/**********************************************************************

  Audacity: A Digital Audio Editor

  @file SpectrumCache.cpp

  Paul Licameli split from WaveClip.cpp

**********************************************************************/

#include "SpectrumCache.h"

#include "SpectrogramSettings.h"
#include "RealFFTf.h"
#include "Sequence.h"
#include "Spectrum.h"
#include "WaveClipUIUtilities.h"
#include "WaveTrack.h"
#include "WideSampleSequence.h"
#include <cmath>

namespace {

static void ComputeSpectrumUsingRealFFTf
   (float * __restrict buffer, const FFTParam *hFFT,
    const float * __restrict window, size_t len, float * __restrict out)
{
   size_t i;
   if(len > hFFT->Points * 2)
      len = hFFT->Points * 2;
   for(i = 0; i < len; i++)
      buffer[i] *= window[i];
   for( ; i < (hFFT->Points * 2); i++)
      buffer[i] = 0; // zero pad as needed
   RealFFTf(buffer, hFFT);
   // Handle the (real-only) DC
   float power = buffer[0] * buffer[0];
   if(power <= 0)
      out[0] = -160.0;
   else
      out[0] = 10.0 * log10f(power);
   for(i = 1; i < hFFT->Points; i++) {
      const int index = hFFT->BitReversed[i];
      const float re = buffer[index], im = buffer[index + 1];
      power = re * re + im * im;
      if(power <= 0)
         out[i] = -160.0;
      else
         out[i] = 10.0*log10f(power);
   }
}

void ComputeSpectrogramGainFactors
   (size_t fftLen, double rate, int frequencyGain, std::vector<float> &gainFactors)
{
   if (frequencyGain > 0) {
      // Compute a frequency-dependent gain factor
      // scaled such that 1000 Hz gets a gain of 0dB

      // This is the reciprocal of the bin number of 1000 Hz:
      const double factor = ((double)rate / (double)fftLen) / 1000.0;

      auto half = fftLen / 2;
      gainFactors.reserve(half);
      // Don't take logarithm of zero!  Let bin 0 replicate the gain factor for bin 1.
      gainFactors.push_back(frequencyGain*log10(factor));
      for (decltype(half) x = 1; x < half; x++) {
         gainFactors.push_back(frequencyGain*log10(factor * x));
      }
   }
}

}

bool SpecCache::isWaveletAnalysis(const SpectrogramSettings& settings) const
{
    return settings.algorithm == SpectrogramSettings::algWavelet;
}

bool SpecCache::Matches(
   int dirty_, double samplesPerPixel,
   const SpectrogramSettings& settings) const
{
   // Make a tolerant comparison of the spp values in this wise:
   // accumulated difference of times over the number of pixels is less than
   // a sample period.
   const bool sppMatch = (fabs(samplesPerPixel - spp) * len < 1.0);

   if (isWaveletAnalysis(settings))
   {
       return
          sppMatch &&
          dirty == dirty_ &&
          frequencyGain == settings.frequencyGain &&
          algorithm == settings.algorithm &&
          windowSize == settings.WindowSize();
   }
   return
      sppMatch &&
      dirty == dirty_ &&
      windowType == settings.windowType &&
      windowSize == settings.WindowSize() &&
      zeroPaddingFactor == settings.ZeroPaddingFactor() &&
      frequencyGain == settings.frequencyGain &&
      algorithm == settings.algorithm;
}

bool SpecCache::CalculateOneSpectrum(
   const SpectrogramSettings& settings, const WaveChannelInterval& clip,
   const int xx, double pixelsPerSecond, int lowerBoundX, int upperBoundX,
   const std::vector<float>& gainFactors, float* __restrict scratch,
   float* __restrict out) const
{
   bool result = false;
   const bool reassignment =
      (settings.algorithm == SpectrogramSettings::algReassignment);
   const size_t windowSizeSetting = settings.WindowSize();

   sampleCount from;

   const auto numSamples = clip.GetSequence().GetNumSamples();
   const auto sampleRate = clip.GetRate();
   const auto stretchRatio = clip.GetStretchRatio();
   const auto samplesPerPixel = sampleRate / pixelsPerSecond / stretchRatio;
   // xx may be for a column that is out of the visible bounds, but only
   // when we are calculating reassignment contributions that may cross into
   // the visible area.

