We are in the process of rolling out a new Bevy Organization role! (Subject Matter Expert)
This adds a new "The Bevy Organization" document and links to it from CONTRIBUTING.md. This doc describes how the Bevy Organization will work going forward. It outlines the functionality of each role, as well as the expectations we have for them. The previously existing roles (Project Lead, Maintainer) still work the same way, but their definition and scope have been made much clearer.
Tomorrow we will be announcing this publicly in a blog post. This will describe the motivation and announce the first round of SMEs . But before that it makes sense to do a quick review round first.
Given the quick turnaround on this PR, this isn't the best platform to discuss changes to the SME system (or its validity). After you have read the announcement tomorrow, feel free to start discussions wherever is preferable to you (this repo, discord, etc). So for now, please just review for clarity / typos / phrasing / missed info / etc.
[Rendered](08ceae43db/docs/the_bevy_organization.md)
# Objective
Pipelines can be customized by wrapping an existing pipeline in a newtype and adding custom logic to its implementation of `SpecializedMeshPipeline::specialize`. To make that easier, the wrapped pipeline type needs to implement `Clone`.
For example, the current non-cloneable pipelines require wrapper pipelines to pull apart the wrapped pipeline like this:
```rust
impl FromWorld for Wireframe2dPipeline {
fn from_world(world: &mut World) -> Self {
let p = &world.resource::<Material2dPipeline<ColorMaterial>>();
Self {
mesh2d_pipeline: p.mesh2d_pipeline.clone(),
material2d_layout: p.material2d_layout.clone(),
vertex_shader: p.vertex_shader.clone(),
fragment_shader: p.fragment_shader.clone(),
}
}
}
```
## Solution
Derive or implement `Clone` on all built-in pipeline types. This is easy to do since they mostly just contain cheaply clonable reference-counted types.
---
## Changelog
Implement `Clone` for all pipeline types.
# Objective
fix error with shadow shader's spotlight direction calculation when direction.y ~= 0
fixes#7152
## Solution
same as #6167: in shadows.wgsl, clamp 1-x^2-z^2 to >= 0 so that we can safely sqrt it
# Objective
There are some utility functions for actually working with `Storages` inside `entity_ref.rs` that are used both for `EntityRef/EntityMut` and `World`, with a `// TODO: move to Storages`.
This PR moves them to private methods on `World`, because that's the safest API boundary. On `Storages` you would need to ensure that you pass `Components` from the same world.
## Solution
- move get_component[_with_type], get_ticks[_with_type], get_component_and_ticks[_with_type] to `World` (still pub(crate))
- replace `pub use entity_ref::*;` with `pub use entity_ref::{EntityRef, EntityMut}` and qualified `entity_ref::get_mut[_by_id]` in `world.rs`
- add safety comments to a bunch of methods
# Objective
* `World::init_resource` and `World::get_resource_or_insert_with` are implemented naively, and as such they perform duplicate `TypeId -> ComponentId` lookups.
* `World::get_resource_or_insert_with` contains an additional duplicate `ComponentId -> ResourceData` lookup.
* This function also contains an unnecessary panic branch, which we rely on the optimizer to be able to remove.
## Solution
Implement the functions using engine-internal code, instead of combining high-level functions. This allows computed variables to persist across different branches, instead of being recomputed.
# Objective
It is often necessary to update an entity's parent
while keeping its GlobalTransform static. Currently
it is cumbersome and error-prone (two questions in
the discord `#help` channel in the past week)
- Part 2, resolves#5475
- Builds on: #7020.
## Solution
- Added the `BuildChildrenTransformExt` trait, it is part
of `bevy::prelude` and adds the following methods to `EntityCommands`:
- `set_parent_in_place`: Change the parent of an entity and
update its `Transform` in order to preserve its `GlobalTransform` after the parent change
- `remove_parent_in_place`: Remove an entity from a hierarchy,
while preserving its `GlobalTransform`.
