# Objective
- Fix broken normals when the NormalPrepass is enabled
## Solution
- Don't use the normal prepass for the world_normal
- Only loadthe normal prepass
- when msaa is disabled
- for opaque or alpha mask meshes and only for use it for N not
world_normal
# Objective
- Use `AppTypeRegistry` on API defined in `bevy_ecs`
(https://github.com/bevyengine/bevy/pull/8895#discussion_r1234748418)
A lot of the API on `Reflect` depends on a registry. When it comes to
the ECS. We should use `AppTypeRegistry` in the general case.
This is however impossible in `bevy_ecs`, since `AppTypeRegistry` is
defined in `bevy_app`.
## Solution
- Move `AppTypeRegistry` resource definition from `bevy_app` to
`bevy_ecs`
- Still add the resource in the `App` plugin, since bevy_ecs itself
doesn't know of plugins
Note that `bevy_ecs` is a dependency of `bevy_app`, so nothing
revolutionary happens.
## Alternative
- Define the API as a trait in `bevy_app` over `bevy_ecs`. (though this
prevents us from using bevy_ecs internals)
- Do not rely on `AppTypeRegistry` for the API in question, requring
users to extract themselves the resource and pass it to the API methods.
---
## Changelog
- Moved `AppTypeRegistry` resource definition from `bevy_app` to
`bevy_ecs`
## Migration Guide
- If you were **not** using a `prelude::*` to import `AppTypeRegistry`,
you should update your imports:
```diff
- use bevy::app::AppTypeRegistry;
+ use bevy::ecs::reflect::AppTypeRegistry
```
# Objective
The "bevy_text" feature attributes for the `PrimaryWindow`, `Window` and
`TextureAtlas` imports in `bevy_ui::render` are used by non-text systems
(`extract_uinode_borders` and `extract_atlas_uinodes`) and need to be
removed.
For those who wish to be able to `#[reflect]` stuff using the `Uuid`
type
I'm very unfamiliar with the codebase, so please tell me if I'm missing
something
# Objective
- Providing a "noob-friendly" example since not many people are
proficient in 3D modeling / rendering concepts.
## Solution
- Adding more information to the example, with an explanation.
~~~~
_Thanks to Nocta on discord for helping out when I didn't understand the
subject well._
---------
Co-authored-by: François <mockersf@gmail.com>
# Objective
- `bevy_log` writes logs to `stdout` (with ANSI formatting), which gets
in the way with program output and complicates parsing.
- Closes#8869
## Solution
- Change `bevy_log` to write to `stderr` instead of `stdout`
---
## Changelog
Changed:
- Logs write to `stderr` rather than `stdout` on desktop targets
## Migration Guide
- Capture logs from `stderr` instead of from `stdout`
- Use `2> output.log` on the command line to save `stderr` to a file
# Objective
Add a get_unclamped method to
[Axis](https://docs.rs/bevy/0.10.1/bevy/input/struct.Axis.html) to allow
it to be used in cases where being able to get a precise relative
movement is important. For example, camera zoom with the mouse wheel.
This would make it possible for libraries like leafwing input manager to
leverage `Axis` for mouse motion and mouse wheel axis mapping. I tried
to use it my PR here
https://github.com/Leafwing-Studios/leafwing-input-manager/pull/346 but
will likely have to revert that and read the mouse wheel events for now
which is what prompted this PR.
## Solution
Instead of clamping the axis value when it is set, it now stores the raw
value and clamps it in the `get` method. This allows a simple
get_unclamped method that just returns the raw value.
## Changelog
- Added a get_unclamped method to Axis that can return values outside of
-1.0 to 1.0
# Objective
Fixes#6920
## Solution
From the issue discussion:
> From looking at the `AsBindGroup` derive macro implementation, the
fallback image's `TextureView` is used when the binding's
`Option<Handle<Image>>` is `None`. Because this relies on already having
a view that matches the desired binding dimensions, I think the solution
will require creating a separate `GpuImage` for each possible
`TextureViewDimension`.
---
## Changelog
Users can now rely on `FallbackImage` to work with a texture binding of
any dimension.
