# Objective
The clippy lint `type_complexity` is known not to play well with bevy.
It frequently triggers when writing complex queries, and taking the
lint's advice of using a type alias almost always just obfuscates the
code with no benefit. Because of this, this lint is currently ignored in
CI, but unfortunately it still shows up when viewing bevy code in an
IDE.
As someone who's made a fair amount of pull requests to this repo, I
will say that this issue has been a consistent thorn in my side. Since
bevy code is filled with spurious, ignorable warnings, it can be very
difficult to spot the *real* warnings that must be fixed -- most of the
time I just ignore all warnings, only to later find out that one of them
was real after I'm done when CI runs.
## Solution
Suppress this lint in all bevy crates. This was previously attempted in
#7050, but the review process ended up making it more complicated than
it needs to be and landed on a subpar solution.
The discussion in https://github.com/rust-lang/rust-clippy/pull/10571
explores some better long-term solutions to this problem. Since there is
no timeline on when these solutions may land, we should resolve this
issue in the meantime by locally suppressing these lints.
### Unresolved issues
Currently, these lints are not suppressed in our examples, since that
would require suppressing the lint in every single source file. They are
still ignored in CI.
# Objective
Make the coordinate systems of screen-space items (cursor position, UI,
viewports, etc.) consistent.
## Solution
Remove the weird double inversion of the cursor position's Y origin.
Once in bevy_winit to the bottom and then again in bevy_ui back to the
top.
This leaves the origin at the top left like it is in every other popular
app framework.
Update the `world_to_viewport`, `viewport_to_world`, and
`viewport_to_world_2d` methods to flip the Y origin (as they should
since the viewport coordinates were always relative to the top left).
## Migration Guide
`Window::cursor_position` now returns the position of the cursor
relative to the top left instead of the bottom left.
This now matches other screen-space coordinates like
`RelativeCursorPosition`, UI, and viewports.
The `world_to_viewport`, `viewport_to_world`, and `viewport_to_world_2d`
methods on `Camera` now return/take the viewport position relative to
the top left instead of the bottom left.
If you were using `world_to_viewport` to position a UI node the returned
`y` value should now be passed into the `top` field on `Style` instead
of the `bottom` field.
Note that this might shift the position of the UI node as it is now
anchored at the top.
If you were passing `Window::cursor_position` to `viewport_to_world` or
`viewport_to_world_2d` no change is necessary.
# Objective
Text glyphs that were clipped were not sized correctly because the
transform extracted from the `extract_text_uinodes` had a scaling on it
that wasn't accounted for.
fixes#8167
## Solution
Remove the scaling from the transform and multiply the size of the
glyphs by the inverse of the scale factor.
# Objective
Add helper functions to `UiImage` for creating flipped images.
## Changelog
* Added `with_flip_x` and `with_flip_y` methods to `UiImage` that return
the `UiImage` flipped along the respective axis.
# Objective
When a `CalculatedSize` component from a UI Node entity is removed, the
corresponding Taffy measure isn't removed which will mess up the layout
in confusing, unpredictable ways.
## Solution
Iterate through all the entities with removed `CalculatedSize`
components and remove the corresponding Taffy measures.
# Objective
In the
[`Text`](3442a13d2c/crates/bevy_text/src/text.rs (L18))
struct the field is named: `linebreak_behaviour`, the British spelling
of _behavior_.
**Update**, also found:
- `FileDragAndDrop::HoveredFileCancelled`
- `TouchPhase::Cancelled`
- `Touches.just_cancelled`
The majority of all spelling is in the US but when you have a lot of
contributors across the world, sometimes
spelling differences can pop up in APIs such as in this case.
For consistency, I think it would be worth a while to ensure that the
API is persistent.
Some examples:
`from_reflect.rs` has `DefaultBehavior`
TextStyle has `color` and uses the `Color` struct.
In `bevy_input/src/Touch.rs` `TouchPhase::Cancelled` and _canceled_ are
used interchangeably in the documentation
I've found that there is also the same type of discrepancies in the
documentation, though this is a low priority but is worth checking.
**Update**: I've now checked the documentation (See #8291)
## Solution
I've only renamed the inconsistencies that have breaking changes and
documentation pertaining to them. The rest of the documentation will be
changed via #8291.
