# Objective
- Fixes#16152
## Solution
- Put `bevy_window` and `bevy_a11y` behind the `bevy_window` feature.
they were the only difference
- Add `ScheduleRunnerPlugin` to the `DefaultPlugins` when `bevy_window`
is disabled
- Remove `HeadlessPlugins`
- Update the `headless` example
# Objective
Fixes#15940
## Solution
Remove the `pub use` and fix the compile errors.
Make `bevy_image` available as `bevy::image`.
## Testing
Feature Frenzy would be good here! Maybe I'll learn how to use it if I
have some time this weekend, or maybe a reviewer can use it.
## Migration Guide
Use `bevy_image` instead of `bevy_render::texture` items.
---------
Co-authored-by: chompaa <antony.m.3012@gmail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
The `headless_renderer` example is meant to showcase running bevy as a
headless renderer, but if run without a display server (for example,
over an SSH connection), a panic occurs in `bevy_winit` despite never
creating a window:
```rust
bevy_winit-0.14.1/src/lib.rs:132:14:
winit-0.30.5/src/platform_impl/linux/mod.rs:
neither WAYLAND_DISPLAY nor WAYLAND_SOCKET nor DISPLAY is set.
```
This example should run successfully in situations without an available
display server, as although the GPU is used for rendering, no window is
ever created.
## Solution
Disabling WinitPlugin, where the above panic occurs, allows the example
to run in a fully headless environment.
## Testing
- I tested this change in normal circumstances with a display server (on
macOS Sequoia and Asahi Linux) and behavior was normal.
- I tested with no display server by connecting via SSH, and running the
example (on Asahi Linux). Previously this panics, but with this change
it runs normally.
## Considerations
- One could argue that ultimately the user should not need to remove
`WinitPlugin`, and instead bevy should only throw the above panic when
the application first attempts to create a window.
# Objective
Continue improving the user experience of our UI Node API in the
direction specified by [Bevy's Next Generation Scene / UI
System](https://github.com/bevyengine/bevy/discussions/14437)
## Solution
As specified in the document above, merge `Style` fields into `Node`,
and move "computed Node fields" into `ComputedNode` (I chose this name
over something like `ComputedNodeLayout` because it currently contains
more than just layout info. If we want to break this up / rename these
concepts, lets do that in a separate PR). `Style` has been removed.
This accomplishes a number of goals:
## Ergonomics wins
Specifying both `Node` and `Style` is now no longer required for
non-default styles
Before:
```rust
commands.spawn((
Node::default(),
Style {
width: Val::Px(100.),
..default()
},
));
```
After:
```rust
commands.spawn(Node {
width: Val::Px(100.),
..default()
});
```
## Conceptual clarity
`Style` was never a comprehensive "style sheet". It only defined "core"
style properties that all `Nodes` shared. Any "styled property" that
couldn't fit that mold had to be in a separate component. A "real" style
system would style properties _across_ components (`Node`, `Button`,
etc). We have plans to build a true style system (see the doc linked
above).
By moving the `Style` fields to `Node`, we fully embrace `Node` as the
driving concept and remove the "style system" confusion.
## Next Steps
* Consider identifying and splitting out "style properties that aren't
core to Node". This should not happen for Bevy 0.15.
---
## Migration Guide
Move any fields set on `Style` into `Node` and replace all `Style`
component usage with `Node`.
Before:
```rust
commands.spawn((
Node::default(),
Style {
width: Val::Px(100.),
..default()
},
));
```
After:
```rust
commands.spawn(Node {
width: Val::Px(100.),
..default()
});
```
For any usage of the "computed node properties" that used to live on
`Node`, use `ComputedNode` instead:
Before:
```rust
fn system(nodes: Query<&Node>) {
for node in &nodes {
let computed_size = node.size();
}
}
```
After:
```rust
fn system(computed_nodes: Query<&ComputedNode>) {
for computed_node in &computed_nodes {
let computed_size = computed_node.size();
}
}
```
# Objective
- closes#15866
## Solution
- Simply migrate where possible.
## Testing
- Expect that CI will do most of the work. Examples is another way of
testing this, as most of the work is in that area.
---
## Notes
For now, this PR doesn't migrate `QueryState::single` and friends as for
now, this look like another issue. So for example, QueryBuilders that
used single or `World::query` that used single wasn't migrated. If there
is a easy way to migrate those, please let me know.
Most of the uses of `Query::single` were removed, the only other uses
that I found was related to tests of said methods, so will probably be
removed when we remove `Query::single`.
**Ready for review. Examples migration progress: 100%.**
# Objective
- Implement https://github.com/bevyengine/bevy/discussions/15014
## Solution
This implements [cart's
proposal](https://github.com/bevyengine/bevy/discussions/15014#discussioncomment-10574459)
faithfully except for one change. I separated `TextSpan` from
`TextSpan2d` because `TextSpan` needs to require the `GhostNode`
component, which is a `bevy_ui` component only usable by UI.
Extra changes:
- Added `EntityCommands::commands_mut` that returns a mutable reference.
This is a blocker for extension methods that return something other than
`self`. Note that `sickle_ui`'s `UiBuilder::commands` returns a mutable
reference for this reason.
## Testing
- [x] Text examples all work.
---
## Showcase
TODO: showcase-worthy
## Migration Guide
TODO: very breaking
### Accessing text spans by index
Text sections are now text sections on different entities in a
hierarchy, Use the new `TextReader` and `TextWriter` system parameters
to access spans by index.
Before:
```rust
fn refresh_text(mut query: Query<&mut Text, With<TimeText>>, time: Res<Time>) {
let text = query.single_mut();
text.sections[1].value = format_time(time.elapsed());
}
```
After:
```rust
fn refresh_text(
query: Query<Entity, With<TimeText>>,
mut writer: UiTextWriter,
time: Res<Time>
) {
let entity = query.single();
*writer.text(entity, 1) = format_time(time.elapsed());
}
```
### Iterating text spans
Text spans are now entities in a hierarchy, so the new `UiTextReader`
and `UiTextWriter` system parameters provide ways to iterate that
hierarchy. The `UiTextReader::iter` method will give you a normal
iterator over spans, and `UiTextWriter::for_each` lets you visit each of
the spans.