---
## Changelog
- Added the `BuildChildrenTransformExt` trait, it is part
of `bevy::prelude` and adds the following methods to `EntityCommands`:
- `set_parent_in_place`: Change the parent of an entity and
update its `Transform` in order to preserve its `GlobalTransform` after the parent change
- `remove_parent_in_place`: Remove an entity from a hierarchy,
while preserving its `GlobalTransform`.
Co-authored-by: Nicola Papale <nicopap@users.noreply.github.com>
# Objective
- While building UI, it makes more sense for most nodes to have a `FocusPolicy` of `Pass`, so that user interaction can correctly bubble
- Only `ButtonBundle` blocks by default
This change means that for someone adding children to a button, it's not needed to change the focus policy of those children to `Pass` for the button to continue to work.
---
## Changelog
- `FocusPolicy` default has changed from `FocusPolicy::Block` to `FocusPolicy::Pass`
## Migration Guide
- `FocusPolicy` default has changed from `FocusPolicy::Block` to `FocusPolicy::Pass`
# Objective
The documentation of the bevy_render crate is still pretty incomplete.
This PR follows up on #6885 and improves the documentation of the `render_phase` module.
This module contains one of our most important rendering abstractions and the current documentation is pretty confusing. This PR tries to clarify what all of these pieces are for and how they work together to form bevy`s modular rendering logic.
## Solution
### Code Reformating
- I have moved the `rangefinder` into the `render_phase` module since it is only used there.
- I have moved the `PhaseItem` (and the `BatchedPhaseItem`) from `render_phase::draw` over to `render_phase::mod`. This does not change the public-facing API since they are reexported anyway, but this change makes the relation between `RenderPhase` and `PhaseItem` clear and easier to discover.
### Documentation
- revised all documentation in the `render_phase` module
- added a module-level explanation of how `RenderPhase`s, `RenderPass`es, `PhaseItem`s, `Draw` functions, and `RenderCommands` relate to each other and how they are used
---
## Changelog
- The `rangefinder` module has been moved into the `render_phase` module.
## Migration Guide
- The `rangefinder` module has been moved into the `render_phase` module.
```rust
//old
use bevy::render::rangefinder::*;
// new
use bevy::render::render_phase::rangefinder::*;
```
# Objective
Following #6681, both `TableRow` and `TableId` are now part of `EntityLocation`. However, the safety invariant on `EntityLocation` requires that all of the constituent fields are `repr(transprent)` or `repr(C)` and the bit pattern of all 1s must be valid. This is not true for `TableRow` and `TableId` currently.
## Solution
Mark `TableRow` and `TableId` to satisfy the safety requirement. Add safety comments on `ArchetypeId`, `ArchetypeRow`, `TableId` and `TableRow`.
# Objective
Improve safety testing when using `bevy_ptr` types. This is a follow-up to #7113.
## Solution
Add a debug-only assertion that pointers are aligned when casting to a concrete type. This should very quickly catch any unsoundness from unaligned pointers, even without miri. However, this can have a large negative perf impact on debug builds.
---
## Changelog
Added: `Ptr::deref` will now panic in debug builds if the pointer is not aligned.
Added: `PtrMut::deref_mut` will now panic in debug builds if the pointer is not aligned.
Added: `OwningPtr::read` will now panic in debug builds if the pointer is not aligned.
Added: `OwningPtr::drop_as` will now panic in debug builds if the pointer is not aligned.
# Objective
- It can be useful for third party crates to work independently on how bevy is imported
## Solution
- Expose an helper to get a subcrate path for macros
# Objective
- There is a warning when building in release:
```
warning: unused import: `bevy_ecs::system::Local`
--> crates/bevy_render/src/extract_resource.rs:5:5
|
5 | use bevy_ecs::system::Local;
| ^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `#[warn(unused_imports)]` on by default
```
- It's used 59751d6e33/crates/bevy_render/src/extract_resource.rs (L47)
- Fix it
## Solution
- Gate the import
- repeat of #5320
# Objective
`MutUntyped` is a struct that stores a `PtrMut` alongside change tick metadata. Working with this type is cumbersome, and has few benefits over storing the pointer and change ticks separately.
