makepad-2-0-app-structure

name

makepad-2.0-app-structure

description

CRITICAL: Use for Makepad 2.0 app structure and Rust integration. Triggers on: makepad app, makepad getting started, app_main!, App::run, MatchEvent, AppMain, handle_event, handle_actions, ScriptVm, from_script_mod, makepad boilerplate, makepad new project, makepad cargo, Cargo.toml setup, hot reload, --hot, live reload, wasm deploy, cargo makepad, media plugin, audio_output, audio_input, AudioBuffer, cx.audio, makepad audio, 音频, 应用结构, 入门, 新项目, 脚手架, 启动, 热重载, 部署

Makepad 2.0 App Structure Skill

Version: makepad-widgets (dev branch) | Last Updated: 2026-03-03

Overview

A Makepad 2.0 app combines Rust code with Splash scripting. The Rust side handles app lifecycle, event routing, and business logic. The Splash side defines UI structure, templates, and inline interactions.

Documentation

Refer to the local files for detailed documentation:

• ./references/app-boilerplate.md - Complete working app template with Cargo.toml
• ./references/rust-splash-integration.md - Rust ↔ Splash communication patterns

IMPORTANT: Documentation Completeness Check

Before answering questions, Claude MUST:

1. Read the relevant reference file(s) listed above
2. If file read fails, answer based on SKILL.md patterns + built-in knowledge

---

Minimal App Template

Cargo.toml

[package]
name = "my-app"
version = "0.1.0"
edition = "2024"

[dependencies]
makepad-widgets = { path = "../path/to/makepad/widgets" }

src/app.rs (or src/main.rs)

use makepad_widgets::*;

app_main!(App);

script_mod! {
    use mod.prelude.widgets.*

    let state = {
        counter: 0
    }
    mod.state = state

    startup() do #(App::script_component(vm)){
        ui: Root{
            on_startup: ||{
                ui.main_view.render()
            }
            main_window := Window{
                window.inner_size: vec2(420, 300)
                body +: {
                    main_view := View{
                        width: Fill height: Fill
                        flow: Down spacing: 12
                        align: Center
                        on_render: ||{
                            Label{
                                text: "Count: " + state.counter
                                draw_text.text_style.font_size: 24
                            }
                        }
                    }
                    increment_button := Button{
                        text: "Increment"
                    }
                }
            }
        }
    }
}

impl App {
    fn run(vm: &mut ScriptVm) -> Self {
        crate::makepad_widgets::script_mod(vm);
        App::from_script_mod(vm, self::script_mod)
    }
}

#[derive(Script, ScriptHook)]
pub struct App {
    #[live]
    ui: WidgetRef,
}

impl MatchEvent for App {
    fn handle_actions(&mut self, cx: &mut Cx, actions: &Actions) {
        if self.ui.button(cx, ids!(increment_button)).clicked(actions) {
            script_eval!(cx, {
                mod.state.counter += 1
                ui.main_view.render()
            });
        }
    }
}

impl AppMain for App {
    fn handle_event(&mut self, cx: &mut Cx, event: &Event) {
        self.match_event(cx, event);
        self.ui.handle_event(cx, event, &mut Scope::empty());
    }
}

---

Key Components Explained

1. app_main!(App)

Registers App as the application entry point. MUST be called at module level.

2. script_mod! { ... }

Defines the Splash script that runs at startup. Contains:

• use mod.prelude.widgets.* - Import widget definitions
• State definitions (let state = {...})
• Functions and templates
• startup() do #(App::script_component(vm)){...} - UI construction

3. App::run(vm) - Initialization Order

CRITICAL: Registration order matters!

fn run(vm: &mut ScriptVm) -> Self {
    // 1. Register theme (optional, for light/dark theme)
    crate::makepad_widgets::theme_mod(vm);
    script_eval!(vm, { mod.theme = mod.themes.light });

    // 2. Register base widgets
    crate::makepad_widgets::widgets_mod(vm);

    // 3. Register custom widget modules (if any)
    // crate::my_widgets::script_mod(vm);

    // 4. Build app from script module
    App::from_script_mod(vm, self::script_mod)
}

Simplified (without theme selection):

fn run(vm: &mut ScriptVm) -> Self {
    crate::makepad_widgets::script_mod(vm);   // Registers both theme + widgets
    App::from_script_mod(vm, self::script_mod)
}

4. #[derive(Script, ScriptHook)] on App struct

#[derive(Script, ScriptHook)]
pub struct App {
    #[live]
    ui: WidgetRef,    // The widget tree root
}

• Script - Enables Splash integration (replaces old Live)
• ScriptHook - Enables lifecycle hooks (replaces old LiveHook)
• #[live] - Field settable from DSL

5. MatchEvent for Action Handling

impl MatchEvent for App {
    fn handle_actions(&mut self, cx: &mut Cx, actions: &Actions) {
        // Check button clicks
        if self.ui.button(cx, ids!(my_button)).clicked(actions) {
            // Handle click
        }
        // Check text input changes
        if let Some(text) = self.ui.text_input(cx, ids!(my_input)).changed(actions) {
            log!("Input: {}", text);
        }
    }
}

6. AppMain for Event Dispatch

impl AppMain for App {
    fn handle_event(&mut self, cx: &mut Cx, event: &Event) {
        self.match_event(cx, event);  // MUST call for MatchEvent to work
        self.ui.handle_event(cx, event, &mut Scope::empty());
    }
}

---

Rust → Splash Communication

script_eval! - Update state and trigger renders

script_eval!(cx, {
    mod.state.counter += 1
    ui.main_view.render()
});

script_apply_eval! - Patch widget properties

script_apply_eval!(cx, self.ui, {
    title.text: "New Title"
    subtitle.draw_text.color: #f00
});

---

Splash → Rust Communication

Inline Event Handlers in script_mod!

