Add an example rendering dioxus-native to a texture in a bevy app (#4427)

Co-authored-by: Jerome Caucat <jerome.caucat@smartshape.com>

examples/native-headless-in-bevy/Cargo.toml

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+# Copyright © SixtyFPS GmbH <info@slint.dev>
+# SPDX-License-Identifier: MIT
+
+[package]
+name = "native-headless-in-bevy"
+version = "0.0.0"
+edition = "2021"
+license = "MIT"
+publish = false
+
+[features]
+tracing = ["dep:tracing-subscriber", "dioxus-native-dom/tracing"]
+
+[dependencies]
+anyrender_vello = "0.4.1"
+async-std = "1.13"
+bevy = { version = "0.16" }
+blitz-dom = { workspace = true, default-features = true }
+blitz-paint = { workspace = true, default-features = true }
+blitz-traits = { workspace = true, default-features = true }
+crossbeam-channel = "0.5"
+dioxus = { workspace = true }
+dioxus-native-dom = { path = "../../packages/native-dom" }
+paste = "1.0"
+rustc-hash = "1"
+tracing-subscriber = { workspace = true, optional = true }
+vello = "0.5"
+wgpu = { workspace = true }
+

examples/native-headless-in-bevy/README.md

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+Example: Integrating Dioxus into a Bevy application
+
+This example demonstrates rendering a Dioxus application onto a texture within a Bevy application.
+
+## Core Concepts
+- Render a headless Dioxus-native app to a texture.
+- Share and display the texture on a quad in the Bevy app.
+- Transmit mouse and keyboard events from Bevy to Dioxus.
+  - Events are captured when hovering over elements with the `catch-events` class, ensuring only Dioxus receives them.
+- Manage application state through channel messages between Dioxus and Bevy.
+

