mirror of
https://github.com/bevyengine/bevy
synced 2024-11-10 15:14:50 +00:00
dfee7879c3
# Objective
- It's pretty common to want to check if an EventReader has received one or multiple events while also needing to consume the iterator to "clear" the EventReader.
- The current approach is to do something like `events.iter().count() > 0` or `events.iter().last().is_some()`. It's not immediately obvious that the purpose of that is to consume the events and check if there were any events. My solution doesn't really solve that part, but it encapsulates the pattern.
## Solution
- Add a `.clear()` method that consumes the iterator.
- It takes the EventReader by value to make sure it isn't used again after it has been called.
---
## Migration Guide
Not a breaking change, but if you ever found yourself in a situation where you needed to consume the EventReader and check if there was any events you can now use
```rust
fn system(events: EventReader<MyEvent>) {
if !events.is_empty {
events.clear();
// Process the fact that one or more event was received
}
}
```
Co-authored-by: Charles <IceSentry@users.noreply.github.com>
424 lines
14 KiB
Rust
424 lines
14 KiB
Rust
//! A simplified implementation of the classic game "Breakout"
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use bevy::{
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core::FixedTimestep,
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math::{const_vec2, const_vec3},
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prelude::*,
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sprite::collide_aabb::{collide, Collision},
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};
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// Defines the amount of time that should elapse between each physics step.
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const TIME_STEP: f32 = 1.0 / 60.0;
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// These constants are defined in `Transform` units.
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// Using the default 2D camera they correspond 1:1 with screen pixels.
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// The `const_vec3!` macros are needed as functions that operate on floats cannot be constant in Rust.
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const PADDLE_SIZE: Vec3 = const_vec3!([120.0, 20.0, 0.0]);
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const GAP_BETWEEN_PADDLE_AND_FLOOR: f32 = 60.0;
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const PADDLE_SPEED: f32 = 500.0;
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// How close can the paddle get to the wall
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const PADDLE_PADDING: f32 = 10.0;
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// We set the z-value of the ball to 1 so it renders on top in the case of overlapping sprites.
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const BALL_STARTING_POSITION: Vec3 = const_vec3!([0.0, -50.0, 1.0]);
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const BALL_SIZE: Vec3 = const_vec3!([30.0, 30.0, 0.0]);
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const BALL_SPEED: f32 = 400.0;
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const INITIAL_BALL_DIRECTION: Vec2 = const_vec2!([0.5, -0.5]);
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const WALL_THICKNESS: f32 = 10.0;
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// x coordinates
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const LEFT_WALL: f32 = -450.;
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const RIGHT_WALL: f32 = 450.;
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// y coordinates
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const BOTTOM_WALL: f32 = -300.;
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const TOP_WALL: f32 = 300.;
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const BRICK_SIZE: Vec2 = const_vec2!([100., 30.]);
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// These values are exact
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const GAP_BETWEEN_PADDLE_AND_BRICKS: f32 = 270.0;
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const GAP_BETWEEN_BRICKS: f32 = 5.0;
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// These values are lower bounds, as the number of bricks is computed
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const GAP_BETWEEN_BRICKS_AND_CEILING: f32 = 20.0;
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const GAP_BETWEEN_BRICKS_AND_SIDES: f32 = 20.0;
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const SCOREBOARD_FONT_SIZE: f32 = 40.0;
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const SCOREBOARD_TEXT_PADDING: Val = Val::Px(5.0);
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const BACKGROUND_COLOR: Color = Color::rgb(0.9, 0.9, 0.9);
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const PADDLE_COLOR: Color = Color::rgb(0.3, 0.3, 0.7);
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const BALL_COLOR: Color = Color::rgb(1.0, 0.5, 0.5);
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const BRICK_COLOR: Color = Color::rgb(0.5, 0.5, 1.0);
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const WALL_COLOR: Color = Color::rgb(0.8, 0.8, 0.8);
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const TEXT_COLOR: Color = Color::rgb(0.5, 0.5, 1.0);
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const SCORE_COLOR: Color = Color::rgb(1.0, 0.5, 0.5);
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.insert_resource(Scoreboard { score: 0 })
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.insert_resource(ClearColor(BACKGROUND_COLOR))
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.add_startup_system(setup)
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.add_event::<CollisionEvent>()
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.add_system_set(
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SystemSet::new()
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.with_run_criteria(FixedTimestep::step(TIME_STEP as f64))
