//! How to use an external thread to run an infinite task and communicate with a channel. use bevy::prelude::*; // Using crossbeam_channel instead of std as std `Receiver` is `!Sync` use crossbeam_channel::{bounded, Receiver}; use rand::{Rng, SeedableRng}; use rand_chacha::ChaCha8Rng; fn main() { App::new() .add_event::<StreamEvent>() .add_plugins(DefaultPlugins) .add_systems(Startup, setup) .add_systems(Update, (spawn_text, move_text)) .add_systems(FixedUpdate, read_stream) .insert_resource(Time::<Fixed>::from_seconds(0.5)) .run(); } #[derive(Resource, Deref)] struct StreamReceiver(Receiver<u32>); #[derive(Event)] struct StreamEvent(u32); fn setup(mut commands: Commands) { commands.spawn(Camera2d); let (tx, rx) = bounded::<u32>(1); std::thread::spawn(move || { // We're seeding the PRNG here to make this example deterministic for testing purposes. // This isn't strictly required in practical use unless you need your app to be deterministic. let mut rng = ChaCha8Rng::seed_from_u64(19878367467713); loop { // Everything here happens in another thread // This is where you could connect to an external data source // This will block until the previous value has been read in system `read_stream` tx.send(rng.gen_range(0..2000)).unwrap(); } }); commands.insert_resource(StreamReceiver(rx)); } // This system reads from the receiver and sends events to Bevy fn read_stream(receiver: Res<StreamReceiver>, mut events: EventWriter<StreamEvent>) { for from_stream in receiver.try_iter() { events.send(StreamEvent(from_stream)); } } fn spawn_text(mut commands: Commands, mut reader: EventReader<StreamEvent>) { for (per_frame, event) in reader.read().enumerate() { commands.spawn(( Text2d::new(event.0.to_string()), TextLayout::new_with_justify(JustifyText::Center), Transform::from_xyz(per_frame as f32 * 100.0, 300.0, 0.0), )); } } fn move_text( mut commands: Commands, mut texts: Query<(Entity, &mut Transform), With<Text2d>>, time: Res<Time>, ) { for (entity, mut position) in &mut texts { position.translation -= Vec3::new(0.0, 100.0 * time.delta_secs(), 0.0); if position.translation.y < -300.0 { commands.entity(entity).despawn(); } } }