## Objective
The `MotionBlur` component exposes renderer internals. Users shouldn't
have to deal with this.
```rust
MotionBlur {
shutter_angle: 1.0,
samples: 2,
#[cfg(all(feature = "webgl2", target_arch = "wasm32", not(feature = "webgpu")))]
_webgl2_padding: Default::default(),
},
```
## Solution
The renderer now uses a separate `MotionBlurUniform` struct for its
internals. `MotionBlur` no longer needs padding.
I was a bit unsure about the name `MotionBlurUniform`. Other modules use
a mix of `Uniform` and `Uniforms`.
## Testing
```
cargo run --example motion_blur
```
Tested on Win10/Nvidia across Vulkan, WebGL/Chrome, WebGPU/Chrome.
# Objective
Adopts / builds on top of #18435.
The `log_diagnostics` example has bit-rotted and accumulated multiple
issues:
- It didn't explain the ordering constraint on DefaultPlugins, as noted
by the original PR
- Apparently `AssetCountDiagnosticsPlugin` no longer exists (?!). I
couldn't figure out when or why it was removed, maybe it got missed in
Assets v2?
- The comments didn't explain what kind of info you get by the various
plugins, making you do work to figure it out
- ~As far as I can tell `RenderDiagnosticsPlugin` currently doesn't
register any diagnostics in the traditional sense, but is only focused
on rendering spans? At least it doesn't print anything extra when added
for me, so having it here is misleading.~ It didn't print anything
because there was nothing to render in this example
## Solution
- Make all plugins be commented in to prevent further bit-rot
- Remove reference to the missing plugin
- Add extra comments describing the diagnostics in more detail
- Add something to render so we get render diagnostics
## Testing
Run the example, see relevant diagnostics printed out
# Objective
In #17905 we swapped to a named field on `ChildOf` to help resolve
variable naming ambiguity of child vs parent (ex: `child_of.parent`
clearly reads as "I am accessing the parent of the child_of
relationship", whereas `child_of.0` is less clear).
Unfortunately this has the side effect of making initialization less
ideal. `ChildOf { parent }` reads just as well as `ChildOf(parent)`, but
`ChildOf { parent: root }` doesn't read nearly as well as
`ChildOf(root)`.
## Solution
Move back to `ChildOf(pub Entity)` but add a `child_of.parent()`
function and use it for all accesses. The downside here is that users
are no longer "forced" to access the parent field with `parent`
nomenclature, but I think this strikes the right balance.
Take a look at the diff. I think the results provide strong evidence for
this change. Initialization has the benefit of reading much better _and_
of taking up significantly less space, as many lines go from 3 to 1, and
we're cutting out a bunch of syntax in some cases.
Sadly I do think this should land in 0.16 as the cost of doing this
_after_ the relationships migration is high.
# Objective
Improve error messages for missing resources.
The default error handler currently prints the `Debug` representation of
the error type instead of `Display`. Most error types use
`#[derive(Debug)]`, resulting in a dump of the structure, but will have
a user-friendly message for `Display`.
Follow-up to #18593
## Solution
Change the default error handler to use `Display` instead of `Debug`.
Change `BevyError` to include the backtrace in the `Display` format in
addition to `Debug` so that it is still included.
## Showcase
Before:
```
Encountered an error in system `system_name`: SystemParamValidationError { skipped: false, message: "Resource does not exist", param: "bevy_ecs::change_detection::Res<app_name::ResourceType>" }
Encountered an error in system `other_system_name`: "String message with\nmultiple lines."
```
After
```
Encountered an error in system `system_name`: Parameter `Res<ResourceType>` failed validation: Resource does not exist
Encountered an error in system `other_system_name`: String message with
multiple lines.
```
# Objective
Unlike for their helper typers, the import paths for
`unique_array::UniqueEntityArray`, `unique_slice::UniqueEntitySlice`,
`unique_vec::UniqueEntityVec`, `hash_set::EntityHashSet`,
`hash_map::EntityHashMap`, `index_set::EntityIndexSet`,
`index_map::EntityIndexMap` are quite redundant.
When looking at the structure of `hashbrown`, we can also see that while
both `HashSet` and `HashMap` have their own modules, the main types
themselves are re-exported to the crate level.
## Solution
Re-export the types in their shared `entity` parent module, and simplify
the imports where they're used.
# Objective
- feature `shader_format_wesl` doesn't compile in Wasm
- once fixed, example `shader_material_wesl` doesn't work in WebGL2
## Solution
- remove special path handling when loading shaders. this seems like a
way to escape the asset folder which we don't want to allow, and can't
compile on android or wasm, and can't work on iOS (filesystem is rooted
there)
- pad material so that it's 16 bits. I couldn't get conditional
compilation to work in wesl for type declaration, it fails to parse
- the shader renders the color `(0.0, 0.0, 0.0, 0.0)` when it's not a
polka dot. this renders as black on WebGPU/metal/..., and white on
WebGL2. change it to `(0.0, 0.0, 0.0, 1.0)` so that it's black
everywhere
- Fixes#18010.
- Revert the offending PRs! These are #15481 and #18013. We now no
longer get an error if there are duplicate subassets.
- In theory we could untangle #18013 from #15481, but that may be
tricky, and may still introduce regressions. To avoid this worry (since
we're already in RC mode), I am just reverting both.
- This is just a revert.
---
<Remove the migration guides for #15481 and #18013>
I will make a PR to the bevy_website repo after this is merged.
# Objective
- Fixes#18539
- Doc failed to build as an example `include_str!` an asset, but assets
are not available in the packaged crate
## Solution
- Don't `include_str!` the shader but read it at runtime
# Objective
Make it easier to short-circuit system parameter validation.
Simplify the API surface by combining `ValidationOutcome` with
`SystemParamValidationError`.
## Solution
Replace `ValidationOutcome` with `Result<(),
SystemParamValidationError>`. Move the docs from `ValidationOutcome` to
`SystemParamValidationError`.
Add a `skipped` field to `SystemParamValidationError` to distinguish the
`Skipped` and `Invalid` variants.
Use the `?` operator to short-circuit validation in tuples of system
params.
# Objective
When introduced, `Single` was intended to simply be silently skipped,
allowing for graceful and efficient handling of systems during invalid
game states (such as when the player is dead).
