Allow timeConstant=0 for setTargetAtTime

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

 /*
  * Copyright (C) 2011 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
@@ skipping 146 matching lines @@
                                                            float initialValue,
                                                            double callTime) {
   return ParamEvent(ParamEvent::ExponentialRampToValue, value, time, 0, 0,
                     nullptr, initialValue, callTime);
 }
 
 AudioParamTimeline::ParamEvent
 AudioParamTimeline::ParamEvent::createSetTargetEvent(float value,
                                                      double time,
                                                      double timeConstant) {
+  // The time line code does not expect a timeConstant of 0. (IT

[hongchan, 2016/10/31 20:50:43]

typo: "(IT" -> "It"

+  // returns NaN or Infinity due to division by zero.  The caller
+  // should have converted this to a SetValueEvent.
+  DCHECK_NE(timeConstant, 0);
   return ParamEvent(ParamEvent::SetTarget, value, time, timeConstant, 0,
                     nullptr);
 }
 
 AudioParamTimeline::ParamEvent
 AudioParamTimeline::ParamEvent::createSetValueCurveEvent(
     const DOMFloat32Array* curve,
     double time,
     double duration) {
   return ParamEvent(ParamEvent::SetValueCurve, 0, time, 0, duration, curve);
@@ skipping 52 matching lines @@
               exceptionState);
 }
 
 void AudioParamTimeline::setTargetAtTime(float target,
                                          double time,
                                          double timeConstant,
                                          ExceptionState& exceptionState) {
   DCHECK(isMainThread());
 
   if (!isNonNegativeAudioParamTime(time, exceptionState) ||
-      !isPositiveAudioParamTime(timeConstant, exceptionState, "Time constant"))
+      !isNonNegativeAudioParamTime(timeConstant, exceptionState,
+                                   "Time constant"))
     return;
 
-  insertEvent(ParamEvent::createSetTargetEvent(target, time, timeConstant),
-              exceptionState);
+  // If timeConstant = 0, we instantly jump to the target value, so
+  // insert a SetValueEvent instead of SetTargetEvent.
+  if (timeConstant == 0) {
+    insertEvent(ParamEvent::createSetValueEvent(target, time), exceptionState);
+  } else {
+    insertEvent(ParamEvent::createSetTargetEvent(target, time, timeConstant),
+                exceptionState);
+  }
 }
 
 void AudioParamTimeline::setValueCurveAtTime(DOMFloat32Array* curve,
                                              double time,
                                              double duration,
                                              ExceptionState& exceptionState) {
   DCHECK(isMainThread());
   DCHECK(curve);
 
   if (!isNonNegativeAudioParamTime(time, exceptionState) ||
@@ skipping 793 matching lines @@
   // propagate the last value to the end of the values buffer.
   for (; writeIndex < numberOfValues; ++writeIndex)
     values[writeIndex] = value;
 
   // This value is used to set the .value attribute of the AudioParam.  it
   // should be the last computed value.
   return values[numberOfValues - 1];
 }
 
 }  // namespace blink