Correctly clamp in distance formulas

third_party/WebKit/Source/platform/audio/Distance.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
@@ skipping 24 matching lines @@
 
 namespace blink {
 
 DistanceEffect::DistanceEffect()
     : model_(kModelInverse),
       ref_distance_(1.0),
       max_distance_(10000.0),
       rolloff_factor_(1.0) {}
 
 double DistanceEffect::Gain(double distance) {
-  // Don't get closer than the reference distance or go beyond the maximum
-  // distance.
-  distance = clampTo(distance, ref_distance_, max_distance_);
-
   switch (model_) {
     case kModelLinear:
       return LinearGain(distance);
     case kModelInverse:
       return InverseGain(distance);
     case kModelExponential:
       return ExponentialGain(distance);
   }
   NOTREACHED();
   return 0.0;
 }
 
 double DistanceEffect::LinearGain(double distance) {
+  // Clamp refDistance and distance according to the spec.
+  double dref = std::min(ref_distance_, max_distance_);
+  double dmax = std::max(ref_distance_, max_distance_);
+  distance = clampTo(distance, dref, dmax);
+
+  if (dref == dmax)
+    return 1 - rolloff_factor_;
+
   // We want a gain that decreases linearly from m_refDistance to
   // m_maxDistance. The gain is 1 at m_refDistance.
-  return (1.0 - clampTo(rolloff_factor_, 0.0, 1.0) *
-                    (distance - ref_distance_) /
-                    (max_distance_ - ref_distance_));
+  return (1.0 - clampTo(rolloff_factor_, 0.0, 1.0) * (distance - dref) /
+                    (dmax - dref));
 }
 
 double DistanceEffect::InverseGain(double distance) {
   if (ref_distance_ == 0)
     return 0;
 
+  // Clamp distance according to spec
+  distance = clampTo(distance, ref_distance_);
+
   return ref_distance_ / (ref_distance_ + clampTo(rolloff_factor_, 0.0) *
                                               (distance - ref_distance_));
 }
 
 double DistanceEffect::ExponentialGain(double distance) {
   if (ref_distance_ == 0)
     return 0;
 
+  // Clamp distance according to spec
+  distance = clampTo(distance, ref_distance_);
+
   return pow(distance / ref_distance_, -clampTo(rolloff_factor_, 0.0));
 }
 
 }  // namespace blink