Observe and WindowResized

[Naarakah]

Hi,

I have a problem with getting WindowResized events with the observe method. The following code with an EventReader works fine (prints when the windows is resized)

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Update, on_window_resized)
        .run();
}

fn on_window_resized(events: EventReader<WindowResized>) {
    for _ in events.read() {
        info!("window resized!");
    }
}

but with observe, nothing happens

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .observe(on_window_resized)
        .run();
}

fn on_window_resized(_: Trigger<WindowResized>) {
    info!("window resized!");
}

I'm learning bevy so surely I have made a mistake, but I can't find what it is.

Thanks

[Jondolf]

Buffered events (using EventReader/EventWriter) are currently treated separately from observer events. So my_event_writer.send(event) adds buffered events that can only be read by an EventReader, not observers. WindowResized is a buffered event like this, and can not be listened to by observers.

I believe there are some plans to further unify buffered events and observers in some way, and to make the API slightly clearer / less footgunny, but I don't remember details of what it'll look like.

Also see Observer docs: https://docs.rs/bevy_ecs/latest/bevy_ecs/observer/struct.Observer.html

[Naarakah]

Okay, thank you! I missed that information in my search.
So there's currently no way to react to a window resize without polling every frame?