Child text components created after initial object creation are invisible

[jansenMurphy]

Bevy version

0.16.0-rc.2

Relevant system information

Rust version: 1.87.0-nightly (6cf826701 2025-03-14)
AdapterInfo

• name: "NVIDIA GeForce RTX 3060",
• vendor: 4318, device: 9476
• device_type: DiscreteGpu
• driver: "NVIDIA"
• driver_info: "560.94"
• backend: Vulkan

Windows 11 (build 22631) - Multi-window, 2 monitors - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3060 (NVIDIA; 32.0.15.6094) - AMD Ryzen 9 5900X 12-Core Processor (24 threads)

What you did

https://github.com/jansenMurphy/bevy_minimum_text_render_failure_example

With this example code, click 'Menu A' and 'Menu B' repeatedly to add and remove the entities and see how the text in menu B fails to render as expected.

This was as minimal as I knew how to get it:

#[derive(States, Debug, Clone, Copy, Eq, PartialEq, PartialOrd, Ord, Hash, Default)]
enum AppState{
    #[default]
    StateA,
    StateB,
}

#[derive(Component)]
struct MenuRoot;
#[derive(Component)]
struct MenuStateARoot;
#[derive(Component)]
struct MenuStateBRoot;

fn main() {

    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(OnEnter(AppState::StateA), setup_a)
        .add_systems(OnExit(AppState::StateA), teardown::<MenuStateARoot>)
        .add_systems(OnEnter(AppState::StateB), setup_b)
        .add_systems(OnExit(AppState::StateB), teardown::<MenuStateBRoot>)
        .add_systems(Startup, setup_root)
        .init_state::<AppState>()
        .run();
}

fn setup_root(mut commands: Commands){

    commands.spawn((
        Camera {
            order: 20,
            ..Default::default()
        },
        Camera2d,
        IsDefaultUiCamera,
    ));

    commands.spawn((
        MenuRoot,
        Node{
            ..Default::default()
        },
        Button
    )).with_children(|parent|{
        parent.spawn((
            Button,
            Text::new("Menu A")
        )).observe(|
            mut _trigger: Trigger<Pointer<Click>>,
            mut next_app_state: ResMut<NextState<AppState>>
        | {
            println!("To A");
            next_app_state.set(AppState::StateA);
        });

        parent.spawn((
            Button,
            Text::new("Menu B")
        )).observe(|
            mut _trigger: Trigger<Pointer<Click>>,
            mut next_app_state: ResMut<NextState<AppState>>
        | {
            println!("To B");
            next_app_state.set(AppState::StateB);
        });
    });
}

fn setup_a(
    mut commands: Commands,
    q: Query<Entity, With<MenuRoot>>,
){
    if let Ok(parent) = q.single(){

        println!("Setup A");
        commands.spawn((
            ChildOf{parent},
            MenuStateARoot,
            Text::new("This text appears"),
            BackgroundColor(Color::srgb(0.0, 1.0, 0.0))
        ));

        commands.spawn((
            ChildOf{parent},
            Button,
            BackgroundColor(Color::srgb(0.5, 0.5, 0.0))
        ));
    }
}

fn setup_b(
    mut commands: Commands,
    q: Query<Entity, With<MenuRoot>>,
){
    if let Ok(parent) = q.single(){

        println!("Setup B");
        commands.spawn((
            ChildOf{parent},
            MenuStateBRoot,
            Node{..Default::default()},
            BackgroundColor(Color::srgb(0.1, 0.1, 0.1))
        )).with_children(|sub_parent|{
            sub_parent.spawn((
                Text::new("This text should appear but does not"),
                BackgroundColor(Color::srgb(0.0, 0.0, 1.0)),
            ));
        });

        commands.spawn((
            ChildOf{parent},
            Button,
            BackgroundColor(Color::srgb(0.0, 0.5, 0.5))
        ));
    }
}

fn teardown<T: Component>(to_despawn: Query<Entity, With<T>>, mut commands: Commands){
    for entity in &to_despawn{
        commands.entity(entity).despawn();
    }
}

What went wrong

I think the problem is that when entities with text components are added as children to already-existing ui entities, the text is laid out properly but not rendered.

I was expecting to be able to add child 'menus' with text to a root menu long after instantiating the root of the menu.

Additional information

The dark grey rectangle should be rendering text but is not. It's the appropriate width for the text content

Apologies if this is already an issue; I didn't see it if it was.

[alice-i-cecile]

Did this work in Bevy 0.15? Trying to evaluate for the milestone + figure out the root cause.

[jansenMurphy]

It looks like it's a 0.16 thing. I made a minimum version in 0,15 with some required API changes and then another in 0.16 that is as close to the match of the 0.15 version as I could. The 0.15 version worked as anticipated, but both 0.16 branches I made have the same undesired behavior.

https://github.com/jansenMurphy/bevy_minimum_text_render_failure_example/tree/bevy-015-version
https://github.com/jansenMurphy/bevy_minimum_text_render_failure_example/tree/bevy-016-version-2

[polygon]

Did a bisect:

300fe4db4d58b1a0a0e74fb9026ab494c2b88e80 is the first bad commit

Looks like this got broken in this commit

[alice-i-cecile]

#17579 by @ickshonpe :) Thanks a ton for bisecting: that will speed things up substantially.

[ickshonpe]

Ah it didn't occur to me there could be a problem with text components, I'll take a look

[ickshonpe]

Right, got it. If both a child and prent are added at the same time and update_ui_context_system's reparent_nodes_query visits the child before its parent, the child's ComputedNodeTarget is left unset as it's updated from the parent's target before the parent's target is set.

The problem is the visited HashSet that tracks which entities update_contexts_recursively has visited but it only works when the reparent_nodes_query is ordered descending from parent to child and is redundant anyway the set_if_neq check is sufficient to track already updated nodes.