Correctly clamp in distance formulas

third_party/WebKit/Source/platform/audio/Distance.cpp

Index: third_party/WebKit/Source/platform/audio/Distance.cpp
diff --git a/third_party/WebKit/Source/platform/audio/Distance.cpp b/third_party/WebKit/Source/platform/audio/Distance.cpp
index 99c5a0221aa10008546f78f776b8f3ca13309ed5..1a77747581dc62082eda2ab115380ad2ede8793c 100644
--- a/third_party/WebKit/Source/platform/audio/Distance.cpp
+++ b/third_party/WebKit/Source/platform/audio/Distance.cpp
@@ -42,10 +42,6 @@ DistanceEffect::DistanceEffect()
       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);
@@ -59,17 +55,27 @@ double DistanceEffect::Gain(double distance) {
 }
 
 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));

[hongchan, 2017/05/05 18:07:58]

Can we align this line somehow?

[Raymond Toy, 2017/05/05 18:18:28]

clang-format did that. :-(

 }
 
 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_));
 }
@@ -78,6 +84,12 @@ double DistanceEffect::ExponentialGain(double distance) {
   if (ref_distance_ == 0)
     return 0;
 
+  // Clamp distance according to spec
+  distance = clampTo(distance, ref_distance_);
+
+  if (ref_distance_ == 0)
+    return 0;

[hongchan, 2017/05/05 18:07:58]

L.90~91 is identical to L84~L85.

[Raymond Toy, 2017/05/05 18:18:29]

90-91 removed.

+
   return pow(distance / ref_distance_, -clampTo(rolloff_factor_, 0.0));
 }