Make setTarget followed by linear or exponential ramp continuous.

third_party/WebKit/Source/modules/webaudio/AudioParamTimeline.cpp

Index: third_party/WebKit/Source/modules/webaudio/AudioParamTimeline.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/AudioParamTimeline.cpp b/third_party/WebKit/Source/modules/webaudio/AudioParamTimeline.cpp
index 4f120b5bb65cceb6e9da08b792a657024302dbe2..6b95a0aa2217fa972ba26b6e2cd572f396ce305a 100644
--- a/third_party/WebKit/Source/modules/webaudio/AudioParamTimeline.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/AudioParamTimeline.cpp
@@ -405,6 +405,19 @@ float AudioParamTimeline::valuesForFrameRangeImpl(
                 continue;
         }
 
+        ParamEvent::Type nextEventType = nextEvent ? static_cast<ParamEvent::Type>(nextEvent->type()) : ParamEvent::LastType /* unknown */;

[hongchan, 2016/04/27 21:40:09]

Are we okay with the comment style here? I've never seen something like this
before.

[Raymond Toy, 2016/04/27 21:43:15]

Don't know.  I just basically moved this line up from line 438 below, without
changing anything.

[Raymond Toy, 2016/04/27 22:57:03]

It means a nextEventType equal to LastType indicates an unknown eventType. 
Because there is no nextEvent.

I'll remove that and add a better comment.

+
+        // If the current event is SetTarget and the next event is a LinearRampToValue or
+        // ExponentialRampToValue, special handling is needed.  In this case, the linear and
+        // exponential ramp should start at wherever the SetTarget processing has reached.
+        if (event.type() == ParamEvent::SetTarget
+            && (nextEventType == ParamEvent::LinearRampToValue
+                || nextEventType == ParamEvent::ExponentialRampToValue)) {
+            // Replace the SetTarget with a SetValue to set the starting time and value for the ramp
+            // using the current frame and value.
+            m_events[i] = ParamEvent::createSetValueEvent(value, currentFrame / sampleRate);
+        }
+
         float value1 = event.value();
         double time1 = event.time();
 
@@ -433,7 +446,6 @@ float AudioParamTimeline::valuesForFrameRangeImpl(
         size_t fillToFrame = fillToEndFrame - startFrame;
         fillToFrame = std::min(fillToFrame, static_cast<size_t>(numberOfValues));
 
-        ParamEvent::Type nextEventType = nextEvent ? static_cast<ParamEvent::Type>(nextEvent->type()) : ParamEvent::LastType /* unknown */;
 
         // First handle linear and exponential ramps which require looking ahead to the next event.
         if (nextEventType == ParamEvent::LinearRampToValue) {
@@ -517,6 +529,10 @@ float AudioParamTimeline::valuesForFrameRangeImpl(
                     value *= multiplier;
                     ++currentFrame;
                 }
+                // Due to roundoff it's possible that value exceeds value2.  Clip value to value2 if
+                // we are within 1/2 frame of time2.
+                if (currentFrame > time2 * sampleRate - 0.5)
+                    value = value2;
             }
         } else {
             // Handle event types not requiring looking ahead to the next event.