# Objective
- The old post processing example doesn't use the actual post processing
features of bevy. It also has some issues with resizing. It's also
causing some confusion for people because accessing the prepass textures
from it is not easy.
- There's already a render to texture example
- At this point, it's mostly obsolete since the post_process_pass
example is more complete and shows the recommended way to do post
processing in bevy. It's a bit more complicated, but it's well
documented and I'm working on simplifying it even more
## Solution
- Remove the old post_processing example
- Rename post_process_pass to post_processing
## Reviewer Notes
The diff is really noisy because of the rename, but I didn't change any
code in the example.
---------
Co-authored-by: James Liu <contact@jamessliu.com>
# Objective
- Example Alien Cake Addict exit when the player lose, it's not supposed
to
## Solution
- Don't despawn the window
---------
Co-authored-by: ira <JustTheCoolDude@gmail.com>
# Objective
The default StandardMaterial values of `pbr_material.rs` and
`pbr_types.wgsl` are out of sync.
I think they are out of sync since
https://github.com/bevyengine/bevy/pull/7664.
## Solution
Adapt the values: `metallic = 0.0`, `perceptual_roughness = 0.5`.
# Objective
We don't have a constructor function for `UiRect` that sets uniform
horizontal and vertical values, even though it is a common pattern.
## Solution
Add a constructor function to `UiRect` called `axes`, that sets both
`left` and `right` to the same given horizontal value,
and sets both `top` and `bottom` to same given vertical value.
## Changelog
* Added a constructor function `axes` to `UiRect`.
# Objective
fixes#8348
## Solution
- Uses multi-line string with backslashes allowing rustfmt to work
properly in the surrounding area.
---------
Co-authored-by: François <mockersf@gmail.com>
# Objective
The behavior of change detection within `PipeSystem` is very tricky and
subtle, and is not currently covered by any of our tests as far as I'm
aware.
# Objective
Fixes#8367
## Solution
Added a comment explaining why linear filtering is required in this
example, with formatting focused specifically on `ImagePlugin` to avoid
confusion
# 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
# Objective
The method `World::try_run_schedule` currently panics if the `Schedules`
resource does not exist, but it should just return an `Err`. Similarly,
`World::add_schedule` panics unnecessarily if the resource does not
exist.
Also, the documentation for `World::add_schedule` is completely wrong.
## Solution
When the `Schedules` resource does not exist, we now treat it the same
as if it did exist but was empty. When calling `add_schedule`, we
initialize it if it does not exist.
# Objective
Fixes#8215 and #8152. When systems panic, it causes the main thread to
panic as well, which clutters the output.
## Solution
Resolves the panic in the multi-threaded scheduler. Also adds an extra
message that tells the user the system that panicked.
Using the example from the issue, here is what the messages now look
like:
```rust
use bevy::prelude::*;
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_systems(Update, panicking_system)
.run();
}
fn panicking_system() {
panic!("oooh scary");
}
```
### Before
```
Compiling bevy_test v0.1.0 (E:\Projects\Rust\bevy_test)
Finished dev [unoptimized + debuginfo] target(s) in 2m 58s
Running `target\debug\bevy_test.exe`
2023-03-30T22:19:09.234932Z INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "Windows 10 Pro", kernel: "19044", cpu: "AMD Ryzen 5 2600 Six-Core Processor", core_count: "6", memory: "15.9 GiB" }
thread 'Compute Task Pool (5)' panicked at 'oooh scary', src\main.rs:11:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'Compute Task Pool (5)' panicked at 'A system has panicked so the executor cannot continue.: RecvError', E:\Projects\Rust\bevy\crates\bevy_ecs\src\schedule\executor\multi_threaded.rs:194:60
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', E:\Projects\Rust\bevy\crates\bevy_tasks\src\task_pool.rs:376:49
error: process didn't exit successfully: `target\debug\bevy_test.exe` (exit code: 101)
```
### After
```
Compiling bevy_test v0.1.0 (E:\Projects\Rust\bevy_test)
Finished dev [unoptimized + debuginfo] target(s) in 2.39s
Running `target\debug\bevy_test.exe`
2023-03-30T22:11:24.748513Z INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "Windows 10 Pro", kernel: "19044", cpu: "AMD Ryzen 5 2600 Six-Core Processor", core_count: "6", memory: "15.9 GiB" }
thread 'Compute Task Pool (5)' panicked at 'oooh scary', src\main.rs:11:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Encountered a panic in system `bevy_test::panicking_system`!