---------
Co-authored-by: ickshonpe <david.curthoys@googlemail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
Yet another PR for migrating stuff to required components. This time,
cameras!
## Solution
As per the [selected
proposal](https://hackmd.io/tsYID4CGRiWxzsgawzxG_g#Combined-Proposal-1-Selected),
deprecate `Camera2dBundle` and `Camera3dBundle` in favor of `Camera2d`
and `Camera3d`.
Adding a `Camera` without `Camera2d` or `Camera3d` now logs a warning,
as suggested by Cart [on
Discord](https://discord.com/channels/691052431525675048/1264881140007702558/1291506402832945273).
I would personally like cameras to work a bit differently and be split
into a few more components, to avoid some footguns and confusing
semantics, but that is more controversial, and shouldn't block this core
migration.
## Testing
I ran a few 2D and 3D examples, and tried cameras with and without
render graphs.
---
## Migration Guide
`Camera2dBundle` and `Camera3dBundle` have been deprecated in favor of
`Camera2d` and `Camera3d`. Inserting them will now also insert the other
components required by them automatically.
# Objective
A big step in the migration to required components: meshes and
materials!
## Solution
As per the [selected
proposal](https://hackmd.io/@bevy/required_components/%2Fj9-PnF-2QKK0on1KQ29UWQ):
- Deprecate `MaterialMesh2dBundle`, `MaterialMeshBundle`, and
`PbrBundle`.
- Add `Mesh2d` and `Mesh3d` components, which wrap a `Handle<Mesh>`.
- Add `MeshMaterial2d<M: Material2d>` and `MeshMaterial3d<M: Material>`,
which wrap a `Handle<M>`.
- Meshes *without* a mesh material should be rendered with a default
material. The existence of a material is determined by
`HasMaterial2d`/`HasMaterial3d`, which is required by
`MeshMaterial2d`/`MeshMaterial3d`. This gets around problems with the
generics.
Previously:
```rust
commands.spawn(MaterialMesh2dBundle {
mesh: meshes.add(Circle::new(100.0)).into(),
material: materials.add(Color::srgb(7.5, 0.0, 7.5)),
transform: Transform::from_translation(Vec3::new(-200., 0., 0.)),
..default()
});
```
Now:
```rust
commands.spawn((
Mesh2d(meshes.add(Circle::new(100.0))),
MeshMaterial2d(materials.add(Color::srgb(7.5, 0.0, 7.5))),
Transform::from_translation(Vec3::new(-200., 0., 0.)),
));
```
If the mesh material is missing, previously nothing was rendered. Now,
it renders a white default `ColorMaterial` in 2D and a
`StandardMaterial` in 3D (this can be overridden). Below, only every
other entity has a material:
Why white? This is still open for discussion, but I think white makes
sense for a *default* material, while *invalid* asset handles pointing
to nothing should have something like a pink material to indicate that
something is broken (I don't handle that in this PR yet). This is kind
of a mix of Godot and Unity: Godot just renders a white material for
non-existent materials, while Unity renders nothing when no materials
exist, but renders pink for invalid materials. I can also change the
default material to pink if that is preferable though.
## Testing
I ran some 2D and 3D examples to test if anything changed visually. I
have not tested all examples or features yet however. If anyone wants to
test more extensively, it would be appreciated!
## Implementation Notes
- The relationship between `bevy_render` and `bevy_pbr` is weird here.
`bevy_render` needs `Mesh3d` for its own systems, but `bevy_pbr` has all
of the material logic, and `bevy_render` doesn't depend on it. I feel
like the two crates should be refactored in some way, but I think that's
out of scope for this PR.
- I didn't migrate meshlets to required components yet. That can
probably be done in a follow-up, as this is already a huge PR.
- It is becoming increasingly clear to me that we really, *really* want
to disallow raw asset handles as components. They caused me a *ton* of
headache here already, and it took me a long time to find every place
that queried for them or inserted them directly on entities, since there
were no compiler errors for it. If we don't remove the `Component`
derive, I expect raw asset handles to be a *huge* footgun for users as
we transition to wrapper components, especially as handles as components
have been the norm so far. I personally consider this to be a blocker
for 0.15: we need to migrate to wrapper components for asset handles
everywhere, and remove the `Component` derive. Also see
https://github.com/bevyengine/bevy/issues/14124.
---
## Migration Guide
Asset handles for meshes and mesh materials must now be wrapped in the
`Mesh2d` and `MeshMaterial2d` or `Mesh3d` and `MeshMaterial3d`
components for 2D and 3D respectively. Raw handles as components no
longer render meshes.
Additionally, `MaterialMesh2dBundle`, `MaterialMeshBundle`, and
`PbrBundle` have been deprecated. Instead, use the mesh and material
components directly.
Previously:
```rust
commands.spawn(MaterialMesh2dBundle {
mesh: meshes.add(Circle::new(100.0)).into(),
material: materials.add(Color::srgb(7.5, 0.0, 7.5)),
transform: Transform::from_translation(Vec3::new(-200., 0., 0.)),
..default()
});
```
Now:
```rust
commands.spawn((
Mesh2d(meshes.add(Circle::new(100.0))),
MeshMaterial2d(materials.add(Color::srgb(7.5, 0.0, 7.5))),
Transform::from_translation(Vec3::new(-200., 0., 0.)),
));
```
If the mesh material is missing, a white default material is now used.
Previously, nothing was rendered if the material was missing.
The `WithMesh2d` and `WithMesh3d` query filter type aliases have also
been removed. Simply use `With<Mesh2d>` or `With<Mesh3d>`.
---------
Co-authored-by: Tim Blackbird <justthecooldude@gmail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
Another step in the migration to required components: lights!
Note that this does not include `EnvironmentMapLight` or reflection
probes yet, because their API hasn't been fully chosen yet.
## Solution
As per the [selected
proposals](https://hackmd.io/@bevy/required_components/%2FLLnzwz9XTxiD7i2jiUXkJg):
- Deprecate `PointLightBundle` in favor of the `PointLight` component
- Deprecate `SpotLightBundle` in favor of the `PointLight` component
- Deprecate `DirectionalLightBundle` in favor of the `DirectionalLight`
component
## Testing
I ran some examples with lights.