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.with_system(check_for_collisions)
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.with_system(move_paddle.before(check_for_collisions))
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.with_system(apply_velocity.before(check_for_collisions))
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.with_system(play_collision_sound.after(check_for_collisions)),
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)
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.add_system(update_scoreboard)
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.add_system(bevy::window::close_on_esc)
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.run();
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}
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#[derive(Component)]
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struct Paddle;
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#[derive(Component)]
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struct Ball;
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#[derive(Component, Deref, DerefMut)]
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struct Velocity(Vec2);
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#[derive(Component)]
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struct Collider;
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#[derive(Default)]
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struct CollisionEvent;
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#[derive(Component)]
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struct Brick;
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struct CollisionSound(Handle<AudioSource>);
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// This bundle is a collection of the components that define a "wall" in our game
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#[derive(Bundle)]
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struct WallBundle {
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// You can nest bundles inside of other bundles like this
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// Allowing you to compose their functionality
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#[bundle]
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sprite_bundle: SpriteBundle,
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collider: Collider,
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}
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/// Which side of the arena is this wall located on?
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enum WallLocation {
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Left,
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Right,
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Bottom,
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Top,
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}
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impl WallLocation {
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fn position(&self) -> Vec2 {
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match self {
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WallLocation::Left => Vec2::new(LEFT_WALL, 0.),
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WallLocation::Right => Vec2::new(RIGHT_WALL, 0.),
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WallLocation::Bottom => Vec2::new(0., BOTTOM_WALL),
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WallLocation::Top => Vec2::new(0., TOP_WALL),
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}
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}
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fn size(&self) -> Vec2 {
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let arena_height = TOP_WALL - BOTTOM_WALL;
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let arena_width = RIGHT_WALL - LEFT_WALL;
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// Make sure we haven't messed up our constants
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assert!(arena_height > 0.0);
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assert!(arena_width > 0.0);
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match self {
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WallLocation::Left => Vec2::new(WALL_THICKNESS, arena_height + WALL_THICKNESS),
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WallLocation::Right => Vec2::new(WALL_THICKNESS, arena_height + WALL_THICKNESS),
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WallLocation::Bottom => Vec2::new(arena_width + WALL_THICKNESS, WALL_THICKNESS),
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WallLocation::Top => Vec2::new(arena_width + WALL_THICKNESS, WALL_THICKNESS),
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}
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}
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}
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impl WallBundle {
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// This "builder method" allows us to reuse logic across our wall entities,
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// making our code easier to read and less prone to bugs when we change the logic
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fn new(location: WallLocation) -> WallBundle {
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WallBundle {
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sprite_bundle: SpriteBundle {
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transform: Transform {
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// We need to convert our Vec2 into a Vec3, by giving it a z-coordinate
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// This is used to determine the order of our sprites
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translation: location.position().extend(0.0),
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// The z-scale of 2D objects must always be 1.0,
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// or their ordering will be affected in surprising ways.
