather than constructing stages
- Run criteria have been renamed to run conditions. These can now be combined with each other and with states.
- Looping run criteria and state stacks have been removed. Use an exclusive system that runs a schedule if you need this level of control over system control flow.
- For app-level control flow over which schedules get run when (such as for rollback networking), create your own schedule and insert it under the `CoreSchedule::Outer` label.
- Fixed timesteps are now evaluated in a schedule, rather than controlled via run criteria. The `run_fixed_timestep` system runs this schedule between `CoreSet::First` and `CoreSet::PreUpdate` by default.
- Command flush points introduced by `AssetStage` have been removed. If you were relying on these, add them back manually.
- Adding extract systems is now typically done directly on the main app. Make sure the `RenderingAppExtension` trait is in scope, then call `app.add_extract_system(my_system)`.
- the `calculate_bounds` system, with the `CalculateBounds` label, is now in `CoreSet::Update`, rather than in `CoreSet::PostUpdate` before commands are applied. You may need to order your movement systems to occur before this system in order to avoid system order ambiguities in culling behavior.
- the `RenderLabel` `AppLabel` was renamed to `RenderApp` for clarity
- `App::add_state` now takes 0 arguments: the starting state is set based on the `Default` impl.
- Instead of creating `SystemSet` containers for systems that run in stages, simply use `.on_enter::<State::Variant>()` or its `on_exit` or `on_update` siblings.
- `SystemLabel` derives should be replaced with `SystemSet`. You will also need to add the `Debug`, `PartialEq`, `Eq`, and `Hash` traits to satisfy the new trait bounds.
- `with_run_criteria` has been renamed to `run_if`. Run criteria have been renamed to run conditions for clarity, and should now simply return a bool.
- States have been dramatically simplified: there is no longer a "state stack". To queue a transition to the next state, call `NextState::set`
## TODO
- [x] remove dead methods on App and World
- [x] add `App::add_system_to_schedule` and `App::add_systems_to_schedule`
- [x] avoid adding the default system set at inappropriate times
- [x] remove any accidental cycles in the default plugins schedule
- [x] migrate benchmarks
- [x] expose explicit labels for the built-in command flush points
- [x] migrate engine code
- [x] remove all mentions of stages from the docs
- [x] verify docs for States
- [x] fix uses of exclusive systems that use .end / .at_start / .before_commands
- [x] migrate RenderStage and AssetStage
- [x] migrate examples
- [x] ensure that transform propagation is exported in a sufficiently public way (the systems are already pub)
- [x] ensure that on_enter schedules are run at least once before the main app
- [x] re-enable opt-in to execution order ambiguities
- [x] revert change to `update_bounds` to ensure it runs in `PostUpdate`
- [x] test all examples
- [x] unbreak directional lights
- [x] unbreak shadows (see 3d_scene, 3d_shape, lighting, transparaency_3d examples)
- [x] game menu example shows loading screen and menu simultaneously
- [x] display settings menu is a blank screen
- [x] `without_winit` example panics
- [x] ensure all tests pass
- [x] SubApp doc test fails
- [x] runs_spawn_local tasks fails
- [x] [Fix panic_when_hierachy_cycle test hanging](https://github.com/alice-i-cecile/bevy/pull/120)
## Points of Difficulty and Controversy
**Reviewers, please give feedback on these and look closely**
1. Default sets, from the RFC, have been removed. These added a tremendous amount of implicit complexity and result in hard to debug scheduling errors. They're going to be tackled in the form of "base sets" by @cart in a followup.
2. The outer schedule controls which schedule is run when `App::update` is called.
3. I implemented `Label for `Box<dyn Label>` for our label types. This enables us to store schedule labels in concrete form, and then later run them. I ran into the same set of problems when working with one-shot systems. We've previously investigated this pattern in depth, and it does not appear to lead to extra indirection with nested boxes.
4. `SubApp::update` simply runs the default schedule once. This sucks, but this whole API is incomplete and this was the minimal changeset.
