electron/lib/renderer/web-view/web-view-init.ts

import { ipcRendererInternal } from '@electron/internal/renderer/ipc-renderer-internal'

const v8Util = process.electronBinding('v8_util')

function handleFocusBlur (guestInstanceId: number) {
  // Note that while Chromium content APIs have observer for focus/blur, they
  // unfortunately do not work for webview.

  window.addEventListener('focus', () => {
    ipcRendererInternal.send('ELECTRON_GUEST_VIEW_MANAGER_FOCUS_CHANGE', true, guestInstanceId)
  })

  window.addEventListener('blur', () => {
    ipcRendererInternal.send('ELECTRON_GUEST_VIEW_MANAGER_FOCUS_CHANGE', false, guestInstanceId)
  })
}

export function webViewInit (
  contextIsolation: boolean, webviewTag: ElectronInternal.WebViewElement, guestInstanceId: number
) {
  // Don't allow recursive `<webview>`.
  if (webviewTag && guestInstanceId == null) {
    const { webViewImplModule } = require('@electron/internal/renderer/web-view/web-view-impl')
    if (contextIsolation) {
      v8Util.setHiddenValue(window, 'web-view-impl', webViewImplModule)
    } else {
      const { setupWebView } = require('@electron/internal/renderer/web-view/web-view-element')
      setupWebView(v8Util, webViewImplModule)
    }
  }

  if (guestInstanceId) {
    // Report focus/blur events of webview to browser.
    handleFocusBlur(guestInstanceId)
  }
}