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// See https://github.com/bevyengine/bevy/issues/4149
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scale: location.size().extend(1.0),
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..default()
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},
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sprite: Sprite {
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color: WALL_COLOR,
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..default()
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},
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..default()
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},
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collider: Collider,
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}
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}
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}
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// This resource tracks the game's score
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struct Scoreboard {
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score: usize,
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}
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// Add the game's entities to our world
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fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
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// Cameras
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commands.spawn_bundle(OrthographicCameraBundle::new_2d());
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commands.spawn_bundle(UiCameraBundle::default());
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// Sound
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let ball_collision_sound = asset_server.load("sounds/breakout_collision.ogg");
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commands.insert_resource(CollisionSound(ball_collision_sound));
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// Paddle
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let paddle_y = BOTTOM_WALL + GAP_BETWEEN_PADDLE_AND_FLOOR;
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commands
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.spawn()
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.insert(Paddle)
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.insert_bundle(SpriteBundle {
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transform: Transform {
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translation: Vec3::new(0.0, paddle_y, 0.0),
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scale: PADDLE_SIZE,
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..default()
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},
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sprite: Sprite {
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color: PADDLE_COLOR,
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..default()
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},
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..default()
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})
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.insert(Collider);
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// Ball
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commands
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.spawn()
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.insert(Ball)
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.insert_bundle(SpriteBundle {
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transform: Transform {
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scale: BALL_SIZE,
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translation: BALL_STARTING_POSITION,
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..default()
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},
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sprite: Sprite {
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color: BALL_COLOR,
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..default()
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},
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..default()
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})
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.insert(Velocity(INITIAL_BALL_DIRECTION.normalize() * BALL_SPEED));
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// Scoreboard
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commands.spawn_bundle(TextBundle {
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text: Text {
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sections: vec![
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TextSection {
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value: "Score: ".to_string(),
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style: TextStyle {
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font: asset_server.load("fonts/FiraSans-Bold.ttf"),
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font_size: SCOREBOARD_FONT_SIZE,
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color: TEXT_COLOR,
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},
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},
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TextSection {
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value: "".to_string(),
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style: TextStyle {
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font: asset_server.load("fonts/FiraMono-Medium.ttf"),
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font_size: SCOREBOARD_FONT_SIZE,
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color: SCORE_COLOR,
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},
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},
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],
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..default()
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},
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style: Style {
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position_type: PositionType::Absolute,
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position: UiRect {
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top: SCOREBOARD_TEXT_PADDING,
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left: SCOREBOARD_TEXT_PADDING,
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..default()
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},
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..default()
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},
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..default()
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});
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// Walls
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commands.spawn_bundle(WallBundle::new(WallLocation::Left));
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commands.spawn_bundle(WallBundle::new(WallLocation::Right));
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commands.spawn_bundle(WallBundle::new(WallLocation::Bottom));
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commands.spawn_bundle(WallBundle::new(WallLocation::Top));
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// Bricks
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// Negative scales result in flipped sprites / meshes,
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// which is definitely not what we want here
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assert!(BRICK_SIZE.x > 0.0);
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assert!(BRICK_SIZE.y > 0.0);
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let total_width_of_bricks = (RIGHT_WALL - LEFT_WALL) - 2. * GAP_BETWEEN_BRICKS_AND_SIDES;
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let bottom_edge_of_bricks = paddle_y + GAP_BETWEEN_PADDLE_AND_BRICKS;
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let total_height_of_bricks = TOP_WALL - bottom_edge_of_bricks - GAP_BETWEEN_BRICKS_AND_CEILING;
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assert!(total_width_of_bricks > 0.0);
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assert!(total_height_of_bricks > 0.0);
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// Given the space available, compute how many rows and columns of bricks we can fit
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let n_columns = (total_width_of_bricks / (BRICK_SIZE.x + GAP_BETWEEN_BRICKS)).floor() as usize;
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let n_rows = (total_height_of_bricks / (BRICK_SIZE.y + GAP_BETWEEN_BRICKS)).floor() as usize;
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let n_vertical_gaps = n_columns - 1;
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// Because we need to round the number of columns,
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// the space on the top and sides of the bricks only captures a lower bound, not an exact value
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let center_of_bricks = (LEFT_WALL + RIGHT_WALL) / 2.0;
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let left_edge_of_bricks = center_of_bricks
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// Space taken up by the bricks
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- (n_columns as f32 / 2.0 * BRICK_SIZE.x)
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// Space taken up by the gaps
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- n_vertical_gaps as f32 / 2.0 * GAP_BETWEEN_BRICKS;
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// In Bevy, the `translation` of an entity describes the center point,
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// not its bottom-left corner
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let offset_x = left_edge_of_bricks + BRICK_SIZE.x / 2.;