   if (xx < 0)
      from = sampleCount(where[0].as_double() + xx * samplesPerPixel);
   else if (xx > (int)len)
      from = sampleCount(where[len].as_double() + (xx - len) * samplesPerPixel);
   else
      from = where[xx];

   const bool autocorrelation =
      settings.algorithm == SpectrogramSettings::algPitchEAC;
   const size_t zeroPaddingFactorSetting = settings.ZeroPaddingFactor();
   const size_t padding = (windowSizeSetting * (zeroPaddingFactorSetting - 1)) / 2;
   const size_t fftLen = windowSizeSetting * zeroPaddingFactorSetting;
   auto nBins = settings.NBins();

   if (from < 0 || from >= numSamples) {
      if (xx >= 0 && xx < (int)len) {
         // Pixel column is out of bounds of the clip!  Should not happen.
         float *const results = &out[nBins * xx];
         std::fill(results, results + nBins, 0.0f);
      }
   }
   else {


      // We can avoid copying memory when ComputeSpectrum is used below
      bool copy = !autocorrelation || (padding > 0) || reassignment;
      std::vector<float> floats;
      float* useBuffer = 0;
      float *adj = scratch + padding;

      {
         auto myLen = windowSizeSetting;
         // Take a window of the track centered at this sample.
         from -= windowSizeSetting >> 1;
         if (from < 0) {
            // Near the start of the clip, pad left with zeroes as needed.
            // from is at least -windowSize / 2
            for (auto ii = from; ii < 0; ++ii)
               *adj++ = 0;
            myLen += from.as_long_long(); // add a negative
            from = 0;
            copy = true;
         }

         if (from + myLen >= numSamples) {
            // Near the end of the clip, pad right with zeroes as needed.
            // newlen is bounded by myLen:
            auto newlen = ( numSamples - from ).as_size_t();
            for (decltype(myLen) ii = newlen; ii < myLen; ++ii)
               adj[ii] = 0;
            myLen = newlen;
            copy = true;
         }

         if (myLen > 0) {
            constexpr auto iChannel = 0u;
            constexpr auto mayThrow = false; // Don't throw just for display
            mSampleCacheHolder.emplace(
               clip.GetSampleView(from, myLen, mayThrow));
            floats.resize(myLen);
            mSampleCacheHolder->Copy(floats.data(), myLen);
            useBuffer = floats.data();
            if (copy) {
               if (useBuffer)
                  memcpy(adj, useBuffer, myLen * sizeof(float));
               else
                  memset(adj, 0, myLen * sizeof(float));
            }
         }
      }

      if (copy || !useBuffer)
         useBuffer = scratch;

      if (autocorrelation) {
         // not reassignment, xx is surely within bounds.
         wxASSERT(xx >= 0);
         float *const results = &out[nBins * xx];
         // This function does not mutate useBuffer
         ComputeSpectrum(
            useBuffer, windowSizeSetting, windowSizeSetting, results,
            autocorrelation, settings.windowType);
      }
      else if (reassignment) {
         static const double epsilon = 1e-16;
         const auto hFFT = settings.hFFT.get();

         float *const scratch2 = scratch + fftLen;
         std::copy(scratch, scratch2, scratch2);

         float *const scratch3 = scratch + 2 * fftLen;
         std::copy(scratch, scratch2, scratch3);

         {
            const float *const window = settings.window.get();
            for (size_t ii = 0; ii < fftLen; ++ii)
               scratch[ii] *= window[ii];
            RealFFTf(scratch, hFFT);
         }

         {
            const float *const dWindow = settings.dWindow.get();
            for (size_t ii = 0; ii < fftLen; ++ii)
               scratch2[ii] *= dWindow[ii];
            RealFFTf(scratch2, hFFT);
         }

