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//! Bevy logo as a desk toy using transparent windows! Now with Googly Eyes!
//!
//! This example demonstrates:
//! - Transparent windows that can be clicked through.
//! - Drag-and-drop operations in 2D.
//! - Using entity hierarchy and [`SpatialBundle`]s to create simple animations.
//! - Creating simple 2D meshes based on shape primitives.
use bevy::{
app::AppExit,
input::common_conditions::{input_just_pressed, input_just_released},
prelude::*,
sprite::{MaterialMesh2dBundle, Mesh2dHandle},
window::{PrimaryWindow, WindowLevel},
};
#[cfg(target_os = "macos")]
use bevy::window::CompositeAlphaMode;
fn main() {
App::new()
.add_plugins(DefaultPlugins.set(WindowPlugin {
primary_window: Some(Window {
title: "Bevy Desk Toy".into(),
transparent: true,
#[cfg(target_os = "macos")]
composite_alpha_mode: CompositeAlphaMode::PostMultiplied,
..default()
}),
..default()
}))
.insert_resource(ClearColor(WINDOW_CLEAR_COLOR))
.insert_resource(WindowTransparency(false))
.insert_resource(CursorWorldPos(None))
.add_systems(Startup, setup)
.add_systems(
Update,
(
get_cursor_world_pos,
update_cursor_hit_test,
(
start_drag.run_if(input_just_pressed(MouseButton::Left)),
end_drag.run_if(input_just_released(MouseButton::Left)),
drag.run_if(resource_exists::<DragOperation>),
quit.run_if(input_just_pressed(MouseButton::Right)),
toggle_transparency.run_if(input_just_pressed(KeyCode::Space)),
move_pupils.after(drag),
),
)
.chain(),
)
.run();
}
/// Whether the window is transparent
#[derive(Resource)]
struct WindowTransparency(bool);
/// The projected 2D world coordinates of the cursor (if it's within primary window bounds).
#[derive(Resource)]
struct CursorWorldPos(Option<Vec2>);
/// The current drag operation including the offset with which we grabbed the Bevy logo.
#[derive(Resource)]
struct DragOperation(Vec2);
/// Marker component for the instructions text entity.
#[derive(Component)]
struct InstructionsText;
/// Marker component for the Bevy logo entity.
#[derive(Component)]
struct BevyLogo;
/// Component for the moving pupil entity (the moving part of the googly eye).
#[derive(Component)]
struct Pupil {
/// Radius of the eye containing the pupil.
eye_radius: f32,
/// Radius of the pupil.
pupil_radius: f32,
/// Current velocity of the pupil.
velocity: Vec2,
}
// Dimensions are based on: assets/branding/icon.png
// Bevy logo radius
const BEVY_LOGO_RADIUS: f32 = 128.0;
// Birds' eyes x y (offset from the origin) and radius
// These values are manually determined from the logo image
const BIRDS_EYES: [(f32, f32, f32); 3] = [
(145.0 - 128.0, -(56.0 - 128.0), 12.0),
(198.0 - 128.0, -(87.0 - 128.0), 10.0),
(222.0 - 128.0, -(140.0 - 128.0), 8.0),
];
const WINDOW_CLEAR_COLOR: Color = Color::srgb(0.2, 0.2, 0.2);
/// Spawn the scene
fn setup(
mut commands: Commands,
asset_server: Res<AssetServer>,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<ColorMaterial>>,
) {
// Spawn a 2D camera
commands.spawn(Camera2dBundle::default());
// Spawn the text instructions
let font = asset_server.load("fonts/FiraSans-Bold.ttf");
let text_style = TextStyle {
font: font.clone(),
font_size: 30.0,
color: Color::WHITE,
};
commands.spawn((
Text2dBundle {
text: Text::from_section(
"Press Space to play on your desktop! Press it again to return.\nRight click Bevy logo to exit.",
text_style.clone(),
),
transform: Transform::from_xyz(0.0, -300.0, 100.0),
..default()
},
InstructionsText,
));
// Create a circle mesh. We will reuse this mesh for all our circles.
let circle = Mesh2dHandle(meshes.add(Circle { radius: 1.0 }));
// Create the different materials we will use for each part of the eyes. For this demo they are basic [`ColorMaterial`]s.