Encountered a panic in system `bevy_app::main_schedule::Main::run_main`!
error: process didn't exit successfully: `target\debug\bevy_test.exe` (exit code: 101)
```
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: François <mockersf@gmail.com>
# Objective
Fix#8191.
Currently, a state transition will be triggered whenever the `NextState`
resource has a value, even if that "transition" is to the same state as
the previous one. This caused surprising/meaningless behavior, such as
the existence of an `OnTransition { from: A, to: A }` schedule.
## Solution
State transition schedules now only run if the new state is not equal to
the old state. Change detection works the same way, only being triggered
when the states compare not equal.
---
## Changelog
- State transition schedules are no longer run when transitioning to and
from the same state.
## Migration Guide
State transitions are now only triggered when the exited and entered
state differ. This means that if the world is currently in state `A`,
the `OnEnter(A)` schedule (or `OnExit`) will no longer be run if you
queue up a state transition to the same state `A`.
# Objective
Noticed while writing #7728 that we are using `trace!` logs in our event
functions. This has shown to have significant overhead, even trace level
logs are disabled globally, as seen in #7639.
## Solution
Use the `detailed_trace!` macro introduced in #7639. Also removed the
`event_trace` function that was only used in one location.
---
## Changelog
Changed: Event trace logs are now feature gated behind the
`detailed-trace` feature.
# Objective
Fix#8321
## Solution
The `old_viewport_size` that is used to detect whether the viewport has
changed was not being updated and thus always `None`.
# Objective
Adds a new resource to control a global volume.
Fixes#7690
---
## Solution
Added a new resource to control global volume, this is then multiplied
with an audio sources volume to get the output volume, individual audio
sources can opt out of this my enabling the `absolute_volume` field in
`PlaybackSettings`.
---
## Changelog
### Added
- `GlobalVolume` a resource to control global volume (in prelude).
- `global_volume` field to `AudioPlugin` or setting the initial value of
`GlobalVolume`.
- `Volume` enum that can be `Relative` or `Absolute`.
- `VolumeLevel` struct for defining a volume level.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
when a mesh uses zero for all bone weights, vertices end up in the
middle of the screen.
## Solution
we can address this by explicitly setting the first bone weight to 1
when the weights are given as zero. this is the approach taken by
[unity](https://forum.unity.com/threads/whats-the-problem-with-this-import-fbx-warning.133736/)
(although that also sets the bone index to zero) and
[three.js](94c1a4b86f/src/objects/SkinnedMesh.js (L98)),
and likely other engines.
## Alternatives
it does add a bit of overhead, and users can always fix this themselves,
though it's a bit awkward particularly with gltfs.
(note - this is for work so my sme status shouldn't apply)
---------
Co-authored-by: ira <JustTheCoolDude@gmail.com>
# Objective
- Fix#7263
This has nothing to do with #7024. This is for the case where the
user opted to **not** keep the same global transform on update.
## Solution
- Add a `RemovedComponent<Parent>` to `propagate_transforms`
- Add a `RemovedComponent<Parent>` and `Local<Vec<Entity>>` to
`sync_simple_transforms`
- Add test to make sure all of this works.
### Performance note
This should only incur a cost in cases where a parent is removed.
A minimal overhead (one look up in the `removed_components`
sparse set) per root entities without children which transform didn't
change. A `Vec` the size of the largest number of entities removed
with a `Parent` component in a single frame, and a binary search on
a `Vec` per root entities.
It could slow up considerably in situations where a lot of entities are
orphaned consistently during every frame, since
`sync_simple_transforms` is not parallel. But in this situation,
it is likely that the overhead of archetype updates overwhelms
everything.
---
## Changelog
- Fix the `GlobalTransform` not getting updated when `Parent` is removed
## Migration Guide
- If you called `bevy_transform::systems::sync_simple_transforms` and
`bevy_transform::systems::propagate_transforms` (which is not
re-exported by bevy) you need to account for the additional
`RemovedComponents<Parent>` parameter.