# Objective
- Document android code that is currently causing clippy warnings due to
not being documented
## Solution
- Document the two previously undocumented items
# Objective
`WorldQuery::Fetch` is a type used to optimize the implementation of
queries. These types are hidden and not intended to be outside of the
engine, so there is no need to provide type aliases to make it easier to
refer to them. If a user absolutely needs to refer to one of these
types, they can always just refer to the associated type directly.
## Solution
Deprecate these type aliases.
---
## Changelog
- Deprecated the type aliases `QueryFetch` and `ROQueryFetch`.
## Migration Guide
The type aliases `bevy_ecs::query::QueryFetch` and `ROQueryFetch` have
been deprecated. If you need to refer to a `WorldQuery` struct's fetch
type, refer to the associated type defined on `WorldQuery` directly:
```rust
// Before:
type MyFetch<'w> = QueryFetch<'w, MyQuery>;
type MyFetchReadOnly<'w> = ROQueryFetch<'w, MyQuery>;
// After:
type MyFetch<'w> = <MyQuery as WorldQuery>::Fetch;
type MyFetchReadOnly<'w> = <<MyQuery as WorldQuery>::ReadOnly as WorldQuery>::Fetch;
```
# Objective
This adds support for using texture atlas sprites in UI. From
discussions today in the ui-dev discord it seems this is a much wanted
feature.
This was previously attempted in #5070 by @ManevilleF however that was
blocked #5103. This work can be easily modified to support #5103 changes
after that merges.
## Solution
I created a new UI bundle that reuses the existing texture atlas
infrastructure. I create a new atlas image component to prevent it from
being drawn by the existing non-UI systems and to remove unused
parameters.
In extract I added new system to calculate the required values for the
texture atlas image, this extracts into the same resource as the
existing UI Image and Text components.
This should have minimal performance impact because if texture atlas is
not present then the exact same code path is followed. Also there should
be no unintended behavior changes because without the new components the
existing systems write the extract same resulting data.
I also added an example showing the sprite working and a system to
advance the animation on space bar presses.
Naming is hard and I would accept any feedback on the bundle name!
---
## Changelog
> Added TextureAtlasImageBundle
---------
Co-authored-by: ickshonpe <david.curthoys@googlemail.com>
# Objective
Discovered that PointLight did not implement FromReflect. Adding
FromReflect where Reflect is used. I overreached and applied this rule
everywhere there was a Reflect without a FromReflect, except from where
the compiler wouldn't allow me.
Based from question: https://github.com/bevyengine/bevy/discussions/8774
## Solution
- Adding FromReflect where Reflect was already derived
## Notes
First PR I do in this ecosystem, so not sure if this is the usual
approach, that is, to touch many files at once.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
`ParsedPath` does not need to be mut to access a field of a `Reflect`.
Be that access mutable or not. Yet `element_mut` requires a mutable
borrow on `self`.
## Solution
- Make `element_mut` take a `&self` over a `&mut self`.
#8887 fixes this, but this is a major limitation in the API and I'd
rather see it merged before 0.11.
---
## Changelog
- `ParsedPath::element_mut` and `ParsedPath::reflect_element_mut` now
accept a non-mutable `ParsedPath` (only the accessed `Reflect` needs to
be mutable)
# Objective
- Implementing reflection for Cow<'static, [T]>
- Hopefully fixes#7429
## Solution
- Implementing Reflect, Typed, GetTypeRegistration, and FromReflect for
Cow<'static, [T]>
---
## Notes
I have not used bevy_reflection much yet, so I may not fully understand
all the use cases. This is also my first attempt at contributing, so I
would appreciate any feedback or recommendations for changes. I tried to
add cases for using Cow<'static, str> and Cow<'static, [u8]> to some of
the bevy_reflect tests, but I can't guarantee those tests are
comprehensive enough.
---------
Co-authored-by: MinerSebas <66798382+MinerSebas@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Repetitively fetching ReflectResource and ReflectComponent from the
TypeRegistry is costly.
