Rewrite many iterations over tracks and channels in src/effects

src/effects/AutoDuck.cpp

@@ -389,19 +389,15 @@ bool EffectAutoDuck::Process()
    if (!cancel)
    {
       CopyInputTracks(); // Set up mOutputTracks.
-      SelectedTrackListOfKindIterator iter(Track::Wave, mOutputTracks.get());
-      Track *iterTrack = iter.First();
 
       int trackNum = 0;
 
-      while (iterTrack)
+      for( auto iterTrack : mOutputTracks->Selected< WaveTrack >() )
       {
-         WaveTrack* t = (WaveTrack*)iterTrack;
-
          for (size_t i = 0; i < regions.size(); i++)
          {
             const AutoDuckRegion& region = regions[i];
-            if (ApplyDuckFade(trackNum, t, region.t0, region.t1))
+            if (ApplyDuckFade(trackNum, iterTrack, region.t0, region.t1))
             {
                cancel = true;
                break;
@@ -411,7 +407,6 @@ bool EffectAutoDuck::Process()
          if (cancel)
             break;
 
-         iterTrack = iter.Next();
          trackNum++;
       }
    }

src/effects/ClickRemoval.cpp

@@ -172,10 +172,8 @@ bool EffectClickRemoval::Process()
    bool bGoodResult = true;
    mbDidSomething = false;
 
-   SelectedTrackListOfKindIterator iter(Track::Wave, mOutputTracks.get());
-   WaveTrack *track = (WaveTrack *) iter.First();
    int count = 0;
-   while (track) {
+   for( auto track : mOutputTracks->Selected< WaveTrack >() ) {
       double trackStart = track->GetStartTime();
       double trackEnd = track->GetEndTime();
       double t0 = mT0 < trackStart? trackStart: mT0;
@@ -193,7 +191,6 @@ bool EffectClickRemoval::Process()
          }
       }
 
-      track = (WaveTrack *) iter.Next();
       count++;
    }
    if (bGoodResult && !mbDidSomething) // Processing successful, but ineffective.

src/effects/Contrast.cpp

@@ -43,24 +43,26 @@
 bool ContrastDialog::GetDB(float &dB)
 {
    float rms = float(0.0);
-   int numberSelecteTracks = 0;
 
    // For stereo tracks: sqrt((mean(L)+mean(R))/2)
-   bool isStereo = false;
    double meanSq = 0.0;
 
    AudacityProject *p = GetActiveProject();
-   SelectedTrackListOfKindIterator iter(Track::Wave, p->GetTracks());
+   auto range =
-   WaveTrack *t = (WaveTrack *) iter.First();
+      p->GetTracks()->SelectedLeaders< const WaveTrack >();
-   while (t) {
+   auto numberSelectedTracks = range.size();
-      numberSelecteTracks++;
+   if (numberSelectedTracks > 1) {
-      if (numberSelecteTracks > 1 && !isStereo) {
+      AudacityMessageDialog m(NULL, _("You can only measure one track at a time."), _("Error"), wxOK);
-         AudacityMessageDialog m(NULL, _("You can only measure one track at a time."), _("Error"), wxOK);
+      m.ShowModal();
-         m.ShowModal();
+      return false;
-         return false;
+   }
-      }
+   if(numberSelectedTracks == 0) {
-      isStereo = t->GetLinked();
+      wxMessageDialog m(NULL, _("Please select an audio track."), _("Error"), wxOK);
+      m.ShowModal();
+      return false;
+   }
 
+   for ( auto t : TrackList::Channels( *range.begin() ) ) {
       wxASSERT(mT0 <= mT1);
 
       // Ignore whitespace beyond ends of track.
@@ -87,19 +89,13 @@ bool ContrastDialog::GetDB(float &dB)
       }
 
       // Don't throw in this analysis dialog
-      rms = ((WaveTrack *)t)->GetRMS(mT0, mT1, false);
+      rms = t->GetRMS(mT0, mT1, false);
       meanSq += rms * rms;
-      t = (WaveTrack *) iter.Next();
    }
    // TODO: This works for stereo, provided the audio clips are in both channels.
    // We should really count gaps between clips as silence.
-   rms = (meanSq > 0.0)? sqrt(meanSq/(double)numberSelecteTracks) : 0.0;
+   rms = (meanSq > 0.0)? sqrt(meanSq/(double)numberSelectedTracks) : 0.0;
 
