[video_player] Add macOS support (flutter#4982)

Adds macOS support to `video_player`, sharing almost all of the code with iOS.

Notes about changes at a high level:
- macOS does not have `CADisplayLink` (prior to 14, and even there without all the functionality we need), so this adds macOS compilation branches that use the lower-level `CVDisplayLink` instead. Per the TODO, this code should be extracted later to reduce `ifdef`s in what is already a complicated file.
- Adds KVO unregistration on `dealloc` if it wasn't done in `dispose`, since unit tests were crashing on macOS with that.
- Temporarily ifdef's out `publish:` for macOS, with a TODO to re-enable it after the next stable.

Most of flutter/flutter#41688
Once this lands, the app-facing package will be updated to endorse it for macOS.

Author: stuartmorgan-g

packages/video_player/video_player_avfoundation/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.5.0
+
+* Adds support for macOS.
+
 ## 2.4.11
 
 * Updates Pigeon.

packages/video_player/video_player_avfoundation/README.md

@@ -1,6 +1,6 @@
 # video\_player\_avfoundation
 
-The iOS implementation of [`video_player`][1].
+The iOS and macOS implementation of [`video_player`][1].
 
 ## Usage
 

packages/video_player/video_player_avfoundation/ios/Assets/.gitkeep renamed to packages/video_player/video_player_avfoundation/darwin/Assets/.gitkeep

@@ -2,7 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#if TARGET_OS_OSX
+#import <FlutterMacOS/FlutterMacOS.h>
+#else
 #import <Flutter/Flutter.h>
+#endif
 
 @interface FVPVideoPlayerPlugin : NSObject <FlutterPlugin>
 - (instancetype)initWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar;

packages/video_player/video_player_avfoundation/ios/Classes/AVAssetTrackUtils.h renamed to packages/video_player/video_player_avfoundation/darwin/Classes/AVAssetTrackUtils.h

@@ -18,7 +18,11 @@
 @interface FVPFrameUpdater : NSObject
 @property(nonatomic) int64_t textureId;
 @property(nonatomic, weak, readonly) NSObject<FlutterTextureRegistry> *registry;
+// The output that this updater is managing.
+@property(nonatomic, weak) AVPlayerItemVideoOutput *videoOutput;
+#if TARGET_OS_IOS
 - (void)onDisplayLink:(CADisplayLink *)link;
+#endif
 @end
 
 @implementation FVPFrameUpdater
@@ -29,11 +33,34 @@ - (FVPFrameUpdater *)initWithRegistry:(NSObject<FlutterTextureRegistry> *)regist
   return self;
 }
 
+#if TARGET_OS_IOS
 - (void)onDisplayLink:(CADisplayLink *)link {
+  // TODO(stuartmorgan): Investigate switching this to displayLinkFired; iOS may also benefit from
+  // the availability check there.
   [_registry textureFrameAvailable:_textureId];
 }
+#endif
+
+- (void)displayLinkFired {
+  // Only report a new frame if one is actually available.
+  CMTime outputItemTime = [self.videoOutput itemTimeForHostTime:CACurrentMediaTime()];
+  if ([self.videoOutput hasNewPixelBufferForItemTime:outputItemTime]) {
+    [_registry textureFrameAvailable:_textureId];
+  }
+}
 @end
 
+#if TARGET_OS_OSX
+static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeStamp *now,
+                                    const CVTimeStamp *outputTime, CVOptionFlags flagsIn,
+                                    CVOptionFlags *flagsOut, void *displayLinkSource) {
+  // Trigger the main-thread dispatch queue, to drive a frame update check.
+  __weak dispatch_source_t source = (__bridge dispatch_source_t)displayLinkSource;
+  dispatch_source_merge_data(source, 1);
+  return kCVReturnSuccess;
+}
+#endif
+
 @interface FVPDefaultPlayerFactory : NSObject <FVPPlayerFactory>
 @end
 
