add examples on how to have a data source running in another thread / in a task pool thread (#2915)

Add two examples on how to communicate with a task that is running either in another thread or in a thread from `AsyncComputeTaskPool`.

Loosely based on https://github.com/bevyengine/bevy/discussions/1150
This commit is contained in:
François 2022-02-05 01:52:47 +00:00
parent 865698548f
commit 385a2b1895
3 changed files with 95 additions and 0 deletions

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@ -105,6 +105,7 @@ serde = { version = "1", features = ["derive"] }
bytemuck = "1.7" bytemuck = "1.7"
# Needed to poll Task examples # Needed to poll Task examples
futures-lite = "1.11.3" futures-lite = "1.11.3"
crossbeam-channel = "0.5.0"
[[example]] [[example]]
name = "hello_world" name = "hello_world"
@ -287,6 +288,10 @@ path = "examples/asset/hot_asset_reloading.rs"
name = "async_compute" name = "async_compute"
path = "examples/async_tasks/async_compute.rs" path = "examples/async_tasks/async_compute.rs"
[[example]]
name = "external_source_external_thread"
path = "examples/async_tasks/external_source_external_thread.rs"
# Audio # Audio
[[example]] [[example]]
name = "audio" name = "audio"

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@ -145,6 +145,7 @@ Example | File | Description
Example | File | Description Example | File | Description
--- | --- | --- --- | --- | ---
`async_compute` | [`async_tasks/async_compute.rs`](async_tasks/async_compute.rs) | How to use `AsyncComputeTaskPool` to complete longer running tasks `async_compute` | [`async_tasks/async_compute.rs`](async_tasks/async_compute.rs) | How to use `AsyncComputeTaskPool` to complete longer running tasks
`external_source_external_thread` | [`async_tasks/external_source_external_thread.rs`](async_tasks/external_source_external_thread.rs) | How to use an external thread to run an infinite task and communicate with a channel
## Audio ## Audio

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@ -0,0 +1,89 @@
use bevy::prelude::*;
// Using crossbeam_channel instead of std as std `Receiver` is `!Sync`
use crossbeam_channel::{bounded, Receiver};
use rand::Rng;
use std::time::{Duration, Instant};
fn main() {
App::new()
.add_event::<StreamEvent>()
.add_plugins(DefaultPlugins)
.add_startup_system(setup)
.add_system(read_stream)
.add_system(spawn_text)
.add_system(move_text)
.run();
}
struct StreamReceiver(Receiver<u32>);
struct StreamEvent(u32);
struct LoadedFont(Handle<Font>);
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands.spawn_bundle(OrthographicCameraBundle::new_2d());
let (tx, rx) = bounded::<u32>(10);
std::thread::spawn(move || loop {
// Everything here happens in another thread
// This is where you could connect to an external data source
let mut rng = rand::thread_rng();
let start_time = Instant::now();
let duration = Duration::from_secs_f32(rng.gen_range(0.0..0.2));
while Instant::now() - start_time < duration {
// Spinning for 'duration', simulating doing hard work!
}
tx.send(rng.gen_range(0..2000)).unwrap();
});
commands.insert_resource(StreamReceiver(rx));
commands.insert_resource(LoadedFont(asset_server.load("fonts/FiraSans-Bold.ttf")));
}
// This system reads from the receiver and sends events to Bevy
fn read_stream(receiver: ResMut<StreamReceiver>, mut events: EventWriter<StreamEvent>) {
for from_stream in receiver.0.try_iter() {
events.send(StreamEvent(from_stream))
}
}
fn spawn_text(
mut commands: Commands,
mut reader: EventReader<StreamEvent>,
loaded_font: Res<LoadedFont>,
) {
let text_style = TextStyle {
font: loaded_font.0.clone(),
font_size: 20.0,
color: Color::WHITE,
};
let text_alignment = TextAlignment {
vertical: VerticalAlign::Center,
horizontal: HorizontalAlign::Center,
};
for (per_frame, event) in reader.iter().enumerate() {
commands.spawn_bundle(Text2dBundle {
text: Text::with_section(format!("{}", event.0), text_style.clone(), text_alignment),
transform: Transform::from_xyz(
per_frame as f32 * 100.0 + rand::thread_rng().gen_range(-40.0..40.0),
300.0,
0.0,
),
..Default::default()
});
}
}
fn move_text(
mut commands: Commands,
mut texts: Query<(Entity, &mut Transform), With<Text>>,
time: Res<Time>,
) {
for (entity, mut position) in texts.iter_mut() {
position.translation -= Vec3::new(0.0, 100.0 * time.delta_seconds(), 0.0);
if position.translation.y < -300.0 {
commands.entity(entity).despawn();
}
}
}