-   if(numberSelecteTracks == 0) {
-      AudacityMessageDialog m(NULL, _("Please select an audio track."), _("Error"), wxOK);
-      m.ShowModal();
-      return false;
-   }
    // Gives warning C4056, Overflow in floating-point constant arithmetic
    // -INFINITY is intentional here.
    // Looks like we are stuck with this warning, as 
@@ -344,9 +340,8 @@ void ContrastDialog::OnClose(wxCommandEvent & WXUNUSED(event))
 void ContrastDialog::OnGetForeground(wxCommandEvent & /*event*/)
 {
    AudacityProject *p = GetActiveProject();
-   SelectedTrackListOfKindIterator iter(Track::Wave, p->GetTracks());
 
-   for (Track *t = iter.First(); t; t = iter.Next()) {
+   for ( auto t : p->GetTracks()->Selected< const WaveTrack >() ) {
       mForegroundStartT->SetValue(p->mViewInfo.selectedRegion.t0());
       mForegroundEndT->SetValue(p->mViewInfo.selectedRegion.t1());
    }
@@ -360,9 +355,8 @@ void ContrastDialog::OnGetForeground(wxCommandEvent & /*event*/)
 void ContrastDialog::OnGetBackground(wxCommandEvent & /*event*/)
 {
    AudacityProject *p = GetActiveProject();
-   SelectedTrackListOfKindIterator iter(Track::Wave, p->GetTracks());
 
-   for (Track *t = iter.First(); t; t = iter.Next()) {
+   for ( auto t : p->GetTracks()->Selected< const WaveTrack >() ) {
       mBackgroundStartT->SetValue(p->mViewInfo.selectedRegion.t0());
       mBackgroundEndT->SetValue(p->mViewInfo.selectedRegion.t1());
    }

src/effects/Effect.cpp

@@ -2262,25 +2262,8 @@ void Effect::ReplaceProcessedTracks(const bool bGoodResult)
 
 void Effect::CountWaveTracks()
 {
-   mNumTracks = 0;
+   mNumTracks = mTracks->Selected< const WaveTrack >().size();
-   mNumGroups = 0;
+   mNumGroups = mTracks->SelectedLeaders< const WaveTrack >().size();
-
-   TrackListOfKindIterator iter(Track::Wave, mTracks);
-   Track *t = iter.First();
-
-   while(t) {
-      if (!t->GetSelected()) {
-         t = iter.Next();
-         continue;
-      }
-
-      if (t->GetKind() == Track::Wave) {
-         mNumTracks++;
-         if (!t->GetLinked())
-            mNumGroups++;
-      }
-      t = iter.Next();
-   }
 }
 
 double Effect::CalcPreviewInputLength(double previewLength)
@@ -2574,17 +2557,13 @@ void Effect::Preview(bool dryOnly)
       }
    }
    else {
-      TrackListOfKindIterator iter(Track::Wave, saveTracks);
+      for (auto src : saveTracks->Any< const WaveTrack >()) {
-      WaveTrack *src = (WaveTrack *) iter.First();
-      while (src)
-      {
          if (src->GetSelected() || mPreviewWithNotSelected) {
             auto dest = src->Copy(mT0, t1);
             dest->SetSelected(src->GetSelected());
             static_cast<WaveTrack*>(dest.get())->SetDisplay(WaveTrack::NoDisplay);
             mTracks->Add(std::move(dest));
          }
-         src = (WaveTrack *) iter.Next();
       }
    }
 

src/effects/Equalization.cpp

@@ -471,23 +471,20 @@ bool EffectEqualization::Init()
 {
    int selcount = 0;
    double rate = 0.0;
-   TrackListIterator iter(GetActiveProject()->GetTracks());
+
-   Track *t = iter.First();
+   auto trackRange =
-   while (t) {
+      GetActiveProject()->GetTracks()->Selected< const WaveTrack >();
-      if (t->GetSelected() && t->GetKind() == Track::Wave) {
+   if (trackRange) {
-         WaveTrack *track = (WaveTrack *)t;
+      rate = (*(trackRange.first++)) -> GetRate();
-         if (selcount==0) {
+      ++selcount;
-            rate = track->GetRate();
+
+      for (auto track : trackRange) {
+         if (track->GetRate() != rate) {
+            Effect::MessageBox(_("To apply Equalization, all selected tracks must have the same sample rate."));
+            return(false);
          }
-         else {
+         ++selcount;
-            if (track->GetRate() != rate) {
-               Effect::MessageBox(_("To apply Equalization, all selected tracks must have the same sample rate."));
-               return(false);
-            }
-         }
-         selcount++;
       }
-      t = iter.Next();
    }
 
    mHiFreq = rate / 2.0;
@@ -532,10 +529,8 @@ bool EffectEqualization::Process()
    this->CopyInputTracks(); // Set up mOutputTracks.
    bool bGoodResult = true;
 
