b3aff9a7b1
# Objective
- Improve documentation.
- Provide helper functions for common uses of `Windows` relating to getting the primary `Window`.
- Reduce repeated `Window` code.
# Solution
- Adds infallible `primary()` and `primary_mut()` functions with standard error text. This replaces the commonly used `get_primary().unwrap()` seen throughout bevy which has inconsistent or nonexistent error messages.
- Adds `scale_factor(WindowId)` to replace repeated code blocks throughout.
# Considerations
- The added functions can panic if the primary window does not exist.
- It is very uncommon for the primary window to not exist, as seen by the regular use of `get_primary().unwrap()`. Most users will have a single window and will need to reference the primary window in their code multiple times.
- The panic provides a consistent error message to make this class of error easy to spot from the panic text.
- This follows the established standard of short names for infallible-but-unlikely-to-panic functions in bevy.
- Removes line noise for common usage of `Windows`.
74 lines
2.5 KiB
Rust
74 lines
2.5 KiB
Rust
use bevy::{prelude::*, tasks::prelude::*};
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use rand::random;
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#[derive(Component)]
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struct Velocity(Vec2);
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fn spawn_system(mut commands: Commands, asset_server: Res<AssetServer>) {
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commands.spawn_bundle(OrthographicCameraBundle::new_2d());
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let texture = asset_server.load("branding/icon.png");
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for _ in 0..128 {
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commands
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.spawn_bundle(SpriteBundle {
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texture: texture.clone(),
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transform: Transform::from_scale(Vec3::splat(0.1)),
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..default()
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})
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.insert(Velocity(
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20.0 * Vec2::new(random::<f32>() - 0.5, random::<f32>() - 0.5),
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));
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}
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}
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// Move sprites according to their velocity
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fn move_system(pool: Res<ComputeTaskPool>, mut sprites: Query<(&mut Transform, &Velocity)>) {
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// Compute the new location of each sprite in parallel on the
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// ComputeTaskPool using batches of 32 sprites
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//
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// This example is only for demonstrative purposes. Using a
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// ParallelIterator for an inexpensive operation like addition on only 128
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// elements will not typically be faster than just using a normal Iterator.
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// See the ParallelIterator documentation for more information on when
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// to use or not use ParallelIterator over a normal Iterator.
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sprites.par_for_each_mut(&pool, 32, |(mut transform, velocity)| {
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transform.translation += velocity.0.extend(0.0);
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});
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}
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// Bounce sprites outside the window
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fn bounce_system(
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pool: Res<ComputeTaskPool>,
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windows: Res<Windows>,
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mut sprites: Query<(&Transform, &mut Velocity)>,
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) {
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let window = windows.primary();
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let width = window.width();
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let height = window.height();
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let left = width / -2.0;
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let right = width / 2.0;
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let bottom = height / -2.0;
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let top = height / 2.0;
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sprites
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// Batch size of 32 is chosen to limit the overhead of
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// ParallelIterator, since negating a vector is very inexpensive.
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.par_for_each_mut(&pool, 32, |(transform, mut v)| {
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if !(left < transform.translation.x
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&& transform.translation.x < right
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&& bottom < transform.translation.y
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&& transform.translation.y < top)
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{
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// For simplicity, just reverse the velocity; don't use realistic bounces
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v.0 = -v.0;
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}
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});
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}
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_startup_system(spawn_system)
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.add_system(move_system)
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.add_system(bounce_system)
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.run();
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}
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