Add stats overlay to iOS AppRTCDemo.

webrtc/examples/objc/AppRTCDemo/ARDAppClient.m

 /*
  *  Copyright 2014 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 15 matching lines @@
 #import "ARDCEODTURNClient.h"
 #import "ARDJoinResponse.h"
 #import "ARDMessageResponse.h"
 #import "ARDSDPUtils.h"
 #import "ARDSignalingMessage.h"
 #import "ARDUtilities.h"
 #import "ARDWebSocketChannel.h"
 #import "RTCICECandidate+JSON.h"
 #import "RTCSessionDescription+JSON.h"
 
-
 static NSString * const kARDDefaultSTUNServerUrl =
     @"stun:stun.l.google.com:19302";
 // TODO(tkchin): figure out a better username for CEOD statistics.
 static NSString * const kARDTurnRequestUrl =
     @"https://computeengineondemand.appspot.com"
     @"/turn?username=iapprtc&key=4080218913";
 
 static NSString * const kARDAppClientErrorDomain = @"ARDAppClient";
 static NSInteger const kARDAppClientErrorUnknown = -1;
 static NSInteger const kARDAppClientErrorRoomFull = -2;
 static NSInteger const kARDAppClientErrorCreateSDP = -3;
 static NSInteger const kARDAppClientErrorSetSDP = -4;
 static NSInteger const kARDAppClientErrorInvalidClient = -5;
 static NSInteger const kARDAppClientErrorInvalidRoom = -6;
 
+// We need a proxy to NSTimer because it causes a strong retain cycle. When
+// using the proxy, |invalidate| must be called before it properly deallocs.
+@interface ARDTimerProxy : NSObject
+
+- (instancetype)initWithInterval:(NSTimeInterval)interval
+                         repeats:(BOOL)repeats
+                    timerHandler:(void (^)(void))timerHandler;
+- (void)invalidate;
+
+@end
+
+@implementation ARDTimerProxy {
+  NSTimer *_timer;
+  void (^_timerHandler)(void);
+}
+
+- (instancetype)initWithInterval:(NSTimeInterval)interval
+                         repeats:(BOOL)repeats
+                    timerHandler:(void (^)(void))timerHandler {
+  NSParameterAssert(timerHandler);
+  if (self = [super init]) {
+    _timerHandler = timerHandler;
+    _timer = [NSTimer scheduledTimerWithTimeInterval:interval
+                                              target:self
+                                            selector:@selector(timerDidFire:)
+                                            userInfo:nil
+                                             repeats:repeats];
+  }
+  return self;
+}
+
+- (void)invalidate {
+  [_timer invalidate];
+}
+
+- (void)timerDidFire:(NSTimer *)timer {
+  _timerHandler();
+}
+
+@end
+
 @implementation ARDAppClient {
   RTCFileLogger *_fileLogger;
+  ARDTimerProxy *_statsTimer;
 }
 
+@synthesize shouldGetStats = _shouldGetStats;
+@synthesize state = _state;
 @synthesize delegate = _delegate;
-@synthesize state = _state;
 @synthesize roomServerClient = _roomServerClient;
 @synthesize channel = _channel;
 @synthesize turnClient = _turnClient;
 @synthesize peerConnection = _peerConnection;
 @synthesize factory = _factory;
 @synthesize messageQueue = _messageQueue;
 @synthesize isTurnComplete = _isTurnComplete;
 @synthesize hasReceivedSdp  = _hasReceivedSdp;
 @synthesize roomId = _roomId;
 @synthesize clientId = _clientId;
@@ skipping 47 matching lines @@
 
 - (void)configure {
   _factory = [[RTCPeerConnectionFactory alloc] init];
   _messageQueue = [NSMutableArray array];
   _iceServers = [NSMutableArray arrayWithObject:[self defaultSTUNServer]];
   _fileLogger = [[RTCFileLogger alloc] init];
   [_fileLogger start];
 }
 
 - (void)dealloc {
+  self.shouldGetStats = NO;
   [self disconnect];
 }
 
+- (void)setShouldGetStats:(BOOL)shouldGetStats {

[jiayl2, 2015/08/13 22:21:50]

I didn't find who calls this method...

[tkchin_webrtc, 2015/08/13 23:55:31]

.shouldGetStats = is a property setter, it calls setShouldGetStats

+  if (_shouldGetStats == shouldGetStats) {
+    return;
+  }
+  if (shouldGetStats) {
+    __weak ARDAppClient *weakSelf = self;
+    _statsTimer = [[ARDTimerProxy alloc] initWithInterval:1
+                                                  repeats:YES
+                                             timerHandler:^{
+      ARDAppClient *strongSelf = weakSelf;

[jiayl2, 2015/08/13 22:21:50]

OOC: what's the magic with stringSelf/weakSelf?

[tkchin_webrtc, 2015/08/13 23:55:31]

We don't want to add a refcount to this object in the timerHandler, if we
referenced self directly we would've done so. So we create a weak pointer
instead and access that within the block. However, within the block we need to
convert the weak pointer to a strong pointer first, otherwise it's possible that
earlier calls will succeed, but later calls will fail (if the weak pointer
disappears in the middle of the block).

+      [strongSelf.peerConnection getStatsWithDelegate:strongSelf

[jiayl2, 2015/08/13 22:21:49]

Is peerConnection guaranteed to exist?

[tkchin_webrtc, 2015/08/13 23:55:31]

No. Messages sent to nil are no-ops so this is safe.

+                                     mediaStreamTrack:nil
+                                     statsOutputLevel:RTCStatsOutputLevelDebug];
+    }];
+  } else {
+    [_statsTimer invalidate];

[jiayl2, 2015/08/13 22:21:50]

Is this guaranteed to be called?
Do we need to release in dealloc if not?

[tkchin_webrtc, 2015/08/13 23:55:31]

This is being released in dealloc by setting to NO.

+    _statsTimer = nil;
+  }
+  _shouldGetStats = shouldGetStats;
+}
+
 - (void)setState:(ARDAppClientState)state {
   if (_state == state) {
     return;
   }
   _state = state;
   [_delegate appClient:self didChangeState:_state];
 }
 
 - (void)connectToRoomWithId:(NSString *)roomId
                     options:(NSDictionary *)options {
@@ skipping 168 matching lines @@
     ARDICECandidateMessage *message =
         [[ARDICECandidateMessage alloc] initWithCandidate:candidate];
     [self sendSignalingMessage:message];
   });
 }
 
 - (void)peerConnection:(RTCPeerConnection*)peerConnection
     didOpenDataChannel:(RTCDataChannel*)dataChannel {
 }
 
+#pragma mark - RTCStatsDelegate
+
+- (void)peerConnection:(RTCPeerConnection*)peerConnection
+           didGetStats:(NSArray*)stats {
+  dispatch_async(dispatch_get_main_queue(), ^{
+    [_delegate appClient:self didGetStats:stats];
+  });
+}
+
 #pragma mark - RTCSessionDescriptionDelegate
 // Callbacks for this delegate occur on non-main thread and need to be
 // dispatched back to main queue as needed.
 
 - (void)peerConnection:(RTCPeerConnection *)peerConnection
     didCreateSessionDescription:(RTCSessionDescription *)sdp
                           error:(NSError *)error {
   dispatch_async(dispatch_get_main_queue(), ^{
     if (error) {
       RTCLogError(@"Failed to create session description. Error: %@", error);
@@ skipping 306 matching lines @@
                                          code:kARDAppClientErrorInvalidRoom
                                      userInfo:@{
         NSLocalizedDescriptionKey: @"Invalid room.",
       }];
       break;
   }
   return error;
 }
 
 @end