Related: #6430 (title is out of date)
## Solution
Add a convenience method for transforming an untyped change detection pointer into its typed counterpart.
---
## Changelog
- Added the method `MutUntyped::with_type`.
As mentioned in https://github.com/bevyengine/bevy/pull/6530. It allows to not create a new constant and simply having it to show up in the documentation when someone is looking for "transparent" (case insensitive) in rustdoc search.
cc @alice-i-cecile
# Objective
Enums are now reflectable, but are not accessible via reflection paths.
This would allow us to do things like:
```rust
#[derive(Reflect)]
struct MyStruct {
data: MyEnum
}
#[derive(Reflect)]
struct MyEnum {
Foo(u32, u32),
Bar(bool)
}
let x = MyStruct {
data: MyEnum::Foo(123),
};
assert_eq!(*x.get_path::<u32>("data.1").unwrap(), 123);
```
## Solution
Added support for enums in reflection paths.
##### Note
This uses a simple approach of just getting the field with the given accessor. It does not do matching or anything else to ensure the enum is the intended variant. This means that the variant must be known ahead of time or matched outside the reflection path (i.e. path to variant, perform manual match, and continue pathing).
---
## Changelog
- Added support for enums in reflection paths
# Objective
There are times where we want to simply take an owned `dyn Reflect` and cast it to a type `T`.
Currently, this involves doing:
```rust
let value = value.take::<T>().unwrap_or_else(|value| {
T::from_reflect(&*value).unwrap_or_else(|| {
panic!(
"expected value of type {} to convert to type {}.",
value.type_name(),
std::any::type_name::<T>()
)
})
});
```
This is a common operation that could be easily be simplified.
## Solution
Add the `FromReflect::take_from_reflect` method. This first tries to `take` the value, calling `from_reflect` iff that fails.
```rust
let value = T::take_from_reflect(value).unwrap_or_else(|value| {
panic!(
"expected value of type {} to convert to type {}.",
value.type_name(),
std::any::type_name::<T>()
)
});
```
Based on suggestion from @soqb on [Discord](https://discord.com/channels/691052431525675048/1002362493634629796/1041046880316043374).
---
## Changelog
- Add `FromReflect::take_from_reflect` method
# Objective
- Fixes#7066
## Solution
- Split the ChangeDetection trait into ChangeDetection and ChangeDetectionMut
- Added Ref as equivalent to &T with change detection
---
## Changelog
- Support for Ref which allow inspecting change detection flags in an immutable way
## Migration Guide
- While bevy prelude includes both ChangeDetection and ChangeDetectionMut any code explicitly referencing ChangeDetection might need to be updated to ChangeDetectionMut or both. Specifically any reading logic requires ChangeDetection while writes requires ChangeDetectionMut.
use bevy_ecs::change_detection::DetectChanges -> use bevy_ecs::change_detection::{DetectChanges, DetectChangesMut}
- Previously Res had methods to access change detection `is_changed` and `is_added` those methods have been moved to the `DetectChanges` trait. If you are including bevy prelude you will have access to these types otherwise you will need to `use bevy_ecs::change_detection::DetectChanges` to continue using them.
# Objective
- https://github.com/bevyengine/bevy/pull/3505 marked `S-Adopt-Me` , this pr is to continue his work.
## Solution
- run `cargo clippy --workspace --all-targets --all-features -- -Aclippy::type_complexity -Wclippy::doc_markdown -Wclippy::redundant_else -Wclippy::match_same_arms -Wclippy::semicolon_if_nothing_returned -Wclippy::explicit_iter_loop -Wclippy::map_flatten -Dwarnings` under benches dir.
- fix issue according to suggestion.
# Objective
The types in the `bevy_ptr` accidentally did not document anything relating to alignment. This is unsound as many methods rely on the pointer being correctly aligned.
## Solution
This PR introduces new safety invariants on the `$ptr::new`, `$ptr::byte_offset` and `$ptr::byte_add` methods requiring them to keep the pointer aligned. This is consistent with the documentation of these pointer types which document them as being "type erased borrows".
