text: 'use strict'
  
  const {ipcMain} = require('electron')
  const {desktopCapturer} = process.atomBinding('desktop_capturer')
  
  const deepEqual = (a, b) => JSON.stringify(a) === JSON.stringify(b)
  
  // A queue for holding all requests from renderer process.
  let requestsQueue = []
  
  const electronSources = 'ELECTRON_BROWSER_DESKTOP_CAPTURER_GET_SOURCES'
  const capturerResult = (id) => `ELECTRON_RENDERER_DESKTOP_CAPTURER_RESULT_${id}`
  
  ipcMain.on(electronSources, (event, captureWindow, captureScreen, thumbnailSize, id) => {
    const request = {
      id,
      options: {
        captureWindow,
        captureScreen,
        thumbnailSize
      },
      webContents: event.sender
    }
    requestsQueue.push(request)
    if (requestsQueue.length === 1) {
      desktopCapturer.startHandling(captureWindow, captureScreen, thumbnailSize)
    }
  
    // If the WebContents is destroyed before receiving result, just remove the
    // reference from requestsQueue to make the module not send the result to it.
    event.sender.once('destroyed', () => {
      request.webContents = null
    })
  })
  
  desktopCapturer.emit = (event, name, sources) => {
    // Receiving sources result from main process, now send them back to renderer.
    const handledRequest = requestsQueue.shift()
    const handledWebContents = handledRequest.webContents
    const unhandledRequestsQueue = []
  
    const result = sources.map(source => {
      return {
        id: source.id,
        name: source.name,
        thumbnail: source.thumbnail.toDataURL(),
        display_id: source.display_id
      }
    })
  
    if (handledWebContents) {
      handledWebContents.send(capturerResult(handledRequest.id), result)
    }
  
    // Check the queue to see whether there is another identical request & handle
    requestsQueue.forEach(request => {
      const webContents = request.webContents
      if (deepEqual(handledRequest.options, request.options)) {
        if (webContents) webContents.send(capturerResult(request.id), result)
      } else {
        unhandledRequestsQueue.push(request)
      }
    })
    requestsQueue = unhandledRequestsQueue
  
    // If the requestsQueue is not empty, start a new request handling.
    if (requestsQueue.length > 0) {
      const {captureWindow, captureScreen, thumbnailSize} = requestsQueue[0].options
      return desktopCapturer.startHandling(captureWindow, captureScreen, thumbnailSize)
    }
  }
  