@@ -53,18 +80,33 @@ @interface FVPVideoPlayer : NSObject <FlutterTexture, FlutterStreamHandler>
 // An invisible AVPlayerLayer is used to overwrite the protection of pixel buffers in those streams
 // for issue #1, and restore the correct width and height for issue #2.
 @property(readonly, nonatomic) AVPlayerLayer *playerLayer;
-@property(readonly, nonatomic) CADisplayLink *displayLink;
+// The plugin registrar, to obtain view information from.
+@property(nonatomic, weak) NSObject<FlutterPluginRegistrar> *registrar;
+// The CALayer associated with the Flutter view this plugin is associated with, if any.
+@property(nonatomic, readonly) CALayer *flutterViewLayer;
 @property(nonatomic) FlutterEventChannel *eventChannel;
 @property(nonatomic) FlutterEventSink eventSink;
 @property(nonatomic) CGAffineTransform preferredTransform;
 @property(nonatomic, readonly) BOOL disposed;
 @property(nonatomic, readonly) BOOL isPlaying;
 @property(nonatomic) BOOL isLooping;
 @property(nonatomic, readonly) BOOL isInitialized;
+// TODO(stuartmorgan): Extract and abstract the display link to remove all the display-link-related
+// ifdefs from this file.
+#if TARGET_OS_OSX
+// The display link to trigger frame reads from the video player.
+@property(nonatomic, assign) CVDisplayLinkRef displayLink;
+// A dispatch source to move display link callbacks to the main thread.
+@property(nonatomic, strong) dispatch_source_t displayLinkSource;
+#else
+@property(nonatomic) CADisplayLink *displayLink;
+#endif
+
 - (instancetype)initWithURL:(NSURL *)url
                frameUpdater:(FVPFrameUpdater *)frameUpdater
                 httpHeaders:(nonnull NSDictionary<NSString *, NSString *> *)headers
-              playerFactory:(id<FVPPlayerFactory>)playerFactory;
+              playerFactory:(id<FVPPlayerFactory>)playerFactory
+                  registrar:(NSObject<FlutterPluginRegistrar> *)registrar;
 @end
 
 static void *timeRangeContext = &timeRangeContext;
@@ -77,12 +119,27 @@ - (instancetype)initWithURL:(NSURL *)url
 @implementation FVPVideoPlayer
 - (instancetype)initWithAsset:(NSString *)asset
                  frameUpdater:(FVPFrameUpdater *)frameUpdater
-                playerFactory:(id<FVPPlayerFactory>)playerFactory {
+                playerFactory:(id<FVPPlayerFactory>)playerFactory
+                    registrar:(NSObject<FlutterPluginRegistrar> *)registrar {
   NSString *path = [[NSBundle mainBundle] pathForResource:asset ofType:nil];
+#if TARGET_OS_OSX
+  // See https://github.com/flutter/flutter/issues/135302
+  // TODO(stuartmorgan): Remove this if the asset APIs are adjusted to work better for macOS.
+  if (!path) {
+    path = [NSURL URLWithString:asset relativeToURL:NSBundle.mainBundle.bundleURL].path;
+  }
+#endif
   return [self initWithURL:[NSURL fileURLWithPath:path]
               frameUpdater:frameUpdater
                httpHeaders:@{}
-             playerFactory:playerFactory];
+             playerFactory:playerFactory
+                 registrar:registrar];
+}
+
+- (void)dealloc {
+  if (!_disposed) {
+    [self removeKeyValueObservers];
+  }
 }
 
 - (void)addObserversForItem:(AVPlayerItem *)item player:(AVPlayer *)player {
@@ -153,15 +210,6 @@ NS_INLINE CGFloat radiansToDegrees(CGFloat radians) {
   return degrees;
 };
 
-NS_INLINE UIViewController *rootViewController(void) {
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wdeprecated-declarations"
-  // TODO: (hellohuanlin) Provide a non-deprecated codepath. See
-  // https://github.com/flutter/flutter/issues/104117
-  return UIApplication.sharedApplication.keyWindow.rootViewController;
-#pragma clang diagnostic pop
-}
-
 - (AVMutableVideoComposition *)getVideoCompositionWithTransform:(CGAffineTransform)transform
                                                       withAsset:(AVAsset *)asset
                                                  withVideoTrack:(AVAssetTrack *)videoTrack {
@@ -202,31 +250,55 @@ - (void)createVideoOutputAndDisplayLink:(FVPFrameUpdater *)frameUpdater {
   };
   _videoOutput = [[AVPlayerItemVideoOutput alloc] initWithPixelBufferAttributes:pixBuffAttributes];
 
+#if TARGET_OS_OSX
+  frameUpdater.videoOutput = _videoOutput;
+  // Create and start the main-thread dispatch queue to drive frameUpdater.
+  self.displayLinkSource =
+      dispatch_source_create(DISPATCH_SOURCE_TYPE_DATA_ADD, 0, 0, dispatch_get_main_queue());
+  dispatch_source_set_event_handler(self.displayLinkSource, ^() {
+    @autoreleasepool {
+      [frameUpdater displayLinkFired];
+    }
+  });
+  dispatch_resume(self.displayLinkSource);
+  if (CVDisplayLinkCreateWithActiveCGDisplays(&_displayLink) == kCVReturnSuccess) {
+    CVDisplayLinkSetOutputCallback(_displayLink, &DisplayLinkCallback,
+                                   (__bridge void *)(self.displayLinkSource));
+  }
+#else
   _displayLink = [CADisplayLink displayLinkWithTarget:frameUpdater
                                              selector:@selector(onDisplayLink:)];
   [_displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
   _displayLink.paused = YES;
+#endif
 }
 
