Add simple collision sound to breakout (#4331)

# Objective

- Add sound effect to the breakout example

## Solution

- Add a collision event and a system that listens to the event and plays a sound

I only added a single sound for all collisions for the sake of simplicity, but this could easily be extended to play a different sound depending on the type of entity hit.

The sound was generated randomly by using https://sfxr.me

https://sfxr.me/#11111GA9soYREjtsWhzjPrpMDEYSjX8Fo1E6PnKhxdw6tu869XW4EAc3nzpKVAYLMzToNcHQtQjeBqjZukqPmMDToGdYQQCWBnC3nEYfp53se5ep9btxRdLK

Closes #4326

https://user-images.githubusercontent.com/8348954/160154727-00e30743-3385-4c2f-97f0-1aaaf9a4dcc5.mp4

For some reason the video has a lot of delay in the sound, but when playing it locally there's no delay

---

## Changelog

- Added sound to breakout example
- Added bevy_audio and vorbis to the feature list ran for examples in CI

## Migration Guide

N/A

.github/workflows/ci.yml

@@ -274,13 +274,13 @@ jobs:
           toolchain: stable
       - name: Build bevy
         run: |
-          cargo build --no-default-features --features "bevy_dynamic_plugin,bevy_gilrs,bevy_gltf,bevy_winit,render,png,hdr,x11,bevy_ci_testing,trace,trace_chrome"
+          cargo build --no-default-features --features "bevy_dynamic_plugin,bevy_gilrs,bevy_gltf,bevy_winit,render,png,hdr,x11,bevy_ci_testing,trace,trace_chrome,bevy_audio,vorbis"
       - name: Run examples
         run: |
           for example in .github/example-run/*.ron; do
             example_name=`basename $example .ron`
             echo "running $example_name - "`date`
-            time CI_TESTING_CONFIG=$example xvfb-run cargo run --example $example_name --no-default-features --features "bevy_dynamic_plugin,bevy_gilrs,bevy_gltf,bevy_winit,render,png,hdr,x11,bevy_ci_testing,trace,trace_chrome"
+            time CI_TESTING_CONFIG=$example xvfb-run cargo run --example $example_name --no-default-features --features "bevy_dynamic_plugin,bevy_gilrs,bevy_gltf,bevy_winit,render,png,hdr,x11,bevy_ci_testing,trace,trace_chrome,bevy_audio,vorbis"
             sleep 10
           done
           zip traces.zip trace*.json

examples/games/breakout.rs

@@ -58,12 +58,14 @@ fn main() {
         .insert_resource(Scoreboard { score: 0 })
         .insert_resource(ClearColor(BACKGROUND_COLOR))
         .add_startup_system(setup)
+        .add_event::<CollisionEvent>()
         .add_system_set(
             SystemSet::new()
                 .with_run_criteria(FixedTimestep::step(TIME_STEP as f64))
                 .with_system(check_for_collisions)
                 .with_system(move_paddle.before(check_for_collisions))
-                .with_system(apply_velocity.before(check_for_collisions)),
+                .with_system(apply_velocity.before(check_for_collisions))
+                .with_system(play_collision_sound.after(check_for_collisions)),
         )
         .add_system(update_scoreboard)
         .add_system(bevy::input::system::exit_on_esc_system)
@@ -82,9 +84,14 @@ struct Velocity(Vec2);
 #[derive(Component)]
 struct Collider;
 
+#[derive(Default)]
+struct CollisionEvent;
+
 #[derive(Component)]
 struct Brick;
 
+struct CollisionSound(Handle<AudioSource>);
+
 // This bundle is a collection of the components that define a "wall" in our game
 #[derive(Bundle)]
 struct WallBundle {
@@ -167,6 +174,10 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
     commands.spawn_bundle(OrthographicCameraBundle::new_2d());
     commands.spawn_bundle(UiCameraBundle::default());
 
+    // Sound
+    let ball_collision_sound = asset_server.load("sounds/breakout_collision.ogg");
+    commands.insert_resource(CollisionSound(ball_collision_sound));
+
     // Paddle
     let paddle_y = BOTTOM_WALL + GAP_BETWEEN_PADDLE_AND_FLOOR;
 
@@ -349,6 +360,7 @@ fn check_for_collisions(
     mut scoreboard: ResMut<Scoreboard>,
     mut ball_query: Query<(&mut Velocity, &Transform), With<Ball>>,
     collider_query: Query<(Entity, &Transform, Option<&Brick>), With<Collider>>,
+    mut collision_events: EventWriter<CollisionEvent>,
 ) {
     let (mut ball_velocity, ball_transform) = ball_query.single_mut();
     let ball_size = ball_transform.scale.truncate();
@@ -362,6 +374,9 @@ fn check_for_collisions(
             transform.scale.truncate(),
         );
         if let Some(collision) = collision {
+            // Sends a collision event so that other systems can react to the collision
+            collision_events.send_default();
+
             // Bricks should be despawned and increment the scoreboard on collision
             if maybe_brick.is_some() {
                 scoreboard.score += 1;
@@ -394,3 +409,15 @@ fn check_for_collisions(
         }
     }
 }
+
+fn play_collision_sound(
+    mut collision_events: EventReader<CollisionEvent>,
+    audio: Res<Audio>,
+    sound: Res<CollisionSound>,
+) {
+    // Play a sound once per frame if a collision occurred. `count` consumes the
+    // events, preventing them from triggering a sound on the next frame.
+    if collision_events.iter().count() > 0 {
+        audio.play(sound.0.clone());
+    }
+}