However, this also caused missing resources to *also* be silently
skipped, leading to confusing and very hard to debug failures. In
0.15.1, this behavior was reverted to a panic, making missing resources
easier to debug, but largely making `Single` (and `Populated`)
worthless, as they would panic during expected game states.
Ultimately, the consensus is that this behavior should differ on a
per-system-param basis. However, there was no sensible way to *do* that
before this PR.
## Solution
Swap `SystemParam::validate_param` from a `bool` to:
```rust
/// The outcome of system / system param validation,
/// used by system executors to determine what to do with a system.
pub enum ValidationOutcome {
/// All system parameters were validated successfully and the system can be run.
Valid,
/// At least one system parameter failed validation, and an error must be handled.
/// By default, this will result in1 a panic. See [crate::error] for more information.
///
/// This is the default behavior, and is suitable for system params that should *always* be valid,
/// either because sensible fallback behavior exists (like [`Query`] or because
/// failures in validation should be considered a bug in the user's logic that must be immediately addressed (like [`Res`]).
Invalid,
/// At least one system parameter failed validation, but the system should be skipped due to [`ValidationBehavior::Skip`].
/// This is suitable for system params that are intended to only operate in certain application states, such as [`Single`].
Skipped,
}
```
Then, inside of each `SystemParam` implementation, return either Valid,
Invalid or Skipped.
Currently, only `Single`, `Option<Single>` and `Populated` use the
`Skipped` behavior. Other params (like resources) retain their current
failing
## Testing
Messed around with the fallible_params example. Added a pair of tests:
one for panicking when resources are missing, and another for properly
skipping `Single` and `Populated` system params.
## To do
- [x] get https://github.com/bevyengine/bevy/pull/18454 merged
- [x] fix the todo!() in the macro-powered tuple implementation (please
help 🥺)
- [x] test
- [x] write a migration guide
- [x] update the example comments
## Migration Guide
Various system and system parameter validation methods
(`SystemParam::validate_param`, `System::validate_param` and
`System::validate_param_unsafe`) now return and accept a
`ValidationOutcome` enum, rather than a `bool`. The previous `true`
values map to `ValidationOutcome::Valid`, while `false` maps to
`ValidationOutcome::Invalid`.
However, if you wrote a custom schedule executor, you should now respect
the new `ValidationOutcome::Skipped` parameter, skipping any systems
whose validation was skipped. By contrast, `ValidationOutcome::Invalid`
systems should also be skipped, but you should call the
`default_error_handler` on them first, which by default will result in a
panic.
If you are implementing a custom `SystemParam`, you should consider
whether failing system param validation is an error or an expected
state, and choose between `Invalid` and `Skipped` accordingly. In Bevy
itself, `Single` and `Populated` now once again skip the system when
their conditions are not met. This is the 0.15.0 behavior, but stands in
contrast to the 0.15.1 behavior, where they would panic.
---------
Co-authored-by: MiniaczQ <xnetroidpl@gmail.com>
Co-authored-by: Dmytro Banin <banind@cs.washington.edu>
Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
There are two related problems here:
1. Users should be able to change the fallback behavior of *all*
ECS-based errors in their application by setting the
`GLOBAL_ERROR_HANDLER`. See #18351 for earlier work in this vein.
2. The existing solution (#15500) for customizing this behavior is high
on boilerplate, not global and adds a great deal of complexity.
The consensus is that the default behavior when a parameter fails
validation should be set based on the kind of system parameter in
question: `Single` / `Populated` should silently skip the system, but
`Res` should panic. Setting this behavior at the system level is a
bandaid that makes getting to that ideal behavior more painful, and can
mask real failures (if a resource is missing but you've ignored a system
to make the Single stop panicking you're going to have a bad day).
I've removed the existing `ParamWarnPolicy`-based configuration, and
wired up the `GLOBAL_ERROR_HANDLER`/`default_error_handler` to the
various schedule executors to properly plumb through errors .
Additionally, I've done a small cleanup pass on the corresponding
example.
I've run the `fallible_params` example, with both the default and a
custom global error handler. The former panics (as expected), and the
latter spams the error console with warnings 🥲
1. Currently, failed system param validation will result in endless
console spam. Do you want me to implement a solution for warn_once-style
debouncing somehow?
2. Currently, the error reporting for failed system param validation is
very limited: all we get is that a system param failed validation and
the name of the system. Do you want me to implement improved error
reporting by bubbling up errors in this PR?
3. There is broad consensus that the default behavior for failed system
param validation should be set on a per-system param basis. Would you
like me to implement that in this PR?
My gut instinct is that we absolutely want to solve 2 and 3, but it will
be much easier to do that work (and review it) if we split the PRs
apart.
`ParamWarnPolicy` and the `WithParamWarnPolicy` have been removed
completely. Failures during system param validation are now handled via
the `GLOBAL_ERROR_HANDLER`: please see the `bevy_ecs::error` module docs
for more information.
---------
Co-authored-by: MiniaczQ <xnetroidpl@gmail.com>
# Objective
Contributes to #18238
Updates the `sprite_slice`, `spatial_audio_3d` and `spatial_audio_2d`
examples to use the `children!` macro.
## Solution
Updates examples to use the Improved Spawning API merged in
https://github.com/bevyengine/bevy/pull/17521
## Testing
- Did you test these changes? If so, how?
- Opened the examples before and after and verified the same behavior
was observed. I did this on Ubuntu 24.04.2 LTS using `--features
wayland`.
- Are there any parts that need more testing?
- Other OS's and features can't hurt, but this is such a small change it
shouldn't be a problem.
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- Run the examples yourself with and without these changes.
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
- see above
---
## Showcase
n/a
## Migration Guide
n/a
# Objective
Fixes#18429
## Solution
Add syncing to the render world for the `ColoredMesh2d` component
## Testing
Ran the example and it works as intended without the warning spam
# Objective
@cart noticed some issues with my work in
https://github.com/bevyengine/bevy/pull/17348#discussion_r2001815637,
which I somehow missed before merging the PR.
## Solution
- feature gate the UiPickingPlugin correctly
- don't manually add the picking plugins
## Testing
Ran the debug_picking and sprite_picking examples (for UI and sprites
respectively): both seem to work fine.