We want to access the underlying `fn`s. to do so, we expose the
`ReflectResourceFns` and `ReflectComponentFns` stored in ReflectResource
and ReflectComponent.
---
## Changelog
- Add the `fn_pointers` methods to `ReflectResource` and
`ReflectComponent` returning the underlying `ReflectResourceFns` and
`ReflectComponentFns`
# Objective
Make the UI code more concise.
## Solution
Add two utility methods to make manipulating `UiRect` from code more
concise:
- `UiRect::px()` create a new `UiRect` like the `new()` function, but
with values in logical pixels directly.
- `UiRect::percent()` is similar, with values as percentages.
This saves a lot of typing and makes UI code more compact while
retaining readability.
---
## Changelog
### Added
Added two new constructors `UiRect::px()` and `UiRect::percent()` to
create a new `UiRect` from values directly specified in logical pixels
and percentages, respectively. The argument order is the same as
`UiRect::new()`, but avoids having to repeat `Val::Px` and
`Val::Percent`, respectively.
# Objective
- Fixes#7811
## Solution
- I added `Has<T>` (and `HasFetch<T>` ) and implemented `WorldQuery`,
`ReadonlyWorldQuery`, and `ArchetypeFilter` it
- I also added documentation with an example and a unit test
I believe I've done everything right but this is my first contribution
and I'm not an ECS expert so someone who is should probably check my
implementation. I based it on what `Or<With<T>,>`, would do. The only
difference is that `Has` does not update component access - adding `Has`
to a query should never affect whether or not it is disjoint with
another query *I think*.
---
## Changelog
## Added
- Added `Has<T>` WorldQuery to find out whether or not an entity has a
particular component.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: JoJoJet <21144246+JoJoJet@users.noreply.github.com>
# Objective
We can currently set `camera.target` to either an `Image` or `Window`.
For OpenXR & WebXR we need to be able to render to a `TextureView`.
This partially addresses #115 as with the addition we can create
internal and external xr crates.
## Solution
A `TextureView` item is added to the `RenderTarget` enum. It holds an id
which is looked up by a `ManualTextureViews` resource, much like how
`Assets<Image>` works.
I believe this approach was first used by @kcking in their [xr
fork](eb39afd51b/crates/bevy_render/src/camera/camera.rs (L322)).
The only change is that a `u32` is used to index the textures as
`FromReflect` does not support `uuid` and I don't know how to implement
that.
---
## Changelog
### Added
Render: Added `RenderTarget::TextureView` as a `camera.target` option,
enabling rendering directly to a `TextureView`.
## Migration Guide
References to the `RenderTarget` enum will need to handle the additional
field, ie in `match` statements.
---
## Comments
- The [wgpu
work](c039a74884)
done by @expenses allows us to create framebuffer texture views from
`wgpu v0.15, bevy 0.10`.
- I got the WebXR techniques from the [xr
fork](https://github.com/dekuraan/xr-bevy) by @dekuraan.
- I have tested this with a wip [external webxr
crate](018e22bb06/crates/bevy_webxr/src/bevy_utils/xr_render.rs (L50))
on an Oculus Quest 2.
---------
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
Co-authored-by: Paul Hansen <mail@paul.rs>
# Objective
- Cleanup the `reflect.rs` file in `bevy_ecs`, it's very large and can
get difficult to navigate
## Solution
- Split the file into 3 modules, re-export the types in the
`reflect/mod.rs` to keep a perfectly identical API.
- Add **internal** architecture doc explaining how `ReflectComponent`
works. Note that this doc is internal only, since `component.rs` is not
exposed publicly.
### Tips to reviewers
To review this change properly, you need to compare it to the previous
version of `reflect.rs`. The diff from this PR does not help at all!
What you will need to do is compare `reflect.rs` individually with each
newly created file.