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let offset_y = bottom_edge_of_bricks + BRICK_SIZE.y / 2.;
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for row in 0..n_rows {
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for column in 0..n_columns {
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let brick_position = Vec2::new(
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offset_x + column as f32 * (BRICK_SIZE.x + GAP_BETWEEN_BRICKS),
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offset_y + row as f32 * (BRICK_SIZE.y + GAP_BETWEEN_BRICKS),
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);
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// brick
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commands
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.spawn()
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.insert(Brick)
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.insert_bundle(SpriteBundle {
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sprite: Sprite {
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color: BRICK_COLOR,
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..default()
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},
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transform: Transform {
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translation: brick_position.extend(0.0),
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scale: Vec3::new(BRICK_SIZE.x, BRICK_SIZE.y, 1.0),
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..default()
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},
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..default()
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})
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.insert(Collider);
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}
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}
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}
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fn move_paddle(
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keyboard_input: Res<Input<KeyCode>>,
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mut query: Query<&mut Transform, With<Paddle>>,
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) {
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let mut paddle_transform = query.single_mut();
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let mut direction = 0.0;
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if keyboard_input.pressed(KeyCode::Left) {
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direction -= 1.0;
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}
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if keyboard_input.pressed(KeyCode::Right) {
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direction += 1.0;
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}
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// Calculate the new horizontal paddle position based on player input
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let new_paddle_position = paddle_transform.translation.x + direction * PADDLE_SPEED * TIME_STEP;
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// Update the paddle position,
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// making sure it doesn't cause the paddle to leave the arena
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let left_bound = LEFT_WALL + WALL_THICKNESS / 2.0 + PADDLE_SIZE.x / 2.0 + PADDLE_PADDING;
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let right_bound = RIGHT_WALL - WALL_THICKNESS / 2.0 - PADDLE_SIZE.x / 2.0 - PADDLE_PADDING;
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paddle_transform.translation.x = new_paddle_position.clamp(left_bound, right_bound);
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}
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fn apply_velocity(mut query: Query<(&mut Transform, &Velocity)>) {
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for (mut transform, velocity) in query.iter_mut() {
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transform.translation.x += velocity.x * TIME_STEP;
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transform.translation.y += velocity.y * TIME_STEP;
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}
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}
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fn update_scoreboard(scoreboard: Res<Scoreboard>, mut query: Query<&mut Text>) {
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let mut text = query.single_mut();
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text.sections[1].value = format!("{}", scoreboard.score);
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}
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fn check_for_collisions(
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mut commands: Commands,
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mut scoreboard: ResMut<Scoreboard>,
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mut ball_query: Query<(&mut Velocity, &Transform), With<Ball>>,
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collider_query: Query<(Entity, &Transform, Option<&Brick>), With<Collider>>,
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mut collision_events: EventWriter<CollisionEvent>,
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) {
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let (mut ball_velocity, ball_transform) = ball_query.single_mut();
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let ball_size = ball_transform.scale.truncate();
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// check collision with walls
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for (collider_entity, transform, maybe_brick) in collider_query.iter() {
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let collision = collide(
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ball_transform.translation,
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ball_size,
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transform.translation,
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transform.scale.truncate(),
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);
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if let Some(collision) = collision {
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// Sends a collision event so that other systems can react to the collision
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collision_events.send_default();
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// Bricks should be despawned and increment the scoreboard on collision
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if maybe_brick.is_some() {
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scoreboard.score += 1;
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commands.entity(collider_entity).despawn();
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}
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// reflect the ball when it collides
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let mut reflect_x = false;
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let mut reflect_y = false;
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// only reflect if the ball's velocity is going in the opposite direction of the
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// collision
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match collision {
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Collision::Left => reflect_x = ball_velocity.x > 0.0,
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Collision::Right => reflect_x = ball_velocity.x < 0.0,
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Collision::Top => reflect_y = ball_velocity.y < 0.0,
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Collision::Bottom => reflect_y = ball_velocity.y > 0.0,
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Collision::Inside => { /* do nothing */ }
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}
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// reflect velocity on the x-axis if we hit something on the x-axis
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if reflect_x {
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ball_velocity.x = -ball_velocity.x;
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}
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// reflect velocity on the y-axis if we hit something on the y-axis
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if reflect_y {
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ball_velocity.y = -ball_velocity.y;
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}
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}
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}
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}
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fn play_collision_sound(
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collision_events: EventReader<CollisionEvent>,
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audio: Res<Audio>,
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sound: Res<CollisionSound>,
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) {
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// Play a sound once per frame if a collision occurred.
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if !collision_events.is_empty() {
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// This prevents events staying active on the next frame.
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collision_events.clear();
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audio.play(sound.0.clone());
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}
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}
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