# Objective
- ECS error handling is a lovely flagship feature for Bevy 0.16, all in
the name of reducing panics and encouraging better error handling
(#14275).
- Currently though, command and system error handling are completely
disjoint and use different mechanisms.
- Additionally, there's a number of distinct ways to set the
default/fallback/global error handler that have limited value. As far as
I can tell, this will be cfg flagged to toggle between dev and
production builds in 99.9% of cases, with no real value in more granular
settings or helpers.
- Fixes#17272
## Solution
- Standardize error handling on the OnceLock global error mechanisms
ironed out in https://github.com/bevyengine/bevy/pull/17215
- As discussed there, there are serious performance concerns there,
especially for commands
- I also think this is a better fit for the use cases, as it's truly
global
- Move from `SystemErrorContext` to a more general purpose
`ErrorContext`, which can handle observers and commands more clearly
- Cut the superfluous setter methods on `App` and `SubApp`
- Rename the limited (and unhelpful) `fallible_systems` example to
`error_handling`, and add an example of command error handling
## Testing
Ran the `error_handling` example.
## Notes for reviewers
- Do you see a clear way to allow commands to retain &mut World access
in the per-command custom error handlers? IMO that's a key feature here
(allowing the ad-hoc creation of custom commands), but I'm not sure how
to get there without exploding complexity.
- I've removed the feature gate on the default_error_handler: contrary
to @cart's opinion in #17215 I think that virtually all apps will want
to use this. Can you think of a category of app that a) is extremely
performance sensitive b) is fine with shipping to production with the
panic error handler? If so, I can try to gather performance numbers
and/or reintroduce the feature flag. UPDATE: see benches at the end of
this message.
- ~~`OnceLock` is in `std`: @bushrat011899 what should we do here?~~
- Do you have ideas for more automated tests for this collection of
features?
## Benchmarks
I checked the impact of the feature flag introduced: benchmarks might
show regressions. This bears more investigation. I'm still skeptical
that there are users who are well-served by a fast always panicking
approach, but I'm going to re-add the feature flag here to avoid
stalling this out.
---------
Co-authored-by: Zachary Harrold <zac@harrold.com.au>
# Objective
Currently, our picking backends are inconsistent:
- Mesh picking and sprite picking both have configurable opt in/out
behavior. UI picking does not.
- Sprite picking uses `SpritePickingCamera` and `Pickable` for control,
but mesh picking uses `RayCastPickable`.
- `MeshPickingPlugin` is not a part of `DefaultPlugins`.
`SpritePickingPlugin` and `UiPickingPlugin` are.
## Solution
- Add configurable opt in/out behavior to UI picking (defaults to opt
out).
- Replace `RayCastPickable` with `MeshPickingCamera` and `Pickable`.
- Remove `SpritePickingPlugin` and `UiPickingPlugin` from
`DefaultPlugins`.
## Testing
Ran some examples.
## Migration Guide
`UiPickingPlugin` and `SpritePickingPlugin` are no longer included in
`DefaultPlugins`. They must be explicitly added.
`RayCastPickable` has been replaced in favor of the `MeshPickingCamera`
and `Pickable` components. You should add them to cameras and entities,
respectively, if you have `MeshPickingSettings::require_markers` set to
`true`.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
Extract sprites into a `Vec` instead of a `HashMap`.
## Solution
Extract UI nodes into a `Vec` instead of an `EntityHashMap`.
Add an index into the `Vec` to `Transparent2d`.
Compare both the index and render entity in prepare so there aren't any
collisions.
## Showcase
yellow this PR, red main
```
cargo run --example many_sprites --release --features "trace_tracy"
```
`extract_sprites`
<img width="452" alt="extract_sprites"
src="https://github.com/user-attachments/assets/66c60406-7c2b-4367-907d-4a71d3630296"
/>
`queue_sprites`
<img width="463" alt="queue_sprites"
src="https://github.com/user-attachments/assets/54b903bd-4137-4772-9f87-e10e1e050d69"
/>
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Fixes#17506
- Fixes#16258
## Solution
- Added a new folder of examples, `no_std`, similar to the `mobile`
folder.
- Added a single example, `no_std_library`, which demonstrates how to
make a `no_std` compatible Bevy library.
- Added a new CI task, `check-compiles-no-std-examples`, which checks
that `no_std` examples compile on `no_std` targets.
- Added `bevy_platform_support::prelude` to `bevy::prelude`.
## Testing
- CI
---
## Notes
- I've structured the folders here to permit further `no_std` examples
(e.g., GameBoy Games, ESP32 firmware, etc.), but I am starting with the
simplest and least controversial example.
- I've tried to be as clear as possible with the documentation for this
example, catering to an audience who may not have even heard of `no_std`
before.
---------
Co-authored-by: Greeble <166992735+greeble-dev@users.noreply.github.com>
# Objective
WESL was broken on windows.
## Solution
- Upgrade to `wesl_rs` 1.2.
- Fix path handling on windows.
- Improve example for khronos demo this week.
# Objective
- #17581 broke gizmos
- Fixes#18325
## Solution
- Revert #17581
- Add gizmos to testbed
## Testing
- Run any example with gizmos, it renders correctly
# Objective
On iOS:
- Allow `std` to do its runtime initialization.
- Avoid requiring the user to specify linked libraries and framework in
Xcode.
- Reduce the amount of work that `#[bevy_main]` does
- In the future we may also be able to eliminate the need for it on
Android, cc @daxpedda.
## Solution
We previously:
- Exposed an `extern "C" fn main_rs` entry point.
- Ran Cargo in a separate Xcode target as an external build system.
- Imported that as a dependency of `bevy_mobile_example.app`.
- Compiled a trampoline C file with Xcode that called `main_rs`.
- Linked that via. Xcode.
All of this is unnecessary; `rustc` is well capable of creating iOS
executables, the trick is just to place it at the correct location for
Xcode to understand it, namely `$TARGET_BUILD_DIR/$EXECUTABLE_PATH`
(places it in `bevy_mobile_example.app/bevy_mobile_example`).
Note: We might want to wait with the changes to `#[bevy_main]` until the
problem is resolved on Android too, to make the migration easier.