---------
Co-authored-by: vyb <vyb@users.noreply.github.com>
Co-authored-by: JoJoJet <21144246+JoJoJet@users.noreply.github.com>
Fixes#8333
# Objective
Fixes issue which causes failure to compile if using
`#![deny(missing_docs)]`.
## Solution
Added some very basic commenting to the generated read-only fields.
honestly I feel this to be up for debate since the comments are very
basic and give very little useful information but the purpose of this PR
is to fix the issue at hand.
---
## Changelog
Added comments to the derive macro and the projects now successfully
compile.
---------
Co-authored-by: lupan <kallll5@hotmail.com>
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
# Objective
The clippy lint `type_complexity` is known not to play well with bevy.
It frequently triggers when writing complex queries, and taking the
lint's advice of using a type alias almost always just obfuscates the
code with no benefit. Because of this, this lint is currently ignored in
CI, but unfortunately it still shows up when viewing bevy code in an
IDE.
As someone who's made a fair amount of pull requests to this repo, I
will say that this issue has been a consistent thorn in my side. Since
bevy code is filled with spurious, ignorable warnings, it can be very
difficult to spot the *real* warnings that must be fixed -- most of the
time I just ignore all warnings, only to later find out that one of them
was real after I'm done when CI runs.
## Solution
Suppress this lint in all bevy crates. This was previously attempted in
#7050, but the review process ended up making it more complicated than
it needs to be and landed on a subpar solution.
The discussion in https://github.com/rust-lang/rust-clippy/pull/10571
explores some better long-term solutions to this problem. Since there is
no timeline on when these solutions may land, we should resolve this
issue in the meantime by locally suppressing these lints.
### Unresolved issues
Currently, these lints are not suppressed in our examples, since that
would require suppressing the lint in every single source file. They are
still ignored in CI.
# Objective
- Add a new example that helps debug different UI overflow scenarios
- This example tests the clipping behavior for images and text when the
node is moved, scaled or rotated.
## Solution
- Add a new `overflow_debug` example
# Preview
**Note:** Only top-left is working properly right now.
https://user-images.githubusercontent.com/188612/227629093-26c94c67-1781-437d-8410-e854b6f1adc1.mp4
---
Related #8095, #8167
---------
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
Co-authored-by: ickshonpe <david.curthoys@googlemail.com>
# Objective
Make the coordinate systems of screen-space items (cursor position, UI,
viewports, etc.) consistent.
## Solution
Remove the weird double inversion of the cursor position's Y origin.
Once in bevy_winit to the bottom and then again in bevy_ui back to the
top.
This leaves the origin at the top left like it is in every other popular
app framework.
Update the `world_to_viewport`, `viewport_to_world`, and
`viewport_to_world_2d` methods to flip the Y origin (as they should
since the viewport coordinates were always relative to the top left).
## Migration Guide
`Window::cursor_position` now returns the position of the cursor
relative to the top left instead of the bottom left.
This now matches other screen-space coordinates like
`RelativeCursorPosition`, UI, and viewports.
The `world_to_viewport`, `viewport_to_world`, and `viewport_to_world_2d`
methods on `Camera` now return/take the viewport position relative to
the top left instead of the bottom left.
If you were using `world_to_viewport` to position a UI node the returned
`y` value should now be passed into the `top` field on `Style` instead
of the `bottom` field.
Note that this might shift the position of the UI node as it is now
anchored at the top.
If you were passing `Window::cursor_position` to `viewport_to_world` or
`viewport_to_world_2d` no change is necessary.
# Objective
Text glyphs that were clipped were not sized correctly because the
transform extracted from the `extract_text_uinodes` had a scaling on it
that wasn't accounted for.
fixes#8167
## Solution
Remove the scaling from the transform and multiply the size of the
glyphs by the inverse of the scale factor.
# Objective
Add helper functions to `UiImage` for creating flipped images.
## Changelog
* Added `with_flip_x` and `with_flip_y` methods to `UiImage` that return
the `UiImage` flipped along the respective axis.
