Getting Started¶

This guide walks through installing Nemo, creating your first application, and understanding the core concepts.

Prerequisites¶

• Rust toolchain (1.75+)
• A supported platform: macOS, Linux, or Windows

Installation¶

Clone the repository and build from source:

git clone https://github.com/geoffjay/nemo.git
cd nemo
cargo build --release

The binary is produced at target/release/nemo.

Your First Application¶

Create a directory for your application and add an app.xml file:

mkdir my-app && cd my-app

1. Define the Application¶

Create app.xml:

<nemo>
  <app>
    <window title="My First App" width="800" height="600">
      <header-bar theme-toggle="true" />
    </window>
    <theme name="kanagawa" mode="dark" />
  </app>

  <script src="./scripts" />

  <layout type="stack">
    <stack id="main" direction="vertical" margin="16" spacing="8">
      <label id="title" text="My First Nemo App" size="xl" />

      <panel id="content" padding="16">
        <label id="greeting" text="Click the button below to see scripting in action." />
      </panel>

      <button id="action" label="Say Hello" variant="primary" on-click="on_say_hello" />

      <label id="output_label" text="" />
    </stack>
  </layout>
</nemo>

2. Add an Event Handler¶

Create scripts/handlers.rhai:

fn on_say_hello(component_id, event_data) {
    set_component_text("output_label", "Hello from RHAI!");
    log_info("Button clicked!");
}

3. Run It¶

nemo --app-config app.xml

You should see a window with a title, a panel, a button, and a label. Clicking the button updates the label text via the RHAI script.

Core Concepts¶

Configuration (XML)¶

Nemo applications are defined in XML files. The configuration contains up to six top-level elements:

Components¶

Components are the building blocks of your UI. Each component has a type and a set of properties specific to that type.

<button id="my_button" label="Click Me" variant="primary" on-click="handle_click" />

Available component types:

Data Sources¶

Data sources connect external systems to your UI. When a source emits new data, bound components update automatically.

<data>
  <source name="ticker" type="timer" interval="1" />
</data>

Supported source types: timer, http, websocket, mqtt, redis, nats, file.

Data Binding¶

Bind data source output directly to component properties:

<label id="counter" text="Waiting...">
  <binding source="data.ticker" target="text" transform="tick" />
</label>

When the ticker source emits { tick: 42, timestamp: "..." }, the binding extracts the tick field and sets the label text to 42.

Event Handlers (RHAI Scripts)¶

RHAI scripts handle user interactions. Handler functions receive two arguments: the component ID and event data.

fn handle_click(component_id, event_data) {
    let data = get_data("ticker");
    set_component_text("output", "Tick: " + data.to_string());
    log_info("Handled click on " + component_id);
}

Link handlers to components with on_click:

<button id="btn" label="Refresh" on-click="handle_click" />

Themes¶

Nemo ships with several built-in themes:

Set the theme in your app block:

<app>
  <theme name="catppuccin" mode="dark" />
</app>

Example Applications¶

The examples/ directory contains complete applications:

Run any example:

nemo --app-config examples/basic/app.xml
nemo --app-config examples/calculator/app.xml

Next Steps¶

• CLI Reference -- All command-line options
• Configuration Reference -- Every block, attribute, and component type
• Plugins -- Extending Nemo with native plugins
• Development Guide -- Writing scripts and building plugins