examples/native-headless-in-bevy/src/bevy_scene_plugin.rs

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+use crate::ui::{UIMessage, UiState};
+use bevy::input::mouse::{MouseButton, MouseMotion};
+use bevy::prelude::*;
+use crossbeam_channel::{Receiver, Sender};
+
+#[derive(Component)]
+pub struct DynamicCube;
+
+#[derive(Component)]
+pub struct OrbitCamera {
+    pub distance: f32,
+    pub yaw: f32,
+    pub pitch: f32,
+    pub sensitivity: f32,
+}
+
+impl Default for OrbitCamera {
+    fn default() -> Self {
+        Self {
+            distance: 3.0,
+            yaw: 0.0,
+            pitch: 0.0,
+            sensitivity: 0.01,
+        }
+    }
+}
+
+#[derive(Resource, Deref)]
+struct UIMessageSender(Sender<UIMessage>);
+
+#[derive(Resource, Deref)]
+struct UIMessageReceiver(Receiver<UIMessage>);
+
+#[derive(Resource)]
+struct CubeTranslationSpeed(f32);
+
+impl Default for CubeTranslationSpeed {
+    fn default() -> Self {
+        Self(UiState::DEFAULT_CUBE_TRANSLATION_SPEED)
+    }
+}
+
+#[derive(Resource)]
+struct CubeRotationSpeed(f32);
+
+impl Default for CubeRotationSpeed {
+    fn default() -> Self {
+        Self(UiState::DEFAULT_CUBE_ROTATION_SPEED)
+    }
+}
+
+pub struct BevyScenePlugin {
+    pub app_sender: Sender<UIMessage>,
+    pub ui_receiver: Receiver<UIMessage>,
+}
+
+impl Plugin for BevyScenePlugin {
+    fn build(&self, app: &mut App) {
+        app.insert_resource(ClearColor(bevy::color::Color::srgba(0.0, 0.0, 0.0, 0.0)));
+        app.insert_resource(UIMessageSender(self.app_sender.clone()));
+        app.insert_resource(UIMessageReceiver(self.ui_receiver.clone()));
+        app.insert_resource(CubeTranslationSpeed::default());
+        app.insert_resource(CubeRotationSpeed::default());
+        app.add_systems(Startup, setup);
+        app.add_systems(Update, (sync_with_ui, animate, orbit_camera_system));
+    }
+}
+
+fn setup(
+    mut commands: Commands,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<StandardMaterial>>,
+) {
+    commands.spawn((
+        Mesh3d(meshes.add(Cuboid::new(1.0, 1.0, 1.0))),
+        MeshMaterial3d(materials.add(StandardMaterial {
+            base_color: Color::Srgba(bevy::color::Srgba::from_f32_array(
+                UiState::DEFAULT_CUBE_COLOR,
+            )),
+            metallic: 0.0,
+            perceptual_roughness: 0.5,
+            ..default()
+        })),
+        Transform::from_xyz(0.0, 0.0, 0.0),
+        DynamicCube,
+    ));
+
+    commands.spawn((
+        DirectionalLight {
+            color: bevy::color::Color::WHITE,
+            illuminance: 10000.0,
+            shadows_enabled: false,
+            ..default()
+        },
+        Transform::from_xyz(1.0, 1.0, 1.0).looking_at(Vec3::ZERO, Vec3::Y),
+    ));
+
+    commands.insert_resource(AmbientLight {
+        color: bevy::color::Color::WHITE,
+        brightness: 100.0,
+        affects_lightmapped_meshes: true,
+    });
+
+    commands.spawn((
+        Camera3d::default(),
+        Transform::from_xyz(0.0, 0.0, 3.0).looking_at(Vec3::new(0.0, 0.0, 0.0), Vec3::Y),
+        Name::new("MainCamera"),
+        OrbitCamera::default(),
+    ));
+}
+
+fn sync_with_ui(
+    sender: Res<UIMessageSender>,
+    receiver: Res<UIMessageReceiver>,
+    cube_query: Query<&MeshMaterial3d<StandardMaterial>, With<DynamicCube>>,
+    mut materials: ResMut<Assets<StandardMaterial>>,
+    mut translation_speed: ResMut<CubeTranslationSpeed>,
+    mut rotation_speed: ResMut<CubeRotationSpeed>,
+    time: Res<Time>,
+) {
+    let fps = 1000.0 / time.delta().as_millis() as f32;
+    sender.send(UIMessage::Fps(fps)).unwrap();
+
+    while let Ok(message) = receiver.try_recv() {
+        match message {
+            UIMessage::CubeColor(c) => {
+                for cube_material in cube_query.iter() {
+                    if let Some(material) = materials.get_mut(&cube_material.0) {
+                        material.base_color = Color::Srgba(bevy::color::Srgba::from_f32_array(c));
+                    }
+                }
+            }
+            UIMessage::CubeTranslationSpeed(speed) => {
+                translation_speed.0 = speed;
+            }
+            UIMessage::CubeRotationSpeed(speed) => {
+                rotation_speed.0 = speed;
+            }
+            _ => {}
+        }
+    }
+}
+
+fn animate(
+    time: Res<Time>,
+    mut cube_query: Query<&mut Transform, With<DynamicCube>>,
+    translation_speed: Res<CubeTranslationSpeed>,
+    rotation_speed: Res<CubeRotationSpeed>,
+) {
+    for mut transform in cube_query.iter_mut() {
+        transform.rotation = Quat::from_rotation_y(time.elapsed_secs() * rotation_speed.0);
+        transform.translation.x = (time.elapsed_secs() * translation_speed.0).sin() * 0.5;
+    }
+}
+
+fn orbit_camera_system(
+    mut camera_query: Query<(&mut Transform, &mut OrbitCamera), With<Camera3d>>,
+    mut mouse_motion_events: EventReader<MouseMotion>,
+    mouse_button_input: Res<ButtonInput<MouseButton>>,
+) {
+    for (mut transform, mut orbit_camera) in camera_query.iter_mut() {
+        // Handle mouse input for camera rotation
+        if mouse_button_input.pressed(MouseButton::Left) {
+            for mouse_motion in mouse_motion_events.read() {
+                orbit_camera.yaw -= mouse_motion.delta.x * orbit_camera.sensitivity;
+                orbit_camera.pitch -= mouse_motion.delta.y * orbit_camera.sensitivity;
+
+                // Clamp pitch to prevent camera flipping
+                orbit_camera.pitch = orbit_camera.pitch.clamp(-1.5, 1.5);
+            }
+        }
+
+        // Calculate camera position based on spherical coordinates
+        let yaw_quat = Quat::from_rotation_y(orbit_camera.yaw);
+        let pitch_quat = Quat::from_rotation_x(orbit_camera.pitch);
+
+        let rotation = yaw_quat * pitch_quat;
+        let position = rotation * Vec3::new(0.0, 0.0, orbit_camera.distance);
+
+        transform.translation = position;
+        transform.look_at(Vec3::ZERO, Vec3::Y);
+    }
+}

