Bug842: rescale clip offsets, envelope times when setting track rate

src/Envelope.cpp

@@ -1038,6 +1038,21 @@ void Envelope::SetTrackLen(double trackLen)
       }
 }
 
+void Envelope::RescaleTimes( double newLength )
+// NOFAIL-GUARANTEE
+{
+   if ( mTrackLen == 0 ) {
+      for ( auto &point : mEnv )
+         point.SetT( 0 );
+   }
+   else {
+      auto ratio = newLength / mTrackLen;
+      for ( auto &point : mEnv )
+         point.SetT( point.GetT() * ratio );
+   }
+   mTrackLen = newLength;
+}
+
 // Accessors
 double Envelope::GetValue(double t) const
 {

src/Envelope.h

@@ -127,6 +127,7 @@ public:
    void SetOffset(double newOffset);
    void SetTrackLen(double trackLen);
    void RescaleValues(double minValue, double maxValue);
+   void RescaleTimes( double newLength );
 
    // Accessors
    /** \brief Get envelope value at time t */

src/WaveClip.cpp

@@ -1832,7 +1832,8 @@ void WaveClip::Unlock()
 void WaveClip::SetRate(int rate)
 {
    mRate = rate;
-   UpdateEnvelopeTrackLen();
+   auto newLength = mSequence->GetNumSamples().as_double() / mRate;
+   mEnvelope->RescaleTimes( newLength );
    MarkChanged();
 }
 

src/WaveTrack.cpp

@@ -394,9 +394,14 @@ double WaveTrack::GetRate() const
 
 void WaveTrack::SetRate(double newRate)
 {
+   wxASSERT( newRate > 0 );
+   newRate = std::max( 1.0, newRate );
+   auto ratio = mRate / newRate;
    mRate = (int) newRate;
-   for (const auto &clip : mClips)
+   for (const auto &clip : mClips) {
       clip->SetRate((int)newRate);
+      clip->SetOffset( clip->GetOffset() * ratio );
+   }
 }
 
 float WaveTrack::GetGain() const