Various improvements to the contributors example (#12217)

# Objective / Solution

- Use `Hsla` for the color constants (Fixes #12203)

And a few other improvements:

- Make contributor colors persistent between runs
- Move text to top left where the birbs can't reach and add padding
- Remove `Contributor:` text. It's obvious what is being shown from
context, and then we can remove `has_triggered`.
- Show the number of commits authored
- Some system names were postfixed with `_system` and some weren't.
Removed `_system` for consistency.
- Clean up collision code slightly with a bounding volume
- Someone accidentally typed "bird" instead of "birb" in one comment.
- Other misc. cleanup

## Before

<img width="1280" alt="image"
src="https://github.com/bevyengine/bevy/assets/200550/9c6229d6-313a-464d-8a97-0220aa16901f">

## After

<img width="1280" alt="image"
src="https://github.com/bevyengine/bevy/assets/200550/0c00e95b-2f50-4f50-b177-def4ca405313">

Author: rparrett

examples/games/contributors.rs

@@ -1,35 +1,29 @@
 //! This example displays each contributor to the bevy source code as a bouncing bevy-ball.
 
 use bevy::{
+    math::bounding::Aabb2d,
     prelude::*,
-    utils::{thiserror, HashSet},
+    utils::{thiserror, HashMap},
 };
 use rand::{prelude::SliceRandom, Rng};
 use std::{
     env::VarError,
+    hash::{DefaultHasher, Hash, Hasher},
     io::{self, BufRead, BufReader},
     process::Stdio,
 };
 
 fn main() {
     App::new()
         .add_plugins(DefaultPlugins)
-        .init_resource::<SelectionState>()
+        .init_resource::<SelectionTimer>()
         .add_systems(Startup, (setup_contributor_selection, setup))
-        .add_systems(
-            Update,
-            (
-                velocity_system,
-                move_system,
-                collision_system,
-                select_system,
-            ),
-        )
+        .add_systems(Update, (gravity, movement, collisions, selection))
         .run();
 }
 
-// Store contributors in a collection that preserves the uniqueness
-type Contributors = HashSet<String>;
+// Store contributors with their commit count in a collection that preserves the uniqueness
+type Contributors = HashMap<String, usize>;
 
 #[derive(Resource)]
 struct ContributorSelection {
@@ -38,17 +32,14 @@ struct ContributorSelection {
 }
 
 #[derive(Resource)]
-struct SelectionState {
-    timer: Timer,
-    has_triggered: bool,
-}
+struct SelectionTimer(Timer);
 
-impl Default for SelectionState {
+impl Default for SelectionTimer {
     fn default() -> Self {
-        Self {
-            timer: Timer::from_seconds(SHOWCASE_TIMER_SECS, TimerMode::Repeating),
-            has_triggered: false,
-        }
+        Self(Timer::from_seconds(
+            SHOWCASE_TIMER_SECS,
+            TimerMode::Repeating,
+        ))
     }
 }
 
@@ -58,6 +49,7 @@ struct ContributorDisplay;
 #[derive(Component)]
 struct Contributor {
     name: String,
+    num_commits: usize,
     hue: f32,
 }
 
@@ -70,23 +62,21 @@ struct Velocity {
 const GRAVITY: f32 = 9.821 * 100.0;
 const SPRITE_SIZE: f32 = 75.0;
 
-const SATURATION_DESELECTED: f32 = 0.3;
-const LIGHTNESS_DESELECTED: f32 = 0.2;
-const SATURATION_SELECTED: f32 = 0.9;
-const LIGHTNESS_SELECTED: f32 = 0.7;
-const ALPHA: f32 = 0.92;
+const SELECTED: Hsla = Hsla::hsl(0.0, 0.9, 0.7);
+const DESELECTED: Hsla = Hsla::new(0.0, 0.3, 0.2, 0.92);
 
 const SHOWCASE_TIMER_SECS: f32 = 3.0;
 
