Bevy_hui

Build bevy_ui design in pseudo Html. Keep your logic in bevy, while iterating fast on design with hot reloading. Create reusable templates in the style of Web Components.

starting with bevy 0.15!

https://github.com/user-attachments/assets/4eb22305-7762-404e-9093-806b6a155ede

Features

• In build support for conditional styles and transitions. Hover animations by default!
• Any value can be a dynamic property and injected into a template at runtime. (recursive!)
• Simple but effective event system. Register any bevy system via function binding and use it in your templates on_press="start_game".
• No widgets, no themes. Just bevy UI serialized with all the tools necessary to build anything in a reusable way.

Example

Like most crates, don't forget to register the plugin!

app.add_plugins((
    HuiPlugin,
    // Optional auto loading. Any template this folder will register as custom component
    // using the file name.
    HuiAutoLoadPlugin::new(&["components"]),
));

Getting Started (Bevy html syntax Cheatsheet)

Create your first component template with external properties!

<!-- /assets/my_button.html-->
<template>
    <property name="action">greet</property>
    <property name="text">Press me</property>
    <property name="primary">#123</property>
    <property name="secondary">#503</property>

    <node padding="10px">
        <button
            id="button"
            padding="5px"
            background="{primary}"
            border_color="{primary}"
            delay="0.2s"
            ease="cubic_in"
            height="80px"
            width="210px"
            border="10px"
            border_radius="30px"
            hover:height="100px"
            hover:background="{secondary}"
            hover:border_color="{secondary}"
            hover:width="230px"
            on_press="{action}"
        >
            <text
                watch="button"
                font_size="20"
                font_color="#FFF"
                hover:font_color="#752"
            >
                {text}
            </text>
        </button>
    </node>
</template>

Register your component and make a custom binding

To use your new component in any other templates, we have to register it first. You can either use the HuiAutoLoadPlugin feature (experimental), which is great for simple components or register the component yourself in a startup system.

This also allows for custom spawning functions. With is great if you need to add custom components as well!

fn startup(
    server: Res<AssetServer>,
    mut html_comps: HtmlComponents,
    mut html_funcs: HtmlFunctions,
) {
    // simple register
    html_comps.register("my_button", server.load("my_button.html"));

    // advanced register, with spawn functions
    html_comps.register_with_spawn_fn("my_button", server.load("my_button.html"), |mut entity_commands| {
        entity_commands.insert(MyCustomComponent);
    })

    // create a system binding that will change the game state.
    // any (one-shot) system with `In<Entity>` is valid!
    // the entity represents the node, the function is called on
    html_funcs.register("start_game", |In(entity): In<Entity>, mut state : ResMut<NextState<GameState>> |{
        state.set(GameState::Play);
    });

Putting it all together

Time to be creative. Include your component in the next template.

<!-- menu.html -->
<template>
    <property name="title">My Game</property>
    ...
    <image
        display="grid"
        grid_template_columns="(2, auto)"
        src="ui_panel.png"
        image_scale_mode="10px tile(1) tile(1) 4"
    >
        <my_button
            text="Start Game"
            action="start_game"
        />
        <my_button
            text="Settings"
            action="to_settings"
        />
        <my_button
            text="Credits"
            action="to_credits"
        />
        <my_button
            text="Exit"
            action="quit_game"
        />
    </image>
    ...
</template>

Spawning your Template

required components make it super simple.

fn setup(
    mut cmd: Commands,
    server: Res<AssetServer>,
) {
    cmd.spawn(Camera2dBundle::default());
    cmd.spawn(HtmlNode(server.load("menu.html"));
}

Hot reload and advanced examples

Hot reload requires bevy file_watcher feature to be enabled.

Checkout the examples for advanced interactions, play with the assets. Keep in mind these are very crude as proof of concept.

# basic menu demo
cargo run -p example --bin ui

# simple text inputs with a submit form
cargo run -p example --bin input

# simple sliders
cargo run -p example --bin slider

Help wanted

I do not plan to offer any widgets on the templating side, but I would like to have common components and system for a general reusable widget toolkit like sliders, drop downs, dragables and so on.

Checkout the examples, if you come up with some really cool widgets, I would be happy to merge them into a

More examples

I am not the greatest designer. I am actively looking for some really fancy and cool examples, using this crate to include in the example crate.

Known limitations and Pitfalls

You currently cannot use propterties on the first node of a template. The first node holds the property state and links one above

• Any manual changes to bevy's styling components will be overwritten
• Do not recursive import. [mem stonks, bug]
• One root node per component.
• docs are uncomplete and sometimes outdated.