Bug 604682 - Remove unnecessary copy of audio data when there's no MozAudioAvailable event listener. r=smaug,kinetik

content/base/public/nsIDocument.h

@@ -124,8 +124,8 @@ class Element;
 } // namespace mozilla
 
 #define NS_IDOCUMENT_IID \
-{ 0xc3e40e8e, 0x8b91, 0x424c, \
-  { 0xbe, 0x9c, 0x9c, 0xc1, 0x76, 0xa7, 0xf7, 0x24 } }
+{ 0x184e0a3c, 0x1899, 0x417d, \
+  { 0xbf, 0xf4, 0x5a, 0x15, 0xe6, 0xe8, 0xaa, 0x94 } }
 
 // Flag for AddStyleSheet().
 #define NS_STYLESHEET_FROM_CATALOG                (1 << 0)
@@ -1562,7 +1562,15 @@ public:
   virtual nsresult SetNavigationTiming(nsDOMNavigationTiming* aTiming) = 0;
 
   virtual Element* FindImageMap(const nsAString& aNormalizedMapName) = 0;
-  
+
+  // Called to notify the document that a listener on the "mozaudioavailable"
+  // event has been added. Media elements in the document need to ensure they
+  // fire the event.
+  virtual void NotifyAudioAvailableListener() = 0;
+
+  // Returns true if the document has "mozaudioavailable" event listeners.
+  virtual bool HasAudioAvailableListeners() = 0;
+
   // Add aLink to the set of links that need their status resolved. 
   void RegisterPendingLinkUpdate(mozilla::dom::Link* aLink);
   

content/base/src/nsDocument.cpp

@@ -8237,6 +8237,25 @@ nsDocument::AddImage(imgIRequest* aImage)
   return rv;
 }
 
+static void
+NotifyAudioAvailableListener(nsIContent *aContent, void *aUnused)
+{
+#ifdef MOZ_MEDIA
+  nsCOMPtr<nsIDOMHTMLMediaElement> domMediaElem(do_QueryInterface(aContent));
+  if (domMediaElem) {
+    nsHTMLMediaElement* mediaElem = static_cast<nsHTMLMediaElement*>(aContent);
+    mediaElem->NotifyAudioAvailableListener();
+  }
+#endif
+}
+
+void
+nsDocument::NotifyAudioAvailableListener()
+{
+  mHasAudioAvailableListener = true;
+  EnumerateFreezableElements(::NotifyAudioAvailableListener, nsnull);
+}
+
 nsresult
 nsDocument::RemoveImage(imgIRequest* aImage)
 {

content/base/src/nsDocument.h

@@ -949,6 +949,13 @@ public:
 
   virtual Element* FindImageMap(const nsAString& aNormalizedMapName);
 
+  virtual void NotifyAudioAvailableListener();
+
+  bool HasAudioAvailableListeners()
+  {
+    return mHasAudioAvailableListener;
+  }
+
   virtual Element* GetFullScreenElement();
   virtual void AsyncRequestFullScreen(Element* aElement);
   virtual void CancelFullScreen();
@@ -1157,6 +1164,10 @@ protected:
   // Whether we currently require our images to animate
   bool mAnimatingImages:1;
 
+  // Whether some node in this document has a listener for the
+  // "mozaudioavailable" event.
+  bool mHasAudioAvailableListener:1;
+
   // Whether we are currently in full-screen mode, as per the DOM API.
   bool mIsFullScreen:1;
 

content/html/content/public/nsHTMLMediaElement.h

@@ -178,6 +178,13 @@ public:
   // (no data has arrived for a while).
   void DownloadStalled();
 
+  // Called when a "MozAudioAvailable" event listener is added. The media
+  // element will then notify its decoder that it needs to make a copy of
+  // the audio data sent to hardware and dispatch it in "mozaudioavailable"
+  // events. This allows us to not perform the copy and thus reduce overhead
+  // in the common case where we don't have a "MozAudioAvailable" listener.
+  void NotifyAudioAvailableListener();
+
   // Called by the media decoder and the video frame to get the
   // ImageContainer containing the video data.
   ImageContainer* GetImageContainer();
@@ -301,12 +308,6 @@ public:
   void NotifyAudioAvailable(float* aFrameBuffer, PRUint32 aFrameBufferLength,
                             float aTime);
 
-  /**
-   * Called in order to check whether some node (this window, its document,
-   * or content in that document) has a MozAudioAvailable event listener.
-   */
-  bool MayHaveAudioAvailableEventListener();
-
   virtual bool IsNodeOfType(PRUint32 aFlags) const;
 
