refactor: re-implement desktop-capturer in TypeScript (#18580)

lib/browser/desktop-capturer.js

@@ -1,91 +0,0 @@
-'use strict'
-
-const { createDesktopCapturer } = process.electronBinding('desktop_capturer')
-
-const deepEqual = (a, b) => JSON.stringify(a) === JSON.stringify(b)
-
-let currentlyRunning = []
-
-exports.getSources = (event, captureWindow, captureScreen, thumbnailSize, fetchWindowIcons) => {
-  const options = {
-    captureWindow,
-    captureScreen,
-    thumbnailSize,
-    fetchWindowIcons
-  }
-
-  for (const running of currentlyRunning) {
-    if (deepEqual(running.options, options)) {
-      // If a request is currently running for the same options
-      // return that promise
-      return running.getSources
-    }
-  }
-
-  const getSources = new Promise((resolve, reject) => {
-    const stopRunning = () => {
-      // Remove from currentlyRunning once we resolve or reject
-      currentlyRunning = currentlyRunning.filter(running => running.options !== options)
-    }
-    const request = {
-      options,
-      resolve: (value) => {
-        stopRunning()
-        resolve(value)
-      },
-      reject: (err) => {
-        stopRunning()
-        reject(err)
-      },
-      capturer: createDesktopCapturer()
-    }
-    request.capturer.emit = createCapturerEmitHandler(request.capturer, request)
-    request.capturer.startHandling(captureWindow, captureScreen, thumbnailSize, fetchWindowIcons)
-
-    // If the WebContents is destroyed before receiving result, just remove the
-    // reference to resolve, emit and the capturer itself so that it never dispatches
-    // back to the renderer
-    event.sender.once('destroyed', () => {
-      request.resolve = null
-      delete request.capturer.emit
-      delete request.capturer
-      stopRunning()
-    })
-  })
-
-  currentlyRunning.push({
-    options,
-    getSources
-  })
-
-  return getSources
-}
-
-const createCapturerEmitHandler = (capturer, request) => {
-  return function handlEmitOnCapturer (event, name, sources, fetchWindowIcons) {
-    // Ensure that this capturer instance can only ever receive a single event
-    // if we get more than one it is a bug but will also cause strange behavior
-    // if we still try to handle it
-    delete capturer.emit
-
-    if (name === 'error') {
-      const error = sources
-      request.reject(error)
-      return
-    }
-
-    const result = sources.map(source => {
-      return {
-        id: source.id,
-        name: source.name,
-        thumbnail: source.thumbnail.toDataURL(),
-        display_id: source.display_id,
-        appIcon: (fetchWindowIcons && source.appIcon) ? source.appIcon.toDataURL() : null
-      }
-    })
-
-    if (request.resolve) {
-      request.resolve(result)
-    }
-  }
-}

lib/browser/desktop-capturer.ts

@@ -0,0 +1,66 @@
+import { EventEmitter } from 'events'
+
+const { createDesktopCapturer } = process.electronBinding('desktop_capturer')
+
+const deepEqual = (a: ElectronInternal.GetSourcesOptions, b: ElectronInternal.GetSourcesOptions) => JSON.stringify(a) === JSON.stringify(b)
+
+let currentlyRunning: {
+  options: ElectronInternal.GetSourcesOptions;
+  getSources: Promise<ElectronInternal.GetSourcesResult[]>;
+}[] = []
+
+export const getSources = (event: Electron.IpcMainEvent, options: ElectronInternal.GetSourcesOptions) => {
+  for (const running of currentlyRunning) {
+    if (deepEqual(running.options, options)) {
+      // If a request is currently running for the same options
+      // return that promise
+      return running.getSources
+    }
+  }
+
+  const getSources = new Promise<ElectronInternal.GetSourcesResult[]>((resolve, reject) => {
+    const stopRunning = () => {
+      // Remove from currentlyRunning once we resolve or reject
+      currentlyRunning = currentlyRunning.filter(running => running.options !== options)
+    }
+
+    const emitter = new EventEmitter()
+
+    emitter.once('error', (event, error: string) => {
+      stopRunning()
+      reject(error)
+    })
+
+    emitter.once('finished', (event, sources: Electron.DesktopCapturerSource[], fetchWindowIcons: boolean) => {
+      stopRunning()
+      resolve(sources.map(source => ({
+        id: source.id,
+        name: source.name,
+        thumbnail: source.thumbnail.toDataURL(),
+        display_id: source.display_id,
+        appIcon: (fetchWindowIcons && source.appIcon) ? source.appIcon.toDataURL() : null
+      })))
+    })
+
+    let capturer: ElectronInternal.DesktopCapturer | null = createDesktopCapturer()
+
+    capturer.emit = emitter.emit.bind(emitter)
+    capturer.startHandling(options.captureWindow, options.captureScreen, options.thumbnailSize, options.fetchWindowIcons)
+
+    // If the WebContents is destroyed before receiving result, just remove the
+    // reference to emit and the capturer itself so that it never dispatches
+    // back to the renderer
+    event.sender.once('destroyed', () => {
+      capturer!.emit = null
+      capturer = null
+      stopRunning()
+    })
+  })
+
+  currentlyRunning.push({
+    options,
+    getSources
+  })
+
+  return getSources
+}