---
## Migration Guide
`PointLightBundle`, `SpotLightBundle`, and `DirectionalLightBundle` have
been deprecated. Use the `PointLight`, `SpotLight`, and
`DirectionalLight` components instead. Adding them will now insert the
other components required by them automatically.
Added a `HeadlessPlugins` plugin group, that adds more default
functionality (like logging) than the `MinimumPlugins`. Fixes#15203
Changed the headless example to use the new plugin group.
I am not entirely sure if the list of plugins is correct. Are there ones
that should be added / removed?
----
The `TerminalCtrlCHandlerPlugin` has interesting effects in the headless
example: Installing it a second time it will give a log message about
skipping installation, because it is already installed. Ctrl+C will
terminate the application in that case. However, _not_ installing it the
second time (so only on the app that runs once) has the effect that the
app that runs continuously cannot be stopped using Ctrl+C.
This implies that, even though the second app did not install the Ctrl+C
handler, it did _something_ because it was keeping the one from the
first app alive.
Not sure if this is a problem or issue, or can be labeled a wierd quirk
of having multiple Apps in one executable.
# Objective
- Fixes#14974
## Solution
- Replace all* instances of `NonZero*` with `NonZero<*>`
## Testing
- CI passed locally.
---
## Notes
Within the `bevy_reflect` implementations for `std` types,
`impl_reflect_value!()` will continue to use the type aliases instead,
as it inappropriately parses the concrete type parameter as a generic
argument. If the `ZeroablePrimitive` trait was stable, or the macro
could be modified to accept a finite list of types, then we could fully
migrate.
# Objective
```rust
// Currently:
builder.add_after::<FooPlugin, _>(BarPlugin);
// After this PR:
builder.add_after::<FooPlugin>(BarPlugin);
```
This removes some weirdness and better parallels the rest of the
`PluginGroupBuilder` API.
## Solution
Define a helper method `type_id_of_val` to use in `.add_before` and
`.add_after` instead of `TypeId::of::<T>` (which requires the plugin
type to be nameable, preventing `impl Plugin` from being used).
## Testing
Ran `cargo run -p ci lints` successfully.
## Migration Guide
Removed second generic from `PluginGroupBuilder` methods: `add_before`
and `add_after`.
```rust
// Before:
DefaultPlugins
.build()
.add_before::<WindowPlugin, _>(FooPlugin)
.add_after::<WindowPlugin, _>(BarPlugin)
// After:
DefaultPlugins
.build()
.add_before::<WindowPlugin>(FooPlugin)
.add_after::<WindowPlugin>(BarPlugin)
```
---------
Co-authored-by: BD103 <59022059+BD103@users.noreply.github.com>
# Objective
- The default font size is too small to be useful in examples or for
debug text.
- Fixes#13587
## Solution
- Updated the default font size value in `TextStyle` from 12px to 24px.
- Resorted to Text defaults in examples to use the default font size in
most of them.
## Testing
- WIP
---
## Migration Guide
- The default font size has been increased to 24px from 12px. Make sure
you set the font to the appropriate values in places you were using
`Default` text style.
## Objective
Use the "standard" text size / placement for the new text in these
examples.
Continuation of an effort started here:
https://github.com/bevyengine/bevy/pull/8478
This is definitely not comprehensive. I did the ones that were easy to
find and relatively straightforward updates. I meant to just do
`3d_shapes` and `2d_shapes`, but one thing lead to another.
## Solution
Use `font_size: 20.0`, the default (built-in) font, `Color::WHITE`
(default), and `Val::Px(12.)` from the edges of the screen.
There are a few little drive-by cleanups of defaults not being used,
etc.
## Testing
Ran the changed examples, verified that they still look reasonable.
# Objective
- Fixes#13384 .
## Solution
- If the image became wider when copying from the texture to the buffer,
then the data is reduced to its original size when copying from the
buffer to the image.
## Testing
- Ran example with 1919x1080 resolution
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: François Mockers <francois.mockers@vleue.com>
# Objective
- Fixes https://github.com/bevyengine/bevy/issues/12597
The current tracing customization option (the `update_subscriber` field)
was basically unusable because it provides a `dyn Subscriber` and most
layers require a `Subscriber` that also implements `for<'a>
LookupSpan<'a, Data=Data<'a>>`, so it was impossible to add a layer on
top of the `dyn Subscriber`.
This PR provides an alternative way of adding additional tracing layers
to the LogPlugin by instead creating an `Option<Layer>`.
This is enough for most situations because `Option<Layer>` and
`Vec<Layer>` both implement `Layer`.
## Solution
- Replace the `update_subscriber` field of `LogPlugin` with a
`custom_layer` field which is function pointer returning an
`Option<BoxedLayer>`
- Update the examples to showcase that this works:
- with multiple additional layers
- with Layers that were previously problematic, such as
`bevy::log::tracing_subscriber::fmt::layer().with_file(true)` (mentioned
in the issue)
Note that in the example this results in duplicate logs, since we have
our own layer on top of the default `fmt_layer` added in the LogPlugin;
maybe in the future we might want to provide a single one? Or to let the
user customize the default `fmt_layer` ? I still think this change is an
improvement upon the previous solution, which was basically broken.
---
## Changelog
> This section is optional. If this was a trivial fix, or has no
externally-visible impact, you can delete this section.
- The `LogPlugin`'s `update_subscriber` field has been replaced with
`custom_layer` to allow the user to flexibly add a `tracing::Layer` to
the layer stack
## Migration Guide
- The `LogPlugin`'s `update_subscriber` field has been replaced with
`custom_layer`
---------
Co-authored-by: BD103 <59022059+BD103@users.noreply.github.com>
# Objective
The `custom_loop` example didn't replicate the `app.finish` /
`app.cleanup` calls from the default runner; I discovered this when
trying to troubleshoot why my application with a custom loop wasn't
calling its plugin finalizers, and realised that the upstream example
that I'd referenced didn't have the relevant calls.
