SmartMirror-Projektarbeit/node_modules/@electron/remote/README.md

@electron/remote

@electron/remote is an Electron module that bridges JavaScript objects from the main process to the renderer process. This lets you access main-process-only objects as if they were available in the renderer process.

⚠️ Warning! This module has many subtle pitfalls. There is almost always a better way to accomplish your task than using this module. For example, ipcRenderer.invoke can serve many common use cases.

@electron/remote is a replacement for the built-in remote module in Electron, which is deprecated and will eventually be removed.

Migrating from remote

NOTE: @electron/remote requires Electron 10 or higher.

There are three things you need to do to migrate from the built-in remote module to @electron/remote.

First, you need to install it from NPM:

$ npm install --save @electron/remote

Second, @electron/remote/main must be initialized in the main process before it can be used from the renderer:

// in the main process:
require('@electron/remote/main').initialize()

Third, require('electron').remote in the renderer process must be replaced with require('@electron/remote').

// in the renderer process:

// Before
const { BrowserWindow } = require('electron').remote

// After
const { BrowserWindow } = require('@electron/remote')

Note: Since this is requiring a module through npm rather than a built-in module, if you’re using remote from a sandboxed process, you’ll need to configure your bundler appropriately to package the code of @electron/remote in the preload script. Of course, using @electron/remote makes the sandbox much less effective.

Note: @electron/remote respects the enableRemoteModule WebPreferences value. You must pass { webPreferences: { enableRemoteModule: true } } to the constructor of BrowserWindows that should be granted permission to use @electron/remote.

API Reference

The remote module provides a simple way to do inter-process communication (IPC) between the renderer process (web page) and the main process.

In Electron, GUI-related modules (such as dialog, menu etc.) are only available in the main process, not in the renderer process. In order to use them from the renderer process, the ipc module is necessary to send inter-process messages to the main process. With the remote module, you can invoke methods of the main process object without explicitly sending inter-process messages, similar to Java’s RMI. An example of creating a browser window from a renderer process:

const { BrowserWindow } = require('@electron/remote')
let win = new BrowserWindow({ width: 800, height: 600 })
win.loadURL('https://github.com')

In order for this to work, you first need to initialize the main-process side of the remote module:

// in the main process:
require('@electron/remote/main').initialize()

Note: The remote module can be disabled for security reasons in the following contexts:

• BrowserWindow - by setting the enableRemoteModule option to false.
• <webview> - by setting the enableremotemodule attribute to false.

Remote Objects

Each object (including functions) returned by the remote module represents an object in the main process (we call it a remote object or remote function). When you invoke methods of a remote object, call a remote function, or create a new object with the remote constructor (function), you are actually sending synchronous inter-process messages.

In the example above, both BrowserWindow and win were remote objects and new BrowserWindow didn’t create a BrowserWindow object in the renderer process. Instead, it created a BrowserWindow object in the main process and returned the corresponding remote object in the renderer process, namely the win object.

Note: Only enumerable properties which are present when the remote object is first referenced are accessible via remote.

Note: Arrays and Buffers are copied over IPC when accessed via the remote module. Modifying them in the renderer process does not modify them in the main process and vice versa.

Lifetime of Remote Objects

Electron makes sure that as long as the remote object in the renderer process lives (in other words, has not been garbage collected), the corresponding object in the main process will not be released. When the remote object has been garbage collected, the corresponding object in the main process will be dereferenced.

If the remote object is leaked in the renderer process (e.g. stored in a map but never freed), the corresponding object in the main process will also be leaked, so you should be very careful not to leak remote objects.

Primary value types like strings and numbers, however, are sent by copy.

Passing callbacks to the main process

Code in the main process can accept callbacks from the renderer - for instance the remote module - but you should be extremely careful when using this feature.

First, in order to avoid deadlocks, the callbacks passed to the main process are called asynchronously. You should not expect the main process to get the return value of the passed callbacks.

For instance you can’t use a function from the renderer process in an Array.map called in the main process:

// main process mapNumbers.js
exports.withRendererCallback = (mapper) => {
  return [1, 2, 3].map(mapper)
}

exports.withLocalCallback = () => {
  return [1, 2, 3].map(x => x + 1)
}

// renderer process
const mapNumbers = require('@electron/remote').require('./mapNumbers')
const withRendererCb = mapNumbers.withRendererCallback(x => x + 1)
const withLocalCb = mapNumbers.withLocalCallback()

console.log(withRendererCb, withLocalCb)
// [undefined, undefined, undefined], [2, 3, 4]

As you can see, the renderer callback’s synchronous return value was not as expected, and didn’t match the return value of an identical callback that lives in the main process.

