Access UIApplication on main thread

Track UIApplication applicationState changes from a C++ class. Uses
NSNotificationCenter to access changes on the main thread and exposes
a local variable that can be checked from any thread.

This fixes a runtime warning on iOS 11 beta.

My Objective-C++ is a little rusty so please check if this follows
the conventions for C++ code in the project. It also changes the
interface exposed by RTCUIApplication.h, not sure if that has impact
on any public APIs that needs to be documented somewhere?

Bug: webrtc:7773
Change-Id: I9c8ba090ef9f28d812114026a906cef742192c39
Reviewed-on: https://chromium-review.googlesource.com/527442
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Kári Tristan Helgason <kthelgason@webrtc.org>
Commit-Queue: Anders Carlsson <andersc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18558}

webrtc/sdk/BUILD.gn

@@ -47,8 +47,8 @@ if (is_ios || is_mac) {
       "objc/Framework/Classes/Common/RTCDispatcher.m",
       "objc/Framework/Classes/Common/RTCFieldTrials.mm",
       "objc/Framework/Classes/Common/RTCLogging.mm",
-      "objc/Framework/Classes/Common/RTCUIApplication.h",
-      "objc/Framework/Classes/Common/RTCUIApplication.mm",
+      "objc/Framework/Classes/Common/RTCUIApplicationStatusObserver.h",
+      "objc/Framework/Classes/Common/RTCUIApplicationStatusObserver.m",
       "objc/Framework/Classes/Common/helpers.h",
       "objc/Framework/Classes/Common/helpers.mm",
       "objc/Framework/Headers/WebRTC/RTCDispatcher.h",
@@ -546,8 +546,8 @@ if (is_ios || is_mac) {
         "objc/Framework/Classes/VideoToolbox/encoder.mm",
         "objc/Framework/Classes/VideoToolbox/nalu_rewriter.cc",
         "objc/Framework/Classes/VideoToolbox/nalu_rewriter.h",
-        "objc/Framework/Classes/VideoToolbox/videocodecfactory.cc",
         "objc/Framework/Classes/VideoToolbox/videocodecfactory.h",
+        "objc/Framework/Classes/VideoToolbox/videocodecfactory.mm",
       ]
 
       configs += [ "..:common_objc" ]

webrtc/sdk/objc/Framework/Classes/Common/RTCUIApplication.h

@@ -1,21 +0,0 @@
-/*
- *  Copyright 2016 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.
- */
-
-#ifndef WEBRTC_SDK_OBJC_FRAMEWORK_CLASSES_UI_RTCUIAPPLICATION_H_
-#define WEBRTC_SDK_OBJC_FRAMEWORK_CLASSES_UI_RTCUIAPPLICATION_H_
-
-#include "WebRTC/RTCMacros.h"
-
-#if defined(WEBRTC_IOS)
-/** Convenience function to get UIApplicationState from C++. */
-RTC_EXTERN bool RTCIsUIApplicationActive();
-#endif  // WEBRTC_IOS
-
-#endif  // WEBRTC_SDK_OBJC_FRAMEWORK_CLASSES_UI_RTCUIAPPLICATION_H_

webrtc/sdk/objc/Framework/Classes/Common/RTCUIApplicationStatusObserver.h

@@ -8,15 +8,16 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include "RTCUIApplication.h"
-
 #if defined(WEBRTC_IOS)
 
-#import <UIKit/UIKit.h>
+#import <Foundation/Foundation.h>
 
-bool RTCIsUIApplicationActive() {
-  UIApplicationState state = [UIApplication sharedApplication].applicationState;
-  return state == UIApplicationStateActive;
-}
+@interface RTCUIApplicationStatusObserver : NSObject
+
++ (instancetype)sharedInstance;
+
+- (BOOL)isApplicationActive;
+
+@end
 