## Solution
Added the missing calls, replicating what the default runner does:
d390420093/crates/bevy_app/src/app.rs (L895-L896)
## Testing
I've confirmed that adding these two calls to my application fixed the
issue I was encountering. I haven't tested it within the example itself
as it's relatively straightforward and I didn't want to pollute the
example with a plugin using a finalizer.
# Objective
Closes#13017.
## Solution
- Make `AppExit` a enum with a `Success` and `Error` variant.
- Make `App::run()` return a `AppExit` if it ever returns.
- Make app runners return a `AppExit` to signal if they encountered a
error.
---
## Changelog
### Added
- [`App::should_exit`](https://example.org/)
- [`AppExit`](https://docs.rs/bevy/latest/bevy/app/struct.AppExit.html)
to the `bevy` and `bevy_app` preludes,
### Changed
- [`AppExit`](https://docs.rs/bevy/latest/bevy/app/struct.AppExit.html)
is now a enum with 2 variants (`Success` and `Error`).
- The app's [runner
function](https://docs.rs/bevy/latest/bevy/app/struct.App.html#method.set_runner)
now has to return a `AppExit`.
-
[`App::run()`](https://docs.rs/bevy/latest/bevy/app/struct.App.html#method.run)
now also returns the `AppExit` produced by the runner function.
## Migration Guide
- Replace all usages of
[`AppExit`](https://docs.rs/bevy/latest/bevy/app/struct.AppExit.html)
with `AppExit::Success` or `AppExit::Failure`.
- Any custom app runners now need to return a `AppExit`. We suggest you
return a `AppExit::Error` if any `AppExit` raised was a Error. You can
use the new [`App::should_exit`](https://example.org/) method.
- If not exiting from `main` any other way. You should return the
`AppExit` from `App::run()` so the app correctly returns a error code if
anything fails e.g.
```rust
fn main() -> AppExit {
App::new()
//Your setup here...
.run()
}
```
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Fix some doc warnings
- Add doc-scrape-examples to all examples
Moved from #12692
I run `cargo +nightly doc --workspace --all-features --no-deps
-Zunstable-options -Zrustdoc-scrape-examples`
<details>
```
warning: public documentation for `GzAssetLoaderError` links to private item `GzAssetLoader`
--> examples/asset/asset_decompression.rs:24:47
|
24 | /// Possible errors that can be produced by [`GzAssetLoader`]
| ^^^^^^^^^^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
= note: `#[warn(rustdoc::private_intra_doc_links)]` on by default
warning: `bevy` (example "asset_decompression") generated 1 warning
warning: unresolved link to `shape::Quad`
--> examples/2d/mesh2d.rs:3:15
|
3 | //! [`Quad`]: shape::Quad
| ^^^^^^^^^^^ no item named `shape` in scope
|
= note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default
warning: `bevy` (example "mesh2d") generated 1 warning
warning: unresolved link to `WorldQuery`
--> examples/ecs/custom_query_param.rs:1:49
|
1 | //! This example illustrates the usage of the [`WorldQuery`] derive macro, which allows
| ^^^^^^^^^^ no item named `WorldQuery` in scope
|
= help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
= note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default
warning: `bevy` (example "custom_query_param") generated 1 warning
warning: unresolved link to `shape::Quad`
--> examples/2d/mesh2d_vertex_color_texture.rs:4:15
|
4 | //! [`Quad`]: shape::Quad
| ^^^^^^^^^^^ no item named `shape` in scope
|
= note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default
warning: `bevy` (example "mesh2d_vertex_color_texture") generated 1 warning
warning: public documentation for `TextPlugin` links to private item `CoolText`
--> examples/asset/processing/asset_processing.rs:48:9
|
48 | /// * [`CoolText`]: a custom RON text format that supports dependencies and embedded dependencies
| ^^^^^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
= note: `#[warn(rustdoc::private_intra_doc_links)]` on by default
warning: public documentation for `TextPlugin` links to private item `Text`
--> examples/asset/processing/asset_processing.rs:49:9
|
49 | /// * [`Text`]: a "normal" plain text file
| ^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
warning: public documentation for `TextPlugin` links to private item `CoolText`
--> examples/asset/processing/asset_processing.rs:51:57
|
51 | /// It also defines an asset processor that will load [`CoolText`], resolve embedded dependenc...
| ^^^^^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
warning: `bevy` (example "asset_processing") generated 3 warnings
warning: public documentation for `CustomAssetLoaderError` links to private item `CustomAssetLoader`
--> examples/asset/custom_asset.rs:20:47
|
20 | /// Possible errors that can be produced by [`CustomAssetLoader`]
| ^^^^^^^^^^^^^^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
= note: `#[warn(rustdoc::private_intra_doc_links)]` on by default
warning: public documentation for `BlobAssetLoaderError` links to private item `CustomAssetLoader`
--> examples/asset/custom_asset.rs:61:47
|
61 | /// Possible errors that can be produced by [`CustomAssetLoader`]
| ^^^^^^^^^^^^^^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
```
```
warning: `bevy` (example "mesh2d") generated 1 warning
warning: public documentation for `log_layers_ecs` links to private item `update_subscriber`
--> examples/app/log_layers_ecs.rs:6:18
|
6 | //! Inside the [`update_subscriber`] function we will create a [`mpsc::Sender`] and a [`mpsc::R...
| ^^^^^^^^^^^^^^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
= note: `#[warn(rustdoc::private_intra_doc_links)]` on by default
warning: unresolved link to `AdvancedLayer`
--> examples/app/log_layers_ecs.rs:7:72
|
7 | ... will go into the [`AdvancedLayer`] and the [`Receiver`](mpsc::Receiver) will
| ^^^^^^^^^^^^^ no item named `AdvancedLayer` in scope
|
= help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
= note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default
warning: unresolved link to `LogEvents`
--> examples/app/log_layers_ecs.rs:8:42
|
8 | //! go into a non-send resource called [`LogEvents`] (It has to be non-send because [`Receiver`...
