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Update/FixedUpdate Stepping #8168

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Update/FixedUpdate Stepping #8168

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28 changes: 28 additions & 0 deletions crates/bevy_app/src/main_schedule.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -142,13 +142,41 @@ impl Main {
}

world.resource_scope(|world, order: Mut<MainScheduleOrder>| {
let step = world
.get_resource_mut::<Stepping>()
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.and_then(|mut s| s.try_step());
for label in &order.labels {
if let Some(false) = step {
let label = &**label;
if label.eq(&Update) || label.eq(&RunFixedUpdateLoop) {
continue;
}
}
let _ = world.try_run_schedule_ref(&**label);
}
});
}
}

#[derive(Resource)]
pub enum Stepping {
Disabled,
Enabled { frames: usize },
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@alice-i-cecile alice-i-cecile Mar 22, 2023 •
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The frames field is hard to understand at a glance. It either needs a clearer name, or we should embed the "this still needs to step" information out into an enum variant.

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Yeah im not convinced either. Just a convenience at this point / provides functionality to help test things.

}

impl Stepping {
pub fn try_step(&mut self) -> Option<bool> {
match self {
Stepping::Disabled => None,
Stepping::Enabled { frames } => {
let should_step = *frames > 0;
*frames = frames.saturating_sub(1);
Some(should_step)
}
}
}
}

/// Initializes the [`Main`] schedule, sub schedules, and resources for a given [`App`].
pub struct MainSchedulePlugin;

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9 changes: 9 additions & 0 deletions examples/games/breakout.rs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
//! A simplified implementation of the classic game "Breakout".

use bevy::{
app::Stepping,
prelude::*,
sprite::collide_aabb::{collide, Collision},
sprite::MaterialMesh2dBundle,
Expand Down Expand Up @@ -47,14 +48,22 @@ const WALL_COLOR: Color = Color::rgb(0.8, 0.8, 0.8);
const TEXT_COLOR: Color = Color::rgb(0.5, 0.5, 1.0);
const SCORE_COLOR: Color = Color::rgb(1.0, 0.5, 0.5);

fn step_on_press(input: Res<Input<KeyCode>>, mut stepping: ResMut<Stepping>) {
if input.pressed(KeyCode::Space) {
*stepping = Stepping::Enabled { frames: 1 };
}
}

fn main() {
App::new()
.add_plugins(DefaultPlugins)
.insert_resource(Stepping::Enabled { frames: 0 })
.insert_resource(Scoreboard { score: 0 })
.insert_resource(ClearColor(BACKGROUND_COLOR))
.add_event::<CollisionEvent>()
// Configure how frequently our gameplay systems are run
.insert_resource(FixedTime::new_from_secs(1.0 / 60.0))
.add_systems(PreUpdate, step_on_press)
.add_systems(Startup, setup)
// Add our gameplay simulation systems to the fixed timestep schedule
.add_systems(
Expand Down