-   SelectedTrackListOfKindIterator iter(Track::Wave, mOutputTracks.get());
-   WaveTrack *track = (WaveTrack *) iter.First();
    int count = 0;
-   while (track) {
+   for( auto track : mOutputTracks->Selected< WaveTrack >() ) {
       double trackStart = track->GetStartTime();
       double trackEnd = track->GetEndTime();
       double t0 = mT0 < trackStart? trackStart: mT0;
@@ -553,7 +548,6 @@ bool EffectEqualization::Process()
          }
       }
 
-      track = (WaveTrack *) iter.Next();
       count++;
    }
 

src/effects/Equalization48x.cpp

@@ -296,10 +296,9 @@ bool EffectEqualization48x::Process(EffectEqualization* effectEqualization)
       mEffectEqualization->mM=(mEffectEqualization->mM&(~15))+1;
    AllocateBuffersWorkers(sMathPath&MATH_FUNCTION_THREADED);
    auto cleanup = finally( [&] { FreeBuffersWorkers(); } );
-   SelectedTrackListOfKindIterator iter(Track::Wave, mEffectEqualization->mOutputTracks.get());
-   WaveTrack *track = (WaveTrack *) iter.First();
    int count = 0;
-   while (track) {
+   for( auto track :
+        mEffectEqualization->mOutputTracks->Selected< WaveTrack >() {
       double trackStart = track->GetStartTime();
       double trackEnd = track->GetEndTime();
       double t0 = mEffectEqualization->mT0 < trackStart? trackStart: mEffectEqualization->mT0;
@@ -313,7 +312,6 @@ bool EffectEqualization48x::Process(EffectEqualization* effectEqualization)
          if( bBreakLoop )
             break;
       }
-      track = (WaveTrack *) iter.Next();
       count++;
    }
 
@@ -340,10 +338,7 @@ bool EffectEqualization48x::TrackCompare()
    
    TrackList      SecondOutputTracks;
 
-   //iterate over tracks of type trackType (All types if Track::All)
+   for (auto aTrack : mEffectEqualization->mTracks->Any< WaveTrack >()) {
-   TrackListOfKindIterator aIt(mEffectEqualization->mOutputTracksType, mEffectEqualization->mTracks);
-
-   for (Track *aTrack = aIt.First(); aTrack; aTrack = aIt.Next()) {
 
       // Include selected tracks, plus sync-lock selected tracks for Track::All.
       if (aTrack->GetSelected() ||
@@ -357,15 +352,12 @@ bool EffectEqualization48x::TrackCompare()
       }
    }
 