| ^^^^^^^^^ no item named `LogEvents` in scope
|
= help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
warning: public documentation for `log_layers_ecs` links to private item `transfer_log_events`
--> examples/app/log_layers_ecs.rs:9:30
|
9 | //! From there we will use [`transfer_log_events`] to transfer log events from [`LogEvents`] to...
| ^^^^^^^^^^^^^^^^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
warning: unresolved link to `LogEvents`
--> examples/app/log_layers_ecs.rs:9:82
|
9 | ...nsfer log events from [`LogEvents`] to an ECS event called [`LogEvent`].
| ^^^^^^^^^ no item named `LogEvents` in scope
|
= help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
warning: public documentation for `log_layers_ecs` links to private item `LogEvent`
--> examples/app/log_layers_ecs.rs:9:119
|
9 | ...nts`] to an ECS event called [`LogEvent`].
| ^^^^^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
warning: public documentation for `log_layers_ecs` links to private item `LogEvent`
--> examples/app/log_layers_ecs.rs:11:49
|
11 | //! Finally, after all that we can access the [`LogEvent`] event from our systems and use it.
| ^^^^^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
```
<details/>
# Objective
- There are several redundant imports in the tests and examples that are
not caught by CI because additional flags need to be passed.
## Solution
- Run `cargo check --workspace --tests` and `cargo check --workspace
--examples`, then fix all warnings.
- Add `test-check` to CI, which will be run in the check-compiles job.
This should catch future warnings for tests. Examples are already
checked, but I'm not yet sure why they weren't caught.
## Discussion
- Should the `--tests` and `--examples` flags be added to CI, so this is
caught in the future?
- If so, #12818 will need to be merged first. It was also a warning
raised by checking the examples, but I chose to split off into a
separate PR.
---------
Co-authored-by: François Mockers <francois.mockers@vleue.com>
# Objective
This is a necessary precursor to #9122 (this was split from that PR to
reduce the amount of code to review all at once).
Moving `!Send` resource ownership to `App` will make it unambiguously
`!Send`. `SubApp` must be `Send`, so it can't wrap `App`.
## Solution
Refactor `App` and `SubApp` to not have a recursive relationship. Since
`SubApp` no longer wraps `App`, once `!Send` resources are moved out of
`World` and into `App`, `SubApp` will become unambiguously `Send`.
There could be less code duplication between `App` and `SubApp`, but
that would break `App` method chaining.
## Changelog
- `SubApp` no longer wraps `App`.
- `App` fields are no longer publicly accessible.
- `App` can no longer be converted into a `SubApp`.
- Various methods now return references to a `SubApp` instead of an
`App`.
## Migration Guide
- To construct a sub-app, use `SubApp::new()`. `App` can no longer
convert into `SubApp`.
- If you implemented a trait for `App`, you may want to implement it for
`SubApp` as well.
- If you're accessing `app.world` directly, you now have to use
`app.world()` and `app.world_mut()`.
- `App::sub_app` now returns `&SubApp`.
- `App::sub_app_mut` now returns `&mut SubApp`.
- `App::get_sub_app` now returns `Option<&SubApp>.`
- `App::get_sub_app_mut` now returns `Option<&mut SubApp>.`
# Objective
In my library,
[`bevy_dev_console`](https://github.com/doonv/bevy_dev_console) I need
access to `App` within `LogPlugin::update_subscriber` in order to
communicate with the `App` from my custom `Layer`.
## Solution
Give access to `App`.
---
## Changelog
- Added access to `App` within `LogPlugin::update_subscriber`
## Migration Guide
`LogPlugin::update_subscriber` now has a `&mut App` parameter. If you
don't need access to `App`, you can ignore the parameter with an
underscore (`_`).
```diff,rust
- fn update_subscriber(subscriber: BoxedSubscriber) -> BoxedSubscriber {
+ fn update_subscriber(_: &mut App, subscriber: BoxedSubscriber) -> BoxedSubscriber {
Box::new(subscriber.with(CustomLayer))
}
```
# Objective
Fixes#11846
## Solution
Add a `synchronous_pipeline_compilation ` field to `RenderPlugin`,
defaulting to `false`.
Most of the diff is whitespace.
## Changelog
Added `synchronous_pipeline_compilation ` to `RenderPlugin` for
disabling async pipeline creation.
## Migration Guide
TODO: consider combining this with the guide for #11846
`RenderPlugin` has a new `synchronous_pipeline_compilation ` property.
The default value is `false`. Set this to `true` if you want to retain
the previous synchronous behavior.
---------
Co-authored-by: JMS55 <47158642+JMS55@users.noreply.github.com>
Co-authored-by: François <mockersf@gmail.com>
# Objective
Currently the `missing_docs` lint is allowed-by-default and enabled at
crate level when their documentations is complete (see #3492).
This PR proposes to inverse this logic by making `missing_docs`
warn-by-default and mark crates with imcomplete docs allowed.
## Solution
Makes `missing_docs` warn at workspace level and allowed at crate level
when the docs is imcomplete.
# Objective
This PR is heavily inspired by
https://github.com/bevyengine/bevy/pull/7682
It aims to solve the same problem: allowing the user to extend the
tracing subscriber with extra layers.
(in my case, I'd like to use `use
metrics_tracing_context::{MetricsLayer, TracingContextLayer};`)
## Solution
I'm proposing a different api where the user has the opportunity to take
the existing `subscriber` and apply any transformations on it.
---
## Changelog
- Added a `update_subscriber` option on the `LogPlugin` that lets the
user modify the `subscriber` (for example to extend it with more tracing
`Layers`
## Migration Guide
> This section is optional. If there are no breaking changes, you can
delete this section.
- Added a new field `update_subscriber` in the `LogPlugin`
---------
Co-authored-by: Charles Bournhonesque <cbournhonesque@snapchat.com>
# Objective
- Update winit dependency to 0.29
## Changelog
### KeyCode changes
- Removed `ScanCode`, as it was [replaced by
KeyCode](https://github.com/rust-windowing/winit/blob/master/CHANGELOG.md#0292).
- `ReceivedCharacter.char` is now a `SmolStr`, [relevant
doc](https://docs.rs/winit/latest/winit/event/struct.KeyEvent.html#structfield.text).
- Changed most `KeyCode` values, and added more.