let outline_material = materials.add(Color::BLACK);
let sclera_material = materials.add(Color::WHITE);
let pupil_material = materials.add(Color::srgb(0.2, 0.2, 0.2));
let pupil_highlight_material = materials.add(Color::srgba(1.0, 1.0, 1.0, 0.2));
// Spawn the Bevy logo sprite
commands
.spawn((
SpriteBundle {
texture: asset_server.load("branding/icon.png"),
..default()
},
BevyLogo,
))
.with_children(|commands| {
// For each bird eye
for (x, y, radius) in BIRDS_EYES {
// eye outline
commands.spawn(MaterialMesh2dBundle {
mesh: circle.clone(),
material: outline_material.clone(),
transform: Transform::from_xyz(x, y - 1.0, 1.0)
.with_scale(Vec2::splat(radius + 2.0).extend(1.0)),
..default()
});
// sclera
commands
.spawn(SpatialBundle::from_transform(Transform::from_xyz(
x, y, 2.0,
)))
.with_children(|commands| {
// sclera
commands.spawn(MaterialMesh2dBundle {
mesh: circle.clone(),
material: sclera_material.clone(),
transform: Transform::from_scale(Vec3::new(radius, radius, 0.0)),
..default()
});
let pupil_radius = radius * 0.6;
let pupil_highlight_radius = radius * 0.3;
let pupil_highlight_offset = radius * 0.3;
// pupil
commands
.spawn((
SpatialBundle::from_transform(Transform::from_xyz(0.0, 0.0, 1.0)),
Pupil {
eye_radius: radius,
pupil_radius,
velocity: Vec2::ZERO,
},
))
.with_children(|commands| {
// pupil main
commands.spawn(MaterialMesh2dBundle {
mesh: circle.clone(),
material: pupil_material.clone(),
transform: Transform::from_xyz(0.0, 0.0, 0.0)
.with_scale(Vec3::new(pupil_radius, pupil_radius, 1.0)),
..default()
});
// pupil highlight
commands.spawn(MaterialMesh2dBundle {
mesh: circle.clone(),
material: pupil_highlight_material.clone(),
transform: Transform::from_xyz(
-pupil_highlight_offset,
pupil_highlight_offset,
1.0,
)
.with_scale(Vec3::new(
pupil_highlight_radius,
pupil_highlight_radius,
1.0,
)),
..default()
});
});
});
}
});
}
/// Project the cursor into the world coordinates and store it in a resource for easy use
fn get_cursor_world_pos(
mut cursor_world_pos: ResMut<CursorWorldPos>,
q_primary_window: Query<&Window, With<PrimaryWindow>>,
q_camera: Query<(&Camera, &GlobalTransform)>,
) {
let primary_window = q_primary_window.single();
let (main_camera, main_camera_transform) = q_camera.single();
// Get the cursor position in the world
cursor_world_pos.0 = primary_window
.cursor_position()
.and_then(|cursor_pos| main_camera.viewport_to_world_2d(main_camera_transform, cursor_pos));
}
/// Update whether the window is clickable or not
fn update_cursor_hit_test(
cursor_world_pos: Res<CursorWorldPos>,
mut q_primary_window: Query<&mut Window, With<PrimaryWindow>>,
q_bevy_logo: Query<&Transform, With<BevyLogo>>,
) {
let mut primary_window = q_primary_window.single_mut();
// If the window has decorations (e.g. a border) then it should be clickable
if primary_window.decorations {
primary_window.cursor.hit_test = true;
return;
}
// If the cursor is not within the window we don't need to update whether the window is clickable or not
let Some(cursor_world_pos) = cursor_world_pos.0 else {
return;
};
// If the cursor is within the radius of the Bevy logo make the window clickable otherwise the window is not clickable
let bevy_logo_transform = q_bevy_logo.single();
primary_window.cursor.hit_test = bevy_logo_transform
.translation
.truncate()
.distance(cursor_world_pos)
< BEVY_LOGO_RADIUS;
}
/// Start the drag operation and record the offset we started dragging from
fn start_drag(
mut commands: Commands,
cursor_world_pos: Res<CursorWorldPos>,
q_bevy_logo: Query<&Transform, With<BevyLogo>>,
) {
// If the cursor is not within the primary window skip this system
let Some(cursor_world_pos) = cursor_world_pos.0 else {
return;
};
// Get the offset from the cursor to the Bevy logo sprite
let bevy_logo_transform = q_bevy_logo.single();
let drag_offset = bevy_logo_transform.translation.truncate() - cursor_world_pos;
// If the cursor is within the Bevy logo radius start the drag operation and remember the offset of the cursor from the origin
if drag_offset.length() < BEVY_LOGO_RADIUS {
commands.insert_resource(DragOperation(drag_offset));
}
}
/// Stop the current drag operation
fn end_drag(mut commands: Commands) {
commands.remove_resource::<DragOperation>();
}
/// Drag the Bevy logo
fn drag(
drag_offset: Res<DragOperation>,
cursor_world_pos: Res<CursorWorldPos>,
time: Res<Time>,
mut q_bevy_logo: Query<&mut Transform, With<BevyLogo>>,
mut q_pupils: Query<&mut Pupil>,
) {
// If the cursor is not within the primary window skip this system
let Some(cursor_world_pos) = cursor_world_pos.0 else {
return;
};
// Get the current Bevy logo transform
let mut bevy_transform = q_bevy_logo.single_mut();
// Calculate the new translation of the Bevy logo based on cursor and drag offset
let new_translation = cursor_world_pos + drag_offset.0;
// Calculate how fast we are dragging the Bevy logo (unit/second)
let drag_velocity =
(new_translation - bevy_transform.translation.truncate()) / time.delta_seconds();
// Update the translation of Bevy logo transform to new translation
bevy_transform.translation = new_translation.extend(bevy_transform.translation.z);
// Add the cursor drag velocity in the opposite direction to each pupil.