 const CONTRIBUTORS_LIST: &[&str] = &["Carter Anderson", "And Many More"];
 
 fn setup_contributor_selection(mut commands: Commands, asset_server: Res<AssetServer>) {
     // Load contributors from the git history log or use default values from
-    // the constant array. Contributors must be unique, so they are stored in a HashSet
+    // the constant array. Contributors are stored in a HashMap with their
+    // commit count.
     let contribs = contributors().unwrap_or_else(|_| {
         CONTRIBUTORS_LIST
             .iter()
-            .map(|name| name.to_string())
+            .map(|name| (name.to_string(), 1))
             .collect()
     });
 
@@ -99,28 +89,31 @@ fn setup_contributor_selection(mut commands: Commands, asset_server: Res<AssetSe
 
     let mut rng = rand::thread_rng();
 
-    for name in contribs {
-        let pos = (rng.gen_range(-400.0..400.0), rng.gen_range(0.0..400.0));
+    for (name, num_commits) in contribs {
+        let transform =
+            Transform::from_xyz(rng.gen_range(-400.0..400.0), rng.gen_range(0.0..400.0), 0.0);
         let dir = rng.gen_range(-1.0..1.0);
         let velocity = Vec3::new(dir * 500.0, 0.0, 0.0);
-        let hue = rng.gen_range(0.0..=360.0);
-
-        // some sprites should be flipped
-        let flipped = rng.gen_bool(0.5);
+        let hue = name_to_hue(&name);
 
-        let transform = Transform::from_xyz(pos.0, pos.1, 0.0);
+        // Some sprites should be flipped for variety
+        let flipped = rng.gen();
 
         let entity = commands
             .spawn((
-                Contributor { name, hue },
+                Contributor {
+                    name,
+                    num_commits,
+                    hue,
+                },
                 Velocity {
                     translation: velocity,
                     rotation: -dir * 5.0,
                 },
                 SpriteBundle {
                     sprite: Sprite {
-                        custom_size: Some(Vec2::new(1.0, 1.0) * SPRITE_SIZE),
-                        color: Color::hsla(hue, SATURATION_DESELECTED, LIGHTNESS_DESELECTED, ALPHA),
+                        custom_size: Some(Vec2::splat(SPRITE_SIZE)),
+                        color: DESELECTED.with_hue(hue).into(),
                         flip_x: flipped,
                         ..default()
                     },
@@ -142,53 +135,51 @@ fn setup_contributor_selection(mut commands: Commands, asset_server: Res<AssetSe
 fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
     commands.spawn(Camera2dBundle::default());
 
+    let text_style = TextStyle {
+        font: asset_server.load("fonts/FiraSans-Bold.ttf"),
+        font_size: 60.0,
+        ..default()
+    };
+
     commands.spawn((
         TextBundle::from_sections([
-            TextSection::new(
-                "Contributor showcase",
-                TextStyle {
-                    font: asset_server.load("fonts/FiraSans-Bold.ttf"),
-                    font_size: 60.0,
-                    ..default()
-                },
-            ),
+            TextSection::new("Contributor showcase", text_style.clone()),
             TextSection::from_style(TextStyle {
-                font: asset_server.load("fonts/FiraSans-Bold.ttf"),
-                font_size: 60.0,
-                ..default()
+                font_size: 30.,
+                ..text_style
             }),
         ])
         .with_style(Style {
-            align_self: AlignSelf::FlexEnd,
+            position_type: PositionType::Absolute,
+            top: Val::Px(12.),
+            left: Val::Px(12.),
             ..default()
         }),
         ContributorDisplay,
     ));
 }
 
