[chrome.displaySource] Add example extension

chrome/common/extensions/docs/examples/api/displaySource/tabCast/background.js

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+var g_sessionInfo = {};
+
+/**
+ * When extension icon clicked, get device list
+ * Then return the list to popup page
+ */
+chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) {
+  if (message.browserActionClicked) {
+    getDeviceList(function(deviceList) {
+      sendResponse({ returnDeviceList: deviceList });
+    });
+  }
+  return true;
+});
+
+function getDeviceList(callback) {
+  chrome.displaySource.getAvailableSinks(callback);
+}
+
+chrome.displaySource.onSessionTerminated.addListener(function(terminatedSink) {
+  chrome.runtime.sendMessage({ sessionTerminated: true,
+                               currentSinkId: terminatedSink });
+
+  if (g_sessionInfo.stream) {
+    g_sessionInfo.stream.getTracks().forEach(function (track) {
+        track.stop(); });
+    delete g_sessionInfo.stream;
+  }
+  delete g_sessionInfo.sinkId;
+});
+
+chrome.displaySource.onSinksUpdated.addListener(function(updatedSinks) {
+  console.log('Sinks updated');
+  chrome.runtime.sendMessage({ sinksUpdated: true,
+                               currentSinkId: g_sessionInfo.sinkId,
+                               sinksList: updatedSinks});
+});
+
+function start(sinkId) {
+  // If no session, proceed.
+  if (!g_sessionInfo.sinkId) {
+    g_sessionInfo.sinkId = parseInt(sinkId);
+    captureTabAndStartSession(g_sessionInfo.sinkId);
+  }
+}
+
+function captureTabAndStartSession(sink_id) {
+  chrome.tabs.getCurrent(function(tab) {
+      var video_constraints = {
+          mandatory: {
+              chromeMediaSource: 'tab',
+              minWidth: 1920,
+              minHeight: 1080,
+              maxWidth: 1920,
+              maxHeight: 1080,
+              minFrameRate: 60,
+              maxFrameRate: 60
+          }
+       };
+
+       var constraints = {
+           audio: true,
+           video: true,
+           videoConstraints: video_constraints
+       };
+
+       function onStream(stream) {
+         g_sessionInfo.stream = stream;
+         var session_info = {
+             sinkId: sink_id,
+             videoTrack: g_sessionInfo.stream.getVideoTracks()[0],
+             audioTrack: g_sessionInfo.stream.getAudioTracks()[0]
+         };
+
+         function onStarted() {
+           if (chrome.runtime.error) {
+           console.log('The Session to sink ' + g_sessionInfo.sinkId
+               + 'could not start, error: '
+               + chrome.runtime.lastError.message);
+           } else {
+             console.log('The Session to sink ' + g_sessionInfo.sinkId
+             + ' has started.');
+           }
+         }
+         console.log('Starting session to sink: ' + sink_id);
+         chrome.displaySource.startSession(session_info, onStarted);
+       }
+
+       chrome.tabCapture.capture(constraints, onStream);
+  });
+}
+
+function stop() {
+  function onTerminated() {
+    if (chrome.runtime.lastError) {
+      console.log('The Session to sink ' + g_sessionInfo.sinkId
+          + 'could not terminate, error: '
+          + chrome.runtime.lastError.message);
+    } else {
+      console.log('The Session to sink ' + g_sessionInfo.sinkId
+          + ' has terminated.');
+    }
+  }
+  console.log('Terminating session to sink: ' + g_sessionInfo.sinkId);
+  chrome.displaySource.terminateSession(g_sessionInfo.sinkId, onTerminated);
+}