bevy/crates/bevy_text/src/lib.rs
Carter Anderson dc3f801239 Exclusive Systems Now Implement System. Flexible Exclusive System Params (#6083)
# Objective

The [Stageless RFC](https://github.com/bevyengine/rfcs/pull/45) involves allowing exclusive systems to be referenced and ordered relative to parallel systems. We've agreed that unifying systems under `System` is the right move.

This is an alternative to #4166 (see rationale in the comments I left there). Note that this builds on the learnings established there (and borrows some patterns).

## Solution

This unifies parallel and exclusive systems under the shared `System` trait, removing the old `ExclusiveSystem` trait / impls. This is accomplished by adding a new `ExclusiveFunctionSystem` impl similar to `FunctionSystem`. It is backed by `ExclusiveSystemParam`, which is similar to `SystemParam`. There is a new flattened out SystemContainer api (which cuts out a lot of trait and type complexity). 

This means you can remove all cases of `exclusive_system()`:

```rust
// before
commands.add_system(some_system.exclusive_system());
// after
commands.add_system(some_system);
```

I've also implemented `ExclusiveSystemParam` for `&mut QueryState` and `&mut SystemState`, which makes this possible in exclusive systems:

```rust
fn some_exclusive_system(
    world: &mut World,
    transforms: &mut QueryState<&Transform>,
    state: &mut SystemState<(Res<Time>, Query<&Player>)>,
) {
    for transform in transforms.iter(world) {
        println!("{transform:?}");
    }
    let (time, players) = state.get(world);
    for player in players.iter() {
        println!("{player:?}");
    }
}
```

Note that "exclusive function systems" assume `&mut World` is present (and the first param). I think this is a fair assumption, given that the presence of `&mut World` is what defines the need for an exclusive system.

I added some targeted SystemParam `static` constraints, which removed the need for this:
``` rust
fn some_exclusive_system(state: &mut SystemState<(Res<'static, Time>, Query<&'static Player>)>) {}
```

## Related

- #2923
- #3001
- #3946

## Changelog

- `ExclusiveSystem` trait (and implementations) has been removed in favor of sharing the `System` trait.
- `ExclusiveFunctionSystem` and `ExclusiveSystemParam` were added, enabling flexible exclusive function systems
- `&mut SystemState` and `&mut QueryState` now implement `ExclusiveSystemParam`
- Exclusive and parallel System configuration is now done via a unified `SystemDescriptor`, `IntoSystemDescriptor`, and `SystemContainer` api.

## Migration Guide

Calling `.exclusive_system()` is no longer required (or supported) for converting exclusive system functions to exclusive systems:

```rust
// Old (0.8)
app.add_system(some_exclusive_system.exclusive_system());
// New (0.9)
app.add_system(some_exclusive_system);
```

Converting "normal" parallel systems to exclusive systems is done by calling the exclusive ordering apis:

```rust
// Old (0.8)
app.add_system(some_system.exclusive_system().at_end());
// New (0.9)
app.add_system(some_system.at_end());
```

Query state in exclusive systems can now be cached via ExclusiveSystemParams, which should be preferred for clarity and performance reasons:
```rust
// Old (0.8)
fn some_system(world: &mut World) {
  let mut transforms = world.query::<&Transform>();
  for transform in transforms.iter(world) {
  }
}
// New (0.9)
fn some_system(world: &mut World, transforms: &mut QueryState<&Transform>) {
  for transform in transforms.iter(world) {
  }
}
```
2022-09-26 23:57:07 +00:00

86 lines
2.4 KiB
Rust

mod error;
mod font;
mod font_atlas;
mod font_atlas_set;
mod font_loader;
mod glyph_brush;
mod pipeline;
mod text;
mod text2d;
pub use error::*;
pub use font::*;
pub use font_atlas::*;
pub use font_atlas_set::*;
pub use font_loader::*;
pub use glyph_brush::*;
pub use pipeline::*;
pub use text::*;
pub use text2d::*;
pub mod prelude {
#[doc(hidden)]
pub use crate::{
Font, HorizontalAlign, Text, Text2dBundle, TextAlignment, TextError, TextSection,
TextStyle, VerticalAlign,
};
}
use bevy_app::prelude::*;
use bevy_asset::AddAsset;
use bevy_ecs::{schedule::IntoSystemDescriptor, system::Resource};
use bevy_render::{RenderApp, RenderStage};
use bevy_sprite::SpriteSystem;
use bevy_window::ModifiesWindows;
use std::num::NonZeroUsize;
#[derive(Default)]
pub struct TextPlugin;
/// [`TextPlugin`] settings
#[derive(Resource)]
pub struct TextSettings {
/// Maximum number of font atlases supported in a ['FontAtlasSet']
pub max_font_atlases: NonZeroUsize,
/// Allows font size to be set dynamically exceeding the amount set in max_font_atlases.
/// Note each font size has to be generated which can have a strong performance impact.
pub allow_dynamic_font_size: bool,
}
impl Default for TextSettings {
fn default() -> Self {
Self {
max_font_atlases: NonZeroUsize::new(16).unwrap(),
allow_dynamic_font_size: false,
}
}
}
impl Plugin for TextPlugin {
fn build(&self, app: &mut App) {
app.add_asset::<Font>()
.add_asset::<FontAtlasSet>()
.register_type::<Text>()
.register_type::<TextSection>()
.register_type::<Vec<TextSection>>()
.register_type::<TextStyle>()
.register_type::<TextAlignment>()
.register_type::<VerticalAlign>()
.register_type::<HorizontalAlign>()
.init_asset_loader::<FontLoader>()
.init_resource::<TextSettings>()
.insert_resource(TextPipeline::default())
.add_system_to_stage(
CoreStage::PostUpdate,
update_text2d_layout.after(ModifiesWindows),
);
if let Ok(render_app) = app.get_sub_app_mut(RenderApp) {
render_app.add_system_to_stage(
RenderStage::Extract,
extract_text2d_sprite.after(SpriteSystem::ExtractSprites),
);
}
}
}