Second, the callbacks passed to the main process will persist until the main process garbage-collects them.

For example, the following code seems innocent at first glance. It installs a callback for the close event on a remote object:

require('@electron/remote').getCurrentWindow().on('close', () => {
  // window was closed...
})

But remember the callback is referenced by the main process until you explicitly uninstall it. If you do not, each time you reload your window the callback will be installed again, leaking one callback for each restart.

To make things worse, since the context of previously installed callbacks has been released, exceptions will be raised in the main process when the close event is emitted.

To avoid this problem, ensure you clean up any references to renderer callbacks passed to the main process. This involves cleaning up event handlers, or ensuring the main process is explicitly told to dereference callbacks that came from a renderer process that is exiting.

Accessing built-in modules in the main process

The built-in modules in the main process are added as getters in the remote module, so you can use them directly like the electron module.

const app = require('@electron/remote').app
console.log(app)

Methods

The remote module has the following methods:

remote.require(module)

• module String

Returns any - The object returned by require(module) in the main process. Modules specified by their relative path will resolve relative to the entrypoint of the main process.

e.g.

project/
├── main
│   ├── foo.js
│   └── index.js
├── package.json
└── renderer
    └── index.js

// main process: main/index.js
const { app } = require('@electron/remote')
app.whenReady().then(() => { /* ... */ })

// some relative module: main/foo.js
module.exports = 'bar'

// renderer process: renderer/index.js
const foo = require('@electron/remote').require('./foo') // bar

remote.getCurrentWindow()

Returns BrowserWindow - The window to which this web page belongs.

Note: Do not use removeAllListeners on BrowserWindow. Use of this can remove all blur listeners, disable click events on touch bar buttons, and other unintended consequences.

remote.getCurrentWebContents()

Returns WebContents - The web contents of this web page.

remote.getGlobal(name)

• name String

Returns any - The global variable of name (e.g. global[name]) in the main process.

Properties

remote.process Readonly

A NodeJS.Process object. The process object in the main process. This is the same as remote.getGlobal('process') but is cached.

Overriding exposed objects

Without filtering, @electron/remote will provide access to any JavaScript object that any renderer requests. In order to control what can be accessed, @electron/remote provides an opportunity to the app to return a custom result for any of getGlobal, require, getCurrentWindow, getCurrentWebContents, or any of the builtin module properties.

The following events will be emitted first on the app Electron module, and then on the specific WebContents which requested the object. When emitted on the app module, the first parameter after the Event object will be the WebContents which originated the request. If any handler calls preventDefault, the request will be denied. If a returnValue parameter is set on the result, then that value will be returned to the renderer instead of the default.

Events

Event: ‘remote-require’

Returns:

• event Event
• moduleName String

Emitted when remote.require() is called in the renderer process of webContents. Calling event.preventDefault() will prevent the module from being returned. Custom value can be returned by setting event.returnValue.

Event: ‘remote-get-global’

Returns:

• event Event
• globalName String

Emitted when remote.getGlobal() is called in the renderer process of webContents. Calling event.preventDefault() will prevent the global from being returned. Custom value can be returned by setting event.returnValue.

Event: ‘remote-get-builtin’

Returns:

• event Event
• moduleName String

Emitted when remote.getBuiltin() is called in the renderer process of webContents, including when a builtin module is accessed as a property (e.g. require("@electron/remote").BrowserWindow). Calling event.preventDefault() will prevent the module from being returned. Custom value can be returned by setting event.returnValue.

Event: ‘remote-get-current-window’

Returns:

• event Event

Emitted when remote.getCurrentWindow() is called in the renderer process of webContents. Calling event.preventDefault() will prevent the object from being returned. Custom value can be returned by setting event.returnValue.

Event: ‘remote-get-current-web-contents’

Returns:

• event Event

Emitted when remote.getCurrentWebContents() is called in the renderer process of webContents. Calling event.preventDefault() will prevent the object from being returned. Custom value can be returned by setting event.returnValue.