# Objective
Exposes `empty()` method for `AudioSink`.
Based on `0.10.0`, should be a non-breaking change.
---
## Changelog
- Expose `empty()` method for `AudioSink`
- Add `AudioSink::empty()` example
---------
Co-authored-by: hank <hank@hank.co.in>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
When a `CalculatedSize` component from a UI Node entity is removed, the
corresponding Taffy measure isn't removed which will mess up the layout
in confusing, unpredictable ways.
## Solution
Iterate through all the entities with removed `CalculatedSize`
components and remove the corresponding Taffy measures.
# Objective
In the
[`Text`](3442a13d2c/crates/bevy_text/src/text.rs (L18))
struct the field is named: `linebreak_behaviour`, the British spelling
of _behavior_.
**Update**, also found:
- `FileDragAndDrop::HoveredFileCancelled`
- `TouchPhase::Cancelled`
- `Touches.just_cancelled`
The majority of all spelling is in the US but when you have a lot of
contributors across the world, sometimes
spelling differences can pop up in APIs such as in this case.
For consistency, I think it would be worth a while to ensure that the
API is persistent.
Some examples:
`from_reflect.rs` has `DefaultBehavior`
TextStyle has `color` and uses the `Color` struct.
In `bevy_input/src/Touch.rs` `TouchPhase::Cancelled` and _canceled_ are
used interchangeably in the documentation
I've found that there is also the same type of discrepancies in the
documentation, though this is a low priority but is worth checking.
**Update**: I've now checked the documentation (See #8291)
## Solution
I've only renamed the inconsistencies that have breaking changes and
documentation pertaining to them. The rest of the documentation will be
changed via #8291.
Do note that the winit API is written with UK spelling, thus this may be
a cause for confusion:
`winit::event::TouchPhase::Cancelled => TouchPhase::Canceled`
`winit::event::WindowEvent::HoveredFileCancelled` -> Related to
`FileDragAndDrop::HoveredFileCanceled`
But I'm hoping to maybe outline other spelling inconsistencies in the
API, and maybe an addition to the contribution guide.
---
## Changelog
- `Text` field `linebreak_behaviour` has been renamed to
`linebreak_behavior`.
- Event `FileDragAndDrop::HoveredFileCancelled` has been renamed to
`HoveredFileCanceled`
- Function `Touches.just_cancelled` has been renamed to
`Touches.just_canceled`
- Event `TouchPhase::Cancelled` has been renamed to
`TouchPhase::Canceled`
## Migration Guide
Update where `linebreak_behaviour` is used to `linebreak_behavior`
Updated the event `FileDragAndDrop::HoveredFileCancelled` where used to
`HoveredFileCanceled`
Update `Touches.just_cancelled` where used as `Touches.just_canceled`
The event `TouchPhase::Cancelled` is now called `TouchPhase::Canceled`
# Objective
- RenderGraphExt was merged, but only used in limited situations
## Solution
- Fix some remaining issues with the existing api
- Use the new api in the main pass and mass writeback
- Add CORE_2D and CORE_3D constant to make render_graph code shorter
# Objective
While working on #8299, I noticed that we're using a `capacity` field,
even though `wgpu::Buffer` exposes a `size` accessor that does the same
thing.
## Solution
Remove it from all buffer wrappers. Use `wgpu::Buffer::size` instead.
Default to 0 if no buffer has been allocated yet.
# Objective
Fixes#8284. `values` is being pushed to separately from the actual
scratch buffer in `DynamicUniformBuffer::push` and
`DynamicStorageBuffer::push`. In both types, `values` is really only
used to track the number of elements being added to the buffer, yet is
causing extra allocations, size increments and excess copies.
## Solution
Remove it and its remaining uses. Replace it with accesses to `scratch`
instead.
I removed the `len` accessor, as it may be non-trivial to compute just
from `scratch`. If this is still desirable to have, we can keep a `len`
member field to track it instead of relying on `scratch`.
# Objective
State requires a kind of awkward `state.0` to get the current state and
exposes the field directly to manipulation.
## Solution
Make it accessible through a getter method as well as privatize the
field to make sure false assumptions about setting the state aren't
made.