         {
            const float *const tWindow = settings.tWindow.get();
            for (size_t ii = 0; ii < fftLen; ++ii)
               scratch3[ii] *= tWindow[ii];
            RealFFTf(scratch3, hFFT);
         }

         for (size_t ii = 0; ii < hFFT->Points; ++ii) {
            const int index = hFFT->BitReversed[ii];
            const float
               denomRe = scratch[index],
               denomIm = ii == 0 ? 0 : scratch[index + 1];
            const double power = denomRe * denomRe + denomIm * denomIm;
            if (power < epsilon)
               // Avoid dividing by near-zero below
               continue;

            double freqCorrection;
            {
               const double multiplier = -(fftLen / (2.0f * M_PI));
               const float
                  numRe = scratch2[index],
                  numIm = ii == 0 ? 0 : scratch2[index + 1];
               // Find complex quotient --
               // Which means, multiply numerator by conjugate of denominator,
               // then divide by norm squared of denominator --
               // Then just take its imaginary part.
               const double
                  quotIm = (-numRe * denomIm + numIm * denomRe) / power;
               // With appropriate multiplier, that becomes the correction of
               // the frequency bin.
               freqCorrection = multiplier * quotIm;
            }

            const int bin = (int)((int)ii + freqCorrection + 0.5f);
            // Must check if correction takes bin out of bounds, above or below!
            // bin is signed!
            if (bin >= 0 && bin < (int)hFFT->Points) {
               double timeCorrection;
               {
                  const float
                     numRe = scratch3[index],
                     numIm = ii == 0 ? 0 : scratch3[index + 1];
                  // Find another complex quotient --
                  // Then just take its real part.
                  // The result has sample interval as unit.
                  timeCorrection =
                     (numRe * denomRe + numIm * denomIm) / power;
               }

               // PRL: timeCorrection is scaled to the clip's raw sample rate,
               // without the stretching ratio correction for real time. We want
               // to find the correct X coordinate for that.
               int correctedX = (floor(
                  0.5 + xx + timeCorrection * pixelsPerSecond / sampleRate));
               if (correctedX >= lowerBoundX && correctedX < upperBoundX)
               {
                  result = true;

                  // This is non-negative, because bin and correctedX are
                  auto ind = (int)nBins * correctedX + bin;
#ifdef _OPENMP
                  // This assignment can race if index reaches into another thread's bins.
                  // The probability of a race very low, so this carries little overhead,
                  // about 5% slower vs allowing it to race.
                  #pragma omp atomic update
#endif
                  out[ind] += power;
               }
            }
         }
      }
      else {
         // not reassignment, xx is surely within bounds.
         wxASSERT(xx >= 0);
         float *const results = &out[nBins * xx];

         // Do the FFT.  Note that useBuffer is multiplied by the window,
         // and the window is initialized with leading and trailing zeroes
         // when there is padding.  Therefore we did not need to reinitialize
         // the part of useBuffer in the padding zones.

         // This function mutates useBuffer
         ComputeSpectrumUsingRealFFTf
            (useBuffer, settings.hFFT.get(), settings.window.get(), fftLen, results);
         if (!gainFactors.empty()) {
            // Apply a frequency-dependent gain factor
            for (size_t ii = 0; ii < nBins; ++ii)
               results[ii] += gainFactors[ii];
         }
      }
   }

   return result;
}

bool SpecCache::CalculateOneWaveletSpectrum(
   const SpectrogramSettings& settings, const WaveChannelInterval& clip,
   const int xx, double pixelsPerSecond, int lowerBoundX, int upperBoundX,
   const std::vector<float>& gainFactors,
   float* __restrict out) const
{
   bool result = false;
   sampleCount from;

   const auto numSamples = clip.GetSequence().GetNumSamples();
   const auto sampleRate = clip.GetRate();
   const auto stretchRatio = clip.GetStretchRatio();
   const auto samplesPerPixel = sampleRate / pixelsPerSecond / stretchRatio;
   const size_t nBins = settings.NBins();
   float *const results = &out[nBins * xx];

