Track.cpp does not depend directly on its subclasses

src/export/Export.cpp

@@ -248,9 +248,14 @@ std::unique_ptr<Mixer> ExportPlugin::CreateMixer(const TrackList &tracks,
          double outRate, sampleFormat outFormat,
          bool highQuality, MixerSpec *mixerSpec)
 {
-   const WaveTrackConstArray inputTracks =
-      tracks.GetWaveTrackConstArray(selectionOnly, false);
-   const TimeTrack *timeTrack = tracks.GetTimeTrack();
+   WaveTrackConstArray inputTracks;
+   auto range = tracks.Any< const WaveTrack >()
+      + (selectionOnly ? &Track::IsSelected : &Track::Any )
+      - &WaveTrack::GetMute;
+   for (auto pTrack: range)
+      inputTracks.push_back(
+         pTrack->SharedPointer< const WaveTrack >() );
+   const auto timeTrack = *tracks.Any<const TimeTrack>().begin();
    auto envelope = timeTrack ? timeTrack->GetEnvelope() : nullptr;
    // MB: the stop time should not be warped, this was a bug.
    return std::make_unique<Mixer>(inputTracks,

src/export/ExportMultiple.cpp

@@ -646,6 +646,57 @@ bool ExportMultiple::DirOk()
    return fn.Mkdir(0777, wxPATH_MKDIR_FULL);
 }
 
+static unsigned GetNumExportChannels( const TrackList &tracks )
+{
+   /* counters for tracks panned different places */
+   int numLeft = 0;
+   int numRight = 0;
+   //int numMono = 0;
+   /* track iteration kit */
+
+   // Want only unmuted wave tracks.
+   for (auto tr :
+         tracks.Any< const WaveTrack >() - &WaveTrack::GetMute
+   ) {
+      // Found a left channel
+      if (tr->GetChannel() == Track::LeftChannel) {
+         numLeft++;
+      }
+
+      // Found a right channel
+      else if (tr->GetChannel() == Track::RightChannel) {
+         numRight++;
+      }
+
+      // Found a mono channel, but it may be panned
+      else if (tr->GetChannel() == Track::MonoChannel) {
+         float pan = tr->GetPan();
+
+         // Figure out what kind of channel it should be
+         if (pan == -1.0) {   // panned hard left
+            numLeft++;
+         }
+         else if (pan == 1.0) {  // panned hard right
+            numRight++;
+         }
+         else if (pan == 0) { // panned dead center
+            // numMono++;
+         }
+         else {   // panned somewhere else
+            numLeft++;
+            numRight++;
+         }
+      }
+   }
+
+   // if there is stereo content, report 2, else report 1
+   if (numRight > 0 || numLeft > 0) {
+      return 2;
+   }
+
+   return 1;
+}
+
 // TODO: JKC July2016: Merge labels/tracks duplicated export code.
 // TODO: JKC Apr2019: Doubly so merge these!  Too much duplication.
 ProgressResult ExportMultiple::ExportMultipleByLabel(bool byName,
@@ -664,7 +715,7 @@ ProgressResult ExportMultiple::ExportMultipleByLabel(bool byName,
    }
 
    // Figure out how many channels we should export.
-   auto channels = mTracks->GetNumExportChannels(false);
+   auto channels = GetNumExportChannels( *mTracks );
 
    FilePaths otherNames;  // keep track of file names we will use, so we
    // don't duplicate them