Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/AudioContext.cpp

 /*
  * Copyright (C) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 712 matching lines @@
 }
 
 void AudioContext::notifyStateChange()
 {
     dispatchEvent(Event::create(EventTypeNames::statechange));
 }
 
 ScriptPromise AudioContext::suspendContext(ScriptState* scriptState)
 {
     ASSERT(isMainThread());
+    ASSERT(!isOfflineContext());
+
     AutoLocker locker(this);
 
-    if (isOfflineContext()) {
-        return ScriptPromise::rejectWithDOMException(
-            scriptState,
-            DOMException::create(
-                InvalidAccessError,
-                "cannot suspend an OfflineAudioContext"));
-    }
-
     RefPtrWillBeRawPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
 
     if (m_contextState == Closed) {
         resolver->reject(
             DOMException::create(InvalidStateError, "Cannot suspend a context that has been closed"));
     } else {
         // Stop rendering now.
         if (m_destinationNode)
             stopRendering();
@@ skipping 92 matching lines @@
             AudioBufferSourceNode* sourceNode = static_cast<AudioBufferSourceNode*>(node);
             sourceNode->audioBufferSourceHandler().handleStoppableSourceNode();
         }
     }
 }
 
 void AudioContext::handlePreRenderTasks()
 {
     ASSERT(isAudioThread());
 
+    // If this is Offline Audio Context, simply lock the graph and do the tasks.

[Raymond Toy, 2015/06/15 20:42:13]

You should probably mention why it's ok to wait for the lock.

+    // For the precise offline audio rendering, we need these tasks to be
+    // performed every render quantum without deferring them. The trylock()
+    // below is not suitable for this purpose.
+    if (isOfflineContext()) {
+        deferredTaskHandler().forceLock();
+        deferredTaskHandler().handleDeferredTasks();
+        handleStoppableSourceNodes();
+        unlock();
+        return;
+    }

[Raymond Toy, 2015/06/15 20:42:13]

Previous version had this as part of the trylock below at line 863.  Why this
change?  Does it not work?

+
     // At the beginning of every render quantum, try to update the internal rendering graph state (from main thread changes).
     // It's OK if the tryLock() fails, we'll just take slightly longer to pick up the changes.
     if (tryLock()) {
         deferredTaskHandler().handleDeferredTasks();
 
         resolvePromisesForResume();
 
         // Check to see if source nodes can be stopped because the end time has passed.
         handleStoppableSourceNodes();
 
         unlock();
     }
 }
 
 void AudioContext::handlePostRenderTasks()
 {
     ASSERT(isAudioThread());
 
+    // Same as |handlePreRenderTasks()|. We perform these for Offline Audio
+    // Context.
+    if (isOfflineContext()) {
+        deferredTaskHandler().forceLock();
+        deferredTaskHandler().breakConnections();
+        releaseFinishedSourceNodes();
+        deferredTaskHandler().handleDeferredTasks();
+        deferredTaskHandler().requestToDeleteHandlersOnMainThread();
+        unlock();
+        return;
+    }
+
     // Must use a tryLock() here too.  Don't worry, the lock will very rarely be contended and this method is called frequently.
     // The worst that can happen is that there will be some nodes which will take slightly longer than usual to be deleted or removed
     // from the render graph (in which case they'll render silence).
     if (tryLock()) {
         // Take care of AudioNode tasks where the tryLock() failed previously.
         deferredTaskHandler().breakConnections();
 
         // Dynamically clean up nodes which are no longer needed.
         releaseFinishedSourceNodes();
 
@@ skipping 55 matching lines @@
     return EventTargetNames::AudioContext;
 }
 
 ExecutionContext* AudioContext::executionContext() const
 {
     return m_isStopScheduled ? 0 : ActiveDOMObject::executionContext();
 }
 
 void AudioContext::startRendering()
 {
-    // This is called for both online and offline contexts.
+    // This is only for the real-time context.
     ASSERT(isMainThread());
     ASSERT(m_destinationNode);
+    ASSERT(!isOfflineContext());
 
     if (m_contextState == Suspended) {
         destination()->audioDestinationHandler().startRendering();
         setContextState(Running);
     }
 }
 
 void AudioContext::stopRendering()
 {
     ASSERT(isMainThread());
     ASSERT(m_destinationNode);
     ASSERT(!isOfflineContext());
 
     if (m_contextState == Running) {
         destination()->audioDestinationHandler().stopRendering();
         setContextState(Suspended);
         deferredTaskHandler().clearHandlersToBeDeleted();
     }
 }
 
 void AudioContext::fireCompletionEvent()
 {
-    ASSERT(isMainThread());
-    if (!isMainThread())
-        return;
+    ASSERT_WITH_MESSAGE(1, "fireCompletionEvent() only valid for offline audio context");
+}
 
-    AudioBuffer* renderedBuffer = m_renderTarget.get();
+bool AudioContext::shouldSuspendNow()
+{
+    ASSERT_WITH_MESSAGE(1, "shouldSuspendNow() only valid for offline audio context");
+    return false;
+}
 
-    // For an offline context, we set the state to closed here so that the oncomplete handler sees
-    // that the context has been closed.
-    setContextState(Closed);
-
-    ASSERT(renderedBuffer);
-    if (!renderedBuffer)
-        return;
-
-    // Avoid firing the event if the document has already gone away.
-    if (executionContext()) {
-        // Call the offline rendering completion event listener and resolve the promise too.
-        dispatchEvent(OfflineAudioCompletionEvent::create(renderedBuffer));
-        m_offlineResolver->resolve(renderedBuffer);
-    }
+void AudioContext::resolvePendingSuspendPromises()
+{
+    ASSERT_WITH_MESSAGE(1, "clearResolvedSuspend() only valid for offline audio context");
 }
 
 DEFINE_TRACE(AudioContext)
 {
     visitor->trace(m_closeResolver);
-    visitor->trace(m_offlineResolver);
     visitor->trace(m_renderTarget);
     visitor->trace(m_destinationNode);
     visitor->trace(m_listener);
     // trace() can be called in AudioContext constructor, and
     // m_contextGraphMutex might be unavailable.
     if (m_didInitializeContextGraphMutex) {
         AutoLocker lock(this);
         visitor->trace(m_activeSourceNodes);
     } else {
         visitor->trace(m_activeSourceNodes);
@@ skipping 36 matching lines @@
     // the destination node can GCed if JS has no references. stop() will also resolve the Promise
     // created here.
     stop();
 
     return promise;
 }
 
 } // namespace blink
 
 #endif // ENABLE(WEB_AUDIO)