Here is how I did it:
- Adding my fork as remote `git remote add nicopap
https://github.com/nicopap/bevy.git`
- Checkout out the branch `git checkout nicopap/split_ecs_reflect`
- Checkout the old `reflect.rs` by running `git checkout HEAD~1 --
crates/bevy_ecs/src/reflect.rs`
- Compare the old with the new with `git diff --no-index
crates/bevy_ecs/src/reflect.rs crates/bevy_ecs/src/reflect/component.rs`
You could also concatenate everything into a single file and compare
against it:
- `cat
crates/bevy_ecs/src/reflect/{component,resource,map_entities,mod}.rs >
new_reflect.rs`
- `git diff --no-index crates/bevy_ecs/src/reflect.rs new_reflect.rs`
# Objective
Fix https://github.com/bevyengine/bevy/issues/1018 (Textures on the
`Plane` shape appear flipped).
This bug have been around for a very long time apparently, I tested it
was still there (see test code bellow) and sure enough, this image:
... is flipped vertically when used as a texture on a plane (in main,
0.10.1 and 0.9):
I'm pretty confused because this bug is so easy to fix, it has been
around for so long, it is easy to encounter, and PRs touching this code
still didn't fix it: https://github.com/bevyengine/bevy/pull/7546 To the
point where I'm wondering if it's actually intended. If it is, please
explain why and this PR can be changed to "mention that in the doc".
## Solution
Fix the UV mapping on the Plane shape
Here is how it looks after the PR
## Test code
```rust
use bevy::{
prelude::*,
};
fn main () {
App::new()
.add_plugins(DefaultPlugins)
.add_startup_system(setup)
.run();
}
fn setup(
mut commands: Commands,
assets: ResMut<AssetServer>,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<StandardMaterial>>,
) {
commands.spawn(Camera3dBundle {
transform: Transform::from_xyz(0., 3., 0.).looking_at(Vec3::ZERO, Vec3::NEG_Z),
..default()
});
let mesh = meshes.add(Mesh::from(shape::Plane::default()));
let texture_image = assets.load("test.png");
let material = materials.add(StandardMaterial {
base_color_texture: Some(texture_image),
..default()
});
commands.spawn(PbrBundle {
mesh,
material,
..default()
});
}
```
## Changelog
Fix textures on `Plane` shapes being flipped vertically.
## Migration Guide
Flip the textures you use on `Plane` shapes.
# Objective
Resolves#7558.
Systems that are known to never modify the world implement the trait
`ReadOnlySystem`. This is a perfect place to add a safe API for running
a system with a shared reference to a World.
---
## Changelog
- Added the trait method `ReadOnlySystem::run_readonly`, which allows a
system to be run using `&World`.
# Objective
- The function `QueryParIter::for_each_unchecked` is a footgun: the only
ways to use it soundly can be done in safe code using `for_each` or
`for_each_mut`. See [this discussion on
discord](https://discord.com/channels/691052431525675048/749335865876021248/1118642977275924583).
## Solution
- Make `for_each_unchecked` private.
---
## Changelog
- Removed `QueryParIter::for_each_unchecked`. All use-cases of this
method were either unsound or doable in safe code using `for_each` or
`for_each_mut`.
## Migration Guide
The method `QueryParIter::for_each_unchecked` has been removed -- use
`for_each` or `for_each_mut` instead. If your use case can not be
achieved using either of these, then your code was likely unsound.
If you have a use-case for `for_each_unchecked` that you believe is
sound, please [open an
issue](https://github.com/bevyengine/bevy/issues/new/choose).
# 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
Follow-up to #6404 and #8292.
Mutating the world through a shared reference is surprising, and it
makes the meaning of `&World` unclear: sometimes it gives read-only
access to the entire world, and sometimes it gives interior mutable
access to only part of it.
This is an up-to-date version of #6972.
## Solution
Use `UnsafeWorldCell` for all interior mutability. Now, `&World`
*always* gives you read-only access to the entire world.
---
## Changelog
TODO - do we still care about changelogs?
## Migration Guide
Mutating any world data using `&World` is now considered unsound -- the
type `UnsafeWorldCell` must be used to achieve interior mutability. The
following methods now accept `UnsafeWorldCell` instead of `&World`:
- `QueryState`: `get_unchecked`, `iter_unchecked`,
`iter_combinations_unchecked`, `for_each_unchecked`,
`get_single_unchecked`, `get_single_unchecked_manual`.