 - (instancetype)initWithURL:(NSURL *)url
                frameUpdater:(FVPFrameUpdater *)frameUpdater
                 httpHeaders:(nonnull NSDictionary<NSString *, NSString *> *)headers
-              playerFactory:(id<FVPPlayerFactory>)playerFactory {
+              playerFactory:(id<FVPPlayerFactory>)playerFactory
+                  registrar:(NSObject<FlutterPluginRegistrar> *)registrar {
   NSDictionary<NSString *, id> *options = nil;
   if ([headers count] != 0) {
     options = @{@"AVURLAssetHTTPHeaderFieldsKey" : headers};
   }
   AVURLAsset *urlAsset = [AVURLAsset URLAssetWithURL:url options:options];
   AVPlayerItem *item = [AVPlayerItem playerItemWithAsset:urlAsset];
-  return [self initWithPlayerItem:item frameUpdater:frameUpdater playerFactory:playerFactory];
+  return [self initWithPlayerItem:item
+                     frameUpdater:frameUpdater
+                    playerFactory:playerFactory
+                        registrar:registrar];
 }
 
 - (instancetype)initWithPlayerItem:(AVPlayerItem *)item
                       frameUpdater:(FVPFrameUpdater *)frameUpdater
-                     playerFactory:(id<FVPPlayerFactory>)playerFactory {
+                     playerFactory:(id<FVPPlayerFactory>)playerFactory
+                         registrar:(NSObject<FlutterPluginRegistrar> *)registrar {
   self = [super init];
   NSAssert(self, @"super init cannot be nil");
 
+  _registrar = registrar;
+
   AVAsset *asset = [item asset];
   void (^assetCompletionHandler)(void) = ^{
     if ([asset statusOfValueForKey:@"tracks" error:nil] == AVKeyValueStatusLoaded) {
@@ -265,7 +337,7 @@ - (instancetype)initWithPlayerItem:(AVPlayerItem *)item
   // invisible AVPlayerLayer is used to overwrite the protection of pixel buffers in those streams
   // for issue #1, and restore the correct width and height for issue #2.
   _playerLayer = [AVPlayerLayer playerLayerWithPlayer:_player];
-  [rootViewController().view.layer addSublayer:_playerLayer];
+  [self.flutterViewLayer addSublayer:_playerLayer];
 
   [self createVideoOutputAndDisplayLink:frameUpdater];
 
@@ -350,7 +422,23 @@ - (void)updatePlayingState {
   } else {
     [_player pause];
   }
+#if TARGET_OS_OSX
+  if (_displayLink) {
+    if (_isPlaying) {
+      NSScreen *screen = self.registrar.view.window.screen;
+      if (screen) {
+        CGDirectDisplayID viewDisplayID =
+            (CGDirectDisplayID)[screen.deviceDescription[@"NSScreenNumber"] unsignedIntegerValue];
+        CVDisplayLinkSetCurrentCGDisplay(_displayLink, viewDisplayID);
+      }
+      CVDisplayLinkStart(_displayLink);
+    } else {
+      CVDisplayLinkStop(_displayLink);
+    }
+  }
+#else
   _displayLink.paused = !_isPlaying;
+#endif
 }
 
 - (void)setupEventSinkIfReadyToPlay {
@@ -515,14 +603,17 @@ - (void)disposeSansEventChannel {
 
   _disposed = YES;
   [_playerLayer removeFromSuperlayer];
+#if TARGET_OS_OSX
+  if (_displayLink) {
+    CVDisplayLinkStop(_displayLink);
+    CVDisplayLinkRelease(_displayLink);
+    _displayLink = NULL;
+  }
+  dispatch_source_cancel(_displayLinkSource);
+#else
   [_displayLink invalidate];
-  AVPlayerItem *currentItem = self.player.currentItem;
-  [currentItem removeObserver:self forKeyPath:@"status"];
-  [currentItem removeObserver:self forKeyPath:@"loadedTimeRanges"];
-  [currentItem removeObserver:self forKeyPath:@"presentationSize"];
-  [currentItem removeObserver:self forKeyPath:@"duration"];
-  [currentItem removeObserver:self forKeyPath:@"playbackLikelyToKeepUp"];
-  [self.player removeObserver:self forKeyPath:@"rate"];
+#endif
+  [self removeKeyValueObservers];
 
