bevy/crates/bevy_window/src/system.rs

use crate::{PrimaryWindow, Window, WindowCloseRequested};

use bevy_app::AppExit;
use bevy_ecs::prelude::*;
use bevy_input::{keyboard::KeyCode, Input};

/// Exit the application when there are no open windows.
///
/// This system is added by the [`WindowPlugin`] in the default configuration.
/// To disable this behaviour, set `close_when_requested` (on the [`WindowPlugin`]) to `false`.
/// Ensure that you read the caveats documented on that field if doing so.
///
/// [`WindowPlugin`]: crate::WindowPlugin
pub fn exit_on_all_closed(mut app_exit_events: EventWriter<AppExit>, windows: Query<&Window>) {
    if windows.is_empty() {
        bevy_utils::tracing::info!("No windows are open, exiting");
        app_exit_events.send(AppExit);
    }
}

/// Exit the application when the primary window has been closed
///
/// This system is added by the [`WindowPlugin`]
///
/// [`WindowPlugin`]: crate::WindowPlugin
pub fn exit_on_primary_closed(
    mut app_exit_events: EventWriter<AppExit>,
    windows: Query<(), (With<Window>, With<PrimaryWindow>)>,
) {
    if windows.is_empty() {
        bevy_utils::tracing::info!("Primary windows was closed, exiting");
        app_exit_events.send(AppExit);
    }
}

/// Close windows in response to [`WindowCloseRequested`] (e.g.  when the close button is pressed).
///
/// This system is added by the [`WindowPlugin`] in the default configuration.
/// To disable this behaviour, set `close_when_requested` (on the [`WindowPlugin`]) to `false`.
/// Ensure that you read the caveats documented on that field if doing so.
///
/// [`WindowPlugin`]: crate::WindowPlugin
pub fn close_when_requested(mut commands: Commands, mut closed: EventReader<WindowCloseRequested>) {
    for event in closed.iter() {
        commands.entity(event.window).despawn();
    }
}

/// Close the focused window whenever the escape key (<kbd>Esc</kbd>) is pressed
///
/// This is useful for examples or prototyping.
pub fn close_on_esc(
    mut commands: Commands,
    focused_windows: Query<(Entity, &Window)>,
    input: Res<Input<KeyCode>>,
) {
    for (window, focus) in focused_windows.iter() {
        if !focus.focused {
            continue;
        }

        if input.just_pressed(KeyCode::Escape) {
            commands.entity(window).despawn();
        }
    }
}