 /// Finds the next contributor to display and selects the entity
-fn select_system(
-    mut timer: ResMut<SelectionState>,
+fn selection(
+    mut timer: ResMut<SelectionTimer>,
     mut contributor_selection: ResMut<ContributorSelection>,
     mut text_query: Query<&mut Text, With<ContributorDisplay>>,
     mut query: Query<(&Contributor, &mut Sprite, &mut Transform)>,
     time: Res<Time>,
 ) {
-    if !timer.timer.tick(time.delta()).just_finished() {
+    if !timer.0.tick(time.delta()).just_finished() {
         return;
     }
-    if !timer.has_triggered {
-        let mut text = text_query.single_mut();
-        text.sections[0].value = "Contributor: ".to_string();
 
-        timer.has_triggered = true;
-    }
+    // Deselect the previous contributor
 
     let entity = contributor_selection.order[contributor_selection.idx];
     if let Ok((contributor, mut sprite, mut transform)) = query.get_mut(entity) {
         deselect(&mut sprite, contributor, &mut transform);
     }
 
+    // Select the next contributor
+
     if (contributor_selection.idx + 1) < contributor_selection.order.len() {
         contributor_selection.idx += 1;
     } else {
@@ -211,99 +202,91 @@ fn select(
     transform: &mut Transform,
     text: &mut Text,
 ) {
-    sprite.color = Color::hsla(
-        contributor.hue,
-        SATURATION_SELECTED,
-        LIGHTNESS_SELECTED,
-        ALPHA,
-    );
+    sprite.color = SELECTED.with_hue(contributor.hue).into();
 
     transform.translation.z = 100.0;
 
-    text.sections[1].value.clone_from(&contributor.name);
-    text.sections[1].style.color = sprite.color;
+    text.sections[0].value.clone_from(&contributor.name);
+    text.sections[1].value = format!(
+        "\n{} commit{}",
+        contributor.num_commits,
+        if contributor.num_commits > 1 { "s" } else { "" }
+    );
+    text.sections[0].style.color = sprite.color;
 }
 
-/// Change the modulate color to the "deselected" color and push
+/// Change the tint color to the "deselected" color and push
 /// the object to the back.
 fn deselect(sprite: &mut Sprite, contributor: &Contributor, transform: &mut Transform) {
-    sprite.color = Color::hsla(
-        contributor.hue,
-        SATURATION_DESELECTED,
-        LIGHTNESS_DESELECTED,
-        ALPHA,
-    );
+    sprite.color = DESELECTED.with_hue(contributor.hue).into();
 
     transform.translation.z = 0.0;
 }
 
-/// Applies gravity to all entities with velocity
-fn velocity_system(time: Res<Time>, mut velocity_query: Query<&mut Velocity>) {
+/// Applies gravity to all entities with a velocity.
+fn gravity(time: Res<Time>, mut velocity_query: Query<&mut Velocity>) {
     let delta = time.delta_seconds();
 
     for mut velocity in &mut velocity_query {
         velocity.translation.y -= GRAVITY * delta;
     }
 }
 
-/// Checks for collisions of contributor-birds.
+/// Checks for collisions of contributor-birbs.
 ///
 /// On collision with left-or-right wall it resets the horizontal
 /// velocity. On collision with the ground it applies an upwards
 /// force.
-fn collision_system(
+fn collisions(
     windows: Query<&Window>,
     mut query: Query<(&mut Velocity, &mut Transform), With<Contributor>>,
 ) {
     let window = windows.single();
+    let window_size = Vec2::new(window.width(), window.height());
 
-    let ceiling = window.height() / 2.;
-    let ground = -window.height() / 2.;
-
-    let wall_left = -window.width() / 2.;
-    let wall_right = window.width() / 2.;
+    let collision_area = Aabb2d::new(Vec2::ZERO, (window_size - SPRITE_SIZE) / 2.);
 