Do note that the winit API is written with UK spelling, thus this may be
a cause for confusion:
`winit::event::TouchPhase::Cancelled => TouchPhase::Canceled`
`winit::event::WindowEvent::HoveredFileCancelled` -> Related to
`FileDragAndDrop::HoveredFileCanceled`
But I'm hoping to maybe outline other spelling inconsistencies in the
API, and maybe an addition to the contribution guide.
---
## Changelog
- `Text` field `linebreak_behaviour` has been renamed to
`linebreak_behavior`.
- Event `FileDragAndDrop::HoveredFileCancelled` has been renamed to
`HoveredFileCanceled`
- Function `Touches.just_cancelled` has been renamed to
`Touches.just_canceled`
- Event `TouchPhase::Cancelled` has been renamed to
`TouchPhase::Canceled`
## Migration Guide
Update where `linebreak_behaviour` is used to `linebreak_behavior`
Updated the event `FileDragAndDrop::HoveredFileCancelled` where used to
`HoveredFileCanceled`
Update `Touches.just_cancelled` where used as `Touches.just_canceled`
The event `TouchPhase::Cancelled` is now called `TouchPhase::Canceled`
# Objective
Fixes#8089.
## Solution
Splits the MainPass3dNode into 2 nodes, one for the opaque + alpha
passes and one for the transparent pass.
---
## Changelog
- Split MainPass3dNode into MainOpaquePass3dNode and
MainTransparentPass3dNode
- Combine opaque and alpha phases in MainOpaquePass3dNode into one pass
- Create `START_MAIN_PASS` and `END_MAIN_PASS` empty nodes as labels
- Main pass becomes `START_MAIN_PASS -> MAIN_OPAQUE_PASS ->
MAIN_TRANSPARENT_PASS -> END_MAIN_PASS`
## Migration Guide
Nodes that previously added edges involving `MAIN_PASS` should now add
edges to or from `START_MAIN_PASS` or `END_MAIN_PASS` respectively.
# Objective
- Currently, the render graph slots are only used to pass the
view_entity around. This introduces significant boilerplate for very
little value. Instead of using slots for this, make the view_entity part
of the `RenderGraphContext`. This also means we won't need to have
`IN_VIEW` on every node and and we'll be able to use the default impl of
`Node::input()`.
## Solution
- Add `view_entity: Option<Entity>` to the `RenderGraphContext`
- Update all nodes to use this instead of entity slot input
---
## Changelog
- Add optional `view_entity` to `RenderGraphContext`
## Migration Guide
You can now get the view_entity directly from the `RenderGraphContext`.
When implementing the Node:
```rust
// 0.10
struct FooNode;
impl FooNode {
const IN_VIEW: &'static str = "view";
}
impl Node for FooNode {
fn input(&self) -> Vec<SlotInfo> {
vec![SlotInfo::new(Self::IN_VIEW, SlotType::Entity)]
}
fn run(
&self,
graph: &mut RenderGraphContext,
// ...
) -> Result<(), NodeRunError> {
let view_entity = graph.get_input_entity(Self::IN_VIEW)?;
// ...
Ok(())
}
}
// 0.11
struct FooNode;
impl Node for FooNode {
fn run(
&self,
graph: &mut RenderGraphContext,
// ...
) -> Result<(), NodeRunError> {
let view_entity = graph.view_entity();
// ...
Ok(())
}
}
```
When adding the node to the graph, you don't need to specify a slot_edge
for the view_entity.
```rust
// 0.10
let mut graph = RenderGraph::default();
graph.add_node(FooNode::NAME, node);
let input_node_id = draw_2d_graph.set_input(vec![SlotInfo::new(
graph::input::VIEW_ENTITY,
SlotType::Entity,
)]);
graph.add_slot_edge(
input_node_id,
graph::input::VIEW_ENTITY,
FooNode::NAME,
FooNode::IN_VIEW,
);
// add_node_edge ...
// 0.11
let mut graph = RenderGraph::default();
graph.add_node(FooNode::NAME, node);
// add_node_edge ...
```
## Notes
This PR paired with #8007 will help reduce a lot of annoying boilerplate
with the render nodes. Depending on which one gets merged first. It will
require a bit of clean up work to make both compatible.
I tagged this as a breaking change, because using the old system to get
the view_entity will break things because it's not a node input slot
anymore.