## Migration Guide
- Use `State::get` instead of accessing the tuple field directly.
# Objective
Closes#7821. A good chunk of performance related issues filed are tough
to take action on without much deeper investigation by the author, who
may or may not be responsive after filing the issue.
## Solution
Add a performance regression issue template and use it to direct users
to take a more proactive role in investigating the source of the
regression.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: François <mockersf@gmail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
- Adding a node to the render_graph can be quite verbose and error prone
because there's a lot of moving parts to it.
## Solution
- Encapsulate this in a simple utility method
- Mostly intended for optional nodes that have specific ordering
- Requires that the `Node` impl `FromWorld`, but every internal node is
built using a new function taking a `&mut World` so it was essentially
already `FromWorld`
- Use it for the bloom, fxaa and taa, nodes.
- The main nodes don't use it because they rely more on the order of
many nodes being added
---
## Changelog
- Impl `FromWorld` for `BloomNode`, `FxaaNode` and `TaaNode`
- Added `RenderGraph::add_node_edges()`
- Added `RenderGraph::sub_graph()`
- Added `RenderGraph::sub_graph_mut()`
- Added `RenderGraphApp`, `RenderGraphApp::add_render_graph_node`,
`RenderGraphApp::add_render_graph_edges`,
`RenderGraphApp::add_render_graph_edge`
## Notes
~~This was taken out of https://github.com/bevyengine/bevy/pull/7995
because it works on it's own. Once the linked PR is done, the new
`add_node()` will be simplified a bit since the input/output params
won't be necessary.~~
This feature will be useful in most of the upcoming render nodes so it's
impact will be more relevant at that point.
Partially fixes#7985
## Future work
* Add a way to automatically label nodes or at least make it part of the
trait. This would remove one more field from the functions added in this
PR
* Use it in the main pass 2d/3d
---------
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
The `#[derive(WorldQuery)]` macro currently only supports structs with
named fields.
Same motivation as #6957. Remove sharp edges from the derive macro, make
it just work more often.
## Solution
Support tuple structs.
---
## Changelog
+ Added support for tuple structs to the `#[derive(WorldQuery)]` macro.
# Objective
bevy-scene does not have a reason to depend on bevy-render except to
include the `Visibility` and `ComputedVisibility` components. Including
that in the dependency chain is unnecessary for people not using
`bevy_render`.
Also fixed a problem where compilation fails when the `serialize`
feature was not enabled.
## Solution
This was added in #5335 to address some of the problems caused by #5310.
Imo the user just always have to remember to include `VisibilityBundle`
when they spawn `SceneBundle` or `DynamicSceneBundle`, but that will be
a breaking change. This PR makes `bevy_render` an optional dependency of
`bevy_scene` instead to respect the existing behavior.
# Objective
While migrating the engine to use the `Tick` type in #7905, I forgot to
update `UnsafeWorldCell::increment_change_tick`.
## Solution
Update the function.
---
## Changelog
- The function `UnsafeWorldCell::increment_change_tick` is now
strongly-typed, returning a value of type `Tick` instead of a raw `u32`.
## Migration Guide
The function `UnsafeWorldCell::increment_change_tick` is now
strongly-typed, returning a value of type `Tick` instead of a raw `u32`.
# Objective
TAA, FXAA, and some other post processing effects can cause the image to
become blurry. Sharpening helps to counteract that.
## Solution
~~This is a port of AMD's Contrast Adaptive Sharpening (I ported it from
the
[SweetFX](https://github.com/CeeJayDK/SweetFX/blob/master/Shaders/CAS.fx)
version, which is still MIT licensed). CAS is a good sharpening
algorithm that is better at avoiding the full screen oversharpening
artifacts that simpler algorithms tend to create.~~
This is a port of AMD's Robust Contrast Adaptive Sharpening (RCAS) which
they developed for FSR 1 ([and continue to use in FSR
2](149cf26e12/src/ffx-fsr2-api/shaders/ffx_fsr1.h (L599))).
RCAS is a good sharpening algorithm that is better at avoiding the full
screen oversharpening artifacts that simpler algorithms tend to create.
