Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/OfflineAudioContext.cpp

Index: Source/modules/webaudio/OfflineAudioContext.cpp
diff --git a/Source/modules/webaudio/OfflineAudioContext.cpp b/Source/modules/webaudio/OfflineAudioContext.cpp
index d3488419e947e373d50f13cb105be0fb0604d178..629b853e6205e569b79fe61b281bdc2cf2acd59f 100644
--- a/Source/modules/webaudio/OfflineAudioContext.cpp
+++ b/Source/modules/webaudio/OfflineAudioContext.cpp
@@ -31,7 +31,10 @@
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/ExecutionContext.h"
+#include "modules/webaudio/OfflineAudioDestinationNode.h"
+#include "platform/ThreadSafeFunctional.h"
 #include "platform/audio/AudioUtilities.h"
+#include "public/platform/Platform.h"
 
 namespace blink {
 
@@ -92,6 +95,8 @@ OfflineAudioContext* OfflineAudioContext::create(ExecutionContext* context, unsi
 
 OfflineAudioContext::OfflineAudioContext(Document* document, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate)
     : AudioContext(document, numberOfChannels, numberOfFrames, sampleRate)
+    , m_isSuspendScheduled(false)
+    , m_suspendTime(-0.0)

[Raymond Toy, 2015/05/13 17:16:08]

Why -0.0?  This probably won't do what you think it does.

[hongchan, 2015/05/13 17:30:53]

What would be the proper 'null' value for this case? Actually it really doesn't
matter since we have another flag for the validity of suspend time. Just want to
ask your opinion.

 {
 }
 
@@ -99,8 +104,24 @@ OfflineAudioContext::~OfflineAudioContext()
 {
 }
 
+bool OfflineAudioContext::suspendIfNecessary()
+{
+    ASSERT(!isMainThread());
+
+    if (m_isSuspendScheduled && m_suspendTime <= currentTime()) {
+        m_isSuspendScheduled = false;
+        m_suspendTime = -0.0;
+        return true;
+    }
+
+    return false;
+}
+
 ScriptPromise OfflineAudioContext::startOfflineRendering(ScriptState* scriptState)
 {
+    ASSERT(isMainThread());
+    AutoLocker locker(this);
+
     // Calling close() on an OfflineAudioContext is not supported/allowed,
     // but it might well have been stopped by its execution context.
     if (isContextClosed()) {
@@ -121,10 +142,60 @@ ScriptPromise OfflineAudioContext::startOfflineRendering(ScriptState* scriptStat
     }
 
     m_offlineResolver = ScriptPromiseResolver::create(scriptState);
-    startRendering();
+
+    // This calls AudioContext.startRendering(). It seems to be odd to go up the
+    // chain and call the parent's method, but the current OAC is basically a
+    // thin wrapper on AudioContext. (a container-like object.)
+    //
+    // If we decide to fix this structural issue completely, we have to touch
+    // AudioContext and AudioNode.
+    // startRendering();
+
+    destination()->audioDestinationHandler().startRendering();
+    setContextState(Running);
+
     return m_offlineResolver->promise();
 }
 
+ScriptPromise OfflineAudioContext::suspendOfflineRendering(ScriptState* scriptState, double suspendTime)
+{
+    ASSERT(isMainThread());
+    AutoLocker locker(this);
+
+    // suspendTime should be greater than currentTime. Otherwise stop the
+    // rendering as soon as possible.
+    //
+    // TODO: add extra time when suspendTime is earlier than currentTime
+    if (currentTime() < suspendTime) {
+        m_isSuspendScheduled = true;
+        m_suspendTime = suspendTime;
+    }
+
+    RefPtrWillBeRawPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(scriptState);
+    ScriptPromise promise = resolver->promise();
+    m_offlineSuspendResolvers.append(resolver);
+
+    // fprintf(stderr, "suspend scheduled = %f\n", m_suspendTime);
+
+    return promise;
+}
+
+ScriptPromise OfflineAudioContext::resumeOfflineRendering(ScriptState* scriptState)
+{
+    ASSERT(isMainThread());
+    AutoLocker locker(this);
+
+    RefPtrWillBeRawPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(scriptState);
+    ScriptPromise promise = resolver->promise();
+    m_offlineResumeResolvers.append(resolver);
+
+    // Calling startRendering() in OfflineAudioDestinationHandler.
+    destination()->audioDestinationHandler().startRendering();
+    setContextState(Running);
+
+    return promise;
+}
+
 } // namespace blink
 
 #endif // ENABLE(WEB_AUDIO)