Bug 1627999 - part2 : update the active media session when the owner of the audio focus changes. r=bryce

This patch will do :
- using the audio focus to decide which media session is the active media session. That is a recommend way of the spec [1].

The advantage of doing so :
- prevent to routing media control keys to incorrect media session
- prevent showing the incorrect metadata on the virtual control interface

[1] https://w3c.github.io/mediasession/#active-media-session

Differential Revision: https://phabricator.services.mozilla.com/D72496

dom/media/mediacontrol/MediaStatusManager.cpp

@@ -48,7 +48,14 @@ MediaStatusManager::MediaStatusManager(uint64_t aBrowsingContextId)
 
 void MediaStatusManager::NotifyMediaAudibleChanged(uint64_t aBrowsingContextId,
                                                    MediaAudibleState aState) {
+  Maybe<uint64_t> oldAudioFocusOwnerId =
+      mPlaybackStatusDelegate.GetAudioFocusOwnerContextId();
   mPlaybackStatusDelegate.UpdateMediaAudibleState(aBrowsingContextId, aState);
+  Maybe<uint64_t> newAudioFocusOwnerId =
+      mPlaybackStatusDelegate.GetAudioFocusOwnerContextId();
+  if (oldAudioFocusOwnerId != newAudioFocusOwnerId) {
+    HandleAudioFocusOwnerChanged(newAudioFocusOwnerId);
+  }
 }
 
 void MediaStatusManager::NotifySessionCreated(uint64_t aBrowsingContextId) {
@@ -56,18 +63,23 @@ void MediaStatusManager::NotifySessionCreated(uint64_t aBrowsingContextId) {
     return;
   }
 
-  LOG("Session %" PRId64 " has been created", aBrowsingContextId);
+  LOG("Session %" PRIu64 " has been created", aBrowsingContextId);
   mMediaSessionInfoMap.Put(aBrowsingContextId, MediaSessionInfo::EmptyInfo());
-  UpdateActiveMediaSessionContextId();
+  if (IsSessionOwningAudioFocus(aBrowsingContextId)) {
+    SetActiveMediaSessionContextId(aBrowsingContextId);
+  }
 }
 
 void MediaStatusManager::NotifySessionDestroyed(uint64_t aBrowsingContextId) {
   if (!mMediaSessionInfoMap.Contains(aBrowsingContextId)) {
     return;
   }
-  LOG("Session %" PRId64 " has been destroyed", aBrowsingContextId);
+  LOG("Session %" PRIu64 " has been destroyed", aBrowsingContextId);
   mMediaSessionInfoMap.Remove(aBrowsingContextId);
-  UpdateActiveMediaSessionContextId();
+  if (mActiveMediaSessionContextId &&
+      *mActiveMediaSessionContextId == aBrowsingContextId) {
+    ClearActiveMediaSessionContextIdIfNeeded();
+  }
 }
 
 void MediaStatusManager::UpdateMetadata(
@@ -78,10 +90,10 @@ void MediaStatusManager::UpdateMetadata(
 
   MediaSessionInfo* info = mMediaSessionInfoMap.GetValue(aBrowsingContextId);
   if (IsMetadataEmpty(aMetadata)) {
-    LOG("Reset metadata for session %" PRId64, aBrowsingContextId);
+    LOG("Reset metadata for session %" PRIu64, aBrowsingContextId);
     info->mMetadata.reset();
   } else {
-    LOG("Update metadata for session %" PRId64 " title=%s artist=%s album=%s",
+    LOG("Update metadata for session %" PRIu64 " title=%s artist=%s album=%s",
         aBrowsingContextId, NS_ConvertUTF16toUTF8((*aMetadata).mTitle).get(),
         NS_ConvertUTF16toUTF8(aMetadata->mArtist).get(),
         NS_ConvertUTF16toUTF8(aMetadata->mAlbum).get());
@@ -96,48 +108,54 @@ void MediaStatusManager::UpdateMetadata(
   }
 }
 
-void MediaStatusManager::UpdateActiveMediaSessionContextId() {
-  // If there is a media session created from top level browsing context, it
-  // would always be chosen as an active media session. Otherwise, we would
-  // check if we have an active media session already. If we do have, it would
-  // still remain as an active session. But if we don't, we would simply choose
-  // arbitrary one as an active session.
-  uint64_t candidateId = 0;
-  if (mActiveMediaSessionContextId &&
-      mMediaSessionInfoMap.Contains(*mActiveMediaSessionContextId)) {
-    candidateId = *mActiveMediaSessionContextId;
+void MediaStatusManager::HandleAudioFocusOwnerChanged(
+    Maybe<uint64_t>& aBrowsingContextId) {
+  // No one is holding the audio focus.
+  if (!aBrowsingContextId) {
+    LOG("No one is owning audio focus");
+    return ClearActiveMediaSessionContextIdIfNeeded();
   }
 