## Notes for reviewers
A lot of the diffs are just removing the slots in every nodes and graph
creation. The important part is mostly in the
graph_runner/CameraDriverNode.
# Objective
Add viewport variants to `Val` that specify a percentage length based on
the size of the window.
## Solution
Add the variants `Vw`, `Vh`, `VMin` and `VMax` to `Val`.
Add a physical window size parameter to the `from_style` function and
use it to convert the viewport variants to Taffy Points values.
One issue: It isn't responsive to window resizes. So `flex_node_system`
has to do a full update every time the window size changes. Perhaps this
can be fixed with support from Taffy.
---
## Changelog
* Added `Val` viewport unit variants `Vw`, `Vh`, `VMin` and `VMax`.
* Modified `convert` module to support the new `Val` variants.
* Changed `flex_node_system` to support the new `Val` variants.
* Perform full layout update on screen resizing, to propagate the new
viewport size to all nodes.
# Objective
Add comments explaining:
* That `Val::Px` is a value in logical pixels
* That `Val::Percent` is based on the length of its parent along a
specific axis.
* How the layout algorithm determines which axis the percentage should
be based on.
# Objective
Current `Node` doc comment:
```rust
/// The size of the node as width and height in pixels
/// automatically calculated by [`super::flex::flex_node_system`]
```
It should be changed to make it clear that `Node` stores the size in logical pixels, not physical.
# Objective
Upgrade to Taffy 0.3.3
Fixes: #7712
## Solution
Upgrade to Taffy 0.3.3 with the `grid` feature disabled.
---
## Changelog
* Changed Taffy version to 0.3.3 and disabled its `grid` feature.
* Added the `Start` and `End` variants to `AlignItems`, `AlignSelf`, `AlignContent` and `JustifyContent`.
* Added the `SpaceEvenly` variant to `AlignContent`.
* Updated `from_style` for Taffy 0.3.3.
# Objective
- Fixes#7874.
- The `bevy_text` dependency is optional for `bevy_ui`, but the `accessibility` module depended on it.
## Solution
- Guard the `accessibility` module behind the `bevy_text` feature and only add the plugin when it's enabled.
# Objective
UIs created for Bevy cannot currently be made accessible. This PR aims to address that.
## Solution
Integrate AccessKit as a dependency, adding accessibility support to existing bevy_ui widgets.
## Changelog
### Added
* Integrate with and expose [AccessKit](https://accesskit.dev) for platform accessibility.
* Add `Label` for marking text specifically as a label for UI controls.
# Objective
Support the following syntax for adding systems:
```rust
App::new()
.add_system(setup.on_startup())
.add_systems((
show_menu.in_schedule(OnEnter(GameState::Paused)),
menu_ssytem.in_set(OnUpdate(GameState::Paused)),
hide_menu.in_schedule(OnExit(GameState::Paused)),
))
```
## Solution
Add the traits `IntoSystemAppConfig{s}`, which provide the extension methods necessary for configuring which schedule a system belongs to. These extension methods return `IntoSystemAppConfig{s}`, which `App::add_system{s}` uses to choose which schedule to add systems to.
---
## Changelog
+ Added the extension methods `in_schedule(label)` and `on_startup()` for configuring the schedule a system belongs to.
## Future Work
* Replace all uses of `add_startup_system` in the engine.
* Deprecate this method
# Objective
- `bevy_text` used to be "optional". the feature could be disabled, which meant that the systems were not added but `bevy_text` was still compiled because of a hard dependency in `bevy_ui`
- Running something without `bevy_text` enabled and with `bevy_ui` enabled now crashes:
```
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /bevy/crates/bevy_ecs/src/schedule/schedule.rs:1147:34
```
- This is because `bevy_ui` declares some of its systems in ambiguity sets with systems from `bevy_text`, which were not added if `bevy_text` is disabled
## Solution
- Make `bevy_text` completely optional
## Migration Guide
- feature `bevy_text` now completely removes `bevy_text` from the dependencies when not enabled. Enable feature `bevy_text` if you use Bevy to render text
# Objective
`TextBundle` should have a `BackgroundColor` component.
Apart from adding emphasis etc to text, adding a background color to text nodes can be extremely useful for understanding how Bevy aligns, sizes and positions text, and identifying and debugging problems.