   // not reassignment, xx is surely within bounds.
   wxASSERT(xx >= 0);
   if (xx > (int)len)
      from = sampleCount(where[len].as_double() + (xx - len) * samplesPerPixel);
   else
      from = where[xx];

   if (from < 0 || from >= numSamples) {
      if (xx >= 0 && xx < (int)len) {
         // Pixel column is out of bounds of the clip!  Should not happen.
         std::fill(results, results + nBins, 0.0f);
      }
   }
   else
   {
      // Iterate frequencies in turn
      // Note that as opposed to Fourier Transform, using wavelets implies a window length that varies with frequency
      // We extract samples corresponding to max wavelet length (the first)
    
      // Locate longest wavelet (first one)
      const auto longestWaveletLen = settings.waveletMaxLength;
      wxASSERT(longestWaveletLen);
       
      auto myLen = 2 * longestWaveletLen - 1;
      std::vector<float> scratch(myLen);

      // Take a window of the track centered at this sample.
      from -= longestWaveletLen;
      float * adj = &scratch[0];
      if (from < 0) {
         // Near the start of the clip, pad left with zeroes as needed.
         for (auto ii = from; ii < 0; ++ii)
             *adj++ = 0;
         myLen += from.as_long_long(); // add a negative
         from = 0;
      }
      if (from + myLen >= numSamples) {
         // Near the end of the clip, pad right with zeroes as needed.
         // newlen is bounded by myLen:
         auto newlen = ( numSamples - from ).as_size_t();
         for (decltype(myLen) ii = newlen; ii < myLen; ++ii)
             adj[ii] = 0;
         myLen = newlen;
      }
      std::vector<float> floats;
      if (myLen > 0) {
         constexpr auto iChannel = 0u;
         constexpr auto mayThrow = false; // Don't throw just for display
         mSampleCacheHolder.emplace(
             clip.GetSampleView(from, myLen, mayThrow));
         floats.resize(myLen);
         mSampleCacheHolder->Copy(floats.data(), myLen);
         float *useBuffer = floats.data();
         memcpy(adj, useBuffer, myLen * sizeof(float));
      }

      // Done preparing samples. Now onward with calculations
      const float * middleSample = &scratch[longestWaveletLen - 1];
      for (size_t iBin = 0; iBin < nBins; iBin++)
      {
          if (settings.waveletSizes[iBin] == 0)
          {
             results[iBin] = -160.0;
             continue;
          }
         
          const float *right = middleSample;
          const float *left = middleSample;
          // Do the inner product
          const float * wRe = &settings.waveletsRe[iBin][0];
          const float * wIm = &settings.waveletsIm[iBin][0];
          double sumRe = *middleSample * *wRe;
          double sumIm = 0.0;
          wRe++, wIm++, right++, left--;
          const auto halfLen = settings.waveletSizes[iBin];
          for (auto ii = 1; ii < halfLen; ii++)
          {
              sumRe +=  (*right + *left) * *wRe;
              sumIm +=  (*left - *right) * *wIm;
              wRe++, wIm++, right++, left--;
          }

          // Calculate magnitude
          float power = sumRe * sumRe + sumIm * sumIm;
          
          
          // Do the log thing
          if (power <= 0)
             power = -160.0;
          else
             power = 10.0*log10f(power);

          results[iBin] = power;
      }


       if (!gainFactors.empty()) {
          // Apply a frequency-dependent gain factor
          for (size_t ii = 0; ii < nBins; ++ii)
             results[ii] += gainFactors[ii];
       }
       result = true;
   }

   return result;
}

void SpecCache::Grow(
   size_t len_, SpectrogramSettings& settings, double samplesPerPixel,
   double start_)
{
   settings.CacheWindows();

   // len columns, and so many rows, column-major.
   // Don't take column literally -- this isn't pixel data yet, it's the
   // raw data to be mapped onto the display.
   freq.resize(len_ * settings.NBins());