5. `time_system` and `tick_global_task_pools_on_main_thread` no longer use exclusive systems to attempt to force scheduling order
6. Implemetnation strategy for fixed timesteps
7. `AssetStage` was migrated to `AssetSet` without reintroducing command flush points. These did not appear to be used, and it's nice to remove these bottlenecks.
8. Migration of `bevy_render/lib.rs` and pipelined rendering. The logic here is unusually tricky, as we have complex scheduling requirements.
## Future Work (ideally before 0.10)
- Rename schedule_v3 module to schedule or scheduling
- Add a derive macro to states, and likely a `EnumIter` trait of some form
- Figure out what exactly to do with the "systems added should basically work by default" problem
- Improve ergonomics for working with fixed timesteps and states
- Polish FixedTime API to match Time
- Rebase and merge #7415
- Resolve all internal ambiguities (blocked on better tools, especially #7442)
- Add "base sets" to replace the removed default sets.
# Objective
Removal events are unwieldy and require some knowledge of when to put systems that need to catch events for them, it is very easy to end up missing one and end up with memory leak-ish issues where you don't clean up after yourself.
## Solution
Consolidate removals with the benefits of `Events<...>` (such as double buffering and per system ticks for reading the events) and reduce the special casing of it, ideally I was hoping to move the removals to a `Resource` in the world, but that seems a bit more rough to implement/maintain because of double mutable borrowing issues.
This doesn't go the full length of change detection esque removal detection a la https://github.com/bevyengine/rfcs/pull/44.
Just tries to make the current workflow a bit more user friendly so detecting removals isn't such a scheduling nightmare.
---
## Changelog
- RemovedComponents<T> is now backed by an `Events<Entity>` for the benefits of double buffering.
## Migration Guide
- Add a `mut` for `removed: RemovedComponents<T>` since we are now modifying an event reader internally.
- Iterating over removed components now requires `&mut removed_components` or `removed_components.iter()` instead of `&removed_components`.
# Objective
- `Components::resource_id` doesn't exist. Like `Components::component_id` but for resources.
## Solution
- Created `Components::resource_id` and added some docs.
---
## Changelog
- Added `Components::resource_id`.
- Changed `World::init_resource` to return the generated `ComponentId`.
- Changed `World::init_non_send_resource` to return the generated `ComponentId`.
# Objective
It's not clear to users how to handle `!Sync` types as components and resources in the absence of engine level support for them.
## Solution
Added a section to `Component`'s and `Resource`'s type level docs on available options for making a type `Sync` when it holds `!Sync` fields, linking `bevy_utils::synccell::SyncCell` and the currently unstable `std::sync::Exclusive`.
Also added a compile_fail doctest that illustrates how to apply `SyncCell`. These will break when/if #6572 gets merged, at which point these docs should be updated.
# Objective
Fixes#4884. `ComponentTicks` stores both added and changed ticks contiguously in the same 8 bytes. This is convenient when passing around both together, but causes half the bytes fetched from memory for the purposes of change detection to effectively go unused. This is inefficient when most queries (no filter, mutating *something*) only write out to the changed ticks.
## Solution
Split the storage for change detection ticks into two separate `Vec`s inside `Column`. Fetch only what is needed during iteration.
This also potentially also removes one blocker from autovectorization of dense queries.
EDIT: This is confirmed to enable autovectorization of dense queries in `for_each` and `par_for_each` where possible. Unfortunately `iter` has other blockers that prevent it.
### TODO
- [x] Microbenchmark
- [x] Check if this allows query iteration to autovectorize simple loops.
- [x] Clean up all of the spurious tuples now littered throughout the API
### Open Questions
- ~~Is `Mut::is_added` absolutely necessary? Can we not just use `Added` or `ChangeTrackers`?~~ It's optimized out if unused.
- ~~Does the fetch of the added ticks get optimized out if not used?~~ Yes it is.
