move_camera_with_keyboard.md

Move a camera with a keyboard

This chapter shows how to move a camera with a keyboard.

!!! note "Not ready for yet"

This section remains unfinished until feedback about the previous sections
has been received.

The idea is to change the camera's position, rotation and zoom upon a key press.

This chapter introduces:

• TODO

First test: an empty App has no cameras

fn test_empty_app_has_no_cameras() {
    let mut app = App::new();
    assert_eq!(count_n_cameras(&mut app), 0);
}

Second test: our App has one camera

fn test_create_app_has_a_moving_camera() {
    let mut app = create_app();
    app.update();
    assert_eq!(count_n_cameras(&mut app), 1);
}

Third test: our player is at the origin

fn test_player_is_at_origin() {
    let mut app = create_app();
    app.update();
    assert_eq!(get_player_position(&mut app), Vec2::new(0.0, 0.0));
}

Fourth test: our player has a proper size

fn test_player_has_a_custom_size() {
    let mut app = create_app();
    app.update();
    assert_eq!(get_player_size(&mut app), Vec2::new(64.0, 32.0));
}

Fifth test: our camera starts at the origin

fn test_camera_is_at_origin() {
    let mut app = create_app();
    app.update();
    assert_eq!(get_camera_position(&mut app), Vec2::new(0.0, 0.0));
}

Sixth test: our camera moves when pressing the arrow up key

fn test_camera_moves_when_pressed_up() {
    let mut app = create_app();
    app.update();
    assert_eq!(get_camera_position(&mut app), Vec2::new(0.0, 0.0));

    // Press the key
    app.world_mut()
        .resource_mut::<ButtonInput<KeyCode>>()
        .press(KeyCode::ArrowUp);
    app.update();
    assert_ne!(get_camera_position(&mut app), Vec2::new(0.0, 0.0));

}

Seventh test: our camera is not rotated at the start

fn test_camera_is_not_rotated_at_start() {
    let mut app = create_app();
    app.update();
    assert_eq!(get_camera_rotation(&mut app), 0.0);
}

Eighth test: our camera rotates when pressing the Q key

fn test_camera_rotates_when_pressed_q() {
    let mut app = create_app();
    app.update();
    assert_eq!(get_camera_rotation(&mut app), 0.0);

    // Press the key
    app.world_mut()
        .resource_mut::<ButtonInput<KeyCode>>()
        .press(KeyCode::KeyQ);
    app.update();

    assert_ne!(get_camera_rotation(&mut app), 0.0);
}

Ninth test: our camera is not zoomed in or out at the start

fn test_camera_is_not_zoomed_in_or_out_at_start() {
    let mut app = create_app();
    app.update();
    assert_eq!(get_camera_zoom(&mut app), 1.0);
}

Tenth test: our camera zooms in when pressing the W key

fn test_camera_zooms_in_when_pressed_w() {
    let mut app = create_app();
    app.update();
    assert_eq!(get_camera_zoom(&mut app), 1.0);

    // Press the key
    app.world_mut()
        .resource_mut::<ButtonInput<KeyCode>>()
        .press(KeyCode::KeyW);
    app.update();

    assert!(get_camera_zoom(&mut app) < 1.0);
}

Eleventh test: our camera zooms out when pressing the S key

fn test_camera_zoom_out_when_pressed_s() {
    let mut app = create_app();
    app.update();
    assert_eq!(get_camera_zoom(&mut app), 1.0);

    // Press the key
    app.world_mut()
        .resource_mut::<ButtonInput<KeyCode>>()
        .press(KeyCode::KeyS);
    app.update();

    assert!(get_camera_zoom(&mut app) > 1.0);
}

main.rs

Running the application shows the camera movement in action.

Conclusion

We can now create an App with a camera that responds to key presses. We have tested everything that the App does!

Full code can be found at https://github.com/richelbilderbeek/bevy_tdd_book_move_camera_with_keyboard.