robius-app-architecture – Coding skill for AI agents

Supporting material availability

This catalog copy contains the inline guidance below, but does not include the following supporting paths. They are external prerequisites, not bundled files:

• <support-root>/references/tokio-integration.md
• <support-root>/references/channel-patterns.md
• <support-root>/references/moly-async-patterns.md

Ask for the original supporting material or an existing installation before using a step that depends on these paths; this catalog does not identify a verified download source for them. Resolve each path relative to that installation, inspect its contents, and verify any applicable license and execution prerequisites. Do not run a command or claim a referenced procedure was followed until its required file exists. Do not fabricate the missing scripts or treat an unrelated file with the same name as equivalent. Independent steps fully documented here can proceed within the user’s authorized scope; report any dependent step as unavailable.

Robius App Architecture Skill

Best practices for structuring Makepad applications based on the Robrix and Moly codebases - production applications built with Makepad and Robius framework.

Source codebases:

• Robrix: Matrix chat client - complex sync/async with background subscriptions
• Moly: AI chat application - cross-platform (native + WASM) with streaming APIs

When to Use

Use this skill when:

• Building a Makepad application with async backend integration
• Designing sync/async communication patterns in Makepad
• Structuring a Robius-style application
• Keywords: robrix, robius, makepad app structure, async makepad, tokio makepad

Production Patterns

The upstream _base/ directory is not bundled; these are historical pattern names, not production-certified implementations:

| Pattern | Description |

|---------|-------------|

| 08-async-loading | Async data loading with loading states |

| 09-streaming-results | Incremental results with SignalToUI |

| 13-tokio-integration | Full tokio runtime integration |

Core Architecture Pattern

┌─────────────────────────────────────────────────────────────┐
│                     UI Thread (Makepad)                     │
│  ┌─────────┐     ┌──────────┐     ┌──────────────────────┐ │
│  │   App   │────▶│ WidgetRef │────▶│ Widget Tree (View)  │ │
│  │ State   │     │    ui     │     │ Scope::with_data()  │ │
│  └────┬────┘     └──────────┘     └──────────────────────┘ │
│       │                                                     │
│       │ submit_async_request()                              │
│       ▼                                                     │
│  ┌─────────────────┐          ┌─────────────────────────┐  │
│  │ REQUEST_SENDER  │─────────▶│  Crossbeam SegQueue     │  │
│  │ (MPSC Channel)  │          │  (Lock-free Updates)    │  │
│  └─────────────────┘          └─────────────────────────┘  │
└───────────────────────────────────┬─────────────────────────┘
                                    │
                    SignalToUI::set_ui_signal()
                                    │
┌───────────────────────────────────┴─────────────────────────┐
│                   Tokio Runtime (Async)                      │
│  ┌──────────────────────────────────────────────────────┐   │
│  │           worker_task (Request Handler)               │   │
│  │  - Receives Request from UI                           │   │
│  │  - Spawns async tasks per request                     │   │
│  │  - Posts actions back via Cx::post_action()           │   │
│  └──────────────────────────────────────────────────────┘   │
│  ┌──────────────────────────────────────────────────────┐   │
│  │         Per-Item Subscriber Tasks                     │   │
│  │  - Listens to external data stream                    │   │
│  │  - Sends Update via crossbeam channel                 │   │
│  │  - Calls SignalToUI::set_ui_signal() to wake UI       │   │
│  └──────────────────────────────────────────────────────┘   │
└─────────────────────────────────────────────────────────────┘

App Structure

Top-Level App Definition

use makepad_widgets::*;

live_design! {
    use link::theme::*;
    use link::widgets::*;

    App = {{App}} {
        ui: <Root>{
            main_window = <Window> {
                window: {inner_size: vec2(1280, 800), title: "MyApp"},
                body = {
                    // Main content here
                }
            }
        }
    }
}

app_main!(App);