- `SystemState`: `get_unchecked_manual`
```rust
let mut world = World::new();
let mut query = world.query::<&mut T>();
// Before:
let t1 = query.get_unchecked(&world, entity_1);
let t2 = query.get_unchecked(&world, entity_2);
// After:
let world_cell = world.as_unsafe_world_cell();
let t1 = query.get_unchecked(world_cell, entity_1);
let t2 = query.get_unchecked(world_cell, entity_2);
```
The methods `QueryState::validate_world` and
`SystemState::matches_world` now take a `WorldId` instead of `&World`:
```rust
// Before:
query_state.validate_world(&world);
// After:
query_state.validate_world(world.id());
```
The methods `QueryState::update_archetypes` and
`SystemState::update_archetypes` now take `UnsafeWorldCell` instead of
`&World`:
```rust
// Before:
query_state.update_archetypes(&world);
// After:
query_state.update_archetypes(world.as_unsafe_world_cell_readonly());
```
# Objective
Implement borders for UI nodes.
Relevant discussion: #7785
Related: #5924, #3991
<img width="283" alt="borders"
src="https://user-images.githubusercontent.com/27962798/220968899-7661d5ec-6f5b-4b0f-af29-bf9af02259b5.PNG">
## Solution
Add an extraction function to draw the borders.
---
Can only do one colour rectangular borders due to the limitations of the
Bevy UI renderer.
Maybe it can be combined with #3991 eventually to add curved border
support.
## Changelog
* Added a component `BorderColor`.
* Added the `extract_uinode_borders` system to the UI Render App.
* Added the UI example `borders`
---------
Co-authored-by: Nico Burns <nico@nicoburns.com>
# Objective
The method `UnsafeWorldCell::read_change_tick` was renamed in #8588, but
I forgot to update a usage of this method in a doctest.
## Solution
Update the method call.
# Objective
To mirror the `Ref` added as `WorldQuery`, and the `Mut` in
`EntityMut::get_mut`, we add `EntityRef::get_ref`, which retrieves `T`
with tick information, but *immutably*.
## Solution
- Add the method in question, also add it to`UnsafeEntityCell` since
this seems to be the best way of getting that information.
Also update/add safety comments to neighboring code.
---
## Changelog
- Add `EntityRef::get_ref` to get an `Option<Ref<T>>` from `EntityRef`
---------
Co-authored-by: James Liu <contact@jamessliu.com>
# Objective
The method `QueryState::par_iter` does not currently force the query to
be read-only. This means you can unsoundly mutate a world through an
immutable reference in safe code.
```rust
fn bad_system(world: &World, mut query: Local<QueryState<&mut T>>) {
query.par_iter(world).for_each_mut(|mut x| *x = unsoundness);
}
```
## Solution
Use read-only versions of the `WorldQuery` types.
---
## Migration Guide
The function `QueryState::par_iter` now forces any world accesses to be
read-only, similar to how `QueryState::iter` works. Any code that
previously mutated the world using this method was *unsound*. If you
need to mutate the world, use `par_iter_mut` instead.
# Objective
Make a combined system cloneable if both systems are cloneable on their
own. This is necessary for using chained conditions (e.g
`cond1.and_then(cond2)`) with `distributive_run_if()`.
## Solution
Implement `Clone` for `CombinatorSystem<Func, A, B>` where `A, B:
Clone`.
# Objective
- Fixes#8782
## Solution
- Call `init_resource` on `register_diagnostic` so that a
`DiagnosticStore` gets initialized if it does not exist.
---------
Co-authored-by: François <mockersf@gmail.com>
# Objective
The `extract` function is given the main app world, and the subapp, not
vice versa as the comment would lead us to believe.
## Solution
Fix the doc.