---
## Changelog
Added: `Tick`, a wrapper around a single change detection tick.
Added: `Column::get_added_ticks`
Added: `Column::get_column_ticks`
Added: `SparseSet::get_added_ticks`
Added: `SparseSet::get_column_ticks`
Changed: `Column` now stores added and changed ticks separately internally.
Changed: Most APIs returning `&UnsafeCell<ComponentTicks>` now returns `TickCells` instead, which contains two separate `&UnsafeCell<Tick>` for either component ticks.
Changed: `Query::for_each(_mut)`, `Query::par_for_each(_mut)` will now leverage autovectorization to speed up query iteration where possible.
## Migration Guide
TODO
## Objective
Fixes https://github.com/bevyengine/bevy/issues/6063
## Solution
- Use `then_some(x)` instead of `then( || x)`.
- Updated error logs from `bevy_ecs_compile_fail_tests`.
## Migration Guide
From Rust 1.63 to 1.64, a new Clippy error was added; now one should use `then_some(x)` instead of `then( || x)`.
# Objective
`SAFETY` comments are meant to be placed before `unsafe` blocks and should contain the reasoning of why in this case the usage of unsafe is okay. This is useful when reading the code because it makes it clear which assumptions are required for safety, and makes it easier to spot possible unsoundness holes. It also forces the code writer to think of something to write and maybe look at the safety contracts of any called unsafe methods again to double-check their correct usage.
There's a clippy lint called `undocumented_unsafe_blocks` which warns when using a block without such a comment.
## Solution
- since clippy expects `SAFETY` instead of `SAFE`, rename those
- add `SAFETY` comments in more places
- for the last remaining 3 places, add an `#[allow()]` and `// TODO` since I wasn't comfortable enough with the code to justify their safety
- add ` #![warn(clippy::undocumented_unsafe_blocks)]` to `bevy_ecs`
### Note for reviewers
The first commit only renames `SAFETY` to `SAFE` so it doesn't need a thorough review.
cb042a416e..55cef2d6fa is the diff for all other changes.
### Safety comments where I'm not too familiar with the code
774012ece5/crates/bevy_ecs/src/entity/mod.rs (L540-L546)774012ece5/crates/bevy_ecs/src/world/entity_ref.rs (L249-L252)
### Locations left undocumented with a `TODO` comment
5dde944a30/crates/bevy_ecs/src/schedule/executor_parallel.rs (L196-L199)5dde944a30/crates/bevy_ecs/src/world/entity_ref.rs (L287-L289)5dde944a30/crates/bevy_ecs/src/world/entity_ref.rs (L413-L415)
Co-authored-by: Jakob Hellermann <hellermann@sipgate.de>
# Objective
Fixes#5153
## Solution
Search for all enums and manually check if they have default impls that can use this new derive.
By my reckoning:
| enum | num |
|-|-|
| total | 159 |
| has default impl | 29 |
| default is unit variant | 23 |
# Objective
- Simplify the process of obtaining a `ComponentId` instance corresponding to a `Component`.
- Resolves#5060.
## Solution
- Add a `component_id::<T: Component>(&self)` function to both `World` and `Components` to retrieve the `ComponentId` associated with `T` from a immutable reference.
---
## Changelog
- Added `World::component_id::<C>()` and `Components::component_id::<C>()` to retrieve a `Component`'s corresponding `ComponentId` if it exists.
# Objective
The descriptions included in the API docs of `entity` module, `Entity` struct, and `Component` trait have some issues:
1. the concept of entity is not clearly defined,
2. descriptions are a little bit out of place,
3. in a case the description leak too many details about the implementation,
4. some descriptions are not exhaustive,
5. there are not enough examples,
6. the content can be formatted in a much better way.