## Testing
Open the Xcode project, and build for an iOS target.
---
## Migration Guide
**If you have been building your application for iOS:**
Previously, the `#[bevy_main]` attribute created a `main_rs` entry point
that most Xcode templates were using to run your Rust code from C. This
was found to be unnecessary, as you can simply let Rust build your
application as a binary, and run that directly.
You have two options for dealing with this:
If you've added further C code and Xcode customizations, or it makes
sense for your use-case to continue link with Xcode, you can revert to
the old behaviour by adding `#[no_mangle] extern "C" main_rs() { main()
}` to your `main.rs`. Note that the old approach of linking a static
library prevents the Rust standard library from doing runtime
initialization, so certain functionality provided by `std` might be
unavailable (stack overflow handlers, stdout/stderr flushing and other
such functionality provided by the initialization routines).
The other, preferred option is to remove your "compile" and "link" build
phases, and instead replace it with a "run script" phase that invokes
`cargo build --bin ...`, and moves the built binary to the Xcode path
`$TARGET_BUILD_DIR/$EXECUTABLE_PATH`. An example of how to do this can
be viewed at [INSERT LINK TO UPDATED EXAMPLE PROJECT].
To make the debugging experience in Xcode nicer after this, you might
also want to consider either enabling `panic = "abort"` or to set a
breakpoint on the `rust_panic` symbol.
---------
Co-authored-by: François Mockers <mockersf@gmail.com>
Co-authored-by: François Mockers <francois.mockers@vleue.com>
# Objective
Now that #13432 has been merged, it's important we update our reflected
types to properly opt into this feature. If we do not, then this could
cause issues for users downstream who want to make use of
reflection-based cloning.
## Solution
This PR is broken into 4 commits:
1. Add `#[reflect(Clone)]` on all types marked `#[reflect(opaque)]` that
are also `Clone`. This is mandatory as these types would otherwise cause
the cloning operation to fail for any type that contains it at any
depth.
2. Update the reflection example to suggest adding `#[reflect(Clone)]`
on opaque types.
3. Add `#[reflect(clone)]` attributes on all fields marked
`#[reflect(ignore)]` that are also `Clone`. This prevents the ignored
field from causing the cloning operation to fail.
Note that some of the types that contain these fields are also `Clone`,
and thus can be marked `#[reflect(Clone)]`. This makes the
`#[reflect(clone)]` attribute redundant. However, I think it's safer to
keep it marked in the case that the `Clone` impl/derive is ever removed.
I'm open to removing them, though, if people disagree.
4. Finally, I added `#[reflect(Clone)]` on all types that are also
`Clone`. While not strictly necessary, it enables us to reduce the
generated output since we can just call `Clone::clone` directly instead
of calling `PartialReflect::reflect_clone` on each variant/field. It
also means we benefit from any optimizations or customizations made in
the `Clone` impl, including directly dereferencing `Copy` values and
increasing reference counters.
Along with that change I also took the liberty of adding any missing
registrations that I saw could be applied to the type as well, such as
`Default`, `PartialEq`, and `Hash`. There were hundreds of these to
edit, though, so it's possible I missed quite a few.
That last commit is **_massive_**. There were nearly 700 types to
update. So it's recommended to review the first three before moving onto
that last one.
Additionally, I can break the last commit off into its own PR or into
smaller PRs, but I figured this would be the easiest way of doing it
(and in a timely manner since I unfortunately don't have as much time as
I used to for code contributions).
## Testing
You can test locally with a `cargo check`:
```
cargo check --workspace --all-features
```
# Objective
#13432 added proper reflection-based cloning. This is a better method
than cloning via `clone_value` for reasons detailed in the description
of that PR. However, it may not be immediately apparent to users why one
should be used over the other, and what the gotchas of `clone_value`
are.
## Solution
This PR marks `PartialReflect::clone_value` as deprecated, with the
deprecation notice pointing users to `PartialReflect::reflect_clone`.
However, it also suggests using a new method introduced in this PR:
`PartialReflect::to_dynamic`.
`PartialReflect::to_dynamic` is essentially a renaming of
`PartialReflect::clone_value`. By naming it `to_dynamic`, we make it
very obvious that what's returned is a dynamic type. The one caveat to
this is that opaque types still use `reflect_clone` as they have no
corresponding dynamic type.
Along with changing the name, the method is now optional, and comes with
a default implementation that calls out to the respective reflection
subtrait method. This was done because there was really no reason to
require manual implementors provide a method that almost always calls
out to a known set of methods.
Lastly, to make this default implementation work, this PR also did a
similar thing with the `clone_dynamic ` methods on the reflection
subtraits. For example, `Struct::clone_dynamic` has been marked
deprecated and is superseded by `Struct::to_dynamic_struct`. This was
necessary to avoid the "multiple names in scope" issue.
### Open Questions
This PR maintains the original signature of `clone_value` on
`to_dynamic`. That is, it takes `&self` and returns `Box<dyn
PartialReflect>`.
However, in order for this to work, it introduces a panic if the value
is opaque and doesn't override the default `reflect_clone`
implementation.
One thing we could do to avoid the panic would be to make the conversion
fallible, either returning `Option<Box<dyn PartialReflect>>` or
`Result<Box<dyn PartialReflect>, ReflectCloneError>`.
This makes using the method a little more involved (i.e. users have to
either unwrap or handle the rare possibility of an error), but it would
set us up for a world where opaque types don't strictly need to be
`Clone`. Right now this bound is sort of implied by the fact that
`clone_value` is a required trait method, and the default behavior of
the macro is to use `Clone` for opaque types.
Alternatively, we could keep the signature but make the method required.
This maintains that implied bound where manual implementors must provide
some way of cloning the value (or YOLO it and just panic), but also
makes the API simpler to use.
Finally, we could just leave it with the panic. It's unlikely this would
occur in practice since our macro still requires `Clone` for opaque
types, and thus this would only ever be an issue if someone were to
manually implement `PartialReflect` without a valid `to_dynamic` or
`reflect_clone` method.
## Testing
You can test locally using the following command:
```
cargo test --package bevy_reflect --all-features
```
---
## Migration Guide
`PartialReflect::clone_value` is being deprecated. Instead, use
`PartialReflect::to_dynamic` if wanting to create a new dynamic instance
of the reflected value. Alternatively, use
`PartialReflect::reflect_clone` to attempt to create a true clone of the
underlying value.