 #endif  // WEBRTC_IOS

webrtc/sdk/objc/Framework/Classes/Common/RTCUIApplicationStatusObserver.m

@@ -0,0 +1,68 @@
+/*
+ *  Copyright 2016 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.
+ */
+
+#include "RTCUIApplicationStatusObserver.h"
+
+#if defined(WEBRTC_IOS)
+
+#import <UIKit/UIKit.h>
+
+@implementation RTCUIApplicationStatusObserver {
+  UIApplicationState _state;
+}
+
++ (instancetype)sharedInstance {
+  static id sharedInstance;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    sharedInstance = [[self alloc] init];
+  });
+
+  return sharedInstance;
+}
+
+- (id)init {
+  if (self = [super init]) {
+    NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
+    [center addObserverForName:UIApplicationDidBecomeActiveNotification
+                        object:nil
+                         queue:[NSOperationQueue mainQueue]
+                    usingBlock:^(NSNotification *note) {
+                      _state = [UIApplication sharedApplication].applicationState;
+                    }];
+
+    [center addObserverForName:UIApplicationDidEnterBackgroundNotification
+                        object:nil
+                         queue:[NSOperationQueue mainQueue]
+                    usingBlock:^(NSNotification *note) {
+                      _state = [UIApplication sharedApplication].applicationState;
+                    }];
+
+    dispatch_block_t initializeBlock = ^{
+      _state = [UIApplication sharedApplication].applicationState;
+    };
+
+    if ([NSThread isMainThread]) {
+      initializeBlock();
+    } else {
+      dispatch_sync(dispatch_get_main_queue(), initializeBlock);
+    }
+  }
+
+  return self;
+}
+
+- (BOOL)isApplicationActive {
+  return _state == UIApplicationStateActive;
+}
+
+@end
+
+#endif  // WEBRTC_IOS

webrtc/sdk/objc/Framework/Classes/VideoToolbox/decoder.mm

@@ -13,9 +13,6 @@
 
 #include <memory>
 
-#if defined(WEBRTC_IOS)
-#include "Common/RTCUIApplication.h"
-#endif
 #include "libyuv/convert.h"
 #include "webrtc/api/video/video_frame.h"
 #include "webrtc/base/checks.h"
@@ -24,6 +21,10 @@
 #include "webrtc/sdk/objc/Framework/Classes/Video/corevideo_frame_buffer.h"
 #include "webrtc/sdk/objc/Framework/Classes/VideoToolbox/nalu_rewriter.h"
 
+#if defined(WEBRTC_IOS)
+#import "Common/RTCUIApplicationStatusObserver.h"
+#endif
+
 namespace webrtc {
 namespace {
 
@@ -74,9 +75,7 @@ void VTDecompressionOutputCallback(void* decoder,
 }  // namespace
 
 H264VideoToolboxDecoder::H264VideoToolboxDecoder()
-    : callback_(nullptr),
-      video_format_(nullptr),
-      decompression_session_(nullptr) {}
+    : callback_(nullptr), video_format_(nullptr), decompression_session_(nullptr) {}
 
 H264VideoToolboxDecoder::~H264VideoToolboxDecoder() {
   DestroyDecompressionSession();
@@ -97,7 +96,7 @@ int H264VideoToolboxDecoder::Decode(
   RTC_DCHECK(input_image._buffer);
 
 #if defined(WEBRTC_IOS)
-  if (!RTCIsUIApplicationActive()) {
+  if (![[RTCUIApplicationStatusObserver sharedInstance] isApplicationActive]) {
     // Ignore all decode requests when app isn't active. In this state, the
     // hardware decoder has been invalidated by the OS.
     // Reset video format so that we won't process frames until the next

webrtc/sdk/objc/Framework/Classes/VideoToolbox/encoder.mm

@@ -16,8 +16,8 @@
 #include <vector>
 
 #if defined(WEBRTC_IOS)
+#import "Common/RTCUIApplicationStatusObserver.h"
 #import "WebRTC/UIDevice+RTCDevice.h"
-#include "Common/RTCUIApplication.h"
 #endif
 #include "libyuv/convert_from.h"
 #include "webrtc/base/checks.h"
@@ -386,7 +386,7 @@ int H264VideoToolboxEncoder::Encode(
     return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
   }
 #if defined(WEBRTC_IOS)
-  if (!RTCIsUIApplicationActive()) {
+  if (![[RTCUIApplicationStatusObserver sharedInstance] isApplicationActive]) {
     // Ignore all encode requests when app isn't active. In this state, the
     // hardware encoder has been invalidated by the OS.
     return WEBRTC_VIDEO_CODEC_OK;

webrtc/sdk/objc/Framework/Classes/VideoToolbox/videocodecfactory.mm

@@ -28,8 +28,7 @@ bool IsHighProfileEnabled() {
 
 // VideoToolboxVideoEncoderFactory
 
-VideoToolboxVideoEncoderFactory::VideoToolboxVideoEncoderFactory() {
-}
+VideoToolboxVideoEncoderFactory::VideoToolboxVideoEncoderFactory() {}
 