## Solution
1. ~~Stress the fact that entity is an abstract and elementary concept. Abstract because the concept of entity is not hardcoded into the library but emerges from the interaction of `Entity` with every other part of `bevy_ecs`, like components and world methods. Elementary because it is a fundamental concept that cannot be defined with other terms (like point in euclidean geometry, or time in classical physics).~~ We decided to omit the definition of entity in the API docs ([see why]). It is only described in its relationship with components.
2. Information has been moved to relevant places and links are used instead in the other places.
3. Implementation details about `Entity` have been reduced.
4. Descriptions have been made more exhaustive by stating how to obtain and use items. Entity operations are enriched with `World` methods.
5. Examples have been added or enriched.
6. Sections have been added to organize content. Entity operations are now laid out in a table.
### Todo list
- [x] Break lines at sentence-level.
## For reviewers
- ~~I added a TODO over `Component` docs, make sure to check it out and discuss it if necessary.~~ ([Resolved])
- You can easily check the rendered documentation by doing `cargo doc -p bevy_ecs --no-deps --open`.
[see why]: https://github.com/bevyengine/bevy/pull/4767#discussion_r875106329
[Resolved]: https://github.com/bevyengine/bevy/pull/4767#discussion_r874127825
# Objective
Don't allocate memory for Component types known at compile-time. Save a bit of memory.
## Solution
Change `ComponentDescriptor::name` from `String` to `Cow<'static, str>` to use the `&'static str` returned by `std::any::type_name`.
# Objective
Even if bevy itself does not provide any builtin scripting or modding APIs, it should have the foundations for building them yourself.
For that it should be enough to have APIs that are not tied to the actual rust types with generics, but rather accept `ComponentId`s and `bevy_ptr` ptrs.
## Solution
Add the following APIs to bevy
```rust
fn EntityRef::get_by_id(ComponentId) -> Option<Ptr<'w>>;
fn EntityMut::get_by_id(ComponentId) -> Option<Ptr<'_>>;
fn EntityMut::get_mut_by_id(ComponentId) -> Option<MutUntyped<'_>>;
fn World::get_resource_by_id(ComponentId) -> Option<Ptr<'_>>;
fn World::get_resource_mut_by_id(ComponentId) -> Option<MutUntyped<'_>>;
// Safety: `value` must point to a valid value of the component
unsafe fn World::insert_resource_by_id(ComponentId, value: OwningPtr);
fn ComponentDescriptor::new_with_layout(..) -> Self;
fn World::init_component_with_descriptor(ComponentDescriptor) -> ComponentId;
```
~~This PR would definitely benefit from #3001 (lifetime'd pointers) to make sure that the lifetimes of the pointers are valid and the my-move pointer in `insert_resource_by_id` could be an `OwningPtr`, but that can be adapter later if/when #3001 is merged.~~
### Not in this PR
- inserting components on entities (this is very tied to types with bundles and the `BundleInserter`)
- an untyped version of a query (needs good API design, has a large implementation complexity, can be done in a third-party crate)
Co-authored-by: Jakob Hellermann <hellermann@sipgate.de>
# Objective
- We do a lot of function pointer calls in a hot loop (clearing entities in render). This is slow, since calling function pointers cannot be optimised out. We can avoid that in the cases where the function call is a no-op.
- Alternative to https://github.com/bevyengine/bevy/pull/2897
- On my machine, in `many_cubes`, this reduces dropping time from ~150μs to ~80μs.
## Solution
- Make `drop` in `BlobVec` an `Option`, recording whether the given drop impl is required or not.
- Note that this does add branching in some cases - we could consider splitting this into two fields, i.e. unconditionally call the `drop` fn pointer.
- My intuition of how often types stored in `World` should have non-trivial drops makes me think that would be slower, however.
N.B. Even once this lands, we should still test having a 'drop_multiple' variant - for types with a real `Drop` impl, the current implementation is definitely optimal.
## Objective
- ~~Make absurdly long-lived changes stay detectable for even longer (without leveling up to `u64`).~~
- Give all changes a consistent maximum lifespan.
- Improve code clarity.