It's easy for users to insert the `BackgroundColor` component themselves but not immediately obvious or discoverable that it's possible. A `BackgroundColor` component allows us to add a `with_background_color` helper function to `TextBundle`.
related issue: #5935
## Solution
Add a `BackgroundColor` component to `TextBundle`.
---
## Changelog
* Added a `BackgroundColor` component to `TextBundle`.
* Added a helper method `with_background_color` to `TextBundle`.
## Migration Guide
`TextBundle` now has a `BackgroundColor` component.
Use `TextBundle`'s `background_color` field or the `with_background_color` method to set a background color for text when spawning a text node, in place of manual insertion of a `BackgroundColor` component.
# Objective
Splits tone mapping from https://github.com/bevyengine/bevy/pull/6677 into a separate PR.
Address https://github.com/bevyengine/bevy/issues/2264.
Adds tone mapping options:
- None: Bypasses tonemapping for instances where users want colors output to match those set.
- Reinhard
- Reinhard Luminance: Bevy's exiting tonemapping
- [ACES](https://github.com/TheRealMJP/BakingLab/blob/master/BakingLab/ACES.hlsl) (Fitted version, based on the same implementation that Godot 4 uses) see https://github.com/bevyengine/bevy/issues/2264
- [AgX](https://github.com/sobotka/AgX)
- SomewhatBoringDisplayTransform
- TonyMcMapface
- Blender Filmic
This PR also adds support for EXR images so they can be used to compare tonemapping options with reference images.
## Migration Guide
- Tonemapping is now an enum with NONE and the various tonemappers.
- The DebandDither is now a separate component.
Co-authored-by: JMS55 <47158642+JMS55@users.noreply.github.com>
# Objective
Allow for creating pipelines that use push constants. To be able to use push constants. Fixes#4825
As of right now, trying to call `RenderPass::set_push_constants` will trigger the following error:
```
thread 'main' panicked at 'wgpu error: Validation Error
Caused by:
In a RenderPass
note: encoder = `<CommandBuffer-(0, 59, Vulkan)>`
In a set_push_constant command
provided push constant is for stage(s) VERTEX | FRAGMENT | VERTEX_FRAGMENT, however the pipeline layout has no push constant range for the stage(s) VERTEX | FRAGMENT | VERTEX_FRAGMENT
```
## Solution
Add a field push_constant_ranges to` RenderPipelineDescriptor` and `ComputePipelineDescriptor`.
This PR supersedes #4908 which now contains merge conflicts due to significant changes to `bevy_render`.
Meanwhile, this PR also made the `layout` field of `RenderPipelineDescriptor` and `ComputePipelineDescriptor` non-optional. If the user do not need to specify the bind group layouts, they can simply supply an empty vector here. No need for it to be optional.
---
## Changelog
- Add a field push_constant_ranges to RenderPipelineDescriptor and ComputePipelineDescriptor
- Made the `layout` field of RenderPipelineDescriptor and ComputePipelineDescriptor non-optional.
## Migration Guide
- Add push_constant_ranges: Vec::new() to every `RenderPipelineDescriptor` and `ComputePipelineDescriptor`
- Unwrap the optional values on the `layout` field of `RenderPipelineDescriptor` and `ComputePipelineDescriptor`. If the descriptor has no layout, supply an empty vector.
Co-authored-by: Zhixing Zhang <me@neoto.xin>
# Objective
The current doc comment for `flex-basis` states that it is "The initial size of the item", which is a bit confusing since size in Bevy is mostly used to refer to two-dimensional extents but `flex-basis` is a one-dimensional value.
It also needs to explain that:
* `flex-basis` sets the initial length of the main axis.
* Overrides `size` on the main axis.
* Obeys the `min_size` and `max_size` constraints.
# Objective
The text contained by a text node is only recomputed when its `Style` or `Text` components change, or when the scale factor changes. Not when the geometry of the text node is modified.
Make it so that any change in text node size triggers a text recomputation.
## Solution
Change `text_system` so that it queries for text nodes with changed `Node` components and recomputes their text.
---
Most users won't notice any difference but it should fix some confusing edge cases in more complicated and interactive layouts.
## Changelog
* Added `Changed<Node>` to the change detection query of `text_system`. This ensures that any change in the size of a text node will cause any text it contains to be recomputed.
# Objective
Add doc tests for the `Size` constructor functions.
Also changed the function descriptions so they explicitly state the values that elided values are given.