examples/native-headless-in-bevy/src/main.rs

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+mod bevy_scene_plugin;
+mod dioxus_in_bevy_plugin;
+mod ui;
+
+use crate::bevy_scene_plugin::BevyScenePlugin;
+use crate::dioxus_in_bevy_plugin::DioxusInBevyPlugin;
+use crate::ui::{ui, UIProps};
+use bevy::prelude::*;
+
+fn main() {
+    #[cfg(feature = "tracing")]
+    tracing_subscriber::fmt::init();
+
+    let (ui_sender, ui_receiver) = crossbeam_channel::unbounded();
+    let (app_sender, app_receiver) = crossbeam_channel::unbounded();
+    let props = UIProps {
+        ui_sender,
+        app_receiver,
+    };
+
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .add_plugins(DioxusInBevyPlugin::<UIProps> { ui, props })
+        .add_plugins(BevyScenePlugin {
+            app_sender,
+            ui_receiver,
+        })
+        .run();
+}

examples/native-headless-in-bevy/src/ui.css

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+html, body, #main {
+    color: white;
+    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
+    height: 100%;
+    width: 100%;
+    overflow: hidden;
+    margin: 0;
+}
+
+#panel {
+    background-color: #C0C0C033;
+    display: flex;
+    flex-direction: column;
+    height: 100%;
+    width: 30%;
+    justify-content: start;
+}
+
+#title {
+    color: #FFFFFF;
+    text-align: center;
+    padding-top: 10px;
+    border-bottom: 1px solid #a8a8a8;
+    display: flex;
+    flex-direction: row;
+    justify-content: space-evenly;
+    align-items: center;
+}
+
+#buttons {
+    display: flex;
+    flex-direction: row;
+    justify-content: center;
+    gap: 20px;
+    padding-top: 20px;
+    padding-bottom: 20px;
+}
+
+.color-button {
+    width: 50px;
+    height: 50px;
+    border-radius: 3px;
+}
+
+.color-button:hover {
+    box-shadow: 0px 0px 1px #c1c1c1;
+}
+
+.color-button:active {
+    box-shadow: 0px 0px 5px #c1c1c1;
+}
+
+#button-red {
+    background-color: red;
+}
+
+#button-green {
+    background-color: green;
+}
+
+#button-blue {
+    background-color: blue;
+}
+
+#translation-speed-control, #rotation-speed-control {
+    display: flex;
+    flex-direction: row;
+    align-items: start;
+    padding: 20px;
+    gap: 10px;
+}
+
+input[type="number"] {
+    width: 3em;
+    height: 1.5em;
+    line-height: 1.5em;
+    background: #444;
+    border: 2px solid #666;
+    border-radius: 4px;
+    color: #ffffff;
+    font-size: 16px;
+    font-weight: bold;
+    text-align: center;
+    padding: 0 10px;
+    outline: none;
+    margin-left: auto;
+}
+
+#footer {
+    margin-top: auto;
+    margin-left: 10px;
+}
+