   [self.player replaceCurrentItemWithPlayerItem:nil];
   [[NSNotificationCenter defaultCenter] removeObserver:self];
@@ -533,6 +624,33 @@ - (void)dispose {
   [_eventChannel setStreamHandler:nil];
 }
 
+- (CALayer *)flutterViewLayer {
+#if TARGET_OS_OSX
+  return self.registrar.view.layer;
+#else
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+  // TODO(hellohuanlin): Provide a non-deprecated codepath. See
+  // https://github.com/flutter/flutter/issues/104117
+  UIViewController *root = UIApplication.sharedApplication.keyWindow.rootViewController;
+#pragma clang diagnostic pop
+  return root.view.layer;
+#endif
+}
+
+/// Removes all key-value observers set up for the player.
+///
+/// This is called from dealloc, so must not use any methods on self.
+- (void)removeKeyValueObservers {
+  AVPlayerItem *currentItem = _player.currentItem;
+  [currentItem removeObserver:self forKeyPath:@"status"];
+  [currentItem removeObserver:self forKeyPath:@"loadedTimeRanges"];
+  [currentItem removeObserver:self forKeyPath:@"presentationSize"];
+  [currentItem removeObserver:self forKeyPath:@"duration"];
+  [currentItem removeObserver:self forKeyPath:@"playbackLikelyToKeepUp"];
+  [_player removeObserver:self forKeyPath:@"rate"];
+}
+
 @end
 
 @interface FVPVideoPlayerPlugin () <FVPAVFoundationVideoPlayerApi>
@@ -547,7 +665,11 @@ @interface FVPVideoPlayerPlugin () <FVPAVFoundationVideoPlayerApi>
 @implementation FVPVideoPlayerPlugin
 + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar {
   FVPVideoPlayerPlugin *instance = [[FVPVideoPlayerPlugin alloc] initWithRegistrar:registrar];
+#if !TARGET_OS_OSX
+  // TODO(stuartmorgan): Remove the ifdef once >3.13 reaches stable. See
+  // https://github.com/flutter/flutter/issues/135320
   [registrar publish:instance];
+#endif
   FVPAVFoundationVideoPlayerApiSetup(registrar.messenger, instance);
 }
 
@@ -592,8 +714,10 @@ - (FVPTextureMessage *)onPlayerSetup:(FVPVideoPlayer *)player
 }
 
 - (void)initialize:(FlutterError *__autoreleasing *)error {
+#if TARGET_OS_IOS
   // Allow audio playback when the Ring/Silent switch is set to silent
   [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
+#endif
 
   [self.playersByTextureId
       enumerateKeysAndObjectsUsingBlock:^(NSNumber *textureId, FVPVideoPlayer *player, BOOL *stop) {
@@ -616,7 +740,8 @@ - (FVPTextureMessage *)create:(FVPCreateMessage *)input error:(FlutterError **)e
     @try {
       player = [[FVPVideoPlayer alloc] initWithAsset:assetPath
                                         frameUpdater:frameUpdater
-                                       playerFactory:_playerFactory];
+                                       playerFactory:_playerFactory
+                                           registrar:self.registrar];
       return [self onPlayerSetup:player frameUpdater:frameUpdater];
     } @catch (NSException *exception) {
       *error = [FlutterError errorWithCode:@"video_player" message:exception.reason details:nil];
@@ -626,7 +751,8 @@ - (FVPTextureMessage *)create:(FVPCreateMessage *)input error:(FlutterError **)e
     player = [[FVPVideoPlayer alloc] initWithURL:[NSURL URLWithString:input.uri]
                                     frameUpdater:frameUpdater
                                      httpHeaders:input.httpHeaders
-                                   playerFactory:_playerFactory];
+                                   playerFactory:_playerFactory
+                                       registrar:self.registrar];
     return [self onPlayerSetup:player frameUpdater:frameUpdater];
   } else {
     *error = [FlutterError errorWithCode:@"video_player" message:@"not implemented" details:nil];
@@ -702,13 +828,17 @@ - (void)pause:(FVPTextureMessage *)input error:(FlutterError **)error {
 
 - (void)setMixWithOthers:(FVPMixWithOthersMessage *)input
                    error:(FlutterError *_Nullable __autoreleasing *)error {
+#if TARGET_OS_OSX
+  // AVAudioSession doesn't exist on macOS, and audio always mixes, so just no-op.
+#else
   if (input.mixWithOthers.boolValue) {
     [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback
                                      withOptions:AVAudioSessionCategoryOptionMixWithOthers
                                            error:nil];
   } else {
     [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
   }
+#endif
 }
 
 @end