## Changelog
* Added doc tests for the `Size` constructor functions.
# Objective
The `size` field of `CalculatedSize` shouldn't be a `Size` as it only ever stores (unscaled) pixel values. By default its fields are `Val::Auto` but these are converted to `0`s before being sent to Taffy.
## Solution
Change the `size` field of `CalculatedSize` to a Vec2.
## Changelog
* Changed the `size` field of `CalculatedSize` to a Vec2.
* Removed the `Val` <-> `f32` conversion code for `CalculatedSize`.
## Migration Guide
* The size field of `CalculatedSize` has been changed to a `Vec2`.
# Objective
`Size::width` sets the `height` field to `Val::DEFAULT` which is `Val::Undefined`, but the default for `Size` `height` is `Val::Auto`.
`Size::height` has the same problem, but with the `width` field.
The UI examples specify numeric values in many places where they could either be elided or replaced by composition of the Flex enum properties.
related: https://github.com/bevyengine/bevy/pull/7468
fixes: https://github.com/bevyengine/bevy/issues/6498
## Solution
Change `Size::width` so it sets `height` to `Val::AUTO` and change `Size::height` so it sets `width` to `Val::AUTO`.
Added some tests so this doesn't happen again.
## Changelog
Changed `Size::width` so it sets the `height` to `Val::AUTO`.
Changed `Size::height` so it sets the `width` to `Val::AUTO`.
Added tests to `geometry.rs` for `Size` and `UiRect` to ensure correct behaviour.
Simplified the UI examples. Replaced numeric values with the Flex property enums or elided them where possible, and removed the remaining use of auto margins.
## Migration Guide
The `Size::width` constructor function now sets the `height` to `Val::Auto` instead of `Val::Undefined`.
The `Size::height` constructor function now sets the `width` to `Val::Auto` instead of `Val::Undefined`.
fixes#6799
# Objective
We should be able to reuse the `Globals` or `View` shader struct definitions from anywhere (including third party plugins) without needing to worry about defining unrelated shader defs.
Also we'd like to refactor these structs to not be repeatedly defined.
## Solution
Refactor both `Globals` and `View` into separate importable shaders.
Use the imports throughout.
Co-authored-by: Torstein Grindvik <52322338+torsteingrindvik@users.noreply.github.com>
# Objective
The current `AlignSelf` doc comments:
```rust
pub enum AlignSelf {
/// Use the value of [`AlignItems`]
Auto,
/// If the parent has [`AlignItems::Center`] only this item will be at the start
FlexStart,
/// If the parent has [`AlignItems::Center`] only this item will be at the end
FlexEnd,
/// If the parent has [`AlignItems::FlexStart`] only this item will be at the center
Center,
/// If the parent has [`AlignItems::Center`] only this item will be at the baseline
Baseline,
/// If the parent has [`AlignItems::Center`] only this item will stretch along the whole cross axis
Stretch,
}
```
Actual behaviour of `AlignSelf` in Bevy main:
<img width="642" alt="align_self" src="https://user-images.githubusercontent.com/27962798/217795178-7a82638f-118d-4474-b7f9-ca27f204731d.PNG">
The white label at the top of each column is the parent node's `AlignItems` setting.
`AlignSelf` is always applied, not (as the documentation states) only when the parent has `AlignItems::Center` or `AlignItems::FlexStart` set.