Similarly, the following methods have been deprecated and should be
replaced with these alternatives:
- `Array::clone_dynamic` → `Array::to_dynamic_array`
- `Enum::clone_dynamic` → `Enum::to_dynamic_enum`
- `List::clone_dynamic` → `List::to_dynamic_list`
- `Map::clone_dynamic` → `Map::to_dynamic_map`
- `Set::clone_dynamic` → `Set::to_dynamic_set`
- `Struct::clone_dynamic` → `Struct::to_dynamic_struct`
- `Tuple::clone_dynamic` → `Tuple::to_dynamic_tuple`
- `TupleStruct::clone_dynamic` → `TupleStruct::to_dynamic_tuple_struct`
# Objective
Contributes to #18238
Updates the `computed_states`, example to use the `children!` macro.
Note that this example requires `--features bevy_dev_tools` to run
## Solution
Updates examples to use the Improved Spawning API merged in
https://github.com/bevyengine/bevy/pull/17521
## Testing
- Did you test these changes? If so, how?
- Opened the examples before and after and verified the same behavior
was observed. I did this on Ubuntu 24.04.2 LTS using `--features
wayland`.
- Are there any parts that need more testing?
- Other OS's and features can't hurt, but this is such a small change it
shouldn't be a problem.
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- Run the examples yourself with and without these changes.
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
- see above
---
## Showcase
n/a
## Migration Guide
n/a
# Objective
Some of Bevy's examples contain boilerplate which is split out into the
`helpers` folder. This allows examples to have access to common
functionality without building into Bevy directly. However, these
helpers are themselves quite high-quality code, and we do intend for
users to read them and even use them. But, we don't list them in the
examples document, and they aren't explicitly checked in CI, only
transitively through examples which import them.
## Solution
- Added `camera_controller` and `widgets` as library examples.
## Testing
- CI
---
## Notes
- Library examples are identical to any other example, just with
`crate-type = ["lib"]` in the `Cargo.toml`. Since they are marked as
libraries, they don't require a `main` function but do require public
items to be documented.
- Library examples opens the possibility of creating examples which
don't need to be actual runnable applications. This may be more
appropriate for certain ECS examples, and allows for adding helpers
which (currently) don't have an example that needs them without them
going stale.
- I learned about this as a concept during research for `no_std`
examples, but believe it has value for Bevy outside that specific niche.
---------
Co-authored-by: mgi388 <135186256+mgi388@users.noreply.github.com>
Co-authored-by: Carter Weinberg <weinbergcarter@gmail.com>
# Objective
Contributes to #18238
Updates the `custom_transitions` and `sub_states` examples to use the
`children!` macro.
## Solution
Updates examples to use the Improved Spawning API merged in
https://github.com/bevyengine/bevy/pull/17521
## Testing
- Did you test these changes? If so, how?
- Opened the examples before and after and verified the same behavior
was observed. I did this on Ubuntu 24.04.2 LTS using `--features
wayland`.
- Are there any parts that need more testing?
- Other OS's and features can't hurt, but this is such a small change it
shouldn't be a problem.
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- Run the examples yourself with and without these changes.
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
- see above
---
## Showcase
n/a
## Migration Guide
n/a
# Objective
Contributes to #18238
Updates the `gamepad_viewer`, example to use the `children!` macro.
## Solution
Updates examples to use the Improved Spawning API merged in
https://github.com/bevyengine/bevy/pull/17521
## Testing
- Did you test these changes? If so, how?
- Opened the examples before and after and verified the same behavior
was observed. I did this on Ubuntu 24.04.2 LTS using `--features
wayland`.
- Are there any parts that need more testing?
- Other OS's and features can't hurt, but this is such a small change it
shouldn't be a problem.
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- Run the examples yourself with and without these changes.
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
- see above
---
## Showcase
n/a
## Migration Guide
n/a
# Objective
Contributes to #18238
Updates the `SteppingPlugin` of the `breakout` example to use the
`children!` macro. Note that in order to test this usage you must use
`--features bevy_debug_stepping` and hit the back-tick key to enable
stepping mode to see the proper text spans rendered.
## Solution
Updates examples to use the Improved Spawning API merged in
https://github.com/bevyengine/bevy/pull/17521
## Testing
- Did you test these changes? If so, how?
- Opened the examples before and after and verified the same behavior
was observed. I did this on Ubuntu 24.04.2 LTS using `--features
wayland`.
- Are there any parts that need more testing?
- Other OS's and features can't hurt, but this is such a small change it
shouldn't be a problem.
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- Run the examples yourself with and without these changes.
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
- see above
---
## Showcase
n/a
## Migration Guide
n/a
# Objective
Contributes to #18238
Updates the `render_primitives` example to use the `children!` macro.
## Solution
Updates examples to use the Improved Spawning API merged in
https://github.com/bevyengine/bevy/pull/17521
## Testing
- Did you test these changes? If so, how?
- Opened the examples before and after and verified the same behavior
was observed. I did this on Ubuntu 24.04.2 LTS using `--features
wayland`.
- Are there any parts that need more testing?
- Other OS's and features can't hurt, but this is such a small change it
shouldn't be a problem.
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- Run the examples yourself with and without these changes.
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
- see above
---
## Showcase
n/a
## Migration Guide
n/a
# Objective
In updating examples to use the Improved Spawning API I got tripped up
on being able to spawn children with a Vec. I eventually figured out
that I could use `Children::spawn(SpawnIter(my_vec.into_iter()))` but
thought there might be a more ergonomic way to approach it. After
tinkering with it for a while I came up with the implementation here. It
allows authors to use `Children::spawn(my_vec)` as an equivalent
implementation.
## Solution
- Implements `<R: Relationship, B: Bundle SpawnableList<R> for Vec<B>`
- uses `alloc::vec::Vec` for compatibility with `no_std` (`std::Vec`
also inherits implementations against the `alloc::vec::Vec` because std
is a re-export of the alloc struct, thanks @bushrat011899 for the info
on this!)
## Testing
- Did you test these changes? If so, how?
