npm-reflector-electron-MsgEnv-ipc-main

A reflector between a messaging environment and Electron IPC (main process). Messages published to the messaging environment are forwarded to every registered renderer window, and messages sent from a renderer are published back to it. Duplicate reflections are suppressed via @ipsme/msgcache-dedup.

The messaging environment is chosen per platform by default:

Platform	Default messaging environment
win32	@ipsme/msgenv-mqtt (mqtt://localhost:1883)
darwin	@ipsme/msgenv-electron-nsdnc (NSDistributedNotificationCenter)
anything else	none — you must inject one (see Overriding the default below)

Both msgenv packages are optionalDependencies, and only the one for your platform is ever required at runtime -- default_MsgEnv() loads MQTT on win32, NSDNC on darwin. So the app runs with just the platform's package present, and if you inject your own (see Overriding the default below) you need neither.

Note: optionalDependencies does not make npm install only the platform's package. It means "don't fail the whole install if one of these can't be installed" -- npm skips an optional dep only when it actually fails (e.g. an os/cpu mismatch or a build error). Neither msgenv-* package declares an os field, so a default npm install installs both on every platform; the per-platform choice happens purely at runtime in default_MsgEnv(). If you want npm to prune the wrong one automatically, those packages would each need an os field (darwin on NSDNC, win32 on MQTT) -- nothing in this repo can enforce that. In the meantime you can remove the unused one yourself, or just leave it (harmless, only ever required on its platform).

IPSME — Idempotent Publish/Subscribe Messaging Environment

https://dl.acm.org/doi/abs/10.1145/3458307.3460966

main.js | electron.js

//-------------------------------------------------------------------------------------------------
// reflector msgenv <-> ipc

const { Reflector_IPC_main } = require('@ipsme/reflector-electron-msgenv-ipc-main');
const { ipcMain } = require('electron');

// No second argument -> uses the platform default (MQTT on win32, NSDNC on darwin).
const reflector_IPC_main_ = new Reflector_IPC_main(ipcMain);
reflector_IPC_main_.subscribe();

//-------------------------------------------------------------------------------------------------

function createWindow() {
	// Create the browser window.
	const win = new BrowserWindow({
		// ...
		webPreferences: {
			// nodeIntegration: true,
			preload: __dirname + '/preload.js'
		},
	});

	// ...

	reflector_IPC_main_.add_window(win);

	win.on('closed', () => {
		reflector_IPC_main_.remove_window(win);
		// ...
	});
}

Overriding the default messaging environment

Pass a messaging environment as the second constructor argument and it is used instead of the platform default (which is then never resolved -- so you don't even need the platform's msgenv-* package installed). This is how you run on an unsupported platform, select a non-default ME, or inject a mock/stub in tests.

The injected object must expose:

• publish(msg) -- publish a message to the ME;
• subscribe(handler) -- register handler(msg) for messages arriving from the ME;
• (optional) logr -- a bitlogr-3.x logger; if present it is wired into the reflector's logging (see Logging below).

A provided-but-unusable env (missing publish/subscribe, or an explicit null) throws at construction: Reflector_IPC_main: msgEnv must expose .publish(msg) and .subscribe(handler).

const { Reflector_IPC_main } = require('@ipsme/reflector-electron-msgenv-ipc-main');
const IPSME_MsgEnv = require('@ipsme/msgenv-mqtt'); // or any ME you like

const reflector_IPC_main_ = new Reflector_IPC_main(ipcMain, IPSME_MsgEnv);
reflector_IPC_main_.subscribe();

A stub is enough for tests -- no broker required:

const bus = [];
const fake_env = {
	publish:   (msg) => bus.push(msg),
	// keep the handler so a test can push an inbound ME message: fake_env.deliver(msg)
	subscribe: (handler) => { fake_env.deliver = handler; }
};
const reflector_IPC_main_ = new Reflector_IPC_main(ipcMain, fake_env);

Preload (context bridge)

//-------------------------------------------------------------------------------------------------
// preload.js

// https://github.com/electron/electron/issues/9920#issuecomment-947170941

const { contextBridge, ipcRenderer } = require("electron");

// As an example, here we use the exposeInMainWorld API to expose the IPC renderer
// to the main window. They'll be accessible at "window.ipc_reflector".
process.once("loaded", () => {
    contextBridge.exposeInMainWorld('ipc_reflector',
		{
			// https://github.com/electron/electron/issues/21437#issuecomment-573522360
			send: (msg) => ipcRenderer.send('ipc-reflector-to-main', msg),
			recv: (fn) => {
				// Deliberately strip event as it includes `sender`
				ipcRenderer.on('ipc-reflector-to-window', (event, ...args) => fn(...args));
			}
		}
	);
});

Logging

Logging uses @knev/bitlogr (3.x). On construction the reflector wire()s its own logger (labels DUPLICATES, CONNECTIONS, REFLECTION) together with the loggers of the participants it uses -- the @ipsme/msgcache-dedup dedup cache and the configured messaging environment -- so every label shares one toggle mask on the shared LOGR instance. Only a participant exposing a bitlogr-3.x logger (one with a .lref) is wired; a legacy build is simply left to log on its own.

The wired logger is exported as logr. Toggle categories through the shared LOGR instance, after a reflector has been constructed (construction is when the wire happens):

const { logr } = require('@ipsme/reflector-electron-msgenv-ipc-main');
const { LOGR } = require('@knev/bitlogr');

LOGR.get_instance().toggle(logr.l, { REFLECTION: true, CONNECTIONS: true });

Note: options is currently an inert instance setter -- it stores the value but does not (yet) toggle logging or forward to the messaging environment's config.