```rust
use bevy::prelude::*;
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_startup_system(setup)
.run();
}
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands.spawn(Camera2dBundle::default());
commands.spawn(NodeBundle {
style: Style {
justify_content: JustifyContent::SpaceAround,
align_items: AlignItems::Center,
size: Size::new(Val::Percent(100.), Val::Percent(100.)),
..Default::default()
},
background_color: BackgroundColor(Color::NAVY),
..Default::default()
}).with_children(|builder| {
for align_items in [
AlignItems::Baseline,
AlignItems::FlexStart,
AlignItems::Center,
AlignItems::FlexEnd,
AlignItems::Stretch,
] {
builder.spawn(NodeBundle {
style: Style {
align_items,
flex_direction: FlexDirection::Column,
justify_content: JustifyContent::SpaceBetween,
size: Size::new(Val::Px(150.), Val::Px(500.)),
..Default::default()
},
background_color: BackgroundColor(Color::DARK_GRAY),
..Default::default()
}).with_children(|builder| {
builder.spawn((
TextBundle {
text: Text::from_section(
format!("AlignItems::{align_items:?}"),
TextStyle {
font: asset_server.load("fonts/FiraSans-Regular.ttf"),
font_size: 16.0,
color: Color::BLACK,
},
),
style: Style {
align_self: AlignSelf::Stretch,
..Default::default()
},
..Default::default()
},
BackgroundColor(Color::WHITE),
));
for align_self in [
AlignSelf::Auto,
AlignSelf::FlexStart,
AlignSelf::Center,
AlignSelf::FlexEnd,
AlignSelf::Baseline,
AlignSelf::Stretch,
] {
builder.spawn((
TextBundle {
text: Text::from_section(
format!("AlignSelf::{align_self:?}"),
TextStyle {
font: asset_server.load("fonts/FiraSans-Regular.ttf"),
font_size: 16.0,
color: Color::WHITE,
},
),
style: Style {
align_self,
..Default::default()
},
..Default::default()
},
BackgroundColor(Color::BLACK),
));
}
});
}
});
}
```
# Objective
Fix#7377Fix#7513
## Solution
Record the changes made to the Bevy `Window` from `winit` as 'canon' to avoid Bevy sending those changes back to `winit` again, causing a feedback loop.
## Changelog
* Removed `ModifiesWindows` system label.
Neither `despawn_window` nor `changed_window` actually modify the `Window` component so all the `.after(ModifiesWindows)` shouldn't be necessary.
* Moved `changed_window` and `despawn_window` systems to `CoreStage::Last` to avoid systems making changes to the `Window` between `changed_window` and the end of the frame as they would be ignored.
## Migration Guide
The `ModifiesWindows` system label was removed.
Co-authored-by: devil-ira <justthecooldude@gmail.com>
# Objective
NOTE: This depends on #7267 and should not be merged until #7267 is merged. If you are reviewing this before that is merged, I highly recommend viewing the Base Sets commit instead of trying to find my changes amongst those from #7267.
"Default sets" as described by the [Stageless RFC](https://github.com/bevyengine/rfcs/pull/45) have some [unfortunate consequences](https://github.com/bevyengine/bevy/discussions/7365).
## Solution
This adds "base sets" as a variant of `SystemSet`:
A set is a "base set" if `SystemSet::is_base` returns `true`. Typically this will be opted-in to using the `SystemSet` derive:
```rust
#[derive(SystemSet, Clone, Hash, Debug, PartialEq, Eq)]
#[system_set(base)]
enum MyBaseSet {
A,
B,
}
```
**Base sets are exclusive**: a system can belong to at most one "base set". Adding a system to more than one will result in an error. When possible we fail immediately during system-config-time with a nice file + line number. For the more nested graph-ey cases, this will fail at the final schedule build.
**Base sets cannot belong to other sets**: this is where the word "base" comes from
Systems and Sets can only be added to base sets using `in_base_set`. Calling `in_set` with a base set will fail. As will calling `in_base_set` with a normal set.
```rust
app.add_system(foo.in_base_set(MyBaseSet::A))
// X must be a normal set ... base sets cannot be added to base sets
.configure_set(X.in_base_set(MyBaseSet::A))
```
Base sets can still be configured like normal sets:
```rust
app.add_system(MyBaseSet::B.after(MyBaseSet::Ap))
```
The primary use case for base sets is enabling a "default base set":
```rust
schedule.set_default_base_set(CoreSet::Update)
// this will belong to CoreSet::Update by default
.add_system(foo)
// this will override the default base set with PostUpdate
.add_system(bar.in_base_set(CoreSet::PostUpdate))
```
This allows us to build apis that work by default in the standard Bevy style. This is a rough analog to the "default stage" model, but it use the new "stageless sets" model instead, with all of the ordering flexibility (including exclusive systems) that it provides.
---
## Changelog
- Added "base sets" and ported CoreSet to use them.
## Migration Guide
TODO
Huge thanks to @maniwani, @devil-ira, @hymm, @cart, @superdump and @jakobhellermann for the help with this PR.
# Objective
- Followup #6587.