As it was pointed out (by @JoJoJet in #7117) that working with unaligned pointers can be useful (for example our commands abstraction which does not try to align anything properly, see #7039) this PR also introduces a default type parameter to all the pointer types that specifies whether it has alignment requirements or not. I could not find any code in `bevy_ecs` that would need unaligned pointers right now so this is going unused.
---
## Changelog
- Correctly document alignment requirements on `bevy_ptr` types.
- Support variants of `bevy_ptr` types that do not require being correctly aligned for the pointee type.
## Migration Guide
- Safety invariants on `bevy_ptr` types' `new` `byte_add` and `byte_offset` methods have been changed. All callers should re-audit for soundness.
# Objective
- Spawn tasks from other threads onto an async executor, but limit those tasks to run on a specific thread.
- This is a continuation of trying to break up some of the changes in pipelined rendering.
- Eventually this will be used to allow `NonSend` systems to run on the main thread in pipelined rendering #6503 and also to solve #6552.
- For this specific PR this allows for us to store a thread executor in a thread local, rather than recreating a scope executor for every scope which should save on a little work.
## Solution
- We create a Executor that does a runtime check for what thread it's on before creating a !Send ticker. The ticker is the only way for the executor to make progress.
---
## Changelog
- create a ThreadExecutor that can only be ticked on one thread.
`Query`'s fields being `pub(crate)` means that the struct can be constructed via safe code from anywhere in `bevy_ecs` . This is Not Good since it is intended that all construction of this type goes through `Query::new` which is an `unsafe fn` letting various `Query` methods rely on those invariants holding even though they can be trivially bypassed.
This has no user facing impact
# Objective
It is possible to manually update `GlobalTransform`.
The engine actually assumes this is not possible.
For example, `propagate_transform` does not update children
of an `Entity` which **`GlobalTransform`** changed,
leading to unexpected behaviors.
A `GlobalTransform` set by the user may also be blindly
overwritten by the propagation system.
## Solution
- Remove `translation_mut`
- Explain to users that they shouldn't manually update the `GlobalTransform`
- Remove `global_vs_local.rs` example, since it misleads users
in believing that it is a valid use-case to manually update the
`GlobalTransform`
---
## Changelog
- Remove `GlobalTransform::translation_mut`
## Migration Guide
`GlobalTransform::translation_mut` has been removed without alternative,
if you were relying on this, update the `Transform` instead. If the given entity
had children or parent, you may need to remove its parent to make its transform
independent (in which case the new `Commands::set_parent_in_place` and
`Commands::remove_parent_in_place` may be of interest)
Bevy may add in the future a way to toggle transform propagation on
an entity basis.
# Objective
- Fix#7103.
- The issue is caused because I forgot to add a where clause to a generated struct in #7056.
## Solution
- Add the where clause.
`Query` relies on the `World` it stores being the same as the world used for creating the `QueryState` it stores. If they are not the same then everything is very unsound. This was not actually being checked anywhere, `Query::new` did not have a safety invariant or even an assertion that the `WorldId`'s are the same.
This shouldn't have any user facing impact unless we have really messed up in bevy and have unsoundness elsewhere (in which case we would now get a panic instead of being unsound).
# Objective
- In some cases, you need a `Mut<T>` pointer, but you only have a mutable reference to one. There is no easy way of converting `&'a mut Mut<'_, T>` -> `Mut<'a, T>` outside of the engine.
### Example (Before)
```rust
fn do_with_mut<T>(val: Mut<T>) { ... }
for x: Mut<T> in &mut query {
// The function expects a `Mut<T>`, so `x` gets moved here.
do_with_mut(x);
// Error: use of moved value.
do_a_thing(&x);
}
```
## Solution
- Add the function `reborrow`, which performs the mapping. This is analogous to `PtrMut::reborrow`.
### Example (After)
```rust
fn do_with_mut<T>(val: Mut<T>) { ... }
for x: Mut<T> in &mut query {
// We reborrow `x`, so the original does not get moved.
do_with_mut(x.reborrow());
// Works fine.
do_a_thing(&x);
}
```
---
## Changelog
- Added the method `reborrow` to `Mut`, `ResMut`, `NonSendMut`, and `MutUntyped`.
