MixAndRender returns unique_ptr results (in a std::pair)

src/Mix.h

@@ -12,6 +12,8 @@
 #ifndef __AUDACITY_MIX__
 #define __AUDACITY_MIX__
 
+#include "MemoryX.h"
+#include <utility>
 #include <wx/string.h>
 
 #include "SampleFormat.h"
@@ -36,10 +38,12 @@ class WaveTrackConstArray;
  * no explicit time range to process, and the whole occupied length of the
  * input tracks is processed.
  */
-bool MixAndRender(TrackList * tracks, TrackFactory *factory,
+std::pair<
+   std::unique_ptr<WaveTrack>,
+   std::unique_ptr<WaveTrack>
+> MixAndRender(TrackList * tracks, TrackFactory *factory,
                   double rate, sampleFormat format,
-                  double startTime, double endTime,
-                  WaveTrack **newLeft, WaveTrack **newRight);
+                  double startTime, double endTime);
 
 void MixBuffers(int numChannels, int *channelFlags, float *gains,
                 samplePtr src,