   // Sample counts corresponding to the columns, and to one past the end.
   where.resize(len_ + 1);

   len = len_;
   algorithm = settings.algorithm;
   spp = samplesPerPixel;
   start = start_;
   windowType = settings.windowType;
   windowSize = settings.WindowSize();
   zeroPaddingFactor = settings.ZeroPaddingFactor();
   frequencyGain = settings.frequencyGain;
}

void SpecCache::Populate(
   const SpectrogramSettings& settings, const WaveChannelInterval& clip,
   int copyBegin, int copyEnd, size_t numPixels, double pixelsPerSecond)
{
   const auto sampleRate = clip.GetRate();
   const int &frequencyGainSetting = settings.frequencyGain;
   const size_t windowSizeSetting = settings.WindowSize();
   const bool autocorrelation =
      settings.algorithm == SpectrogramSettings::algPitchEAC;
   const bool reassignment =
      settings.algorithm == SpectrogramSettings::algReassignment;
   const size_t zeroPaddingFactorSetting = settings.ZeroPaddingFactor();

   // FFT length may be longer than the window of samples that affect results
   // because of zero padding done for increased frequency resolution
   const size_t fftLen = windowSizeSetting * zeroPaddingFactorSetting;
   const auto nBins = settings.NBins();

   const size_t bufferSize = fftLen;
   const size_t scratchSize = reassignment ? 3 * bufferSize : bufferSize;
   std::vector<float> scratch(scratchSize);

   std::vector<float> gainFactors;
   if (!autocorrelation)
      ComputeSpectrogramGainFactors(
         fftLen, sampleRate, frequencyGainSetting, gainFactors);

   // Loop over the ranges before and after the copied portion and compute anew.
   // One of the ranges may be empty.
   for (int jj = 0; jj < 2; ++jj) {
      const int lowerBoundX = jj == 0 ? 0 : copyEnd;
      const int upperBoundX = jj == 0 ? copyBegin : numPixels;

// todo(mhodgkinson): I don't find an option to define _OPENMP anywhere. Is this
// still of interest?
#ifdef _OPENMP
      // Storage for mutable per-thread data.
      // private clause ensures one copy per thread
      struct ThreadLocalStorage {
         ThreadLocalStorage()  { }
         ~ThreadLocalStorage() { }

         void init(SampleTrackCache &waveTrackCache, size_t scratchSize) {
            if (!cache) {
               cache = std::make_unique<SampleTrackCache>(waveTrackCache.GetTrack());
               scratch.resize(scratchSize);
            }
         }
         std::unique_ptr<SampleTrackCache> cache;
         std::vector<float> scratch;
      } tls;

      #pragma omp parallel for private(tls)
#endif
      for (auto xx = lowerBoundX; xx < upperBoundX; ++xx)
      {
         if (isWaveletAnalysis(settings))
         {
             CalculateOneWaveletSpectrum(settings, clip, xx, pixelsPerSecond, lowerBoundX, upperBoundX,
                                         gainFactors, &freq[0]);
         }
         else
         {
#ifdef _OPENMP
             tls.init(waveTrackCache, scratchSize);
             SampleTrackCache& cache = *tls.cache;
             float* buffer = &tls.scratch[0];
#else
             float* buffer = &scratch[0];
#endif
             CalculateOneSpectrum(
                         settings, clip, xx, pixelsPerSecond, lowerBoundX, upperBoundX,
                         gainFactors, buffer, &freq[0]);
         }
      }

      if (reassignment) {
         // Need to look beyond the edges of the range to accumulate more
         // time reassignments.
         // I'm not sure what's a good stopping criterion?
         auto xx = lowerBoundX;
         const double pixelsPerSample =
            pixelsPerSecond * clip.GetStretchRatio() / sampleRate;
         const int limit = std::min((int)(0.5 + fftLen * pixelsPerSample), 100);
         for (int ii = 0; ii < limit; ++ii)
         {
            const bool result = CalculateOneSpectrum(
               settings, clip, --xx, pixelsPerSecond, lowerBoundX, upperBoundX,
               gainFactors, &scratch[0], &freq[0]);
            if (!result)
               break;
         }

         xx = upperBoundX;
         for (int ii = 0; ii < limit; ++ii)
         {
            const bool result = CalculateOneSpectrum(
               settings, clip, xx++, pixelsPerSecond, lowerBoundX, upperBoundX,
               gainFactors, &scratch[0], &freq[0]);
            if (!result)
               break;
         }