-   for(int i=0;i<2;i++) {
+   for(int i = 0; i < 2; i++) {
-      SelectedTrackListOfKindIterator iter
-         (Track::Wave, i
-          ? mEffectEqualization->mOutputTracks.get()
-          : &SecondOutputTracks);
       i?sMathPath=sMathPath:sMathPath=0;
-      WaveTrack *track = (WaveTrack *) iter.First();
       int count = 0;
-      while (track) {
+      for( auto track :
+           ( i ? mEffectEqualization->mOutputTracks.get()
+               : &SecondOutputTracks ) -> Selected< WaveTrack >() {
          double trackStart = track->GetStartTime();
          double trackEnd = track->GetEndTime();
          double t0 = mEffectEqualization->mT0 < trackStart? trackStart: mEffectEqualization->mT0;
@@ -379,16 +371,14 @@ bool EffectEqualization48x::TrackCompare()
             if( bBreakLoop )
                break;
          }
-         track = (WaveTrack *) iter.Next();
          count++;
       }
    }
-   SelectedTrackListOfKindIterator
+
-      iter(Track::Wave, mEffectEqualization->mOutputTracks.get());
+   auto iter2 = (SecondOutputTracks.Selected< const WaveTrack >()).first;
-   SelectedTrackListOfKindIterator iter2(Track::Wave, &SecondOutputTracks);
+   auto track2 = *iter2;
-   WaveTrack *track =  (WaveTrack *) iter.First();
+   for ( auto track :
-   WaveTrack *track2 = (WaveTrack *) iter2.First();
+         mEffectEqualization->mOutputTracks->Selected< const WaveTrack >() {
-   while (track) {
       double trackStart = track->GetStartTime();
       double trackEnd = track->GetEndTime();
       double t0 = mEffectEqualization->mT0 < trackStart? trackStart: mEffectEqualization->mT0;
@@ -400,8 +390,7 @@ bool EffectEqualization48x::TrackCompare()
          auto len = end - start;
          DeltaTrack(track, track2, start, len);
       }
-      track = (WaveTrack *) iter.Next();
+      track2 = * ++iter2;
-      track2 = (WaveTrack *) iter2.Next();
    }
    mEffectEqualization->ReplaceProcessedTracks(!bBreakLoop);
    return bBreakLoop; // return !bBreakLoop ?
@@ -447,12 +436,10 @@ bool EffectEqualization48x::Benchmark(EffectEqualization* effectEqualization)
       mEffectEqualization->mM=(mEffectEqualization->mM&(~15))+1;
    AllocateBuffersWorkers(MATH_FUNCTION_THREADED);
    auto cleanup = finally( [&] { FreeBuffersWorkers(); } );
-   SelectedTrackListOfKindIterator
-      iter(Track::Wave, mEffectEqualization->mOutputTracks.get());
    long times[] = { 0,0,0,0,0 };
    wxStopWatch timer;
-   mBenching=true;
+   mBenching = true;
-   for(int i=0;i<5 && !bBreakLoop;i++) {
+   for(int i = 0; i < 5 && !bBreakLoop; i++) {
       int localMathPath;
       switch(i) {
          case 0: localMathPath=MATH_FUNCTION_SSE|MATH_FUNCTION_THREADED;
@@ -471,11 +458,11 @@ bool EffectEqualization48x::Benchmark(EffectEqualization* effectEqualization)
             break;
          default: localMathPath=-1;
       }
-      if(localMathPath>=0) {
+      if(localMathPath >= 0) {
          timer.Start();
-         WaveTrack *track = (WaveTrack *) iter.First();
          int count = 0;
-         while (track) {
+         for (auto track :
+              mEffectEqualization->mOutputTracks->Selected< WaveTrack >() {
             double trackStart = track->GetStartTime();
             double trackEnd = track->GetEndTime();
             double t0 = mEffectEqualization->mT0 < trackStart? trackStart: mEffectEqualization->mT0;
@@ -489,7 +476,6 @@ bool EffectEqualization48x::Benchmark(EffectEqualization* effectEqualization)
                if( bBreakLoop )
                   break;
             }
-            track = (WaveTrack *) iter.Next();
             count++;
          }
          times[i]=timer.Time();

src/effects/NoiseReduction.cpp

@@ -264,7 +264,7 @@ public:
 
    bool Process(EffectNoiseReduction &effect,
                 Statistics &statistics, TrackFactory &factory,
-                SelectedTrackListOfKindIterator &iter, double mT0, double mT1);
+                TrackList &tracks, double mT0, double mT1);
 
 private:
    bool ProcessOne(EffectNoiseReduction &effect,
@@ -606,8 +606,7 @@ bool EffectNoiseReduction::Process()
 
    this->CopyInputTracks(); // Set up mOutputTracks.
 
-   SelectedTrackListOfKindIterator iter(Track::Wave, mOutputTracks.get());
+   auto track = * (mOutputTracks->Selected< const WaveTrack >()).begin();
-   WaveTrack *track = (WaveTrack *) iter.First();
    if (!track)
       return false;
 
