bevy/errors/B0004.md
Alice Cecile de004da8d5
Rename bevy_render::Color to LegacyColor (#12069)
# Objective

The migration process for `bevy_color` (#12013) will be fairly involved:
there will be hundreds of affected files, and a large number of APIs.

## Solution

To allow us to proceed granularly, we're going to keep both
`bevy_color::Color` (new) and `bevy_render::Color` (old) around until
the migration is complete.

However, simply doing this directly is confusing! They're both called
`Color`, making it very hard to tell when a portion of the code has been
ported.

As discussed in #12056, by renaming the old `Color` type, we can make it
easier to gradually migrate over, one API at a time.

## Migration Guide

THIS MIGRATION GUIDE INTENTIONALLY LEFT BLANK.

This change should not be shipped to end users: delete this section in
the final migration guide!

---------

Co-authored-by: Alice Cecile <alice.i.cecil@gmail.com>
2024-02-24 21:35:32 +00:00

4 KiB

B0004

A runtime warning.

An Entity with a hierarchy-inherited component has a Parent without the hierarchy-inherited component in question.

The hierarchy-inherited components defined in bevy include:

Third party plugins may also define their own hierarchy components, so read the warning message carefully and pay attention to the exact type of the missing component.

To fix this warning, add the missing hierarchy component to all ancestors of entities with the hierarchy component you wish to use.

The following code will cause a warning to be emitted:

use bevy::prelude::*;

// WARNING: this code is buggy
fn setup_cube(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    commands
        .spawn(TransformBundle::default())
        .with_children(|parent| {
            // cube
            parent.spawn(PbrBundle {
                mesh: meshes.add(Cuboid::default()),
                material: materials.add(LegacyColor::rgb(0.8, 0.7, 0.6)),
                transform: Transform::from_xyz(0.0, 0.5, 0.0),
                ..default()
            });
        });

    // camera
    commands.spawn(Camera3dBundle {
        transform: Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
        ..default()
    });
}

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup_cube)
        .run();
}

This code will not show a cube on screen. This is because the entity spawned with commands.spawn(…) doesn't have a ViewVisibility or InheritedVisibility component. Since the cube is spawned as a child of an entity without the visibility components, it will not be visible at all.

To fix this, you must use SpatialBundle over TransformBundle, as follows:

use bevy::prelude::*;

fn setup_cube(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    commands
        // We use SpatialBundle instead of TransformBundle, it contains the
        // visibility components needed to display the cube,
        // In addition to the Transform and GlobalTransform components.
        .spawn(SpatialBundle::default())
        .with_children(|parent| {
            // cube
            parent.spawn(PbrBundle {
                mesh: meshes.add(Cuboid::default()),
                material: materials.add(LegacyColor::rgb(0.8, 0.7, 0.6)),
                transform: Transform::from_xyz(0.0, 0.5, 0.0),
                ..default()
            });
        });

    // camera
    commands.spawn(Camera3dBundle {
        transform: Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
        ..default()
    });
}

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup_cube)
        .run();
}

A similar problem occurs when the GlobalTransform component is missing. However, when a parent GlobalTransform is missing, it will simply prevent all transform propagation, including when updating the Transform component of the child.

You will most likely encounter this warning when loading a scene as a child of a pre-existing Entity that does not have the proper components.