# Objective
This a follow-up to #6894, see https://github.com/bevyengine/bevy/pull/6894#discussion_r1045203113
The goal is to avoid cloning any string when getting a `&TypeRegistration` corresponding to a string which is being deserialized. As a bonus code duplication is also reduced.
## Solution
The manual deserialization of a string and lookup into the type registry has been moved into a separate `TypeRegistrationDeserializer` type, which implements `DeserializeSeed` with a `Visitor` that accepts any string with `visit_str`, even ones that may not live longer than that function call.
`BorrowedStr` has been removed since it's no longer used.
---
## Changelog
- The type `TypeRegistrationDeserializer` has been added, which simplifies getting a `&TypeRegistration` while deserializing a string.
# Objective
- Fix the name of function parameter name in docs
## Solution
- Change `f` to `sub_app_runner`
---
It confused me a bit when I was reading the docs in the autocomplete hint.
Hesitated about filing a PR since it's just a one single word change in the comment.
Is this the right process to change these docs?
# Objective
- Fixes#6777, fixes#2998, replaces #5518
- Help avoid confusing error message when using an older version of Rust
## Solution
- Add the `rust-version` field to `Cargo.toml`
- Add a CI job checking the MSRV
- Add the job to bors
# Objective
The type `Local<T>` unnecessarily has the bound `T: Sync` when the local is used in an exclusive system.
## Solution
Lift the bound.
---
## Changelog
Removed the bound `T: Sync` from `Local<T>` when used as an `ExclusiveSystemParam`.
# Objective
Fixes#3310. Fixes#6282. Fixes#6278. Fixes#3666.
## Solution
Split out `!Send` resources into `NonSendResources`. Add a `origin_thread_id` to all `!Send` Resources, check it on dropping `NonSendResourceData`, if there's a mismatch, panic. Moved all of the checks that `MainThreadValidator` would do into `NonSendResources` instead.
All `!Send` resources now individually track which thread they were inserted from. This is validated against for every access, mutation, and drop that could be done against the value.
A regression test using an altered version of the example from #3310 has been added.
This is a stopgap solution for the current status quo. A full solution may involve fully removing `!Send` resources/components from `World`, which will likely require a much more thorough design on how to handle the existing in-engine and ecosystem use cases.
This PR also introduces another breaking change:
```rust
use bevy_ecs::prelude::*;
#[derive(Resource)]
struct Resource(u32);
fn main() {
let mut world = World::new();
world.insert_resource(Resource(1));
world.insert_non_send_resource(Resource(2));
let res = world.get_resource_mut::<Resource>().unwrap();
assert_eq!(res.0, 2);
}
```
This code will run correctly on 0.9.1 but not with this PR, since NonSend resources and normal resources have become actual distinct concepts storage wise.
## Changelog
Changed: Fix soundness bug with `World: Send`. Dropping a `World` that contains a `!Send` resource on the wrong thread will now panic.
## Migration Guide
Normal resources and `NonSend` resources no longer share the same backing storage. If `R: Resource`, then `NonSend<R>` and `Res<R>` will return different instances from each other. If you are using both `Res<T>` and `NonSend<T>` (or their mutable variants), to fetch the same resources, it's strongly advised to use `Res<T>`.
# Objective
- Fixes#7061
## Solution
- Add and implement `insert` and `remove` methods for `List`.
---
## Changelog
- Added `insert` and `remove` methods to `List`.
- Changed the `push` and `pop` methods on `List` to have default implementations.
## Migration Guide
- Manual implementors of `List` need to implement the new methods `insert` and `remove` and
consider whether to use the new default implementation of `push` and `pop`.
Co-authored-by: radiish <thesethskigamer@gmail.com>
# Objective
Speed up the render phase for rendering.
## Solution
- Follow up #6988 and make the internals of atomic IDs `NonZeroU32`. This niches the `Option`s of the IDs in draw state, which reduces the size and branching behavior when evaluating for equality.