#[derive(Live)]
pub struct App {
    #[live] ui: WidgetRef,
    #[rust] app_state: AppState,
}

impl LiveRegister for App {
    fn live_register(cx: &mut Cx) {
        // Order matters: register base widgets first
        makepad_widgets::live_design(cx);
        // Then shared/common widgets
        crate::shared::live_design(cx);
        // Then feature modules
        crate::home::live_design(cx);
    }
}

impl LiveHook for App {
    fn after_new_from_doc(&mut self, cx: &mut Cx) {
        // One-time initialization after widget tree is created
    }
}

AppMain Implementation

impl AppMain for App {
    fn handle_event(&mut self, cx: &mut Cx, event: &Event) {
        // Forward to MatchEvent trait
        self.match_event(cx, event);

        // Pass AppState through widget tree via Scope
        let scope = &mut Scope::with_data(&mut self.app_state);
        self.ui.handle_event(cx, event, scope);
    }
}

Tokio Runtime Integration

Static Runtime Initialization

use std::sync::Mutex;
use tokio::sync::mpsc::{UnboundedReceiver, UnboundedSender};

static TOKIO_RUNTIME: Mutex<Option<tokio::runtime::Runtime>> = Mutex::new(None);
static REQUEST_SENDER: Mutex<Option<UnboundedSender<AppRequest>>> = Mutex::new(None);

pub fn start_async_runtime() -> Result<tokio::runtime::Handle> {
    let (request_sender, request_receiver) = tokio::sync::mpsc::unbounded_channel();

    let rt_handle = TOKIO_RUNTIME.lock().unwrap()
        .get_or_insert_with(|| {
            tokio::runtime::Runtime::new()
                .expect("Failed to create Tokio runtime")
        })
        .handle()
        .clone();

    // Store sender for UI thread to use
    *REQUEST_SENDER.lock().unwrap() = Some(request_sender);

    // Spawn the main worker task
    rt_handle.spawn(worker_task(request_receiver));

    Ok(rt_handle)
}

Request Submission Pattern

pub enum AppRequest {
    FetchData { id: String },
    SendMessage { content: String },
    // ... other request types
}

/// Submit a request from UI thread to async runtime
pub fn submit_async_request(req: AppRequest) -> std::result::Result<(), AppRequest> {
    if let Some(sender) = REQUEST_SENDER.lock().unwrap().as_ref() {
        sender.send(req).map_err(|error| error.0)
    } else {
        Err(req) // report unavailable runtime rather than silently dropping work
    }
}

Worker Task Pattern

async fn worker_task(mut request_receiver: UnboundedReceiver<AppRequest>) -> Result<()> {
    while let Some(request) = request_receiver.recv().await {
        match request {
            AppRequest::FetchData { id } => {
                // Spawn a new task for each request
                let _task = tokio::spawn(async move {
                    let result = fetch_data(&id).await;
                    // Post result back to UI thread
                    Cx::post_action(DataFetchedAction { id, result });
                });
            }
            AppRequest::SendMessage { content } => {
                let _task = tokio::spawn(async move {
                    match send_message(&content).await {
                        Ok(()) => Cx::post_action(MessageSentAction::Success),
                        Err(e) => Cx::post_action(MessageSentAction::Failed(e)),
                    }
                });
            }
        }
    }
    Ok(())
}

Lock-Free Update Queue Pattern

For high-frequency updates from background tasks:

use crossbeam_queue::SegQueue;
use makepad_widgets::SignalToUI;

pub enum DataUpdate {
    NewItem { item: Item },
    ItemChanged { id: String, changes: Changes },
    Status { message: String },
}

static PENDING_UPDATES: SegQueue<DataUpdate> = SegQueue::new();

/// Called from background async tasks
pub fn enqueue_update(update: DataUpdate) {
    PENDING_UPDATES.push(update);
    SignalToUI::set_ui_signal();  // Wake UI thread
}

// In widget's handle_event:
impl Widget for MyWidget {
    fn handle_event(&mut self, cx: &mut Cx, event: &Event, scope: &mut Scope) {
        // Poll for updates on Signal events
        if let Event::Signal = event {
            while let Some(update) = PENDING_UPDATES.pop() {
                match update {
                    DataUpdate::NewItem { item } => {
                        self.items.push(item);
                        self.redraw(cx);
                    }
                    // ... handle other updates
                }
            }
        }
    }
}

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