@@ -633,7 +632,8 @@ bool EffectNoiseReduction::Process()
                  , mF0, mF1
 #endif
       );
-   bool bGoodResult = worker.Process(*this, *mStatistics, *mFactory, iter, mT0, mT1);
+   bool bGoodResult = worker.Process
+      (*this, *mStatistics, *mFactory, *mOutputTracks, mT0, mT1);
    if (mSettings->mDoProfile) {
       if (bGoodResult)
          mSettings->mDoProfile = false; // So that "repeat last effect" will reduce noise
@@ -650,11 +650,10 @@ EffectNoiseReduction::Worker::~Worker()
 
 bool EffectNoiseReduction::Worker::Process
 (EffectNoiseReduction &effect, Statistics &statistics, TrackFactory &factory,
- SelectedTrackListOfKindIterator &iter, double inT0, double inT1)
+ TrackList &tracks, double inT0, double inT1)
 {
    int count = 0;
-   WaveTrack *track = (WaveTrack *) iter.First();
+   for ( auto track : tracks.Selected< WaveTrack >() ) {
-   while (track) {
       if (track->GetRate() != mSampleRate) {
          if (mDoProfile)
             effect.Effect::MessageBox(_("All noise profile data must have the same sample rate."));
@@ -677,7 +676,6 @@ bool EffectNoiseReduction::Worker::Process
                          count, track, start, len))
             return false;
       }
-      track = (WaveTrack *) iter.Next();
       ++count;
    }
 

src/effects/NoiseRemoval.cpp

@@ -208,10 +208,8 @@ bool EffectNoiseRemoval::Process()
    this->CopyInputTracks(); // Set up mOutputTracks.
    bool bGoodResult = true;
 
-   SelectedTrackListOfKindIterator iter(Track::Wave, mOutputTracks.get());
-   WaveTrack *track = (WaveTrack *) iter.First();
    int count = 0;
-   while (track) {
+   for( auto track : mOutputTracks->Selected< WaveTrack >() ) {
       double trackStart = track->GetStartTime();
       double trackEnd = track->GetEndTime();
       double t0 = mT0 < trackStart? trackStart: mT0;
@@ -227,7 +225,6 @@ bool EffectNoiseRemoval::Process()
             break;
          }
       }
-      track = (WaveTrack *) iter.Next();
       count++;
    }
 

src/effects/Paulstretch.cpp

@@ -164,11 +164,9 @@ double EffectPaulstretch::CalcPreviewInputLength(double previewLength)
 bool EffectPaulstretch::Process()
 {
    CopyInputTracks();
-   SelectedTrackListOfKindIterator iter(Track::Wave, mOutputTracks.get());
-   WaveTrack *track = (WaveTrack *) iter.First();
    m_t1=mT1;
    int count=0;
-   while (track) {
+   for( auto track : mOutputTracks->Selected< WaveTrack >() ) {
       double trackStart = track->GetStartTime();
       double trackEnd = track->GetEndTime();
       double t0 = mT0 < trackStart? trackStart: mT0;
@@ -179,7 +177,6 @@ bool EffectPaulstretch::Process()
             return false;
       }
 
-      track = (WaveTrack *) iter.Next();
       count++;
    }
    mT1=m_t1;

src/effects/Repair.cpp

@@ -74,10 +74,8 @@ bool EffectRepair::Process()
    this->CopyInputTracks(); // Set up mOutputTracks. //v This may be too much copying for EffectRepair.
    bool bGoodResult = true;
 
-   SelectedTrackListOfKindIterator iter(Track::Wave, mOutputTracks.get());
-   WaveTrack *track = (WaveTrack *) iter.First();
    int count = 0;
-   while (track) {
+   for( auto track : mOutputTracks->Selected< WaveTrack >() ) {
       const
       double trackStart = track->GetStartTime();
       const double repair_t0 = std::max(mT0, trackStart);
@@ -125,7 +123,6 @@ bool EffectRepair::Process()
          }
       }
 
-      track = (WaveTrack *) iter.Next();
       count++;
    }
 

src/effects/SimpleMono.cpp

@@ -32,10 +32,8 @@ bool EffectSimpleMono::Process()
    this->CopyInputTracks(); // Set up mOutputTracks.
    bool bGoodResult = true;
 
-   SelectedTrackListOfKindIterator iter(Track::Wave, mOutputTracks.get());
-   WaveTrack* pOutWaveTrack = (WaveTrack*)(iter.First());
    mCurTrackNum = 0;
-   while (pOutWaveTrack != NULL)
+   for( auto pOutWaveTrack : mOutputTracks->Selected< WaveTrack >() )
    {
       //Get start and end times from track
       double trackStart = pOutWaveTrack->GetStartTime();
@@ -66,8 +64,6 @@ bool EffectSimpleMono::Process()
          }
       }
 
