From ba4453a832c1f874116876267382525ece22b048 Mon Sep 17 00:00:00 2001
From: karroffel <thomas-github@poto.cafe>
Date: Fri, 6 Nov 2020 17:33:29 +0100
Subject: [PATCH] add example that represents contributors as bevy icons

---
 Cargo.toml                  |   4 +
 examples/2d/contributors.rs | 315 ++++++++++++++++++++++++++++++++++++
 2 files changed, 319 insertions(+)
 create mode 100644 examples/2d/contributors.rs

diff --git a/Cargo.toml b/Cargo.toml
index 8d18c2969c90af..2ce68bbdca1424 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -116,6 +116,10 @@ path = "examples/2d/sprite_sheet.rs"
 name = "texture_atlas"
 path = "examples/2d/texture_atlas.rs"
 
+[[example]]
+name = "contributors"
+path = "examples/2d/contributors.rs"
+
 [[example]]
 name = "load_gltf"
 path = "examples/3d/load_gltf.rs"
diff --git a/examples/2d/contributors.rs b/examples/2d/contributors.rs
new file mode 100644
index 00000000000000..eb97ac5b2b54bf
--- /dev/null
+++ b/examples/2d/contributors.rs
@@ -0,0 +1,315 @@
+use bevy::prelude::*;
+use rand::{prelude::SliceRandom, Rng};
+use std::{
+    collections::BTreeSet,
+    io::{BufRead, BufReader},
+    process::Stdio,
+};
+
+fn main() {
+    App::build()
+        .add_plugins(DefaultPlugins)
+        .add_startup_system(setup.system())
+        .add_system(velocity_system.system())
+        .add_system(move_system.system())
+        .add_system(collision_system.system())
+        .add_system(select_system.system())
+        .run();
+}
+
+type Contributors = BTreeSet<String>;
+
+struct ContributorSelection {
+    order: Vec<(String, Entity)>,
+    idx: usize,
+}
+
+struct SelectTimer;
+
+struct ContributorDisplay;
+
+struct Contributor {
+    color: [f32; 3],
+}
+
+struct Velocity {
+    translation: Vec3,
+    rotation: f32,
+}
+
+const GRAVITY: f32 = -9.821 * 100.0;
+const SPRITE_SIZE: f32 = 75.0;
+
+const COL_DESELECTED: Color = Color::rgb_linear(0.03, 0.03, 0.03);
+const COL_SELECTED: Color = Color::rgb_linear(5.0, 5.0, 5.0);
+
+const SHOWCASE_TIMER_SECS: f32 = 6.0;
+
+fn setup(
+    mut cmd: Commands,
+    asset_server: Res<AssetServer>,
+    mut materials: ResMut<Assets<ColorMaterial>>,
+) {
+    let contribs = contributors();
+
+    let texture_handle = asset_server.load("branding/icon.png");
+
+    cmd.spawn(Camera2dComponents::default())
+        .spawn(UiCameraComponents::default());
+
+    let mut sel = ContributorSelection {
+        order: vec![],
+        idx: 0,
+    };
+
+    let mut rnd = rand::thread_rng();
+
+    for name in contribs {
+        let pos = (rnd.gen_range(-400.0, 400.0), rnd.gen_range(0.0, 400.0));
+        let dir = rnd.gen_range(-1.0, 1.0);
+        let velocity = Vec3::new(dir * 500.0, 0.0, 0.0);
+        let col = gen_color(&mut rnd);
+
+        // some sprites should be flipped
+        let flipped = rnd.gen_bool(0.5);
+
+        let mut transform = Transform::from_translation(Vec3::new(pos.0, pos.1, 0.0));
+        *transform.scale.x_mut() *= if flipped { -1.0 } else { 1.0 };
+
+        cmd.spawn((Contributor { color: col },))
+            .with(Velocity {
+                translation: velocity,
+                rotation: -dir * 5.0,
+            })
+            .with_bundle(SpriteComponents {
+                sprite: Sprite {
+                    size: Vec2::new(1.0, 1.0) * SPRITE_SIZE,
+                    resize_mode: SpriteResizeMode::Manual,
+                },
+                material: materials.add(ColorMaterial {
+                    color: COL_DESELECTED * col,
+                    texture: Some(texture_handle.clone()),
+                }),
+                ..Default::default()
+            })
+            .with(transform);
+
+        let e = cmd.current_entity().unwrap();
+
+        sel.order.push((name, e));
+    }
+
+    sel.order.shuffle(&mut rnd);
+
+    cmd.spawn((SelectTimer, Timer::from_seconds(SHOWCASE_TIMER_SECS, true)));
+
+    cmd.spawn((ContributorDisplay,))
+        .with_bundle(TextComponents {
+            style: Style {
+                align_self: AlignSelf::FlexEnd,
+                ..Default::default()
+            },
+            text: Text {
+                value: "Contributor showcase".to_string(),
+                font: asset_server.load("fonts/FiraSans-Bold.ttf"),
+                style: TextStyle {
+                    font_size: 60.0,
+                    color: Color::WHITE,
+                },
+            },
+            ..Default::default()
+        });
+
+    cmd.insert_resource(sel);
+}
+
+/// Finds the next contributor to display and selects the entity
+fn select_system(
+    mut materials: ResMut<Assets<ColorMaterial>>,
+    mut sel: ResMut<ContributorSelection>,
+    mut dq: Query<(&ContributorDisplay, Mut<Text>)>,
+    mut tq: Query<(&SelectTimer, Mut<Timer>)>,
+    mut q: Query<(&Contributor, &Handle<ColorMaterial>, &mut Transform)>,
+) {
+    let mut timer_fired = false;
+    for (_, mut t) in tq.iter_mut() {
+        if !t.just_finished {
+            continue;
