Ir para o conteúdo principal

desktopCapturer

Access information about media sources that can be used to capture audio and video from the desktop using the navigator.mediaDevices.getUserMedia API.

Process: Main

O exemplo a seguir mostra como capturar vídeo de uma janela desktop com o título Electron:

// main.js
const { app, BrowserWindow, desktopCapturer, session } = require('electron')

app.whenReady().then(() => {
  const mainWindow = new BrowserWindow()

  session.defaultSession.setDisplayMediaRequestHandler((request, callback) => {
    desktopCapturer.getSources({ types: ['screen'] }).then((sources) => {
      // Grant access to the first screen found.
      callback({ video: sources[0], audio: 'loopback' })
    })
    // If true, use the system picker if available.
    // Note: this is currently experimental. If the system picker
    // is available, it will be used and the media request handler
    // will not be invoked.
  }, { useSystemPicker: true })

  mainWindow.loadFile('index.html')
})
// renderer.js
const startButton = document.getElementById('startButton')
const stopButton = document.getElementById('stopButton')
const video = document.querySelector('video')

startButton.addEventListener('click', () => {
  navigator.mediaDevices.getDisplayMedia({
    audio: true,
    video: {
      width: 320,
      height: 240,
      frameRate: 30
    }
  }).then(stream => {
    video.srcObject = stream
    video.onloadedmetadata = (e) => video.play()
  }).catch(e => console.log(e))
})

stopButton.addEventListener('click', () => {
  video.pause()
})
<!-- index.html -->
<html>
<meta http-equiv="content-security-policy" content="script-src 'self' 'unsafe-inline'" />
  <body>
    <button id="startButton" class="button">Start</button>
    <button id="stopButton" class="button">Stop</button>
    <video width="320" height="240" autoplay></video>
    <script src="renderer.js"></script>
  </body>
</html>

See navigator.mediaDevices.getDisplayMedia for more information.

note

navigator.mediaDevices.getDisplayMedia does not permit the use of deviceId for selection of a source - see specification.

Métodos​

O módulo desktopCapturer tem os seguintes métodos:

desktopCapturer.getSources(options)​

  • options Object
    • types string[] - An array of strings that lists the types of desktop sources to be captured, available types can be screen and window.
    • thumbnailSize Size (optional) - The size that the media source thumbnail should be scaled to. Default is 150 x 150. Set width or height to 0 when you do not need the thumbnails. This will save the processing time required for capturing the content of each window and screen.
    • fetchWindowIcons boolean (optional) - Set to true to enable fetching window icons. The default value is false. When false the appIcon property of the sources return null. Same if a source has the type screen.

Returns Promise<DesktopCapturerSource[]> - Resolves with an array of DesktopCapturerSource objects, each DesktopCapturerSource represents a screen or an individual window that can be captured.

note
  • Capturing audio requires NSAudioCaptureUsageDescription Info.plist key on macOS 14.2 Sonoma and higher - read more.
  • Capturing the screen contents requires user consent on macOS 10.15 Catalina or higher, which can detected by systemPreferences.getMediaAccessStatus.

Caveats​

Linux​

desktopCapturer.getSources(options) only returns a single source on Linux when using Pipewire.

PipeWire supports a single capture for both screens and windows. If you request the window and screen type, the selected source will be returned as a window capture.

MacOS versions 14.2 or higher​

NSAudioCaptureUsageDescription Info.plist key must be added in-order for audio to be captured by desktopCapturer. If instead you are running electron from another program like a terminal or IDE then that parent program must contain the Info.plist key.

This is in order to facillitate use of Apple's new CoreAudio Tap API by Chromium.

[!WARNING] Failure of desktopCapturer to start an audio stream due to NSAudioCaptureUsageDescription permission not present will still create a dead audio stream however no warnings or errors are displayed.

As of electron v39.0.0-beta.4 Chromium made Apple's new CoreAudio Tap API the default for desktop audio capture. There is no fallback to the older Screen & System Audio Recording permissions system even if CoreAudio Tap API stream creation fails.

If you need to continue using Screen & System Audio Recording permissions for desktopCapturer on macOS versions 14.2 and later, you can apply a chromium feature flag to force use of that older permissions system:

// main.js (right beneath your require/import statments)
app.commandLine.appendSwitch('disable-features', 'MacCatapLoopbackAudioForScreenShare')

MacOS versions 12.7.6 or lower​

navigator.mediaDevices.getUserMedia does not work on macOS versions 12.7.6 and prior for audio capture due to a fundamental limitation whereby apps that want to access the system's audio require a signed kernel extension. Chromium, and by extension Electron, does not provide this. Only in macOS 13 and onwards does Apple provide APIs to capture desktop audio without the need for a signed kernel extension.

It is possible to circumvent this limitation by capturing system audio with another macOS app like BlackHole or Soundflower and passing it through a virtual audio input device. This virtual device can then be queried with navigator.mediaDevices.getUserMedia.