-      //Iterate to the next track
-      pOutWaveTrack = (WaveTrack*)(iter.Next());
       mCurTrackNum++;
    }
 

src/effects/StereoToMono.cpp

@@ -75,8 +75,8 @@ bool EffectStereoToMono::Process()
    this->CopyInputTracks(); // Set up mOutputTracks.
    bool bGoodResult = true;
 
-   SelectedTrackListOfKindIterator iter(Track::Wave, mOutputTracks.get());
+   auto trackRange = mOutputTracks->Selected< WaveTrack >();
-   mLeftTrack = (WaveTrack *)iter.First();
+   mLeftTrack = *trackRange.first;
    bool refreshIter = false;
 
    if(mLeftTrack)
@@ -87,13 +87,12 @@ bool EffectStereoToMono::Process()
    }
 
    int count = 0;
-   while (mLeftTrack) {
+   while ( trackRange.first != trackRange.second ) {
-      if (mLeftTrack->GetKind() == Track::Wave &&
+      mLeftTrack = *trackRange.first;
-         mLeftTrack->GetSelected() &&
+      if (mLeftTrack->GetLinked()) {
-         mLeftTrack->GetLinked()) {
 
          // Assume linked track is wave
-         mRightTrack = static_cast<WaveTrack*>(iter.Next());
+         mRightTrack = * ++ trackRange.first;
 
          if ((mLeftTrack->GetRate() == mRightTrack->GetRate())) {
             auto leftTrackStart = mLeftTrack->TimeToLongSamples(mLeftTrack->GetStartTime());
@@ -116,12 +115,12 @@ bool EffectStereoToMono::Process()
       }
 
       if (refreshIter) {
-         mLeftTrack = (WaveTrack *)iter.First();
+         trackRange = mOutputTracks->Selected< WaveTrack >();
          refreshIter = false;
       }
-      else {
+      else
-         mLeftTrack = (WaveTrack *)iter.Next();
+         ++trackRange.first;
-      }
+
       count++;
    }
 

src/effects/TruncSilence.cpp

@@ -405,10 +405,10 @@ bool EffectTruncSilence::ProcessAll()
    auto trackRange0 = inputTracks()->Selected< const WaveTrack >();
    if (FindSilences(
          silences, inputTracks(), *trackRange0.begin(), *trackRange0.rbegin())) {
-      TrackListIterator iterOut(mOutputTracks.get());
+      auto trackRange = mOutputTracks->Any();
       double totalCutLen = 0.0;
-      Track *const first = iterOut.First();
+      if (DoRemoval(silences, 0, 1,
-      if (DoRemoval(silences, 0, 1, first, iterOut.Last(), totalCutLen)) {
+         *trackRange.begin(), *trackRange.rbegin(), totalCutLen)) {
          mT1 -= totalCutLen;
          return true;
       }

src/effects/TwoPassSimpleMono.cpp

@@ -47,10 +47,8 @@ bool EffectTwoPassSimpleMono::Process()
 bool EffectTwoPassSimpleMono::ProcessPass()
 {
    //Iterate over each track
-   SelectedTrackListOfKindIterator iter(Track::Wave, mOutputTracks.get());
-   WaveTrack *track = (WaveTrack *) iter.First();
    mCurTrackNum = 0;
-   while (track) {
+   for( auto track : mOutputTracks->Selected< WaveTrack >() ) {
       //Get start and end times from track
       double trackStart = track->GetStartTime();
       double trackEnd = track->GetEndTime();
@@ -85,8 +83,6 @@ bool EffectTwoPassSimpleMono::ProcessPass()
             return false;
       }
 
-      //Iterate to the next track
-      track = (WaveTrack *) iter.Next();
       mCurTrackNum++;
    }
 

src/effects/nyquist/Nyquist.cpp

@@ -48,6 +48,8 @@ effects from this one class.
 #include "../../FileNames.h"
 #include "../../Internat.h"
 #include "../../LabelTrack.h"
+#include "../../NoteTrack.h"
+#include "../../TimeTrack.h"
 #include "../../prefs/SpectrogramSettings.h"
 #include "../../Project.h"
 #include "../../ShuttleGui.h"
@@ -544,8 +546,8 @@ bool NyquistEffect::Init()
       AudacityProject *project = GetActiveProject();
       bool bAllowSpectralEditing = true;
 