   /**

content/html/content/src/nsHTMLMediaElement.cpp

@@ -702,24 +702,6 @@ void nsHTMLMediaElement::NotifyAudioAvailable(float* aFrameBuffer,
   DispatchAudioAvailableEvent(frameBuffer.forget(), aFrameBufferLength, aTime);
 }
 
-bool nsHTMLMediaElement::MayHaveAudioAvailableEventListener()
-{
-  // Determine if the current element is focused, if it is not focused
-  // then we should not try to blur.  Note: we allow for the case of
-  // |var a = new Audio()| with no parent document.
-  nsIDocument *document = GetDocument();
-  if (!document) {
-    return true;
-  }
-
-  nsPIDOMWindow *window = document->GetInnerWindow();
-  if (!window) {
-    return true;
-  }
-
-  return window->HasAudioAvailableEventListeners();
-}
-
 void nsHTMLMediaElement::LoadFromSourceChildren()
 {
   NS_ASSERTION(mDelayingLoadEvent,
@@ -1498,6 +1480,13 @@ nsresult nsHTMLMediaElement::BindToTree(nsIDocument* aDocument, nsIContent* aPar
     // The preload action depends on the value of the autoplay attribute.
     // It's value may have changed, so update it.
     UpdatePreloadAction();
+
+    if (aDocument->HasAudioAvailableListeners()) {
+      // The document already has listeners for the "MozAudioAvailable"
+      // event, so the decoder must be notified so it initiates
+      // "MozAudioAvailable" event dispatch.
+      NotifyAudioAvailableListener();
+    }
   }
 
   return rv;
@@ -1914,6 +1903,10 @@ nsresult nsHTMLMediaElement::FinishDecoderSetup(nsMediaDecoder* aDecoder)
     }
   }
 
+  if (OwnerDoc()->HasAudioAvailableListeners()) {
+    NotifyAudioAvailableListener();
+  }
+
   mBegun = true;
   return rv;
 }
@@ -2714,3 +2707,10 @@ NS_IMETHODIMP nsHTMLMediaElement::GetMozFragmentEnd(double *aTime)
   *aTime = (mFragmentEnd < 0.0 || mFragmentEnd > duration) ? duration : mFragmentEnd;
   return NS_OK;
 }
+
+void nsHTMLMediaElement::NotifyAudioAvailableListener()
+{
+  if (mDecoder) {
+    mDecoder->NotifyAudioAvailableListener();
+  }
+}

content/media/nsAudioAvailableEventManager.cpp

@@ -84,7 +84,8 @@ nsAudioAvailableEventManager::nsAudioAvailableEventManager(nsBuiltinDecoder* aDe
   mSignalBufferLength(mDecoder->GetFrameBufferLength()),
   mNewSignalBufferLength(mSignalBufferLength),
   mSignalBufferPosition(0),
-  mReentrantMonitor("media.audioavailableeventmanager")
+  mReentrantMonitor("media.audioavailableeventmanager"),
+  mHasListener(false)
 {
   MOZ_COUNT_CTOR(nsAudioAvailableEventManager);
 }
@@ -104,6 +105,10 @@ void nsAudioAvailableEventManager::DispatchPendingEvents(PRUint64 aCurrentTime)
 {
   ReentrantMonitorAutoEnter mon(mReentrantMonitor);
 
+  if (!mHasListener) {
+    return;
+  }
+
   while (mPendingEvents.Length() > 0) {
     nsAudioAvailableEventRunner* e =
       (nsAudioAvailableEventRunner*)mPendingEvents[0].get();
@@ -122,6 +127,10 @@ void nsAudioAvailableEventManager::QueueWrittenAudioData(AudioDataValue* aAudioD
 {
   ReentrantMonitorAutoEnter mon(mReentrantMonitor);
 
+  if (!mHasListener) {
+    return;
+  }
+
   PRUint32 currentBufferSize = mNewSignalBufferLength;
   if (currentBufferSize == 0) {
     NS_WARNING("Decoder framebuffer length not set.");
@@ -212,6 +221,10 @@ void nsAudioAvailableEventManager::Drain(PRUint64 aEndTime)
 {
   ReentrantMonitorAutoEnter mon(mReentrantMonitor);
 