+        }
+        t.reset();
+        timer_fired = true;
+    }
+
+    if !timer_fired {
+        return;
+    }
+
+    let prev = sel.idx;
+
+    if sel.idx >= sel.order.len() {
+        sel.idx = 0;
+    } else {
+        sel.idx += 1;
+    }
+
+    {
+        let (_, e) = &sel.order[prev];
+        if let Ok((c, handle, mut tr)) = q.get_mut(*e) {
+            deselect(&mut *materials, handle.clone(), c, &mut *tr);
+        }
+    }
+
+    let (name, e) = &sel.order[sel.idx];
+
+    if let Ok((c, handle, mut tr)) = q.get_mut(*e) {
+        for (_, mut text) in dq.iter_mut() {
+            select(
+                &mut *materials,
+                handle.clone(),
+                c,
+                &mut *tr,
+                &mut *text,
+                name,
+            );
+        }
+    }
+}
+
+/// Change the modulate color to the "selected" colour,
+/// bring the object to the front and display the name.
+fn select(
+    materials: &mut Assets<ColorMaterial>,
+    mat_handle: Handle<ColorMaterial>,
+    cont: &Contributor,
+    trans: &mut Transform,
+    text: &mut Text,
+    name: &str,
+) -> Option<()> {
+    let mat = materials.get_mut(mat_handle)?;
+    mat.color = COL_SELECTED * cont.color;
+
+    trans.translation.set_z(100.0);
+
+    text.value = format!("Contributor: {}", name);
+
+    Some(())
+}
+
+/// Change the modulate color to the "deselected" colour and push
+/// the object to the back.
+fn deselect(
+    materials: &mut Assets<ColorMaterial>,
+    mat_handle: Handle<ColorMaterial>,
+    cont: &Contributor,
+    trans: &mut Transform,
+) -> Option<()> {
+    let mat = materials.get_mut(mat_handle)?;
+    mat.color = COL_DESELECTED * cont.color;
+
+    trans.translation.set_z(0.0);
+
+    Some(())
+}
+
+/// Applies gravity to all entities with velocity
+fn velocity_system(time: Res<Time>, mut q: Query<Mut<Velocity>>) {
+    let delta = time.delta_seconds;
+
+    for mut v in q.iter_mut() {
+        v.translation += Vec3::new(0.0, GRAVITY * delta, 0.0);
+    }
+}
+
+/// Checks for collisions of contributor-birds.
+///
+/// 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(
+    wins: Res<Windows>,
+    mut q: Query<(&Contributor, Mut<Velocity>, Mut<Transform>)>,
+) {
+    let mut rnd = rand::thread_rng();
+
+    let win = wins.get_primary().unwrap();
+
+    let ceiling = (win.height() / 2) as f32;
+    let ground = -((win.height() / 2) as f32);
+
+    let wall_left = -((win.width() / 2) as f32);
+    let wall_right = (win.width() / 2) as f32;
+
+    for (_, mut v, mut t) in q.iter_mut() {
+        let left = t.translation.x() - SPRITE_SIZE / 2.0;
+        let right = t.translation.x() + SPRITE_SIZE / 2.0;
+        let top = t.translation.y() + SPRITE_SIZE / 2.0;
+        let bottom = t.translation.y() - SPRITE_SIZE / 2.0;
+
+        // clamp the translation to not go out of the bounds
+        if bottom < ground {
+            t.translation.set_y(ground + SPRITE_SIZE / 2.0);
+            // apply an impulse upwards
+            *v.translation.y_mut() = rnd.gen_range(700.0, 1000.0);
+        }
+        if top > ceiling {
+            t.translation.set_y(ceiling - SPRITE_SIZE / 2.0);
+        }
+        // on side walls flip the horizontal velocity
+        if left < wall_left {
+            t.translation.set_x(wall_left + SPRITE_SIZE / 2.0);
+            *v.translation.x_mut() *= -1.0;
+            v.rotation *= -1.0;
+        }
+        if right > wall_right {
+            t.translation.set_x(wall_right - SPRITE_SIZE / 2.0);
+            *v.translation.x_mut() *= -1.0;
+            v.rotation *= -1.0;
+        }
+    }
+}
+
+/// Apply velocity to positions and rotations.
+fn move_system(time: Res<Time>, mut q: Query<(&Velocity, Mut<Transform>)>) {
+    let delta = time.delta_seconds;
+
+    for (v, mut t) in q.iter_mut() {
+        t.translation += delta * v.translation;
+        t.rotate(Quat::from_rotation_z(v.rotation * delta));
+    }
+}
+
+/// Get the names 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() -> Contributors {
+    let manifest_dir = std::env::var("CARGO_MANIFEST_DIR")
+        .expect("This example needs to run through `cargo run --example`");
+
+    let mut cmd = std::process::Command::new("git")
+        .args(&["--no-pager", "log", "--pretty=format:%an"])
+        .current_dir(manifest_dir)
+        .stdout(Stdio::piped())
+        .spawn()
+        .expect("git needs to be installed");
+
+    let stdout = cmd.stdout.take().expect("Child should have a stdout");
+
+    BufReader::new(stdout)
+        .lines()
+        .filter_map(|x| x.ok())
+        .collect()
+}
+
+/// Generate a color modulation
+///
+/// Because there is no `Mul<Color> for Color` instead `[f32; 3]` is
+/// used.
+fn gen_color(rng: &mut impl Rng) -> [f32; 3] {
+    let r = rng.gen_range(0.2, 1.0);
+    let g = rng.gen_range(0.2, 1.0);
+    let b = rng.gen_range(0.2, 1.0);
+    let v = Vec3::new(r, g, b);
+    v.normalize().into()
+}