-      SelectedTrackListOfKindIterator sel(Track::Wave, project->GetTracks());
+      for ( auto t :
-      for (WaveTrack *t = (WaveTrack *) sel.First(); t; t = (WaveTrack *) sel.Next()) {
+               project->GetTracks()->Selected< const WaveTrack >() ) {
          if (t->GetDisplay() != WaveTrack::Spectrum ||
              !(t->GetSpectrogramSettings().SpectralSelectionEnabled())) {
             bAllowSpectralEditing = false;
@@ -622,7 +624,6 @@ bool NyquistEffect::Process()
       mProgress->Hide();
    }
 
-
    mOutputTime = 0;
    mCount = 0;
    mProgressIn = 0;
@@ -636,10 +637,8 @@ bool NyquistEffect::Process()
 
    mTrackIndex = 0;
 
-   mNumSelectedChannels = 0;
-
    // If in tool mode, then we don't do anything with the track and selection.
-   bool bOnePassTool = (GetType() == EffectTypeTool);
+   const bool bOnePassTool = (GetType() == EffectTypeTool);
 
    // We must copy all the tracks, because Paste needs label tracks to ensure
    // correct sync-lock group behavior when the timeline is affected; then we just want
@@ -647,16 +646,7 @@ bool NyquistEffect::Process()
    if ( !bOnePassTool )
       CopyInputTracks(true);
 
-   SelectedTrackListOfKindIterator sel(Track::Wave, mOutputTracks.get());
+   mNumSelectedChannels = mOutputTracks->Selected< const WaveTrack >().size();
-   for (WaveTrack *t = (WaveTrack *) sel.First(); t; t = (WaveTrack *) sel.Next()) {
-      mNumSelectedChannels++;
-      if (mT1 >= mT0) {
-         if (t->GetLinked()) {
-            mNumSelectedChannels++;
-            sel.Next();
-         }
-      }
-   }
 
    mDebugOutput.Clear();
    if (!mHelpFile.IsEmpty() && !mHelpFileExists) {
@@ -720,8 +710,6 @@ bool NyquistEffect::Process()
       mProps += wxString::Format(wxT("(putprop '*PROJECT* %d 'PROJECTS)\n"), (int) gAudacityProjects.size());
       mProps += wxString::Format(wxT("(putprop '*PROJECT* \"%s\" 'NAME)\n"), project->GetName());
 
-      TrackListIterator all(project->GetTracks());
-      Track *t;
       int numTracks = 0;
       int numWave = 0;
       int numLabel = 0;
@@ -729,29 +717,21 @@ bool NyquistEffect::Process()
       int numTime = 0;
       wxString waveTrackList = wxT("");   // track positions of selected audio tracks.
 
-      for (t = all.First(); t; t = all.Next())
       {
-         switch (t->GetKind())
+         auto countRange = project->GetTracks()->Leaders();
-         {
+         for (auto t : countRange) {
-            case Track::Wave:
+            t->TypeSwitch( [&](const WaveTrack *) {
                numWave++;
-               if (t->GetSelected()) {
+               if (t->GetSelected())
                   waveTrackList += wxString::Format(wxT("%d "), 1 + numTracks);
-               }
+            });
-            break;
+            numTracks++;
-            case Track::Label: numLabel++; break;
-#if defined(USE_MIDI)
-            case Track::Note: numMidi++; break;
-#endif
-            case Track::Time: numTime++; break;
-            default: break;
-         }
-
-         numTracks++;
-         if (t->GetLinked())
-         {
-            all.Next();
          }
+         numLabel = countRange.Filter<const LabelTrack>().size();
+   #if defined(USE_MIDI)
+         numMidi = countRange.Filter<const NoteTrack>().size();
+   #endif
+         numTime = countRange.Filter<const TimeTrack>().size();
       }
 
       // We use Internat::ToString() rather than "%g" here because we
@@ -789,8 +769,7 @@ bool NyquistEffect::Process()
       Effect::MessageBox(message, wxOK | wxCENTRE | wxICON_EXCLAMATION, _("Nyquist Error"));
    }
 
-   SelectedTrackListOfKindIterator iter(Track::Wave, mOutputTracks.get());
+   auto trackRange = mOutputTracks->Selected< WaveTrack >();
-   mCurTrack[0] = (WaveTrack *) iter.First();
 
    // Keep track of whether the current track is first selected in its sync-lock group
    // (we have no idea what the length of the returned audio will be, so we have
@@ -798,19 +777,21 @@ bool NyquistEffect::Process()
    mFirstInGroup = true;
    Track *gtLast = NULL;
 