---
## Future Work
- Consider porting this to a compute shader for potentially better
performance. (In my testing it is currently ridiculously cheap (0.01ms
in Bistro at 1440p where I'm GPU bound), so this wasn't a priority,
especially since it would increase complexity due to still needing the
non-compute version for webgl2 support).
---
## Changelog
- Added Contrast Adaptive Sharpening.
---------
Co-authored-by: JMS55 <47158642+JMS55@users.noreply.github.com>
# Objective
- Closes https://github.com/bevyengine/bevy/issues/8008
## Solution
- Add a skybox plugin that renders a fullscreen triangle, and then
modifies the vertices in a vertex shader to enforce that it renders as a
skybox background.
- Skybox is run at the end of MainOpaquePass3dNode.
- In the future, it would be nice to get something like bevy_atmosphere
built-in, and have a default skybox+environment map light.
---
## Changelog
- Added `Skybox`.
- `EnvironmentMapLight` now renders in the correct orientation.
## Migration Guide
- Flip `EnvironmentMapLight` maps if needed to match how they previously
rendered (which was backwards).
---------
Co-authored-by: Robert Swain <robert.swain@gmail.com>
Co-authored-by: robtfm <50659922+robtfm@users.noreply.github.com>
# Objective
Some examples still manually implement the States trait, even though
manual implementation is no longer needed as there is now the derive
macro for that.
---------
Signed-off-by: Natalia Asteria <fortressnordlys@outlook.com>
These traits are both implemented, but not reflected, requiring user
code to do `app.register_type_data::<BloomSettings,
ReflectDefault>().register_type_data::<BloomSettings,
ReflectComponent>()` to make these usable via reflection.
# Objective
The type `&World` is currently in an awkward place, since it has two
meanings:
1. Read-only access to the entire world.
2. Interior mutable access to the world; immutable and/or mutable access
to certain portions of world data.
This makes `&World` difficult to reason about, and surprising to see in
function signatures if one does not know about the interior mutable
property.
The type `UnsafeWorldCell` was added in #6404, which is meant to
alleviate this confusion by adding a dedicated type for interior mutable
world access. However, much of the engine still treats `&World` as an
interior mutable-ish type. One of those places is `SystemParam`.
## Solution
Modify `SystemParam::get_param` to accept `UnsafeWorldCell` instead of
`&World`. Simplify the safety invariants, since the `UnsafeWorldCell`
type encapsulates the concept of constrained world access.
---
## Changelog
`SystemParam::get_param` now accepts an `UnsafeWorldCell` instead of
`&World`. This type provides a high-level API for unsafe interior
mutable world access.
## Migration Guide
For manual implementers of `SystemParam`: the function `get_item` now
takes `UnsafeWorldCell` instead of `&World`. To access world data, use:
* `.get_entity()`, which returns an `UnsafeEntityCell` which can be used
to access component data.
* `get_resource()` and its variants, to access resource data.
# Objective
Fix typo in bevy_reflect README: `MyType` is a struct and not a trait,
so `&dyn MyType` is incorrect.
## Solution
Replace `&dyn MyType` with `&dyn DoThing`
# Objective
The function `SyncUnsafeCell::from_mut` returns `&SyncUnsafeCell<T>`,
even though it could return `&mut SyncUnsafeCell<T>`. This means it is
not possible to call `get_mut` on the returned value, so you need to use
unsafe code to get exclusive access back.
## Solution
Return `&mut Self` instead of `&Self` in `SyncUnsafeCell::from_mut`.
This is consistent with my proposal for `UnsafeCell::from_mut`:
https://github.com/rust-lang/libs-team/issues/198.
Replace an unsafe pointer dereference with a safe call to `get_mut`.
---
## Changelog
+ The function `bevy_utils::SyncUnsafeCell::get_mut` now returns a value
of type `&mut SyncUnsafeCell<T>`. Previously, this returned an immutable
reference.
## Migration Guide
The function `bevy_utils::SyncUnsafeCell::get_mut` now returns a value
of type `&mut SyncUnsafeCell<T>`. Previously, this returned an immutable
reference.
# Objective
The documentation on `QueryState::for_each_unchecked` incorrectly says
that it can only be used with read-only queries.
## Solution
Remove the inaccurate sentence.
