desktopCapturer
Access information about media sources that can be used to capture audio and video from the desktop using the
navigator.mediaDevices.getUserMedia
API.
Processo: Main
O exemplo a seguir mostra como capturar vídeo de uma janela desktop com o título Electron
:
// No processo main.
const { desktopCapturer } = require('electron')
desktopCapturer.getSources({ types: ['window', 'screen'] }).then(async sources => {
for (const source of sources) {
if (source.name === 'Electron') {
mainWindow.webContents.send('SET_SOURCE', source.id)
return
}
}
})
// In the preload script.
const { ipcRenderer } = require('electron')
ipcRenderer.on('SET_SOURCE', async (event, sourceId) => {
try {
const stream = await navigator.mediaDevices.getUserMedia({
audio: false,
video: {
mandatory: {
chromeMediaSource: 'desktop',
chromeMediaSourceId: sourceId,
minWidth: 1280,
maxWidth: 1280,
minHeight: 720,
maxHeight: 720
}
}
})
handleStream(stream)
} catch (e) {
handleError(e)
}
})
function handleStream (stream) {
const video = document.querySelector('video')
video.srcObject = stream
video.onloadedmetadata = (e) => video.play()
}
function handleError (e) {
console.log(e)
}
To capture video from a source provided by desktopCapturer
the constraints passed to navigator.mediaDevices.getUserMedia
must include chromeMediaSource: 'desktop'
, and audio: false
.
To capture both audio and video from the entire desktop the constraints passed to navigator.mediaDevices.getUserMedia
must include chromeMediaSource: 'desktop'
, for both audio
and video
, but should not include a chromeMediaSourceId
constraint.
const constraints = {
audio: {
mandatory: {
chromeMediaSource: 'desktop'
}
},
video: {
mandatory: {
chromeMediaSource: 'desktop'
}
}
}
Métodos
O módulo desktopCapturer
tem os seguintes métodos:
desktopCapturer.getSources(options)
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 the screen contents requires user consent on macOS 10.15 Catalina or higher, which can detected by systemPreferences.getMediaAccessStatus
.
Caveats
navigator.mediaDevices.getUserMedia
does not work on macOS 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.
It is possible to circumvent this limitation by capturing system audio with another macOS app like Soundflower and passing it through a virtual audio input device. This virtual device can then be queried with navigator.mediaDevices.getUserMedia
.