-   while (mCurTrack[0] || bOnePassTool) {
+   for (auto &iter = trackRange.first, &end = trackRange.second;
+        bOnePassTool || iter != end; ++iter) {
+      mCurTrack[0] = *iter;
       mCurNumChannels = 1;
-      if ((mT1 >= mT0)||bOnePassTool) {
+      if ( (mT1 >= mT0) || bOnePassTool ) {
          if (bOnePassTool) {
-
+         }
-         } else {
+         else {
             if (mCurTrack[0]->GetLinked()) {
                mCurNumChannels = 2;
 
-               mCurTrack[1] = (WaveTrack *)iter.Next();
+               mCurTrack[1] = * ++ iter;
                if (mCurTrack[1]->GetRate() != mCurTrack[0]->GetRate()) {
                   Effect::MessageBox(_("Sorry, cannot apply effect on stereo tracks where the tracks don't match."),
-                     wxOK | wxCENTRE);
+                               wxOK | wxCENTRE);
                   success = false;
                   goto finish;
                }
@@ -840,6 +821,7 @@ bool NyquistEffect::Process()
 
             mCurLen = std::min(mCurLen, mMaxLen);
          }
+
          mProgressIn = 0.0;
          mProgressOut = 0.0;
 
@@ -914,7 +896,6 @@ bool NyquistEffect::Process()
          mProgressTot += mProgressIn + mProgressOut;
       }
 
-      mCurTrack[0] = (WaveTrack *) iter.Next();
       mCount += mCurNumChannels;
    }
 
@@ -1112,22 +1093,9 @@ bool NyquistEffect::ProcessOne()
       //NOTE: Audacity 2.1.3 True if spectral selection is enabled regardless of track view.
       cmd += wxString::Format(wxT("(putprop '*TRACK* %s 'SPECTRAL-EDIT-ENABLED)\n"), spectralEditp);
 
-      double startTime = 0.0;
+      auto channels = TrackList::Channels( mCurTrack[0] );
-      double endTime = 0.0;
+      double startTime = channels.min( &Track::GetStartTime );
-
+      double endTime = channels.max( &Track::GetEndTime );
-      if (mCurTrack[0]->GetLinked()) {
-         startTime = std::min<double>(mCurTrack[0]->GetStartTime(), mCurTrack[0]->GetLink()->GetStartTime());
-      }
-      else {
-         startTime = mCurTrack[0]->GetStartTime();
-      }
-
-      if (mCurTrack[0]->GetLinked()) {
-         endTime = std::max<double>(mCurTrack[0]->GetEndTime(), mCurTrack[0]->GetLink()->GetEndTime());
-      }
-      else {
-         endTime = mCurTrack[0]->GetEndTime();
-      }
 
       cmd += wxString::Format(wxT("(putprop '*TRACK* (float %s) 'START-TIME)\n"),
                               Internat::ToString(startTime));
@@ -1415,16 +1383,7 @@ bool NyquistEffect::ProcessOne()
       mProjectChanged = true;
       unsigned int numLabels = nyx_get_num_labels();
       unsigned int l;
-      LabelTrack *ltrack = NULL;
+      auto ltrack = * mOutputTracks->Any< LabelTrack >().begin();
-
-      TrackListIterator iter(mOutputTracks.get());
-      for (Track *t = iter.First(); t; t = iter.Next()) {
-         if (t->GetKind() == Track::Label) {
-            ltrack = (LabelTrack *)t;
-            break;
-         }
-      }
-
       if (!ltrack) {
          ltrack = static_cast<LabelTrack*>(AddToOutputTracks(mFactory->NewLabelTrack()));
       }
@@ -1675,12 +1634,10 @@ double NyquistEffect::GetCtrlValue(const wxString &s)
     * be determined.
     *
    AudacityProject *project = GetActiveProject();
-   double rate = INT_MAX;
    if (project && s.IsSameAs(wxT("half-srate"), false)) {
-      SelectedTrackListOfKindIterator sel(Track::Wave, project->GetTracks());
+      auto rate =
-      for (WaveTrack *t = (WaveTrack *) sel.First(); t; t = (WaveTrack *) sel.Next()) {
+         project->GetTracks()->Selected< const WaveTrack >()
-         rate = std::min(t->GetRate(), rate);
+            .min( &WaveTrack::GetRate );
-      }
       return (rate / 2.0);
    }
    */