Letting Flash join MediaSession (stack implementaion)

content/browser/media/session/audio_focus_manager.cc

 // 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.
 
 #include "content/browser/media/session/audio_focus_manager.h"
 
+#include "base/memory/ptr_util.h"
 #include "content/browser/media/session/media_session.h"
 #include "content/public/browser/web_contents.h"
 
 namespace content {
 
-namespace {
-
-const double kDuckingVolumeMultiplier = 0.2;
-const double kDefaultVolumeMultiplier = 1.0;
-
-}  // anonymous namespace
-
 AudioFocusManager::AudioFocusEntry::AudioFocusEntry(
     WebContents* web_contents,
     AudioFocusManager* audio_focus_manager,
     AudioFocusType type)
     : WebContentsObserver(web_contents),
-      audio_focus_manager_(audio_focus_manager) {}
+      audio_focus_manager_(audio_focus_manager),
+      type_(type) {}

[whywhat, 2016/08/30 21:09:37]

nit: this sounds like an initialization bug, should it be a separate cl?

 
 AudioFocusManager::AudioFocusType
 AudioFocusManager::AudioFocusEntry::type() const {
   return type_;
 }
 
 void AudioFocusManager::AudioFocusEntry::WebContentsDestroyed() {
   audio_focus_manager_->OnWebContentsDestroyed(web_contents());
   // |this| will be destroyed now.
 }
 
 // static
 AudioFocusManager* AudioFocusManager::GetInstance() {
   return base::Singleton<AudioFocusManager>::get();
 }
 
 void AudioFocusManager::RequestAudioFocus(MediaSession* media_session,
                                           AudioFocusType type) {
   WebContents* web_contents = media_session->web_contents();
 
+  if (!audio_focus_stack_.empty() &&
+      audio_focus_stack_.back()->web_contents() == web_contents)
+    return;
+
+  MaybeRemoveFocusEntry(web_contents);
+
   if (type == AudioFocusType::GainTransientMayDuck) {
+    for (const auto& focus_entry : audio_focus_stack_) {
+      MediaSession::Get(focus_entry->web_contents())->Duck();

[whywhat, 2016/08/30 21:09:37]

nit: a one-liner, remove the {}

+    }
+  } else {
+    for (const auto& focus_entry : audio_focus_stack_) {
+      MediaSession* session = MediaSession::Get(focus_entry->web_contents());
+      if (session->IsActive())

[whywhat, 2016/08/30 21:09:37]

can we have more than one active session at the time? should it be at the top of
the stack? should we exit early when we find one?

+        session->Suspend(MediaSession::SuspendType::SYSTEM);
+    }
+  }
+  if (!audio_focus_stack_.empty()) {
+    MediaSession::Get(audio_focus_stack_.back()->web_contents())
+        ->SetOnTop(false);

[whywhat, 2016/08/30 21:09:37]

SetOnTop sounds like a dirty hack

+  }
+
+  audio_focus_stack_.push_back(base::MakeUnique<AudioFocusEntry>(
+    web_contents, this, type));
+  MediaSession::Get(audio_focus_stack_.back()->web_contents())->Unduck();

[whywhat, 2016/08/30 21:09:37]

replace audio_focus_stack_.back()->web_contents() with web_contents?

+  MediaSession::Get(audio_focus_stack_.back()->web_contents())->SetOnTop(true);
+}
+
+void AudioFocusManager::AbandonAudioFocus(MediaSession* media_session) {
+  WebContents* web_contents = media_session->web_contents();
+
+  if (audio_focus_stack_.back()->web_contents() != web_contents) {
     MaybeRemoveFocusEntry(web_contents);
-    transient_entries_[web_contents].reset(
-        new AudioFocusEntry(web_contents, this, type));
-    MaybeStartDucking();
     return;
   }
 
-  DCHECK(type == AudioFocusType::Gain);
-  RequestAudioFocusGain(web_contents);
-}
+  MediaSession::Get(audio_focus_stack_.back()->web_contents())->SetOnTop(false);
+  audio_focus_stack_.pop_back();
+  if (audio_focus_stack_.empty())
+    return;
 
-void AudioFocusManager::AbandonAudioFocus(MediaSession* media_session) {
-  AbandonAudioFocusInternal(media_session->web_contents());
+  MediaSession::Get(audio_focus_stack_.back()->web_contents())->SetOnTop(true);
+  // Only try to unduck the new MediaSession on top. The session might be still
+  // inactive but it will not be resumed (so it does surprise the user).
+  MediaSession::Get(audio_focus_stack_.back()->web_contents())->Unduck();
 }
 
 AudioFocusManager::AudioFocusManager() = default;
 
 AudioFocusManager::~AudioFocusManager() = default;
 
-void AudioFocusManager::RequestAudioFocusGain(WebContents* web_contents) {
-  MaybeRemoveTransientEntry(web_contents);
-
-  if (focus_entry_) {
-    if (focus_entry_->web_contents() == web_contents)
-      return;
-
-    MediaSession* other_session =
-        MediaSession::Get(focus_entry_->web_contents());
-    if (other_session->IsActive())
-      other_session->Suspend(MediaSession::SuspendType::SYSTEM);
-  }
-
-  focus_entry_.reset(
-      new AudioFocusEntry(web_contents, this, AudioFocusType::Gain));
-  MaybeStartDucking();
-}
-
 void AudioFocusManager::OnWebContentsDestroyed(WebContents* web_contents) {
-  AbandonAudioFocusInternal(web_contents);
-}
-
-void AudioFocusManager::AbandonAudioFocusInternal(WebContents* web_contents) {
-  MaybeRemoveTransientEntry(web_contents);
-  MaybeRemoveFocusEntry(web_contents);
-}
-
-void AudioFocusManager::MaybeStartDucking() const {
-  if (TransientMayDuckEntriesCount() != 1 || !focus_entry_)
-    return;
-
-  // TODO(mlamouri): add StartDuck to MediaSession.
-  MediaSession::Get(focus_entry_->web_contents())
-      ->SetVolumeMultiplier(kDuckingVolumeMultiplier);
-}
-
-void AudioFocusManager::MaybeStopDucking() const {
-  if (TransientMayDuckEntriesCount() != 0 || !focus_entry_)
-    return;
-
-  // TODO(mlamouri): add StopDuck to MediaSession.
-  MediaSession::Get(focus_entry_->web_contents())
-      ->SetVolumeMultiplier(kDefaultVolumeMultiplier);
-}
-
-int AudioFocusManager::TransientMayDuckEntriesCount() const {
-  return transient_entries_.size();
-}
-
-void AudioFocusManager::MaybeRemoveTransientEntry(WebContents* web_contents) {
-  transient_entries_.erase(web_contents);
-  MaybeStopDucking();
+  AbandonAudioFocus(MediaSession::Get(web_contents));
 }
 
 void AudioFocusManager::MaybeRemoveFocusEntry(WebContents* web_contents) {
-  if (focus_entry_ && focus_entry_->web_contents() == web_contents) {
-    MediaSession::Get(focus_entry_->web_contents())
-        ->SetVolumeMultiplier(kDefaultVolumeMultiplier);
-    focus_entry_.reset();
+  for (auto iter = audio_focus_stack_.begin(); iter != audio_focus_stack_.end();
+       ++iter) {
+    if (web_contents == (*iter)->web_contents()) {
+      audio_focus_stack_.erase(iter);

[whywhat, 2016/08/30 21:09:37]

Should you update OnTop in some cases?

+      return;
+    }
   }
 }
 
 }  // namespace content