-  for (auto iter = mMediaSessionInfoMap.Iter(); !iter.Done(); iter.Next()) {
-    RefPtr<BrowsingContext> bc = BrowsingContext::Get(iter.Key());
-    // The browsing context which media session belongs to has been detroyed,
-    // and it wasn't be removed correctly via the IPC message. That could happen
-    // if the browsing context was destroyed before ContentPatent receives the
-    // remove message. Therefore, we should remove it and continue to iterate
-    // other elements.
-    if (!bc) {
-      iter.Remove();
-      continue;
-    }
-    if (bc->IsTopContent()) {
-      candidateId = iter.Key();
-      break;
-    }
-    if (!candidateId) {
-      candidateId = iter.Key();
-    }
+  // This owner of audio focus doesn't have media session, so we should deactive
+  // the active session because the active session must own the audio focus.
+  if (!mMediaSessionInfoMap.Contains(*aBrowsingContextId)) {
+    LOG("The owner of audio focus doesn't have media session");
+    return ClearActiveMediaSessionContextIdIfNeeded();
   }
 
+  // This owner has media session so it should become an active session context.
+  SetActiveMediaSessionContextId(*aBrowsingContextId);
+}
+
+void MediaStatusManager::SetActiveMediaSessionContextId(
+    uint64_t aBrowsingContextId) {
   if (mActiveMediaSessionContextId &&
-      *mActiveMediaSessionContextId == candidateId) {
-    LOG("Active session %" PRId64 " keeps unchanged",
+      *mActiveMediaSessionContextId == aBrowsingContextId) {
+    LOG("Active session context %" PRIu64 " keeps unchanged",
         *mActiveMediaSessionContextId);
     return;
   }
-
-  mActiveMediaSessionContextId = Some(candidateId);
-  LOG("Session %" PRId64 " becomes active session",
+  mActiveMediaSessionContextId = Some(aBrowsingContextId);
+  LOG("context %" PRIu64 " becomes active session context",
       *mActiveMediaSessionContextId);
+  mMetadataChangedEvent.Notify(GetCurrentMediaMetadata());
+}
+
+void MediaStatusManager::ClearActiveMediaSessionContextIdIfNeeded() {
+  if (!mActiveMediaSessionContextId) {
+    return;
+  }
+  LOG("Clear active session context");
+  mActiveMediaSessionContextId.reset();
+  mMetadataChangedEvent.Notify(GetCurrentMediaMetadata());
+}
+
+bool MediaStatusManager::IsSessionOwningAudioFocus(
+    uint64_t aBrowsingContextId) const {
+  Maybe<uint64_t> audioFocusContextId =
+      mPlaybackStatusDelegate.GetAudioFocusOwnerContextId();
+  return audioFocusContextId ? *audioFocusContextId == aBrowsingContextId
+                             : false;
 }
 
 MediaMetadataBase MediaStatusManager::CreateDefaultMetadata() const {
@@ -236,7 +254,7 @@ MediaSessionPlaybackState MediaStatusManager::GetCurrentDeclaredPlaybackState()
 
 void MediaStatusManager::NotifyMediaPlaybackChanged(uint64_t aBrowsingContextId,
                                                     MediaPlaybackState aState) {
-  LOG("UpdateMediaPlaybackState %s for context %" PRId64,
+  LOG("UpdateMediaPlaybackState %s for context %" PRIu64,
       ToMediaPlaybackStateStr(aState), aBrowsingContextId);
   const bool oldPlaying = mPlaybackStatusDelegate.IsPlaying();
   mPlaybackStatusDelegate.UpdateMediaPlaybackState(aBrowsingContextId, aState);

dom/media/mediacontrol/MediaStatusManager.h

@@ -132,6 +132,9 @@ class MediaStatusManager : public IMediaInfoUpdater {
   virtual void HandleActualPlaybackStateChanged() = 0;
 
   uint64_t mTopLevelBrowsingContextId;
+
+  // Within a tab, the Id of the browsing context which has already created a
+  // media session and owns the audio focus within a tab.
   Maybe<uint64_t> mActiveMediaSessionContextId;
 
  private:
@@ -141,7 +144,10 @@ class MediaStatusManager : public IMediaInfoUpdater {
   bool IsInPrivateBrowsing() const;
   void FillMissingTitleAndArtworkIfNeeded(MediaMetadataBase& aMetadata) const;
 
-  void UpdateActiveMediaSessionContextId();
+  bool IsSessionOwningAudioFocus(uint64_t aBrowsingContextId) const;
+  void SetActiveMediaSessionContextId(uint64_t aBrowsingContextId);
+  void ClearActiveMediaSessionContextIdIfNeeded();
+  void HandleAudioFocusOwnerChanged(Maybe<uint64_t>& aBrowsingContextId);
 
   // When the amount of playing media changes, we would use this function to
   // update the guessed playback state.