bevy/examples/window/window_settings.rs

use bevy::prelude::*;

/// This example illustrates how to customize the default window settings
fn main() {
    App::new()
        .insert_resource(WindowDescriptor {
            title: "I am a window!".to_string(),
            width: 500.,
            height: 300.,
            vsync: true,
            ..Default::default()
        })
        .add_plugins(DefaultPlugins)
        .add_system(change_title)
        .add_system(toggle_cursor)
        .run();
}

/// This system will then change the title during execution
fn change_title(time: Res<Time>, mut windows: ResMut<Windows>) {
    let window = windows.get_primary_mut().unwrap();
    window.set_title(format!(
        "Seconds since startup: {}",
        time.seconds_since_startup().round()
    ));
}

/// This system toggles the cursor's visibility when the space bar is pressed
fn toggle_cursor(input: Res<Input<KeyCode>>, mut windows: ResMut<Windows>) {
    let window = windows.get_primary_mut().unwrap();
    if input.just_pressed(KeyCode::Space) {
        window.set_cursor_lock_mode(!window.cursor_locked());
        window.set_cursor_visibility(!window.cursor_visible());
    }
}