Open app and pass parameters with deep linking using Electron (macOS)

Solved for both macOS and win32 ( Updated project 'electron-deep-linking-mac-win' on GitHub).

---

package.json:

{
  "name": "electron-deeplinking-macos-win32",
  "version": "0.0.1",
  "description": "Minimal Electron application with deep inking (macOS/win32)",
  "main": "main.js",
  "scripts": {
    "start": "electron .",
    "pack": "build --dir",
    "dist": "build"
  },
  "repository": "https://github.com/oikonomopo/electron-deep-linking-osx",
  "author": "oikonomopo",
  "license": "CC0-1.0",
  "devDependencies": {
    "electron": "1.6.6",
    "electron-builder": "17.1.2"
  },
  "build": {
    "appId": "oikonomopo.electron-deeplinking-macos-win32",
    "protocols": {
      "name": "electron-deep-linking",
      "schemes": ["myapp"]
    },
    "mac": {
      "category": "public.app-category.Reference"
    },
    "win": {
    }
  }
}

---

main.js:

const {app, BrowserWindow} = require('electron')
// Module with utilities for working with file and directory paths.
const path = require('path')
// Module with utilities for URL resolution and parsing.
const url = require('url')

// Keep a global reference of the window object, if you don't, the window will
// be closed automatically when the JavaScript object is garbage collected.
let mainWindow

// Deep linked url
let deeplinkingUrl

// Force Single Instance Application
const shouldQuit = app.makeSingleInstance((argv, workingDirectory) => {
  // Someone tried to run a second instance, we should focus our window.

  // Protocol handler for win32
  // argv: An array of the second instance’s (command line / deep linked) arguments
  if (process.platform == 'win32') {
    // Keep only command line / deep linked arguments
    deeplinkingUrl = argv.slice(1)
  }
  logEverywhere("app.makeSingleInstance# " + deeplinkingUrl)

  if (win) {
    if (win.isMinimized()) win.restore()
        win.focus()
  }
})
if (shouldQuit) {
    app.quit()
    return
}

function createWindow () {
  // Create the browser window.
  mainWindow = new BrowserWindow({width: 800, height: 600})

  // and load the index.html of the app.
  mainWindow.loadURL(url.format({
    pathname: path.join(__dirname, 'index.html'),
    protocol: 'file:',
    slashes: true
  }))

  // Open the DevTools.
  mainWindow.webContents.openDevTools()

  // Protocol handler for win32
  if (process.platform == 'win32') {
    // Keep only command line / deep linked arguments
    deeplinkingUrl = process.argv.slice(1)
  }
  logEverywhere("createWindow# " + deeplinkingUrl)

  // Emitted when the window is closed.
  mainWindow.on('closed', function () {
    // Dereference the window object, usually you would store windows
    // in an array if your app supports multi windows, this is the time
    // when you should delete the corresponding element.
    mainWindow = null
  })
}

// This method will be called when Electron has finished
// initialization and is ready to create browser windows.
// Some APIs can only be used after this event occurs.
app.on('ready', createWindow)

// Quit when all windows are closed.
app.on('window-all-closed', function () {
  // On OS X it is common for applications and their menu bar
  // to stay active until the user quits explicitly with Cmd + Q
  if (process.platform !== 'darwin') {
    app.quit()
  }
})

app.on('activate', function () {
  // On OS X it's common to re-create a window in the app when the
  // dock icon is clicked and there are no other windows open.
  if (mainWindow === null) {
    createWindow()
  }
})

// Define custom protocol handler. 
// Deep linking works on packaged versions of the application!
app.setAsDefaultProtocolClient('myapp')

// Protocol handler for osx
app.on('open-url', function (event, url) {
  event.preventDefault()
  deeplinkingUrl = url
  logEverywhere("open-url# " + deeplinkingUrl)
})

// Log both at dev console and at running node console instance
function logEverywhere(s) {
    console.log(s)
    if (mainWindow && mainWindow.webContents) {
        mainWindow.webContents.executeJavaScript(`console.log("${s}")`)
    }
}

main.js code description:

• At let deeplinkingUrl we keep the provided url.

• On macOS you need to listen to the app.open-url event, while on Windows the url should be available in process.argv (in the main process).

  • On macOS platform this is captured at 'open-url' event, we set it with deeplinkingUrl = url! (See // Protocol handler for osx)

  • On win32 platform this is saved at process.argv together with other arguments. To get only the provided url, deeplinkingUrl = argv.slice(1). (See // Protocol handler for win32)

  • At app.makeSingleInstance method we check in which platform we are and we set deeplinkingUrl accordingly! If we are on win32 platform, the url is located at argv variable from callback, else on macOS should have already been set at 'open-url' event! (See // Force Single Instance Application)

You should be setting up the open-url event in the will-finish-launching callback as per the docs. I had similar weird behaviour with open-file until it was setup within the will-finish-launching callback.

You notice they've done it this way in the example you link to.

Although it mentions this under will-finish-launching, it should really mention this under the open-url and open-file docs too as its quite easy to miss.

app.on('will-finish-launching', () => {
  // Protocol handler for osx
  app.on('open-url', (event, url) => {
    event.preventDefault();
    log("open-url event: " + url)
  })
});