         // Now Convert to dB terms.  Do this only after accumulating
         // power values, which may cross columns with the time correction.
#ifdef _OPENMP
         #pragma omp parallel for
#endif
         for (xx = lowerBoundX; xx < upperBoundX; ++xx) {
            float *const results = &freq[nBins * xx];
            for (size_t ii = 0; ii < nBins; ++ii) {
               float &power = results[ii];
               if (power <= 0)
                  power = -160.0;
               else
                  power = 10.0*log10f(power);
            }
            if (!gainFactors.empty()) {
               // Apply a frequency-dependent gain factor
               for (size_t ii = 0; ii < nBins; ++ii)
                  results[ii] += gainFactors[ii];
            }
         }
      }
   }
}

bool WaveClipSpectrumCache::GetSpectrogram(
   const WaveChannelInterval &clip,
   const float*& spectrogram, SpectrogramSettings& settings,
   const sampleCount*& where, size_t numPixels, double t0,
   double pixelsPerSecond)

{
   auto &mSpecCache = mSpecCaches[clip.GetChannelIndex()];

   const auto sampleRate = clip.GetRate();
   const auto stretchRatio = clip.GetStretchRatio();
   const auto samplesPerPixel = sampleRate / pixelsPerSecond / stretchRatio;

   //Trim offset comparison failure forces spectrogram cache rebuild
   //and skip copying "unchanged" data after clip border was trimmed.
   bool match = mSpecCache && mSpecCache->leftTrim == clip.GetTrimLeft() &&
                mSpecCache->rightTrim == clip.GetTrimRight() &&
                mSpecCache->len > 0 &&
                mSpecCache->Matches(mDirty, samplesPerPixel, settings);

   if (match && mSpecCache->start == t0 && mSpecCache->len >= numPixels)
   {
      spectrogram = &mSpecCache->freq[0];
      where = &mSpecCache->where[0];

      return false;  //hit cache completely
   }

   // Caching is not implemented for reassignment, unless for
   // a complete hit, because of the complications of time reassignment
   if (settings.algorithm == SpectrogramSettings::algReassignment)
      match = false;

   // Free the cache when it won't cause a major stutter.
   // If the window size changed, we know there is nothing to be copied
   // If we zoomed out, or resized, we can give up memory. But not too much -
   // up to 2x extra is needed at the end of the clip to prevent stutter.
   if (mSpecCache->freq.capacity() > 2.1 * mSpecCache->freq.size() ||
       mSpecCache->windowSize*mSpecCache->zeroPaddingFactor <
       settings.WindowSize()*settings.ZeroPaddingFactor())
   {
      match = false;
      mSpecCache = std::make_unique<SpecCache>();
   }

   int oldX0 = 0;
   double correction = 0.0;

   int copyBegin = 0, copyEnd = 0;
   if (match) {
      WaveClipUIUtilities::findCorrection(
         mSpecCache->where, mSpecCache->len, numPixels, t0, sampleRate,
         stretchRatio, samplesPerPixel, oldX0, correction);
      // Remember our first pixel maps to oldX0 in the old cache,
      // possibly out of bounds.
      // For what range of pixels can data be copied?
      int oldLen = mSpecCache->len;
      copyBegin = std::min(oldLen, std::max(0, -oldX0));
      copyEnd = std::min(oldLen, std::max(0, oldLen - oldX0));
   }

   mSpecCache->leftTrim = clip.GetTrimLeft();
   mSpecCache->rightTrim = clip.GetTrimRight();
   auto nBins = settings.NBins();

   // Optimization: if the old cache is good and overlaps
   // with the current one, re-use as much of the cache as
   // possible
   if (copyEnd > copyBegin)
   {
      // memmove is required since dst/src overlap
      memmove(&mSpecCache->freq[nBins * copyBegin],
               &mSpecCache->freq[nBins * (copyBegin + oldX0)],
               nBins * (copyEnd - copyBegin) * sizeof(float));
   }