- Opened the examples before and after and verified the same behavior
was observed. I did this on Ubuntu 24.04.2 LTS using `--features
wayland`.
- Are there any parts that need more testing?
- Other OS's and features can't hurt, but this is such a small change it
shouldn't be a problem.
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- Run the examples yourself with and without these changes.
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
- see above
## Showcase
n/a
## Migration Guide
- Optional: you may use the new API to spawn `Vec`s of `Bundle` instead
of using the `SpawnIter` approach.
# Objective
Correct spelling
## Solution
Fix typos, specifically ones that I found in folders other than /crates
## Testing
CI
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
Contributes to #18238
Updates the `text_input` and `virtual_time` examples to use the
`children!` macro. I wanted to keep the PR small but chose to do two
examples since they both included only a single `with_children` call.
## Solution
Updates examples to use the Improved Spawning API merged in
https://github.com/bevyengine/bevy/pull/17521
## Testing
- Did you test these changes? If so, how?
- Opened the examples before and after and verified the same behavior
was observed. I did this on Ubuntu 24.04.2 LTS using `--features
wayland`.
- Are there any parts that need more testing?
- Other OS's and features can't hurt, but this is such a small change it
shouldn't be a problem.
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- Run the examples yourself with and without these changes.
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
- see above
---
## Showcase
n/a
## Migration Guide
n/a
# Objective
Contributes to #18238
Updates the `state/states` example to use the `children!` macro. Note
that this example also requires `--features bevy_dev_tools`
## Solution
Updates examples to use the Improved Spawning API merged in
https://github.com/bevyengine/bevy/pull/17521
## Testing
- Did you test these changes? If so, how?
- Opened the examples before and after and verified the same behavior
was observed. I did this on Ubuntu 24.04.2 LTS using `--features
wayland`.
- Are there any parts that need more testing?
- Other OS's and features can't hurt, but this is such a small change it
shouldn't be a problem.
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- Run the examples yourself with and without these changes.
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
- see above
---
## Showcase
n/a
## Migration Guide
n/a
# Objective
- #16883
- Improve the default behaviour of the exclusive fullscreen API.
## Solution
This PR changes the exclusive fullscreen window mode to require the type
`WindowMode::Fullscreen(MonitorSelection, VideoModeSelection)` and
removes `WindowMode::SizedFullscreen`. This API somewhat intentionally
more closely resembles Winit 0.31's upcoming fullscreen and video mode
API.
The new VideoModeSelection enum is specified as follows:
```rust
pub enum VideoModeSelection {
/// Uses the video mode that the monitor is already in.
Current,
/// Uses a given [`crate::monitor::VideoMode`]. A list of video modes supported by the monitor
/// is supplied by [`crate::monitor::Monitor::video_modes`].
Specific(VideoMode),
}
```
### Changing default behaviour
This might be contentious because it removes the previous behaviour of
`WindowMode::Fullscreen` which selected the highest resolution possible.
While the previous behaviour would be quite easy to re-implement as
additional options, or as an impl method on Monitor, I would argue that
this isn't an implementation that should be encouraged.
From the perspective of a Windows user, I prefer what the majority of
modern games do when entering fullscreen which is to preserve the OS's
current resolution settings, which allows exclusive fullscreen to be
entered faster, and to only have it change if I manually select it in
either the options of the game or the OS. The highest resolution
available is not necessarily what the user prefers.
I am open to changing this if I have just missed a good use case for it.
Likewise, the only functionality that `WindowMode::SizedFullscreen`
provided was that it selected the resolution closest to the current size
of the window so it was removed since this behaviour can be replicated
via the new `VideoModeSelection::Specific` if necessary.
## Out of scope
WindowResolution and scale factor act strangely in exclusive fullscreen,
this PR doesn't address it or regress it.
## Testing
- Tested on Windows 11 and macOS 12.7
- Linux untested
## Migration Guide
`WindowMode::SizedFullscreen(MonitorSelection)` and
`WindowMode::Fullscreen(MonitorSelection)` has become
`WindowMode::Fullscreen(MonitorSelection, VideoModeSelection)`.
Previously, the VideoMode was selected based on the closest resolution
to the current window size for SizedFullscreen and the largest
resolution for Fullscreen. It is possible to replicate that behaviour by
searching `Monitor::video_modes` and selecting it with
`VideoModeSelection::Specific(VideoMode)` but it is recommended to use
`VideoModeSelection::Current` as the default video mode when entering
fullscreen.
# Objective
`Text2d` testing hasn't been as thorough as text in the UI, and it
suffered a bunch of bugs / perf issues in recent cycles.
## Solution
Add some more `Text2d` scenarios to the 2d testbed to catch bugs,
testing bounded and unbounded text with various justification.
## Testing
`cargo run --example testbed_2d` (press space a few times)
<img width="1280" alt="Screenshot 2025-03-10 at 1 02 03 PM"
src="https://github.com/user-attachments/assets/1e4ee39c-809b-4cc6-81bd-68e67b9625b5"
/>
---------
Co-authored-by: Ben Frankel <ben.frankel7@gmail.com>
Update the documentation comment to correctly state that the function
responds to spacebar presses rather than mouse clicks. This aligns the
documentation with the actual implementation, which was already using
keyboard input.
# Objective
- Fix incorrect documentation comment for the cycle_modes function that
inaccurately described using mouse input when the implementation
actually uses spacebar.
- This ensures documentation accuracy and prevents confusion for new
learners.
## Solution
- Updated the documentation comment to correctly state that the function
responds to spacebar presses rather than mouse clicks.
- The code functionality remains unchanged.
# Objective
Add an option to `many_buttons` that spawns a grid of buttons where each
button is rendered through its own camera.
## Testing
Run with:
```
cargo run --example many_buttons --release -- --many-cameras --buttons 20
```
The default buttons count of `110` is too much for my computer.
# Objective
`extract_text_shadows` was still using `UiTargetCamera` and
`DefaultUiCamera` for UI camera resolution, which no longer always
selects the right camera.
