ext_ipc

The ext_ipc crate provides inter-process communication (IPC) between the Deno runtime and WebView renderers through the runtime:ipc module.

Overview

ext_ipc handles:

• Deno → Renderer - Send messages to windows via sendToWindow()
• Renderer → Deno - Receive events via windowEvents() or callbacks
• Channel routing - Route messages by channel name
• Broadcast - Send to multiple windows simultaneously
• Capability-based security - Channel allowlisting

Module: runtime:ipc

import {
  sendToWindow,
  onChannel,
  windowEvents,
  broadcast
} from "runtime:ipc";

Key Types

Event Types

struct IpcEvent {
    window_id: String,
    channel: String,
    payload: serde_json::Value,
    event_type: Option<String>,  // "close", "focus", etc.
}

Command Types

struct ToRendererCmd {
    window_id: String,
    channel: String,
    payload: serde_json::Value,
}

Error Types

enum IpcErrorCode {
    ChannelSend = 7000,
    ChannelRecv = 7001,
    WindowNotFound = 7002,
    Serialization = 7003,
}

struct IpcError {
    code: IpcErrorCode,
    message: String,
}

State Types

struct IpcState {
    event_rx: mpsc::Receiver<IpcEvent>,
    cmd_tx: mpsc::Sender<ToRendererCmd>,
}

struct IpcCapabilities {
    allowed_channels: Vec<String>,
    denied_channels: Vec<String>,
}

trait IpcCapabilityChecker {
    fn check_channel(&self, channel: &str) -> bool;
}

Operations

Op	TypeScript	Description
op_ipc_send	sendToWindow(id, channel, payload)	Send to renderer
op_ipc_recv	recvWindowEvent()	Receive next event

The TypeScript module builds higher-level APIs on these primitives:

// Async generators
function* windowEvents(): AsyncGenerator<IpcEvent>;
function* windowEventsFor(windowId: string): AsyncGenerator<IpcEvent>;
function* channelEvents(channel: string): AsyncGenerator<IpcEvent>;

// Callbacks
function onEvent(callback: (event: IpcEvent) => void): () => void;
function onChannel(channel: string, callback: (payload, windowId) => void): () => void;

// Broadcast
async function broadcast(windowIds: string[], channel: string, payload?: unknown): Promise<void>;

Message Flow

Renderer → Deno

Renderer                    Rust IPC                    Deno
────────────────────────────────────────────────────────────────
window.runtime.send()  ──►  WebView IPC handler  ──►  mpsc channel
                         (wry callback)             │
                                                    ▼
                                              windowEvents()
                                              onChannel()

Deno → Renderer

Deno                       Rust IPC                    Renderer
────────────────────────────────────────────────────────────────
sendToWindow()  ──►  op_ipc_send()  ──►  evaluate_script()
                                               │
                                               ▼
                                    window.__host_dispatch()
                                               │
                                               ▼
                                    window.runtime.on() callbacks

File Structure

crates/ext_ipc/
├── src/
│   └── lib.rs        # Extension implementation
├── ts/
│   └── init.ts       # TypeScript module shim
├── build.rs          # forge-weld build configuration
└── Cargo.toml

Rust Implementation

Operations are annotated with forge-weld macros for automatic TypeScript binding generation:

src/lib.rs

use deno_core::{op2, Extension, OpState};
use forge_weld_macro::{weld_op, weld_struct};
use serde::{Deserialize, Serialize};

#[weld_struct]
#[derive(Debug, Serialize, Deserialize)]
pub struct IpcEvent {
    pub window_id: String,
    pub channel: String,
    pub payload: serde_json::Value,
}

#[weld_op(async)]
#[op2(async)]
#[serde]
pub async fn op_ipc_send(
    state: Rc<RefCell<OpState>>,
    #[string] window_id: String,
    #[string] channel: String,
    #[serde] payload: serde_json::Value,
) -> Result<(), IpcError> {
    // implementation
}

Build Configuration

build.rs

use forge_weld::ExtensionBuilder;

fn main() {
    ExtensionBuilder::new("runtime_ipc", "runtime:ipc")
        .ts_path("ts/init.ts")
        .ops(&["op_ipc_send", "op_ipc_recv"])
        .generate_sdk_module("sdk")
        .use_inventory_types()
        .build()
        .expect("Failed to build runtime_ipc extension");
}

Dependencies

Dependency	Purpose
deno_core	Op definitions
tokio	Async channels
serde, serde_json	Message serialization
tracing	Logging
forge-weld	Build-time code generation
forge-weld-macro	#[weld_op], #[weld_struct] macros
linkme	Compile-time symbol collection

Related

• runtime:ipc API - TypeScript API documentation
• ext_window - Window management
• forge-runtime - Runtime that bridges IPC
• forge-weld - Code generation library