- Require `&RenderDevice` to get the device's `Limits` when initializing a `TrackedRenderPass` to preallocate the bind groups and vertex buffer state in `DrawState`, this removes the branch on needing to resize those `Vec`s.
## Performance
This produces a similar speed up akin to that of #6885. This shows an approximate 6% speed up in `main_opaque_pass_3d` on `many_foxes` (408.79 us -> 388us). This should be orthogonal to the gains seen there.
---
## Changelog
Added: `RenderContext::begin_tracked_render_pass`.
Changed: `TrackedRenderPass` now requires a `&RenderDevice` on construction.
Removed: `bevy_render::render_phase::DrawState`. It was not usable in any form outside of `bevy_render`.
## Migration Guide
TODO
# Objective
- This pulls out some of the changes to Plugin setup and sub apps from #6503 to make that PR easier to review.
- Separate the extract stage from running the sub app's schedule to allow for them to be run on separate threads in the future
- Fixes#6990
## Solution
- add a run method to `SubApp` that runs the schedule
- change the name of `sub_app_runner` to extract to make it clear that this function is only for extracting data between the main app and the sub app
- remove the extract stage from the sub app schedule so it can be run separately. This is done by adding a `setup` method to the `Plugin` trait that runs after all plugin build methods run. This is required to allow the extract stage to be removed from the schedule after all the plugins have added their systems to the stage. We will also need the setup method for pipelined rendering to setup the render thread. See e3267965e1/crates/bevy_render/src/pipelined_rendering.rs (L57-L98)
## Changelog
- Separate SubApp Extract stage from running the sub app schedule.
## Migration Guide
### SubApp `runner` has conceptually been changed to an `extract` function.
The `runner` no longer is in charge of running the sub app schedule. It's only concern is now moving data between the main world and the sub app. The `sub_app.app.schedule` is now run for you after the provided function is called.
```rust
// before
fn main() {
let sub_app = App::empty();
sub_app.add_stage(MyStage, SystemStage::parallel());
App::new().add_sub_app(MySubApp, sub_app, move |main_world, sub_app| {
extract(app_world, render_app);
render_app.app.schedule.run();
});
}
// after
fn main() {
let sub_app = App::empty();
sub_app.add_stage(MyStage, SystemStage::parallel());
App::new().add_sub_app(MySubApp, sub_app, move |main_world, sub_app| {
extract(app_world, render_app);
// schedule is automatically called for you after extract is run
});
}
```
# Objective
- Remove redundant gamepad events
- Simplify consuming gamepad events.
- Refactor: Separate handling of gamepad events into multiple systems.
## Solution
- Removed `GamepadEventRaw`, and `GamepadEventType`.
- Added bespoke `GamepadConnectionEvent`, `GamepadAxisChangedEvent`, and `GamepadButtonChangedEvent`.
- Refactored `gamepad_event_system`.
- Added `gamepad_button_event_system`, `gamepad_axis_event_system`, and `gamepad_connection_system`, which update the `Input` and `Axis` resources using their corresponding event type.
Gamepad events are now handled in their own systems and have their own types.
This allows for querying for gamepad events without having to match on `GamepadEventType` and makes creating handlers for specific gamepad event types, like a `GamepadConnectionEvent` or `GamepadButtonChangedEvent` possible.
We remove `GamepadEventRaw` by filtering the gamepad events, using `GamepadSettings`, _at the source_, in `bevy_gilrs`. This way we can create `GamepadEvent`s directly and avoid creating `GamepadEventRaw` which do not pass the user defined filters.
We expose ordered `GamepadEvent`s and we can respond to individual gamepad event types.
## Migration Guide
- Replace `GamepadEvent` and `GamepadEventRaw` types with their specific gamepad event type.
# Objective
- Fixes https://github.com/bevyengine/bevy/discussions/6338
This PR allows for smooth transitions between different animations.
## Solution
- This PR uses very simple linear blending of animations.
- When starting a new animation, you can give it a duration, and throughout that duration, the previous and the new animation are being linearly blended, until only the new animation is running.