Button{
    text: "Click"
    on_click: || {
        // Splash code runs here
        state.count += 1
        ui.display.render()
    }
}

TextInput{
    on_return: || {
        let text = ui.my_input.text()
        add_item(text)
        ui.my_input.set_text("")
    }
}

// Render callback
on_render: || {
    for i, item in items {
        ItemTemplate{label.text: item.name}
    }
}

---

Widget Access from Rust

// Buttons
self.ui.button(cx, ids!(button_name)).clicked(actions)

// Labels
self.ui.label(cx, ids!(label_name)).set_text(cx, "text")

// Text inputs
self.ui.text_input(cx, ids!(input_name)).text()

// Nested access
self.ui.label(cx, ids!(container.inner.title))

---

Running the App

# Development
cargo run -p my-app

# Development with hot reload (Splash changes apply without recompilation)
cargo run -p my-app -- --hot

# Release
cargo run -p my-app --release

# With cargo-makepad for mobile/web
cargo makepad run -p my-app

Command-Line Flags

Flag	Description
--hot	Enable hot reload: watches script_mod! source files and auto-refreshes UI on save. Only affects Splash DSL; Rust code changes still need recompilation.
--stdin-loop	Studio mode: communicates with Makepad Studio via stdin/websocket. Used internally by Studio, not for manual use.
--linux-backend=<x11|wayland>	(Linux only) Select windowing backend.

---

Makepad Studio: Debugging Splash

Running Splash Scripts in Studio

Studio looks for a makepad.splash file in the project root. It can run Splash scripts directly via the Run List panel (uses start_script_run internally), without needing cargo run.

Debug Output

Use std.println() / std.print() inside Splash scripts — output appears in both Studio's Log View panel and terminal stdout:

// makepad.splash
std.println("debug: value = " + my_var);

Error Display

Script failures show in Studio's Log View with file path and error details:

script failed while evaluating makepad.splash: <error details>

Hub API (Studio-injected hub module)

When running under Studio, Splash scripts get a hub module:

API	Description
hub.run(env, cmd, args)	Launch subprocess from Splash
hub.set_run_items(items)	Register runnable items in Studio's Run List
hub.studio_ip	Studio's WebSocket address

Current Limitations

• No breakpoint debugging — Splash VM does not support breakpoints or stepping
• No AST dump flag — Inspecting parse results requires adding logs in Rust source (script/)
• Print-based debugging — std.println() is the primary debugging tool

---

Audio API (Rust-only, not exposed to Splash)

Makepad 2.0 provides native audio I/O via the CxMediaApi trait. Audio callbacks run on a separate real-time thread.

Audio Output

use makepad_widgets::*;

impl AppMain for App {
    fn handle_event(&mut self, cx: &mut Cx, event: &Event) {
        match event {
            Event::Startup => {
                cx.audio_output(0, move |_info, buffer: &mut AudioBuffer| {
                    for frame in 0..buffer.frame_count() {
                        let sample = /* generate sample */;
                        buffer.set(0, frame, sample);
                        buffer.set(1, frame, sample);
                    }
                });
            }
            _ => {}
        }
        self.match_event(cx, event);
        self.ui.handle_event(cx, event, &mut Scope::empty());
    }
}

Audio Input

cx.audio_input(0, move |info: AudioInfo, buffer: &AudioBuffer| {
    let sample_rate = info.sample_rate;
    for frame in 0..buffer.frame_count() {
        let sample = buffer.get(0, frame);
    }
});

Key Audio Types (platform/src/audio.rs)

Type	Description
AudioBuffer	Multichannel sample container (f32)
AudioInfo	Device ID, sample rate, timing
AudioDeviceDesc	Device metadata (name, type, channels)
AudioStreamSender/Receiver	Decoupled audio routing with adaptive buffering

Cross-Thread Data Flow Pattern (Audio → UI)

Audio callbacks run on a real-time thread. Use atomics to pass data to the UI thread:

use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Arc;

let amplitude = Arc::new(AtomicU64::new(0));
let amp_clone = amplitude.clone();

cx.audio_output(0, move |_info, buffer: &mut AudioBuffer| {
    let mut sum = 0.0f32;
    for frame in 0..buffer.frame_count() {
        let s = buffer.get(0, frame);
        sum += s * s;
    }
    let rms = (sum / buffer.frame_count() as f32).sqrt();
    amp_clone.store(rms.to_bits() as u64, Ordering::Relaxed);
});

// UI thread: read on NextFrame
let rms = f32::from_bits(amplitude.load(Ordering::Relaxed) as u32);