KeyCode has changed meaning. With this PR, it refers to physical
position on keyboard rather than the printed letter on keyboard keys.
In practice this means:
- On QWERTY keyboard layouts, nothing changes
- On any other keyboard layout, `KeyCode` no longer reflects the label
on key.
- This is "good". In bevy 0.12, when you used WASD for movement, users
with non-QWERTY keyboards couldn't play your game! This was especially
bad for non-latin keyboards. Now, WASD represents the physical keys. A
French player will press the ZQSD keys, which are near each other,
Kyrgyz players will use "Цфыв".
- This is "bad" as well. You can't know in advance what the label of the
key for input is. Your UI says "press WASD to move", even if in reality,
they should be pressing "ZQSD" or "Цфыв". You also no longer can use
`KeyCode` for text inputs. In any case, it was a pretty bad API for text
input. You should use `ReceivedCharacter` now instead.
### Other changes
- Use `web-time` rather than `instant` crate.
(https://github.com/rust-windowing/winit/pull/2836)
- winit did split `run_return` in `run_onDemand` and `pump_events`, I
did the same change in bevy_winit and used `pump_events`.
- Removed `return_from_run` from `WinitSettings` as `winit::run` now
returns on supported platforms.
- I left the example "return_after_run" as I think it's still useful.
- This winit change is done partly to allow to create a new window after
quitting all windows: https://github.com/emilk/egui/issues/1918 ; this
PR doesn't address.
- added `width` and `height` properties in the `canvas` from wasm
example
(https://github.com/bevyengine/bevy/pull/10702#discussion_r1420567168)
## Known regressions (important follow ups?)
- Provide an API for reacting when a specific key from current layout
was released.
- possible solutions: use winit::Key from winit::KeyEvent ; mapping
between KeyCode and Key ; or .
- We don't receive characters through alt+numpad (e.g. alt + 151 = "ù")
anymore ; reproduced on winit example "ime". maybe related to
https://github.com/rust-windowing/winit/issues/2945
- (windows) Window content doesn't refresh at all when resizing. By
reading https://github.com/rust-windowing/winit/issues/2900 ; I suspect
we should just fire a `window.request_redraw();` from `AboutToWait`, and
handle actual redrawing within `RedrawRequested`. I'm not sure how to
move all that code so I'd appreciate it to be a follow up.
- (windows) unreleased winit fix for using set_control_flow in
AboutToWait https://github.com/rust-windowing/winit/issues/3215 ; ⚠️ I'm
not sure what the implications are, but that feels bad 🤔
## Follow up
I'd like to avoid bloating this PR, here are a few follow up tasks
worthy of a separate PR, or new issue to track them once this PR is
closed, as they would either complicate reviews, or at risk of being
controversial:
- remove CanvasParentResizePlugin
(https://github.com/bevyengine/bevy/pull/10702#discussion_r1417068856)
- avoid mentionning explicitly winit in docs from bevy_window ?
- NamedKey integration on bevy_input:
https://github.com/rust-windowing/winit/pull/3143 introduced a new
NamedKey variant. I implemented it only on the converters but we'd
benefit making the same changes to bevy_input.
- Add more info in KeyboardInput
https://github.com/bevyengine/bevy/pull/10702#pullrequestreview-1748336313
- https://github.com/bevyengine/bevy/pull/9905 added a workaround on a
bug allegedly fixed by winit 0.29. We should check if it's still
necessary.
- update to raw_window_handle 0.6
- blocked by wgpu
- Rename `KeyCode` to `PhysicalKeyCode`
https://github.com/bevyengine/bevy/pull/10702#discussion_r1404595015
- remove `instant` dependency, [replaced
by](https://github.com/rust-windowing/winit/pull/2836) `web_time`), we'd
need to update to :
- fastrand >= 2.0
- [`async-executor`](https://github.com/smol-rs/async-executor) >= 1.7
- [`futures-lite`](https://github.com/smol-rs/futures-lite) >= 2.0
- Verify license, see
[discussion](https://github.com/bevyengine/bevy/pull/8745#discussion_r1402439800)
- we might be missing a short notice or description of changes made
- Consider using https://github.com/rust-windowing/cursor-icon directly
rather than vendoring it in bevy.
- investigate [this
unwrap](https://github.com/bevyengine/bevy/pull/8745#discussion_r1387044986)
(`winit_window.canvas().unwrap();`)
- Use more good things about winit's update
- https://github.com/bevyengine/bevy/pull/10689#issuecomment-1823560428
## Migration Guide
This PR should have one.
# Objective
Fixes#10291
This adds a way to easily log messages once within system which are
called every frame.
## Solution
Opted for a macro-based approach. The fact that the 'once' call is
tracked per call site makes the `log_once!()` macro very versatile and
easy-to-use. I suspect it will be very handy for all of us, but
especially beginners, to get some initial feedback from systems without
spamming up the place!
I've made the macro's return its internal `has_fired` state, for
situations in which that might be useful to know (trigger something else
alongside the log, for example).
Please let me know if I placed the macro's in the right location, and if
you would like me to do something more clever with the macro's
themselves, since its looking quite copy-pastey at the moment. I've
tried ways to replace 5 with 1 macro's, but no success yet.
One downside of this approach is: Say you wish to warn the user if a
resource is invalid. In this situation, the
`resource.is_valid()` check would still be performed every frame:
```rust
fn my_system(my_res: Res<MyResource>) {
if !my_res.is_valid() {
warn_once!("resource is invalid!");
}
}
```
If you want to prevent that, you would still need to introduce a local
boolean. I don't think this is a very big deal, as expensive checks
shouldn't be called every frame in any case.
## Changelog
Added: `trace_once!()`, `debug_once!()`, `info_once!()`, `warn_once!()`,
and `error_once!()` log macros which fire only once per call site.