- I'm aware of https://github.com/bevyengine/rfcs/pull/49 and https://github.com/bevyengine/rfcs/pull/51, which are more complete solutions to this problem, but they seem still far from being implemented. Until they're ready, this PR allows for the most basic use case of blending, i.e. smoothly transitioning between different animations.
## Migration Guide
- no bc breaking changes
# Objective
- Storage buffers are useful and not currently supported by the `AsBindGroup` derive which means you need to expand the macro if you need a storage buffer
## Solution
- Add a new `#[storage]` attribute to the derive `AsBindGroup` macro.
- Support and optional `read_only` parameter that defaults to false when not present.
- Support visibility parameters like the texture and sampler attributes.
---
## Changelog
- Add a new `#[storage(index)]` attribute to the derive `AsBindGroup` macro.
Co-authored-by: IceSentry <IceSentry@users.noreply.github.com>
# Objective
- Avoid slower than necessary first frame after spawning many entities due to them not having `Aabb`s and so being marked visible
- Avoids unnecessarily large system and VRAM allocations as a consequence
## Solution
- I noticed when debugging the `many_cubes` stress test in Xcode that the `MeshUniform` binding was much larger than it needed to be. I realised that this was because initially, all mesh entities are marked as being visible because they don't have `Aabb`s because `calculate_bounds` is being run in `PostUpdate` and there are no system commands applications before executing the visibility check systems that need the `Aabb`s. The solution then is to run the `calculate_bounds` system just before the previous system commands are applied which is at the end of the `Update` stage.
Spiritual successor to #5205.
Actual successor to #6865.
# Objective
Currently, system params are defined using three traits: `SystemParam`, `ReadOnlySystemParam`, `SystemParamState`. The behavior for each param is specified by the `SystemParamState` trait, while `SystemParam` simply defers to the state.
Splitting the traits in this way makes it easier to implement within macros, but it increases the cognitive load. Worst of all, this approach requires each `MySystemParam` to have a public `MySystemParamState` type associated with it.
## Solution
* Merge the trait `SystemParamState` into `SystemParam`.
* Remove all trivial `SystemParam` state types.
* `OptionNonSendMutState<T>`: you will not be missed.
---
- [x] Fix/resolve the remaining test failure.
## Changelog
* Removed the trait `SystemParamState`, merging its functionality into `SystemParam`.
## Migration Guide
**Note**: this should replace the migration guide for #6865.
This is relative to Bevy 0.9, not main.
The traits `SystemParamState` and `SystemParamFetch` have been removed, and their functionality has been transferred to `SystemParam`.
```rust
// Before (0.9)
impl SystemParam for MyParam<'_, '_> {
type State = MyParamState;
}
unsafe impl SystemParamState for MyParamState {
fn init(world: &mut World, system_meta: &mut SystemMeta) -> Self { ... }
}
unsafe impl<'w, 's> SystemParamFetch<'w, 's> for MyParamState {
type Item = MyParam<'w, 's>;
fn get_param(&mut self, ...) -> Self::Item;
}
unsafe impl ReadOnlySystemParamFetch for MyParamState { }
// After (0.10)
unsafe impl SystemParam for MyParam<'_, '_> {
type State = MyParamState;
type Item<'w, 's> = MyParam<'w, 's>;
fn init_state(world: &mut World, system_meta: &mut SystemMeta) -> Self::State { ... }
fn get_param<'w, 's>(state: &mut Self::State, ...) -> Self::Item<'w, 's>;
}
unsafe impl ReadOnlySystemParam for MyParam<'_, '_> { }
```
The trait `ReadOnlySystemParamFetch` has been replaced with `ReadOnlySystemParam`.
```rust
// Before
unsafe impl ReadOnlySystemParamFetch for MyParamState {}
// After
unsafe impl ReadOnlySystemParam for MyParam<'_, '_> {}
```
# Objective
- The doctest for `Mut::map_unchanged` uses a fake function `set_if_not_equal` to demonstrate usage.
- Now that #6853 has been merged, we can use `Mut::set_if_neq` directly instead of mocking it.