- Minimal integration for the Stageless Scheduling RFC: https://github.com/bevyengine/rfcs/pull/45
## Solution
- [x] Remove old scheduling module
- [x] Migrate new methods to no longer use extension methods
- [x] Fix compiler errors
- [x] Fix benchmarks
- [x] Fix examples
- [x] Fix docs
- [x] Fix tests
## Changelog
### Added
- a large number of methods on `App` to work with schedules ergonomically
- the `CoreSchedule` enum
- `App::add_extract_system` via the `RenderingAppExtension` trait extension method
- the private `prepare_view_uniforms` system now has a public system set for scheduling purposes, called `ViewSet::PrepareUniforms`
### Removed
- stages, and all code that mentions stages
- states have been dramatically simplified, and no longer use a stack
- `RunCriteriaLabel`
- `AsSystemLabel` trait
- `on_hierarchy_reports_enabled` run criteria (now just uses an ad hoc resource checking run condition)
- systems in `RenderSet/Stage::Extract` no longer warn when they do not read data from the main world
- `RunCriteriaLabel`
- `transform_propagate_system_set`: this was a nonstandard pattern that didn't actually provide enough control. The systems are already `pub`: the docs have been updated to ensure that the third-party usage is clear.
### Changed
- `System::default_labels` is now `System::default_system_sets`.
- `App::add_default_labels` is now `App::add_default_sets`
- `CoreStage` and `StartupStage` enums are now `CoreSet` and `StartupSet`
- `App::add_system_set` was renamed to `App::add_systems`
- The `StartupSchedule` label is now defined as part of the `CoreSchedules` enum
- `.label(SystemLabel)` is now referred to as `.in_set(SystemSet)`
- `SystemLabel` trait was replaced by `SystemSet`
- `SystemTypeIdLabel<T>` was replaced by `SystemSetType<T>`
- The `ReportHierarchyIssue` resource now has a public constructor (`new`), and implements `PartialEq`
- Fixed time steps now use a schedule (`CoreSchedule::FixedTimeStep`) rather than a run criteria.
- Adding rendering extraction systems now panics rather than silently failing if no subapp with the `RenderApp` label is found.
- the `calculate_bounds` system, with the `CalculateBounds` label, is now in `CoreSet::Update`, rather than in `CoreSet::PostUpdate` before commands are applied.
- `SceneSpawnerSystem` now runs under `CoreSet::Update`, rather than `CoreStage::PreUpdate.at_end()`.
- `bevy_pbr::add_clusters` is no longer an exclusive system
- the top level `bevy_ecs::schedule` module was replaced with `bevy_ecs::scheduling`
- `tick_global_task_pools_on_main_thread` is no longer run as an exclusive system. Instead, it has been replaced by `tick_global_task_pools`, which uses a `NonSend` resource to force running on the main thread.
## Migration Guide
- Calls to `.label(MyLabel)` should be replaced with `.in_set(MySet)`
- Stages have been removed. Replace these with system sets, and then add command flushes using the `apply_system_buffers` exclusive system where needed.
- The `CoreStage`, `StartupStage, `RenderStage` and `AssetStage` enums have been replaced with `CoreSet`, `StartupSet, `RenderSet` and `AssetSet`. The same scheduling guarantees have been preserved.
- Systems are no longer added to `CoreSet::Update` by default. Add systems manually if this behavior is needed, although you should consider adding your game logic systems to `CoreSchedule::FixedTimestep` instead for more reliable framerate-independent behavior.
- Similarly, startup systems are no longer part of `StartupSet::Startup` by default. In most cases, this won't matter to you.
- For example, `add_system_to_stage(CoreStage::PostUpdate, my_system)` should be replaced with
- `add_system(my_system.in_set(CoreSet::PostUpdate)`
- When testing systems or otherwise running them in a headless fashion, simply construct and run a schedule using `Schedule::new()` and `World::run_schedule` rather than constructing stages
- Run criteria have been renamed to run conditions. These can now be combined with each other and with states.
- Looping run criteria and state stacks have been removed. Use an exclusive system that runs a schedule if you need this level of control over system control flow.
- For app-level control flow over which schedules get run when (such as for rollback networking), create your own schedule and insert it under the `CoreSchedule::Outer` label.
- Fixed timesteps are now evaluated in a schedule, rather than controlled via run criteria. The `run_fixed_timestep` system runs this schedule between `CoreSet::First` and `CoreSet::PreUpdate` by default.