+  if (!mHasListener) {
+    return;
+  }
+
   // Force all pending events to go now.
   for (PRUint32 i = 0; i < mPendingEvents.Length(); ++i) {
     nsCOMPtr<nsIRunnable> event = mPendingEvents[i];
@@ -245,3 +258,9 @@ void nsAudioAvailableEventManager::SetSignalBufferLength(PRUint32 aLength)
   mNewSignalBufferLength = aLength;
 }
 
+void nsAudioAvailableEventManager::NotifyAudioAvailableListener()
+{
+  ReentrantMonitorAutoEnter mon(mReentrantMonitor);
+
+  mHasListener = true;
+}

content/media/nsAudioAvailableEventManager.h

@@ -80,6 +80,11 @@ public:
   // Called from the main and the state machine thread.
   void SetSignalBufferLength(PRUint32 aLength);
 
+  // Called by the media element to notify the manager that there is a
+  // listener on the "MozAudioAvailable" event, and that we need to dispatch
+  // such events. Called from the main thread.
+  void NotifyAudioAvailableListener();
+
 private:
   // The decoder associated with the event manager.  The event manager shares
   // the same lifetime as the decoder (the decoder holds a reference to the
@@ -108,6 +113,11 @@ private:
   // ReentrantMonitor for shared access to mPendingEvents queue or
   // buffer length.
   ReentrantMonitor mReentrantMonitor;
+
+  // True if something in the owning document has a listener on the
+  // "MozAudioAvailable" event. If not, we don't need to bother copying played
+  // audio data and dispatching the event. Synchronized by mReentrantMonitor.
+  bool mHasListener;
 };
 
 #endif

content/media/nsBuiltinDecoder.cpp

@@ -397,14 +397,9 @@ void nsBuiltinDecoder::AudioAvailable(float* aFrameBuffer,
   // to HTMLMediaElement::NotifyAudioAvailable().
   nsAutoArrayPtr<float> frameBuffer(aFrameBuffer);
   NS_ASSERTION(NS_IsMainThread(), "Should be on main thread.");
-  if (mShuttingDown) {
+  if (mShuttingDown || !mElement) {
     return;
   }
-
-  if (!mElement || !mElement->MayHaveAudioAvailableEventListener()) {
-    return;
-  }
-
   mElement->NotifyAudioAvailable(frameBuffer.forget(), aFrameBufferLength, aTime);
 }
 
@@ -1005,6 +1000,16 @@ void nsBuiltinDecoder::UpdatePlaybackOffset(PRInt64 aOffset)
   mPlaybackPosition = NS_MAX(aOffset, mPlaybackPosition);
 }
 
-bool nsBuiltinDecoder::OnStateMachineThread() const {
+bool nsBuiltinDecoder::OnStateMachineThread() const
+{
   return IsCurrentThread(nsBuiltinDecoderStateMachine::GetStateMachineThread());
 }
+
+void nsBuiltinDecoder::NotifyAudioAvailableListener()
+{
+  NS_ASSERTION(NS_IsMainThread(), "Should be on main thread.");
+  if (mDecoderStateMachine) {
+    ReentrantMonitorAutoEnter mon(mReentrantMonitor);
+    mDecoderStateMachine->NotifyAudioAvailableListener();
+  }
+}

content/media/nsBuiltinDecoder.h

@@ -344,6 +344,10 @@ public:
   // Sets the current size of the framebuffer used in MozAudioAvailable events.
   // Called on the state machine thread and the main thread.
   virtual void SetFrameBufferLength(PRUint32 aLength) = 0;
+
+  // Called when a "MozAudioAvailable" event listener is added to the media
+  // element. Called on the main thread.
+  virtual void NotifyAudioAvailableListener() = 0;
 };
 
 class nsBuiltinDecoder : public nsMediaDecoder
@@ -610,6 +614,10 @@ class nsBuiltinDecoder : public nsMediaDecoder
   // Drop reference to state machine.  Only called during shutdown dance.
   void ReleaseStateMachine() { mDecoderStateMachine = nsnull; }
 
+   // Called when a "MozAudioAvailable" event listener is added to the media
+   // element. Called on the main thread.
+   virtual void NotifyAudioAvailableListener();
+
 public:
   // Notifies the element that decoding has failed.
   void DecodeError();

content/media/nsBuiltinDecoderStateMachine.cpp

@@ -2201,4 +2201,8 @@ nsIThread* nsBuiltinDecoderStateMachine::GetStateMachineThread()
   return StateMachineTracker::Instance().GetGlobalStateMachineThread();
 }
 