When `cargo doc -Zunstable-options -Zrustdoc-scrape-examples` (trying to
figure out why it doesn't work with bevy), I had the following warnings:
```
warning: unresolved link to `Quad`
--> examples/2d/mesh2d.rs:1:66
|
1 | //! Shows how to render a polygonal [`Mesh`], generated from a [`Quad`] primitive, in a 2D scene.
| ^^^^ no item named `Quad` in scope
|
= help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
= note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default
warning: `bevy` (example "mesh2d") generated 1 warning
warning: unresolved link to `update_weights`
--> examples/animation/morph_targets.rs:6:17
|
6 | //! See the [`update_weights`] system for details.
| ^^^^^^^^^^^^^^ no item named `update_weights` in scope
|
= help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
= note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default
warning: public documentation for `morph_targets` links to private item `name_morphs`
--> examples/animation/morph_targets.rs:7:43
|
7 | //! - How to read morph target names in [`name_morphs`].
| ^^^^^^^^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
= note: `#[warn(rustdoc::private_intra_doc_links)]` on by default
warning: public documentation for `morph_targets` links to private item `setup_animations`
--> examples/animation/morph_targets.rs:8:48
|
8 | //! - How to play morph target animations in [`setup_animations`].
| ^^^^^^^^^^^^^^^^ this item is private
|
= note: this link will resolve properly if you pass `--document-private-items`
warning: `bevy` (example "morph_targets") generated 3 warnings
warning: unresolved link to `Quad`
--> examples/2d/mesh2d_vertex_color_texture.rs:1:66
|
1 | //! Shows how to render a polygonal [`Mesh`], generated from a [`Quad`] primitive, in a 2D scene.
| ^^^^ no item named `Quad` in scope
|
= help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
= note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default
warning: `bevy` (example "mesh2d_vertex_color_texture") generated 1 warning
warning: unresolved link to `UIScale`
--> examples/ui/ui_scaling.rs:1:36
|
1 | //! This example illustrates the [`UIScale`] resource from `bevy_ui`.
| ^^^^^^^ no item named `UIScale` in scope
|
= help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
= note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default
warning: `bevy` (example "ui_scaling") generated 1 warning
warning: unresolved link to `dependencies`
--> examples/app/headless.rs:5:6
|
5 | //! [dependencies]
| ^^^^^^^^^^^^ no item named `dependencies` in scope
|
= help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
= note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default
warning: `bevy` (example "headless") generated 1 warning
warning: unresolved link to `Material2d`
--> examples/2d/mesh2d_manual.rs:3:26
|
3 | //! It doesn't use the [`Material2d`] abstraction, but changes the vertex buffer to include verte...
| ^^^^^^^^^^ no item named `Material2d` in scope
|
= help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
= note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default
warning: `bevy` (example "mesh2d_manual") generated 1 warning
```
This is a duplicate of #9632, it was created since I forgot to make a
new branch when I first made this PR, so I was having trouble resolving
merge conflicts, meaning I had to rebuild my PR.
# Objective
- Allow other plugins to create the renderer resources. An example of
where this would be required is my [OpenXR
plugin](https://github.com/awtterpip/bevy_openxr)
## Solution
- Changed the bevy RenderPlugin to optionally take precreated render
resources instead of a configuration.
## Migration Guide
The `RenderPlugin` now takes a `RenderCreation` enum instead of
`WgpuSettings`. `RenderSettings::default()` returns
`RenderSettings::Automatic(WgpuSettings::default())`. `RenderSettings`
also implements `From<WgpuSettings>`.
```rust
// before
RenderPlugin {
wgpu_settings: WgpuSettings {
...
},
}
// now
RenderPlugin {
render_creation: RenderCreation::Automatic(WgpuSettings {
...
}),
}
// or
RenderPlugin {
render_creation: WgpuSettings {
...
}.into(),
}
```
---------
Co-authored-by: Malek <pocmalek@gmail.com>
Co-authored-by: Robert Swain <robert.swain@gmail.com>
# Objective
- The current `EventReader::iter` has been determined to cause confusion
among new Bevy users. It was suggested by @JoJoJet to rename the method
to better clarify its usage.
- Solves #9624
## Solution
- Rename `EventReader::iter` to `EventReader::read`.
- Rename `EventReader::iter_with_id` to `EventReader::read_with_id`.
- Rename `ManualEventReader::iter` to `ManualEventReader::read`.
- Rename `ManualEventReader::iter_with_id` to
`ManualEventReader::read_with_id`.
---
## Changelog
- `EventReader::iter` has been renamed to `EventReader::read`.
- `EventReader::iter_with_id` has been renamed to
`EventReader::read_with_id`.
- `ManualEventReader::iter` has been renamed to
`ManualEventReader::read`.
- `ManualEventReader::iter_with_id` has been renamed to
`ManualEventReader::read_with_id`.
- Deprecated `EventReader::iter`
- Deprecated `EventReader::iter_with_id`
- Deprecated `ManualEventReader::iter`
- Deprecated `ManualEventReader::iter_with_id`
## Migration Guide
- Existing usages of `EventReader::iter` and `EventReader::iter_with_id`
will have to be changed to `EventReader::read` and
`EventReader::read_with_id` respectively.
- Existing usages of `ManualEventReader::iter` and
`ManualEventReader::iter_with_id` will have to be changed to
`ManualEventReader::read` and `ManualEventReader::read_with_id`
respectively.
# Objective
- Better consistency with `add_systems`.
- Deprecating `add_plugin` in favor of a more powerful `add_plugins`.
- Allow passing `Plugin` to `add_plugins`.
- Allow passing tuples to `add_plugins`.
## Solution
- `App::add_plugins` now takes an `impl Plugins` parameter.
- `App::add_plugin` is deprecated.
- `Plugins` is a new sealed trait that is only implemented for `Plugin`,
`PluginGroup` and tuples over `Plugins`.
- All examples, benchmarks and tests are changed to use `add_plugins`,
using tuples where appropriate.
---
## Changelog
### Changed
- `App::add_plugins` now accepts all types that implement `Plugins`,
which is implemented for:
- Types that implement `Plugin`.
- Types that implement `PluginGroup`.
- Tuples (up to 16 elements) over types that implement `Plugins`.
- Deprecated `App::add_plugin` in favor of `App::add_plugins`.
## Migration Guide
- Replace `app.add_plugin(plugin)` calls with `app.add_plugins(plugin)`.