     // The maximum height the birbs should try to reach is one birb below the top of the window.
-    let max_bounce_height = (window.height() - SPRITE_SIZE * 2.0).max(0.0);
+    let max_bounce_height = (window_size.y - SPRITE_SIZE * 2.0).max(0.0);
+    let min_bounce_height = max_bounce_height * 0.4;
 
     let mut rng = rand::thread_rng();
 
     for (mut velocity, mut transform) in &mut query {
-        let left = transform.translation.x - SPRITE_SIZE / 2.0;
-        let right = transform.translation.x + SPRITE_SIZE / 2.0;
-        let top = transform.translation.y + SPRITE_SIZE / 2.0;
-        let bottom = transform.translation.y - SPRITE_SIZE / 2.0;
-
-        // clamp the translation to not go out of the bounds
-        if bottom < ground {
-            transform.translation.y = ground + SPRITE_SIZE / 2.0;
+        // Clamp the translation to not go out of the bounds
+        if transform.translation.y < collision_area.min.y {
+            transform.translation.y = collision_area.min.y;
 
             // How high this birb will bounce.
-            let bounce_height = rng.gen_range((max_bounce_height * 0.4)..=max_bounce_height);
+            let bounce_height = rng.gen_range(min_bounce_height..=max_bounce_height);
 
             // Apply the velocity that would bounce the birb up to bounce_height.
             velocity.translation.y = (bounce_height * GRAVITY * 2.).sqrt();
         }
-        if top > ceiling {
-            transform.translation.y = ceiling - SPRITE_SIZE / 2.0;
+
+        // Birbs might hit the ceiling if the window is resized.
+        // If they do, bounce them.
+        if transform.translation.y > collision_area.max.y {
+            transform.translation.y = collision_area.max.y;
             velocity.translation.y *= -1.0;
         }
-        // on side walls flip the horizontal velocity
-        if left < wall_left {
-            transform.translation.x = wall_left + SPRITE_SIZE / 2.0;
+
+        // On side walls flip the horizontal velocity
+        if transform.translation.x < collision_area.min.x {
+            transform.translation.x = collision_area.min.x;
             velocity.translation.x *= -1.0;
             velocity.rotation *= -1.0;
         }
-        if right > wall_right {
-            transform.translation.x = wall_right - SPRITE_SIZE / 2.0;
+        if transform.translation.x > collision_area.max.x {
+            transform.translation.x = collision_area.max.x;
             velocity.translation.x *= -1.0;
             velocity.rotation *= -1.0;
         }
     }
 }
 
 /// Apply velocity to positions and rotations.
-fn move_system(time: Res<Time>, mut query: Query<(&Velocity, &mut Transform)>) {
+fn movement(time: Res<Time>, mut query: Query<(&Velocity, &mut Transform)>) {
     let delta = time.delta_seconds();
 
     for (velocity, mut transform) in &mut query {
@@ -322,9 +305,8 @@ enum LoadContributorsError {
     Stdout,
 }
 
-/// Get the names of all contributors from the git log.
+/// Get the names and commit counts of all contributors from the git log.
 ///
-/// The names are deduplicated.
 /// This function only works if `git` is installed and
 /// the program is run through `cargo`.
 fn contributors() -> Result<Contributors, LoadContributorsError> {
@@ -338,10 +320,22 @@ fn contributors() -> Result<Contributors, LoadContributorsError> {
 
     let stdout = cmd.stdout.take().ok_or(LoadContributorsError::Stdout)?;
 
-    let contributors = BufReader::new(stdout)
-        .lines()
-        .map_while(|x| x.ok())
-        .collect();
+    // Take the list of commit author names and collect them into a HashMap,
+    // keeping a count of how many commits they authored.
+    let contributors = BufReader::new(stdout).lines().map_while(Result::ok).fold(
+        HashMap::new(),
+        |mut acc, word| {
+            *acc.entry(word).or_insert(0) += 1;
+            acc
+        },
+    );
 
     Ok(contributors)
 }
+
+/// Give each unique contributor name a particular hue that is stable between runs.
+fn name_to_hue(s: &str) -> f32 {
+    let mut hasher = DefaultHasher::new();
+    s.hash(&mut hasher);
+    hasher.finish() as f32 / u64::MAX as f32 * 360.
+}