To see this modify the last lines of the `multiple_windows` example
from:
```rust
commands.spawn((
Text::new("First window"),
node.clone(),
// Since we are using multiple cameras, we need to specify which camera UI should be rendered to
UiTargetCamera(first_window_camera),
));
commands.spawn((
Text::new("Second window"),
node,
UiTargetCamera(second_window_camera),
));
```
to:
```rust
commands
.spawn((
node.clone(),
// Since we are using multiple cameras, we need to specify which camera UI should be rendered to
UiTargetCamera(first_window_camera),
))
.with_child((Text::new("First window"), TextShadow::default()));
commands
.spawn((node, UiTargetCamera(second_window_camera)))
.with_child((Text::new("Second window"), TextShadow::default()));
```
which results in the shadow that is meant to be displayed for the
"Second Window" label instead being written over the first:
<img width="800" alt="first_window_label"
src="https://github.com/user-attachments/assets/2eebccba-5749-4064-bb1c-e4f25ff0baf7">
## Solution
Remove the `UiTargetCamera` query and the `default_camera` parameter
from `extract_text_shadows` and use `UiCameraMap` with
`ComputedNodeTarget` instead.
## Testing
The `multiple_windows` example for this PR has been updated to add text
shadow to the window labels. You should see that it displays the "Second
Window" label's shadow correctly now.
# Objective
- In `Camera::viewport_to_world_2d`, `Camera::viewport_to_world`,
`Camera::world_to_viewport` and `Camera::world_to_viewport_with_depth`,
the results were incorrect when the `Camera::viewport` field was
configured with a viewport position that was non-zero. This PR attempts
to correct that.
- Fixes#16200
## Solution
- This PR now takes the viewport position into account in the functions
mentioned above.
- Extended `2d_viewport_to_world` example to test the functions with a
dynamic viewport position and size, camera positions and zoom levels. It
is probably worth discussing whether to change the example, add a new
one or just completely skip touching the examples.
## Testing
Used the modified example to test the functions with dynamic camera
transform as well as dynamic viewport size and position.
# Objective
WESL's pre-MVP `0.1.0` has been
[released](https://docs.rs/wesl/latest/wesl/)!
Add support for WESL shader source so that we can begin playing and
testing WESL, as well as aiding in their development.
## Solution
Adds a `ShaderSource::WESL` that can be used to load `.wesl` shaders.
Right now, we don't support mixing `naga-oil`. Additionally, WESL
shaders currently need to pass through the naga frontend, which the WESL
team is aware isn't great for performance (they're working on compiling
into naga modules). Also, since our shaders are managed using the asset
system, we don't currently support using file based imports like `super`
or package scoped imports. Further work will be needed to asses how we
want to support this.
---
## Showcase
See the `shader_material_wesl` example. Be sure to press space to
activate party mode (trigger conditional compilation)!
https://github.com/user-attachments/assets/ec6ad19f-b6e4-4e9d-a00f-6f09336b08a4
# Objective
simplify some code and improve Event macro
Closes https://github.com/bevyengine/bevy/issues/14336,
# Showcase
you can now write derive Events like so
```rust
#[derive(event)]
#[event(auto_propagate, traversal = MyType)]
struct MyEvent;
```
## Objective
Fixes#18092
Bevy's current error type is a simple type alias for `Box<dyn Error +
Send + Sync + 'static>`. This largely works as a catch-all error, but it
is missing a critical feature: the ability to capture a backtrace at the
point that the error occurs. The best way to do this is `anyhow`-style
error handling: a new error type that takes advantage of the fact that
the `?` `From` conversion happens "inline" to capture the backtrace at
the point of the error.
## Solution
This PR adds a new `BevyError` type (replacing our old
`std::error::Error` type alias), which uses the "from conversion
backtrace capture" approach:
```rust
fn oh_no() -> Result<(), BevyError> {
// this fails with Rust's built in ParseIntError, which
// is converted into the catch-all BevyError type
let number: usize = "hi".parse()?;
println!("parsed {number}");
Ok(())
}
```
This also updates our exported `Result` type alias to default to
`BevyError`, meaning you can write this instead:
```rust
fn oh_no() -> Result {
let number: usize = "hi".parse()?;
println!("parsed {number}");
Ok(())
}
```
When a BevyError is encountered in a system, it will use Bevy's default
system error handler (which panics by default). BevyError does custom
"backtrace filtering" by default, meaning we can cut out the _massive_
amount of "rust internals", "async executor internals", and "bevy system
scheduler internals" that show up in backtraces. It also trims out the
first generally-unnecssary `From` conversion backtrace lines that make
it harder to locate the real error location. The result is a blissfully
simple backtrace by default:
The full backtrace can be shown by setting the `BEVY_BACKTRACE=full`
environment variable. Non-BevyError panics still use the default Rust
backtrace behavior.
One issue that prevented the truly noise-free backtrace during panics
that you see above is that Rust's default panic handler will print the
unfiltered (and largely unhelpful real-panic-point) backtrace by
default, in _addition_ to our filtered BevyError backtrace (with the
helpful backtrace origin) that we capture and print. To resolve this, I
have extended Bevy's existing PanicHandlerPlugin to wrap the default
panic handler. If we panic from the result of a BevyError, we will skip
the default "print full backtrace" panic handler. This behavior can be
enabled and disabled using the new `error_panic_hook` cargo feature in
`bevy_app` (which is enabled by default).
One downside to _not_ using `Box<dyn Error>` directly is that we can no
longer take advantage of the built-in `Into` impl for strings to errors.
To resolve this, I have added the following:
```rust
// Before
Err("some error")?
// After
Err(BevyError::message("some error"))?
```
We can discuss adding shorthand methods or macros for this (similar to
anyhow's `anyhow!("some error")` macro), but I'd prefer to discuss that
later.
I have also added the following extension method:
```rust
// Before
some_option.ok_or("some error")?;
// After
some_option.ok_or_message("some error")?;
```
I've also moved all of our existing error infrastructure from
`bevy_ecs::result` to `bevy_ecs::error`, as I think that is the better
home for it
## Why not anyhow (or eyre)?
The biggest reason is that `anyhow` needs to be a "generically useful
error type", whereas Bevy is a much narrower scope. By using our own
error, we can be significantly more opinionated. For example, anyhow
doesn't do the extensive (and invasive) backtrace filtering that
BevyError does because it can't operate on Bevy-specific context, and
needs to be generically useful.
