macOS pink screen with `Camera2d` on HDR scene

[jsrgb]

Bevy version and features

commit e8b3598
adapter:

AdapterInfo { name: "Apple M1 Max", vendor: 0, device: 0, device_type: IntegratedGpu, device_pci_bus_id: "", driver: "", driver_info: "", backend: Metal, subgroup_min_size: 4, subgroup_max_size: 64, transient_saves_memory: Some(true), limit_bucket: None }

Bug

A pink screen appears on startup when a Camera2d configured without a clear color op is composited on top of a camera with HDR. Resizing the window (or redraw) fixes the issue. Found while trying out hanabi examples. Related #18901

Additional information

Related pink screen Metal bug #25176 #20318 but looks like the issue is still present in specific camera configurations.

A dumb "workaround" is to use ClearColorConfig::Custom(Color::NONE) on the 2d camera, but not a real fix since this will actually clear the render target whereas ClearColorConfig::None shouldn't clear anything. Repro:

use bevy::{
    camera::{CameraOutputMode, Hdr},
    core_pipeline::tonemapping::Tonemapping,
    prelude::*,
    render::render_resource::BlendState,
};

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

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    commands.spawn((
        Camera3d::default(),
        Hdr,
        Tonemapping::None,
        Transform::from_xyz(3.0, 2.0, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
    ));

    commands.spawn((
        PointLight {
            intensity: 2_000_000.0,
            shadow_maps_enabled: true,
            ..default()
        },
        Transform::from_xyz(4.0, 8.0, 4.0),
    ));

    commands.spawn((
        Mesh3d(meshes.add(Cuboid::new(2.0, 2.0, 2.0))),
        MeshMaterial3d(materials.add(Color::WHITE)),
    ));

    let ui_camera = commands
        .spawn((
            Camera2d,
            Camera {
                order: 1,
                clear_color: ClearColorConfig::None, // workaround: clear_color: ClearColorConfig::Custom(Color::NONE),
                output_mode: CameraOutputMode::Write {
                    blend_state: Some(BlendState::ALPHA_BLENDING),
                    clear_color: ClearColorConfig::None, // workaround: clear_color: ClearColorConfig::Custom(Color::NONE),
                },
                ..default()
            },
        ))
        .id();

    commands.spawn((
        UiTargetCamera(ui_camera),
        BackgroundColor(Color::srgba(0.0, 0.0, 0.0, 1.0)),
    ));
}