// Remember pupils are using local coordinates to move. So when the Bevy logo moves right they need to move left to
// simulate inertia, otherwise they will move fixed to the parent.
for mut pupil in &mut q_pupils {
pupil.velocity -= drag_velocity;
}
}
/// Quit when the user right clicks the Bevy logo
fn quit(
cursor_world_pos: Res<CursorWorldPos>,
mut app_exit: EventWriter<AppExit>,
q_bevy_logo: Query<&Transform, With<BevyLogo>>,
) {
// If the cursor is not within the primary window skip this system
let Some(cursor_world_pos) = cursor_world_pos.0 else {
return;
};
// If the cursor is within the Bevy logo radius send the [`AppExit`] event to quit the app
let bevy_logo_transform = q_bevy_logo.single();
if bevy_logo_transform
.translation
.truncate()
.distance(cursor_world_pos)
< BEVY_LOGO_RADIUS
{
app_exit.send(AppExit::Success);
}
}
/// Enable transparency for the window and make it on top
fn toggle_transparency(
mut commands: Commands,
mut window_transparency: ResMut<WindowTransparency>,
mut q_instructions_text: Query<&mut Visibility, With<InstructionsText>>,
mut q_primary_window: Query<&mut Window, With<PrimaryWindow>>,
) {
// Toggle the window transparency resource
window_transparency.0 = !window_transparency.0;
// Show or hide the instructions text
for mut visibility in &mut q_instructions_text {
*visibility = if window_transparency.0 {
Visibility::Hidden
} else {
Visibility::Visible
};
}
// Remove the primary window's decorations (e.g. borders), make it always on top of other desktop windows, and set the clear color to transparent
// only if window transparency is enabled
let mut window = q_primary_window.single_mut();
let clear_color;
(window.decorations, window.window_level, clear_color) = if window_transparency.0 {
(false, WindowLevel::AlwaysOnTop, Color::NONE)
} else {
(true, WindowLevel::Normal, WINDOW_CLEAR_COLOR)
};
// Set the clear color
commands.insert_resource(ClearColor(clear_color));
}
/// Move the pupils and bounce them around
fn move_pupils(time: Res<Time>, mut q_pupils: Query<(&mut Pupil, &mut Transform)>) {
for (mut pupil, mut transform) in &mut q_pupils {
// The wiggle radius is how much the pupil can move within the eye
let wiggle_radius = pupil.eye_radius - pupil.pupil_radius;
// Store the Z component
let z = transform.translation.z;
// Truncate the Z component to make the calculations be on [`Vec2`]
let mut translation = transform.translation.truncate();
// Decay the pupil velocity
pupil.velocity *= (0.04f32).powf(time.delta_seconds());
// Move the pupil
translation += pupil.velocity * time.delta_seconds();
// If the pupil hit the outside border of the eye, limit the translation to be within the wiggle radius and invert the velocity.
// This is not physically accurate but it's good enough for the googly eyes effect.
if translation.length() > wiggle_radius {
translation = translation.normalize() * wiggle_radius;
// Invert and decrease the velocity of the pupil when it bounces
pupil.velocity *= -0.75;
}
// Update the entity transform with the new translation after reading the Z component
transform.translation = translation.extend(z);
}
}