# Objective
- Rename the `render::primitives::Plane` struct as to not confuse it
with `bevy_render::mesh::shape::Plane`
- Fixes https://github.com/bevyengine/bevy/issues/8730
## Solution
- Refactor the `render::primitives::Plane` struct to
`render::primitives::HalfSpace`
- Modify documentation to reflect this change
## Changelog
- Renamed `Plane` to `HalfSpace` to more accurately represent it's use
- Renamed `planes` member in `Frustum` to `half_spaces` to reflect
changes
## Migration Guide
- `Plane` has been renamed to `HalfSpace`
- `planes` member in `Frustum` has been renamed to `half_spaces`
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Nicola Papale <nicopap@users.noreply.github.com>
# Objective
When browsing the bevy source code to try and learn about
`bevy_core_pipeline`, I noticed that the `DrawFunctions` resources,
`sort_phase_system`s and texture preparation for the `Opaque3d` and
`AlphaMask3d` phase items are all set up in `bevy_core_pipeline`, while
the `Opaque3dPrepass` and `AlphaMask3dPrepass` phase items are only
*declared* in `bevy_core_pipeline`, and actually registered properly
with the renderer in `bevy_pbr`.
This means that, if I am trying to make crate that replaces `bevy_pbr`,
I need to make sure I manually fix this unfinished setup the same way
that `bevy_pbr` does. Worse, it means that if I try to use the
`PrepassNode` `bevy_core_pipeline` adds *without* fixing this, the
engine will simply crash because the `DrawFunctions<T>` resources cannot
be accessed.
The only advantage I can think of for bevy doing it this way is an
ambiguous performance save due to the prepass render phases not being
present unless you are using prepass materials with PBR.
## Solution
I have moved the registration of `DrawFunctions<T>`,
`sort_phase_system::<T>`, camera `RenderPhase` extraction, and texture
preparation for prepass's phase items into `bevy_core_pipeline`
alongside the equivalent code that sets up the `Opaque3d`, `AlphaMask3d`
and `Transparent3d` phase items.
Am open to tweaking this to improve the performance impact of prepass
things being around if the app doesn't use them if needed.
I've tested that the `shader_prepass` example still works with this
change.
# Objective
The AccessKit PR removed the loading of the image logo from the UI
example.
It also added some alt text with `TextStyle::default()` as a child of
the logo image node.
If you give an image node a child, then its size is no longer determined
by the measurefunc that preserves its aspect ratio. Instead, its width
and height are determined by the constraints set on the node and the
size of the contents of the node. In this case, the image node is set to
have a width of 500 with no constraints on its height. So it looks at
its child node to determine what height it should take. Because the
child has `TextStyle::default` it allocates no space for the text, the
height of the image node is set to zero and the logo isn't drawn.
Fixes#8805
## Solution
Load the image, and set min_size and max_size constraints of 500 by 125
pixels.
# 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
- Fixes#8811 .
## Solution
- Rename "write" method to "apply" in Command trait definition.
- Rename other implementations of command trait throughout bevy's code
base.
---
## Changelog
- Changed: `Command::write` has been changed to `Command::apply`
- Changed: `EntityCommand::write` has been changed to
`EntityCommand::apply`
## Migration Guide
- `Command::write` implementations need to be changed to implement
`Command::apply` instead. This is a mere name change, with no further
actions needed.
- `EntityCommand::write` implementations need to be changed to implement
`EntityCommand::apply` instead. This is a mere name change, with no
further actions needed.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- I can't map unsized type using `Ref::map` (for example `dyn Reflect`)
## Solution
- Allow unsized types (this is possible because `Ref` stores a reference
to `T`)
# Objective
`QueryState` exposes a `get_manual` and `iter_manual` method. However,
there is now `iter_many_manual`.
`iter_many_manual` is useful when you have a `&World` (eg: the `world`
in a `Scene`) and want to run a query several times on it (eg:
iteratively navigate a hierarchy by calling `iter_many` on `Children`
component).
`iter_many`'s need for a `&mut World` makes the API much less flexible.
The exclusive access pattern requires doing some very funky dance and
excludes a category of algorithms for hierarchy traversal.
## Solution
- Add a `iter_many_manual` method to `QueryState`
### Alternative
My current workaround is to use `get_manual`. However, this doesn't
benefit from the optimizations on `QueryManyIter`.
---
## Changelog
- Add a `iter_many_manual` method to `QueryState`
# 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>