## Solution
- ~~Increase the frequency of `check_tick` scans to increase the oldest reliably-detectable change.~~
(Deferred until we can benchmark the cost of a scan.)
- Ignore changes older than the maximum reliably-detectable age.
- General refactoring—name the constants, use them everywhere, and update the docs.
- Update test cases to check for the specified behavior.
## Related
This PR addresses (at least partially) the concerns raised in:
- #3071
- #3082 (and associated PR #3084)
## Background
- #1471
Given the minimum interval between `check_ticks` scans, `N`, the oldest reliably-detectable change is `u32::MAX - (2 * N - 1)` (or `MAX_CHANGE_AGE`). Reducing `N` from ~530 million (current value) to something like ~2 million would extend the lifetime of changes by a billion.
| minimum `check_ticks` interval | oldest reliably-detectable change | usable % of `u32::MAX` |
| --- | --- | --- |
| `u32::MAX / 8` (536,870,911) | `(u32::MAX / 4) * 3` | 75.0% |
| `2_000_000` | `u32::MAX - 3_999_999` | 99.9% |
Similarly, changes are still allowed to be between `MAX_CHANGE_AGE`-old and `u32::MAX`-old in the interim between `check_tick` scans. While we prevent their age from overflowing, the test to detect changes still compares raw values. This makes failure ultimately unreliable, since when ancient changes stop being detected varies depending on when the next scan occurs.
## Open Question
Currently, systems and system states are incorrectly initialized with their `last_change_tick` set to `0`, which doesn't handle wraparound correctly.
For consistent behavior, they should either be initialized to the world's `last_change_tick` (and detect no changes) or to `MAX_CHANGE_AGE` behind the world's current `change_tick` (and detect everything as a change). I've currently gone with the latter since that was closer to the existing behavior.
## Follow-up Work
(Edited: entire section)
We haven't actually profiled how long a `check_ticks` scan takes on a "large" `World` , so we don't know if it's safe to increase their frequency. However, we are currently relying on play sessions not lasting long enough to trigger a scan and apps not having enough entities/archetypes for it to be "expensive" (our assumption). That isn't a real solution. (Either scanning never costs enough to impact frame times or we provide an option to use `u64` change ticks. Nobody will accept random hiccups.)
To further extend the lifetime of changes, we actually only need to increment the world tick if a system has `Fetch: !ReadOnlySystemParamFetch`. The behavior will be identical because all writes are sequenced, but I'm not sure how to implement that in a way that the compiler can optimize the branch out.
Also, since having no false positives depends on a `check_ticks` scan running at least every `2 * N - 1` ticks, a `last_check_tick` should also be stored in the `World` so that any lull in system execution (like a command flush) could trigger a scan if needed. To be completely robust, all the systems initialized on the world should be scanned, not just those in the current stage.
# Objective
The pointer types introduced in #3001 are useful not just in `bevy_ecs`, but also in crates like `bevy_reflect` (#4475) or even outside of bevy.
## Solution
Extract `Ptr<'a>`, `PtrMut<'a>`, `OwnedPtr<'a>`, `ThinSlicePtr<'a, T>` and `UnsafeCellDeref` from `bevy_ecs::ptr` into `bevy_ptr`.
**Note:** `bevy_ecs` still reexports the `bevy_ptr` as `bevy_ecs::ptr` so that crates like `bevy_transform` can use the `Bundle` derive without needing to depend on `bevy_ptr` themselves.
# Objective
The `Ptr` types gives free access to the underlying `NonNull<u8>`, which adds more publicly visible pointer wrangling than there needs to be. There are also a few edge cases where Ptr types could be more readily utilized for properly validating the soundness of ECS operations.
## Solution
- Replace `*Ptr(Mut)::inner` with `cast` which requires a concrete type to give the pointer. This function could also have a `debug_assert` with an alignment check to ensure that the pointer is aligned properly, but is currently not included.
- Use `OwningPtr::read` in ECS macros over casting the inner pointer around.