---------
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
`ScheduleRunnerPlugin` was still configured via a resource, meaning
users would be able to change the settings while the app is running, but
the changes wouldn't have an effect.
## Solution
Configure plugin directly
---
## Changelog
- Changed: merged `ScheduleRunnerSettings` into `ScheduleRunnerPlugin`
## Migration Guide
- instead of inserting the `ScheduleRunnerSettings` resource, configure
the `ScheduleRunnerPlugin`
# Objective
Fix https://github.com/bevyengine/bevy/issues/4530
- Make it easier to open/close/modify windows by setting them up as `Entity`s with a `Window` component.
- Make multiple windows very simple to set up. (just add a `Window` component to an entity and it should open)
## Solution
- Move all properties of window descriptor to ~components~ a component.
- Replace `WindowId` with `Entity`.
- ~Use change detection for components to update backend rather than events/commands. (The `CursorMoved`/`WindowResized`/... events are kept for user convenience.~
Check each field individually to see what we need to update, events are still kept for user convenience.
---
## Changelog
- `WindowDescriptor` renamed to `Window`.
- Width/height consolidated into a `WindowResolution` component.
- Requesting maximization/minimization is done on the [`Window::state`] field.
- `WindowId` is now `Entity`.
## Migration Guide
- Replace `WindowDescriptor` with `Window`.
- Change `width` and `height` fields in a `WindowResolution`, either by doing
```rust
WindowResolution::new(width, height) // Explicitly
// or using From<_> for tuples for convenience
(1920., 1080.).into()
```
- Replace any `WindowCommand` code to just modify the `Window`'s fields directly and creating/closing windows is now by spawning/despawning an entity with a `Window` component like so:
```rust
let window = commands.spawn(Window { ... }).id(); // open window
commands.entity(window).despawn(); // close window
```
## Unresolved
- ~How do we tell when a window is minimized by a user?~
~Currently using the `Resize(0, 0)` as an indicator of minimization.~
No longer attempting to tell given how finnicky this was across platforms, now the user can only request that a window be maximized/minimized.
## Future work
- Move `exit_on_close` functionality out from windowing and into app(?)
- https://github.com/bevyengine/bevy/issues/5621
- https://github.com/bevyengine/bevy/issues/7099
- https://github.com/bevyengine/bevy/issues/7098
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
See:
- https://github.com/bevyengine/bevy/issues/7067#issuecomment-1381982285
- (This does not fully close that issue in my opinion.)
- https://discord.com/channels/691052431525675048/1063454009769340989
## Solution
This merge request adds documentation:
1. Alert users to the fact that `App::run()` might never return and code placed after it might never be executed.
2. Makes `winit::WinitSettings::return_from_run` discoverable.
3. Better explains why `winit::WinitSettings::return_from_run` is discouraged and better links to up-stream docs. on that topic.
4. Adds notes to the `app/return_after_run.rs` example which otherwise promotes a feature that carries caveats.
Furthermore, w.r.t `winit::WinitSettings::return_from_run`:
- Broken links to `winit` docs are fixed.
- Links now point to BOTH `EventLoop::run()` and `EventLoopExtRunReturn::run_return()` which are the salient up-stream pages and make more sense, taken together.
- Collateral damage: "Supported platforms" heading; disambiguation of "run" → `App::run()`; links.
## Future Work
I deliberately structured the "`run()` might not return" section under `App::run()` to allow for alternative patterns (e.g. `AppExit` event, `WindowClosed` event) to be listed or mentioned, beneath it, in the future.
# Objective
- Fixes#7081.
## Solution
- Moved functionality from kitchen sink plugin `CorePlugin` to separate plugins, `TaskPoolPlugin`, `TypeRegistrationPlugin`, `FrameCountPlugin`. `TaskPoolOptions` resource should now be used with `TaskPoolPlugin`.
## Changelog
Minimal changes made (code kept in `bevy_core/lib.rs`).
## Migration Guide
- `CorePlugin` broken into separate plugins. If not using `DefaultPlugins` or `MinimalPlugins` `PluginGroup`s, the replacement for `CorePlugin` is now to add `TaskPoolPlugin`, `TypeRegistrationPlugin`, and `FrameCountPlugin` to the app.
## Notes
- Consistent with Bevy goal "modularity over deep integration" but the functionality of `TypeRegistrationPlugin` and `FrameCountPlugin` is weak (the code has to go somewhere, though!).
- No additional tests written.
# Objective
The `WgpuSettings` resource is only used during plugin build. Move it into the `RenderPlugin` struct.
Changing these settings requires re-initializing the render context, which is currently not supported.
If it is supported in the future it should probably be more explicit than changing a field on a resource, maybe something similar to the `CreateWindow` event.
## Migration Guide
```rust
// Before (0.9)
App::new()
.insert_resource(WgpuSettings { .. })
.add_plugins(DefaultPlugins)
// After (0.10)
App::new()
.add_plugins(DefaultPlugins.set(RenderPlugin {
wgpu_settings: WgpuSettings { .. },
}))
```
Co-authored-by: devil-ira <justthecooldude@gmail.com>
# Objective
- Fixes #6311
- Make it clearer what should be done in the example (close the Bevy app window)
## Solution
- Remove the second windowed Bevy App [since winit does not support this](https://github.com/rust-windowing/winit/blob/v0.27.4/src/event_loop.rs#L82-L83)
- Add title to the Bevy window asking the user to close it
This is more of a quick fix to have a working example. It would be nicer if we had a small real usecase for this functionality.
Another alternativ that I tried out: If we want to showcase a second Bevy app as it was before, we could still do this as long as one of them does not have a window. But I don't see how this is helpful in the context of the example, so I stuck with only one Bevy app and a simple print afterwards.
# Objective
- Make it impossible to add a plugin twice
- This is going to be more a risk for plugins with configurations, to avoid things like `App::new().add_plugins(DefaultPlugins).add_plugin(ImagePlugin::default_nearest())`
## Solution
- Panic when a plugin is added twice
- It's still possible to mark a plugin as not unique by overriding `is_unique`
- ~~Simpler version of~~ #3988 (not simpler anymore because of how `PluginGroupBuilder` implements `PluginGroup`)