-
+void nsBuiltinDecoderStateMachine::NotifyAudioAvailableListener()
+{
+  mDecoder->GetReentrantMonitor().AssertCurrentThreadIn();
+  mEventManager.NotifyAudioAvailableListener();
+}

content/media/nsBuiltinDecoderStateMachine.h

@@ -265,6 +265,10 @@ public:
   // Drop reference to decoder.  Only called during shutdown dance.
   void ReleaseDecoder() { mDecoder = nsnull; }
 
+   // Called when a "MozAudioAvailable" event listener is added to the media
+   // element. Called on the main thread.
+   void NotifyAudioAvailableListener();
+
 protected:
 
   // Returns true if we've got less than aAudioUsecs microseconds of decoded

content/media/nsMediaDecoder.h

@@ -158,6 +158,11 @@ public:
   // Call in the main thread only.
   virtual bool IsEnded() const = 0;
 
+  // Called when a "MozAudioAvailable" event listener is added. This enables
+  // the decoder to only dispatch "MozAudioAvailable" events when a
+  // handler exists, reducing overhead. Called on the main thread.
+  virtual void NotifyAudioAvailableListener() = 0;
+
   struct Statistics {
     // Estimate of the current playback rate (bytes/second).
     double mPlaybackRate;

dom/base/nsGlobalWindow.cpp

@@ -766,7 +766,6 @@ nsPIDOMWindow::nsPIDOMWindow(nsPIDOMWindow *aOuterWindow)
   mRunningTimeout(nsnull), mMutationBits(0), mIsDocumentLoaded(false),
   mIsHandlingResizeEvent(false), mIsInnerWindow(aOuterWindow != nsnull),
   mMayHavePaintEventListener(false), mMayHaveTouchEventListener(false),
-  mMayHaveAudioAvailableEventListener(false),
   mMayHaveMouseEnterLeaveEventListener(false),
   mIsModalContentWindow(false),
   mIsActive(false), mIsBackground(false),
@@ -10676,6 +10675,14 @@ nsGlobalModalWindow::SetNewDocument(nsIDocument *aDocument,
                                         aForceReuseInnerWindow);
 }
 
+void
+nsGlobalWindow::SetHasAudioAvailableEventListeners()
+{
+  if (mDoc) {
+    mDoc->NotifyAudioAvailableListener();
+  }
+}
+
 //*****************************************************************************
 // nsGlobalWindow: Creator Function (This should go away)
 //*****************************************************************************

dom/base/nsGlobalWindow.h

@@ -447,6 +447,8 @@ public:
   // Prevent further dialogs in this (top level) window
   void PreventFurtherDialogs();
 
+  virtual void SetHasAudioAvailableEventListeners();
+
   nsIScriptContext *GetContextInternal()
   {
     if (mOuterWindow) {

dom/base/nsPIDOMWindow.h

@@ -80,8 +80,8 @@ class nsIArray;
 class nsPIWindowRoot;
 
 #define NS_PIDOMWINDOW_IID \
-{ 0x8ce567b5, 0xcc8d, 0x410b, \
-  { 0xa2, 0x7b, 0x07, 0xaf, 0x31, 0xc0, 0x33, 0xb8 } }
+{ 0x9db588f7, 0x3472, 0x45d0, \
+  { 0x9f, 0x9b, 0x95, 0xca, 0xf6, 0x4d, 0x1a, 0xb1 } }
 
 class nsPIDOMWindow : public nsIDOMWindowInternal
 {
@@ -457,23 +457,11 @@ public:
     return mMayHaveTouchEventListener;
   }
 
-  /**
-   * Call this to check whether some node (this window, its document,
-   * or content in that document) has a MozAudioAvailable event listener.
-   */
-  bool HasAudioAvailableEventListeners()
-  {
-    return mMayHaveAudioAvailableEventListener;
-  }
-
   /**
    * Call this to indicate that some node (this window, its document,
-   * or content in that document) has a MozAudioAvailable event listener.
+   * or content in that document) has a "MozAudioAvailable" event listener.
    */
-  void SetHasAudioAvailableEventListeners()
-  {
-    mMayHaveAudioAvailableEventListener = true;
-  }
+  virtual void SetHasAudioAvailableEventListeners() = 0;
 
   /**
    * Call this to check whether some node (this window, its document,
@@ -657,7 +645,6 @@ protected:
   bool                   mIsInnerWindow;
   bool                   mMayHavePaintEventListener;
   bool                   mMayHaveTouchEventListener;
-  bool                   mMayHaveAudioAvailableEventListener;
   bool                   mMayHaveMouseEnterLeaveEventListener;
 
   // This variable is used on both inner and outer windows (and they