 VideoToolboxVideoEncoderFactory::~VideoToolboxVideoEncoderFactory() {}
 
@@ -43,14 +42,12 @@ VideoEncoder* VideoToolboxVideoEncoderFactory::CreateVideoEncoder(
   return nullptr;
 }
 
-void VideoToolboxVideoEncoderFactory::DestroyVideoEncoder(
-    VideoEncoder* encoder) {
+void VideoToolboxVideoEncoderFactory::DestroyVideoEncoder(VideoEncoder* encoder) {
   delete encoder;
   encoder = nullptr;
 }
 
-const std::vector<cricket::VideoCodec>&
-VideoToolboxVideoEncoderFactory::supported_codecs() const {
+const std::vector<cricket::VideoCodec>& VideoToolboxVideoEncoderFactory::supported_codecs() const {
   supported_codecs_.clear();
 
   // TODO(magjed): Enumerate actual level instead of using hardcoded level 3.1.
@@ -59,10 +56,8 @@ VideoToolboxVideoEncoderFactory::supported_codecs() const {
 
   if (IsHighProfileEnabled()) {
     cricket::VideoCodec constrained_high(cricket::kH264CodecName);
-    const H264::ProfileLevelId constrained_high_profile(
-        H264::kProfileConstrainedHigh, level);
-    constrained_high.SetParam(
-        cricket::kH264FmtpProfileLevelId,
+    const H264::ProfileLevelId constrained_high_profile(H264::kProfileConstrainedHigh, level);
+    constrained_high.SetParam(cricket::kH264FmtpProfileLevelId,
                               *H264::ProfileLevelIdToString(constrained_high_profile));
     constrained_high.SetParam(cricket::kH264FmtpLevelAsymmetryAllowed, "1");
     constrained_high.SetParam(cricket::kH264FmtpPacketizationMode, "1");
@@ -70,10 +65,8 @@ VideoToolboxVideoEncoderFactory::supported_codecs() const {
   }
 
   cricket::VideoCodec constrained_baseline(cricket::kH264CodecName);
-  const H264::ProfileLevelId constrained_baseline_profile(
-      H264::kProfileConstrainedBaseline, level);
-  constrained_baseline.SetParam(
-      cricket::kH264FmtpProfileLevelId,
+  const H264::ProfileLevelId constrained_baseline_profile(H264::kProfileConstrainedBaseline, level);
+  constrained_baseline.SetParam(cricket::kH264FmtpProfileLevelId,
                                 *H264::ProfileLevelIdToString(constrained_baseline_profile));
   constrained_baseline.SetParam(cricket::kH264FmtpLevelAsymmetryAllowed, "1");
   constrained_baseline.SetParam(cricket::kH264FmtpPacketizationMode, "1");
@@ -90,8 +83,7 @@ VideoToolboxVideoDecoderFactory::VideoToolboxVideoDecoderFactory() {
 
 VideoToolboxVideoDecoderFactory::~VideoToolboxVideoDecoderFactory() {}
 
-VideoDecoder* VideoToolboxVideoDecoderFactory::CreateVideoDecoder(
-    VideoCodecType type) {
+VideoDecoder* VideoToolboxVideoDecoderFactory::CreateVideoDecoder(VideoCodecType type) {
   const rtc::Optional<const char*> codec_name = CodecTypeToPayloadName(type);
   if (!codec_name) {
     LOG(LS_ERROR) << "Invalid codec type: " << type;
@@ -106,8 +98,7 @@ VideoDecoder* VideoToolboxVideoDecoderFactory::CreateVideoDecoder(
   return nullptr;
 }
 
-void VideoToolboxVideoDecoderFactory::DestroyVideoDecoder(
-    VideoDecoder* decoder) {
+void VideoToolboxVideoDecoderFactory::DestroyVideoDecoder(VideoDecoder* decoder) {
   delete decoder;
   decoder = nullptr;
 }