   // Resize the cache, keep the contents unchanged.
   mSpecCache->Grow(numPixels, settings, samplesPerPixel, t0);

   // Reassignment accumulates, so it needs a zeroed buffer
   if (settings.algorithm == SpectrogramSettings::algReassignment)
   {
      // The cache could theoretically copy from the middle, resulting
      // in two regions to update. This won't happen in zoom, since
      // old cache doesn't match. It won't happen in resize, since the
      // spectrum view is pinned to left side of window.
      wxASSERT(
         (copyBegin >= 0 && copyEnd == (int)numPixels) || // copied the end
         (copyBegin == 0 && copyEnd <= (int)numPixels)    // copied the beginning
      );

      int zeroBegin = copyBegin > 0 ? 0 : copyEnd-copyBegin;
      int zeroEnd = copyBegin > 0 ? copyBegin : numPixels;

      memset(&mSpecCache->freq[nBins*zeroBegin], 0, nBins*(zeroEnd-zeroBegin)*sizeof(float));
   }

   // purposely offset the display 1/2 sample to the left (as compared
   // to waveform display) to properly center response of the FFT
   constexpr auto addBias = true;
   WaveClipUIUtilities::fillWhere(
      mSpecCache->where, numPixels, addBias, correction, t0, sampleRate,
      stretchRatio, samplesPerPixel);

   mSpecCache->Populate(settings, clip, copyBegin, copyEnd, numPixels, pixelsPerSecond);
   mSpecCache->dirty = mDirty;
   spectrogram = &mSpecCache->freq[0];
   where = &mSpecCache->where[0];

   return true;
}

WaveClipSpectrumCache::WaveClipSpectrumCache(size_t nChannels)
   : mSpecCaches(nChannels)
   , mSpecPxCaches(nChannels)
{
   for (auto &pCache : mSpecCaches)
      pCache = std::make_unique<SpecCache>();
}

WaveClipSpectrumCache::~WaveClipSpectrumCache()
{
}

std::unique_ptr<WaveClipListener> WaveClipSpectrumCache::Clone() const
{
   // Don't need to copy contents
   return std::make_unique<WaveClipSpectrumCache>(mSpecCaches.size());
}

static WaveClip::Attachments::RegisteredFactory sKeyS{ [](WaveClip &clip){
   return std::make_unique<WaveClipSpectrumCache>(clip.NChannels());
} };

WaveClipSpectrumCache &
WaveClipSpectrumCache::Get(const WaveChannelInterval &clip)
{
   return const_cast<WaveClip&>(clip.GetClip()) // Consider it mutable data
      .Attachments::Get< WaveClipSpectrumCache >( sKeyS );
}

void WaveClipSpectrumCache::MarkChanged() noexcept
{
   ++mDirty;
}

void WaveClipSpectrumCache::Invalidate()
{
   // Invalidate the spectrum display cache
   for (auto &pCache : mSpecCaches)
      pCache = std::make_unique<SpecCache>();
}

void WaveClipSpectrumCache::MakeStereo(WaveClipListener &&other, bool)
{
   auto pOther = dynamic_cast<WaveClipSpectrumCache *>(&other);
   assert(pOther); // precondition
   mSpecCaches.push_back(move(pOther->mSpecCaches[0]));
   mSpecPxCaches.push_back(move(pOther->mSpecPxCaches[0]));
}

void WaveClipSpectrumCache::SwapChannels()
{
   mSpecCaches.resize(2);
   std::swap(mSpecCaches[0], mSpecCaches[1]);
   mSpecPxCaches.resize(2);
   std::swap(mSpecPxCaches[0], mSpecPxCaches[1]);
}

void WaveClipSpectrumCache::Erase(size_t index)
{
   if (index < mSpecCaches.size())
      mSpecCaches.erase(mSpecCaches.begin() + index);
   if (index < mSpecPxCaches.size())
      mSpecPxCaches.erase(mSpecPxCaches.begin() + index);
}
