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https://github.com/bevyengine/bevy
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07ed1d053e
This implements the most minimal variant of #1843 - a derive for marker trait. This is a prerequisite to more complicated features like statically defined storage type or opt-out component reflection. In order to make component struct's purpose explicit and avoid misuse, it must be annotated with `#[derive(Component)]` (manual impl is discouraged for compatibility). Right now this is just a marker trait, but in the future it might be expanded. Making this change early allows us to make further changes later without breaking backward compatibility for derive macro users. This already prevents a lot of issues, like using bundles in `insert` calls. Primitive types are no longer valid components as well. This can be easily worked around by adding newtype wrappers and deriving `Component` for them. One funny example of prevented bad code (from our own tests) is when an newtype struct or enum variant is used. Previously, it was possible to write `insert(Newtype)` instead of `insert(Newtype(value))`. That code compiled, because function pointers (in this case newtype struct constructor) implement `Send + Sync + 'static`, so we allowed them to be used as components. This is no longer the case and such invalid code will trigger a compile error. Co-authored-by: = <=> Co-authored-by: TheRawMeatball <therawmeatball@gmail.com> Co-authored-by: Carter Anderson <mcanders1@gmail.com>
65 lines
2.1 KiB
Rust
65 lines
2.1 KiB
Rust
use bevy::prelude::*;
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/// This example illustrates how to create parent->child relationships between entities how parent
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/// transforms are propagated to their descendants
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fn main() {
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App::new()
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.insert_resource(Msaa { samples: 4 })
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.add_plugins(DefaultPlugins)
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.add_startup_system(setup)
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.add_system(rotator_system)
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.run();
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}
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/// this component indicates what entities should rotate
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#[derive(Component)]
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struct Rotator;
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/// rotates the parent, which will result in the child also rotating
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fn rotator_system(time: Res<Time>, mut query: Query<&mut Transform, With<Rotator>>) {
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for mut transform in query.iter_mut() {
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transform.rotation *= Quat::from_rotation_x(3.0 * time.delta_seconds());
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}
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}
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/// set up a simple scene with a "parent" cube and a "child" cube
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fn setup(
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mut commands: Commands,
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mut meshes: ResMut<Assets<Mesh>>,
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mut materials: ResMut<Assets<StandardMaterial>>,
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) {
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let cube_handle = meshes.add(Mesh::from(shape::Cube { size: 2.0 }));
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let cube_material_handle = materials.add(StandardMaterial {
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base_color: Color::rgb(0.8, 0.7, 0.6),
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..Default::default()
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});
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// parent cube
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commands
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.spawn_bundle(PbrBundle {
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mesh: cube_handle.clone(),
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material: cube_material_handle.clone(),
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transform: Transform::from_xyz(0.0, 0.0, 1.0),
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..Default::default()
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})
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.insert(Rotator)
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.with_children(|parent| {
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// child cube
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parent.spawn_bundle(PbrBundle {
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mesh: cube_handle,
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material: cube_material_handle,
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transform: Transform::from_xyz(0.0, 0.0, 3.0),
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..Default::default()
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});
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});
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// light
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commands.spawn_bundle(PointLightBundle {
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transform: Transform::from_xyz(4.0, 5.0, -4.0),
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..Default::default()
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});
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// camera
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commands.spawn_bundle(PerspectiveCameraBundle {
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transform: Transform::from_xyz(5.0, 10.0, 10.0).looking_at(Vec3::ZERO, Vec3::Y),
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..Default::default()
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});
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}
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