Bevy also has a lot of operational context (ex: system info) that could
be useful to attach to errors. If we have control over the error type,
we can add whatever context we want to in a structured way. This could
be increasingly useful as we add more visual / interactive error
handling tools and editor integrations.
Additionally, the core approach used is simple and requires almost no
code. anyhow clocks in at ~2500 lines of code, but the impl here uses
160. We are able to boil this down to exactly what we need, and by doing
so we improve our compile times and the understandability of our code.
# Objective
- Today, enabling asset processing can generate many meta files. This
makes it a painful transition for users as they get a "mega commit"
containing tons of meta files.
## Solution
- Stop automatically generating meta files! Users can just leave the
meta files defaulted.
- Add a function `AssetServer::write_default_meta_file_for_path`
## Testing
- Tested this manually on the asset_processing example (by removing the
meta files for the assets that had default meta files).
- I did not add a unit test for the `write_default_meta_file_for_path`
since we don't have an in-memory asset writer. Writing one could be
useful in the future.
---
## Showcase
Asset processing no longer automatically generates meta files! This
makes it much easier to transition to using asset processing since you
don't suddenly get many meta files when turning it on.
You can still manually generate meta files using the new
`AssetServer::write_default_meta_file_for_path` function.
## Objective
`insert_or_spawn_batch` is due to be deprecated eventually (#15704), and
removing uses internally will make that easier.
## Solution
Replaced internal uses of `insert_or_spawn_batch` with
`try_insert_batch` (non-panicking variant because
`insert_or_spawn_batch` didn't panic).
All of the internal uses are in rendering code. Since retained rendering
was meant to get rid non-opaque entity IDs, I assume the code was just
using `insert_or_spawn_batch` because `insert_batch` didn't exist and
not because it actually wanted to spawn something. However, I am *not*
confident in my ability to judge rendering code.
This reverts commit 0b5302d96a.
# Objective
- Fixes#18158
- #17482 introduced rendering changes and was merged a bit too fast
## Solution
- Revert #17482 so that it can be redone and rendering changes discussed
before being merged. This will make it easier to compare changes with
main in the known "valid" state
This is not an issue with the work done in #17482 that is still
interesting
Fixes#17720
## Objective
Spawning RelationshipTargets from scenes currently fails to preserve
RelationshipTarget ordering (ex: `Children` has an arbitrary order).
This is because it uses the normal hook flow to set up the collection,
which means we are pushing onto the collection in _spawn order_ (which
is currently in archetype order, which will often produce mismatched
orderings).
We need to preserve the ordering in the original RelationshipTarget
collection. Ideally without expensive checking / fixups.
## Solution
One solution would be to spawn in hierarchy-order. However this gets
complicated as there can be multiple hierarchies, and it also means we
can't spawn in more cache-friendly orders (ex: the current per-archetype
spawning, or future even-smarter per-table spawning). Additionally,
same-world cloning has _slightly_ more nuanced needs (ex: recursively
clone linked relationships, while maintaining _original_ relationships
outside of the tree via normal hooks).
The preferred approach is to directly spawn the remapped
RelationshipTarget collection, as this trivially preserves the ordering.
Unfortunately we can't _just_ do that, as when we spawn the children
with their Relationships (ex: `ChildOf`), that will insert a duplicate.
We could "fixup" the collection retroactively by just removing the back
half of duplicates, but this requires another pass / more lookups /
allocating twice as much space. Additionally, it becomes complicated
because observers could insert additional children, making it harder
(aka more expensive) to determine which children are dupes and which are
not.
The path I chose is to support "opting out" of the relationship target
hook in the contexts that need that, as this allows us to just cheaply
clone the mapped collection. The relationship hook can look for this
configuration when it runs and skip its logic when that happens. A
"simple" / small-amount-of-code way to do this would be to add a "skip
relationship spawn" flag to World. Sadly, any hook / observer that runs
_as the result of an insert_ would also read this flag. We really need a
way to scope this setting to a _specific_ insert.
Therefore I opted to add a new `RelationshipInsertHookMode` enum and an
`entity.insert_with_relationship_insert_hook_mode` variant. Obviously
this is verbose and ugly. And nobody wants _more_ insert variants. But
sadly this was the best I could come up with from a performance and
capability perspective. If you have alternatives let me know!
There are three variants:
1. `RelationshipInsertHookMode::Run`: always run relationship insert
hooks (this is the default)
2. `RelationshipInsertHookMode::Skip`: do not run any relationship
insert hooks for this insert (this is used by spawner code)
3. `RelationshipInsertHookMode::RunIfNotLinked`: only run hooks for
_unlinked_ relationships (this is used in same-world recursive entity
cloning to preserve relationships outside of the deep-cloned tree)
Note that I have intentionally only added "insert with relationship hook
mode" variants to the cases we absolutely need (everything else uses the
default `Run` mode), just to keep the code size in check. I do not think
we should add more without real _very necessary_ use cases.
I also made some other minor tweaks:
1. I split out `SourceComponent` from `ComponentCloneCtx`. Reading the
source component no longer needlessly blocks mutable access to
`ComponentCloneCtx`.
2. Thanks to (1), I've removed the `RefCell` wrapper over the cloned
component queue.
3. (1) also allowed me to write to the EntityMapper while queuing up
clones, meaning we can reserve entities during the component clone and
write them to the mapper _before_ inserting the component, meaning
cloned collections can be mapped on insert.
4. I've removed the closure from `write_target_component_ptr` to
simplify the API / make it compatible with the split `SourceComponent`
approach.
5. I've renamed `EntityCloner::recursive` to
`EntityCloner::linked_cloning` to connect that feature more directly
with `RelationshipTarget::LINKED_SPAWN`
6. I've removed `EntityCloneBehavior::RelationshipTarget`. This was
always intended to be temporary, and this new behavior removes the need
for it.
---------
Co-authored-by: Viktor Gustavsson <villor94@gmail.com>
# Objective
- have a testbed for UI
## Solution
- move previous `ui` example to `full_ui`
- add a testbed ui with several scenes
- `ui_layout_rounding` is one of those scenes, so remove it as a
standalone example
the previous `ui` / new `full_ui` is I think still useful as it has some
things like scroll, debug ui that are not shown anywhere else