- Command flush points introduced by `AssetStage` have been removed. If you were relying on these, add them back manually.
- Adding extract systems is now typically done directly on the main app. Make sure the `RenderingAppExtension` trait is in scope, then call `app.add_extract_system(my_system)`.
- the `calculate_bounds` system, with the `CalculateBounds` label, is now in `CoreSet::Update`, rather than in `CoreSet::PostUpdate` before commands are applied. You may need to order your movement systems to occur before this system in order to avoid system order ambiguities in culling behavior.
- the `RenderLabel` `AppLabel` was renamed to `RenderApp` for clarity
- `App::add_state` now takes 0 arguments: the starting state is set based on the `Default` impl.
- Instead of creating `SystemSet` containers for systems that run in stages, simply use `.on_enter::<State::Variant>()` or its `on_exit` or `on_update` siblings.
- `SystemLabel` derives should be replaced with `SystemSet`. You will also need to add the `Debug`, `PartialEq`, `Eq`, and `Hash` traits to satisfy the new trait bounds.
- `with_run_criteria` has been renamed to `run_if`. Run criteria have been renamed to run conditions for clarity, and should now simply return a bool.
- States have been dramatically simplified: there is no longer a "state stack". To queue a transition to the next state, call `NextState::set`
## TODO
- [x] remove dead methods on App and World
- [x] add `App::add_system_to_schedule` and `App::add_systems_to_schedule`
- [x] avoid adding the default system set at inappropriate times
- [x] remove any accidental cycles in the default plugins schedule
- [x] migrate benchmarks
- [x] expose explicit labels for the built-in command flush points
- [x] migrate engine code
- [x] remove all mentions of stages from the docs
- [x] verify docs for States
- [x] fix uses of exclusive systems that use .end / .at_start / .before_commands
- [x] migrate RenderStage and AssetStage
- [x] migrate examples
- [x] ensure that transform propagation is exported in a sufficiently public way (the systems are already pub)
- [x] ensure that on_enter schedules are run at least once before the main app
- [x] re-enable opt-in to execution order ambiguities
- [x] revert change to `update_bounds` to ensure it runs in `PostUpdate`
- [x] test all examples
- [x] unbreak directional lights
- [x] unbreak shadows (see 3d_scene, 3d_shape, lighting, transparaency_3d examples)
- [x] game menu example shows loading screen and menu simultaneously
- [x] display settings menu is a blank screen
- [x] `without_winit` example panics
- [x] ensure all tests pass
- [x] SubApp doc test fails
- [x] runs_spawn_local tasks fails
- [x] [Fix panic_when_hierachy_cycle test hanging](https://github.com/alice-i-cecile/bevy/pull/120)
## Points of Difficulty and Controversy
**Reviewers, please give feedback on these and look closely**
1. Default sets, from the RFC, have been removed. These added a tremendous amount of implicit complexity and result in hard to debug scheduling errors. They're going to be tackled in the form of "base sets" by @cart in a followup.
2. The outer schedule controls which schedule is run when `App::update` is called.
3. I implemented `Label for `Box<dyn Label>` for our label types. This enables us to store schedule labels in concrete form, and then later run them. I ran into the same set of problems when working with one-shot systems. We've previously investigated this pattern in depth, and it does not appear to lead to extra indirection with nested boxes.
4. `SubApp::update` simply runs the default schedule once. This sucks, but this whole API is incomplete and this was the minimal changeset.
5. `time_system` and `tick_global_task_pools_on_main_thread` no longer use exclusive systems to attempt to force scheduling order
6. Implemetnation strategy for fixed timesteps
7. `AssetStage` was migrated to `AssetSet` without reintroducing command flush points. These did not appear to be used, and it's nice to remove these bottlenecks.
8. Migration of `bevy_render/lib.rs` and pipelined rendering. The logic here is unusually tricky, as we have complex scheduling requirements.
## Future Work (ideally before 0.10)
- Rename schedule_v3 module to schedule or scheduling
- Add a derive macro to states, and likely a `EnumIter` trait of some form
- Figure out what exactly to do with the "systems added should basically work by default" problem
- Improve ergonomics for working with fixed timesteps and states
- Polish FixedTime API to match Time
- Rebase and merge #7415
- Resolve all internal ambiguities (blocked on better tools, especially #7442)
- Add "base sets" to replace the removed default sets.
