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ext_ipc

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

import {
  sendToWindow,
  onChannel,
  windowEvents,
  broadcast
} from "host: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.host.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.host.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

Dependencies

Dependency	Purpose
`deno_core`	Op definitions
`tokio`	Async channels
`serde`, `serde_json`	Message serialization
`tracing`	Logging
`forge-weld`	Build-time code generation

host:ipc API - TypeScript API documentation
ext_window - Window management
forge-host - Runtime that bridges IPC