examples/native-headless-in-bevy/src/ui.rs

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+use async_std::task::sleep;
+use crossbeam_channel::{Receiver, Sender};
+use dioxus::prelude::*;
+use paste::paste;
+
+macro_rules! define_ui_state {
+    (
+        $($field:ident : $type:ty = $default:expr),* $(,)?
+    ) => { paste! {
+        #[allow(dead_code)]
+        #[derive(Clone, Copy)]
+        pub struct UiState {
+            $($field: Signal<$type>,)*
+        }
+
+        #[allow(dead_code)]
+        impl UiState {
+            fn default() -> Self {
+                Self {
+                    $($field: Signal::new($default),)*
+                }
+            }
+
+            $(pub const [<DEFAULT_ $field:upper>]: $type = $default;)*
+        }
+
+        #[allow(dead_code)]
+        pub enum UIMessage {
+            $([<$field:camel>]($type),)*
+        }
+    }};
+}
+
+define_ui_state! {
+    cube_color: [f32; 4] = [0.0, 0.0, 1.0, 1.0],
+    cube_translation_speed: f32 = 2.0,
+    cube_rotation_speed: f32 = 1.0,
+    fps: f32 = 0.0,
+}
+
+#[derive(Clone)]
+pub struct UIProps {
+    pub ui_sender: Sender<UIMessage>,
+    pub app_receiver: Receiver<UIMessage>,
+}
+
+pub fn ui(props: UIProps) -> Element {
+    let mut state = use_context_provider(UiState::default);
+
+    use_effect({
+        let ui_sender = props.ui_sender.clone();
+        move || {
+            println!("Color changed to {:?}", state.cube_color);
+            ui_sender
+                .send(UIMessage::CubeColor((state.cube_color)()))
+                .unwrap();
+        }
+    });
+
+    use_effect({
+        let ui_sender = props.ui_sender.clone();
+        move || {
+            println!("Rotation speed changed to {:?}", state.cube_rotation_speed);
+            ui_sender
+                .send(UIMessage::CubeRotationSpeed((state.cube_rotation_speed)()))
+                .unwrap();
+        }
+    });
+
+    use_effect({
+        let ui_sender = props.ui_sender.clone();
+        move || {
+            println!(
+                "Translation speed changed to {:?}",
+                state.cube_translation_speed
+            );
+            ui_sender
+                .send(UIMessage::CubeTranslationSpeed((state
+                    .cube_translation_speed)(
+                )))
+                .unwrap();
+        }
+    });
+
+    use_future(move || {
+        let app_receiver = props.app_receiver.clone();
+        async move {
+            loop {
+                // Update UI every 1s in this demo.
+                sleep(std::time::Duration::from_millis(1000)).await;
+
+                let mut fps = Option::<f32>::None;
+
+                while let Ok(message) = app_receiver.try_recv() {
+                    if let UIMessage::Fps(v) = message {
+                        fps = Some(v)
+                    }
+                }
+
+                if let Some(fps) = fps {
+                    state.fps.set(fps);
+                }
+            }
+        }
+    });
+
+    rsx! {
+        style { {include_str!("./ui.css")} }
+        div {
+            id: "panel",
+            class: "catch-events",
+            div {
+                id: "title",
+                h1 { "Dioxus In Bevy Example" }
+            }
+            div {
+                id: "buttons",
+                button {
+                    id: "button-red",
+                    class: "color-button",
+                    onclick: move |_| state.cube_color.set([1.0, 0.0, 0.0, 1.0]),
+                }
+                button {
+                    id: "button-green",
+                    class: "color-button",
+                    onclick: move |_| state.cube_color.set([0.0, 1.0, 0.0, 1.0]),
+                }
+                button {
+                    id: "button-blue",
+                    class: "color-button",
+                    onclick: move |_| state.cube_color.set([0.0, 0.0, 1.0, 1.0]),
+                }
+            }
+            div {
+                id: "translation-speed-control",
+                label { "Translation Speed:" }
+                input {
+                    r#type: "number",
+                    min: "0.0",
+                    max: "10.0",
+                    step: "0.1",
+                    value: "{state.cube_translation_speed}",
+                    oninput: move |event| {
+                        if let Ok(speed) = event.value().parse::<f32>() {
+                            state.cube_translation_speed.set(speed);
+                        }
+                    }
+                }
+            }
+            div {
+                id: "rotation-speed-control",
+                label { "Rotation Speed:" }
+                input {
+                    r#type: "number",
+                    min: "0.0",
+                    max: "10.0",
+                    step: "0.1",
+                    value: "{state.cube_rotation_speed}",
+                    oninput: move |event| {
+                        if let Ok(speed) = event.value().parse::<f32>() {
+                            state.cube_rotation_speed.set(speed);
+                        }
+                    }
+                }
+            }
+            div {
+                id: "footer",
+                p { "Bevy framerate: {state.fps}" }
+            }
+        }
+    }
+}