Specify whether to throw on bad read in Mixer and WaveTrackCache...

... Do throw when exporting or mixing-and-rendering; don't if playing back or
drawing a spectrogram, but then just use zeroes.

src/AudioIO.cpp

@@ -1883,6 +1883,8 @@ int AudioIO::StartStream(const ConstWaveTrackArray &playbackTracks,
                // MB: use normal time for the end time, not warped time!
                mPlaybackMixers[i] = std::make_unique<Mixer>
                   (WaveTrackConstArray{ mPlaybackTracks[i] },
+                  // Don't throw for read errors, just play silence:
+                  false,
                   warpOptions,
                   mT0, mT1, 1,
                   playbackMixBufferSize, false,

src/Mix.cpp

@@ -160,6 +160,8 @@ void MixAndRender(TrackList *tracks, TrackFactory *trackFactory,
    }
 
    Mixer mixer(waveArray,
+      // Throw to abort mix-and-render if read fails:
+      true,
       Mixer::WarpOptions(tracks->GetTimeTrack()),
       startTime, endTime, mono ? 1 : 2, maxBlockLen, false,
       rate, format);
@@ -239,6 +241,7 @@ Mixer::WarpOptions::WarpOptions(double min, double max)
 }
 
 Mixer::Mixer(const WaveTrackConstArray &inputTracks,
+             bool mayThrow,
              const WarpOptions &warpOptions,
              double startTime, double stopTime,
              unsigned numOutChannels, size_t outBufferSize, bool outInterleaved,
@@ -254,6 +257,8 @@ Mixer::Mixer(const WaveTrackConstArray &inputTracks,
 
    , mNumChannels{ static_cast<size_t>(numOutChannels) }
    , mGains{ mNumChannels }
+
+   , mMayThrow{ mayThrow }
 {
    mHighQuality = highQuality;
    mInputTrack.reinit(mNumInputTracks);
@@ -434,7 +439,7 @@ size_t Mixer::MixVariableRates(int *channelFlags, WaveTrackCache &cache,
          // Nothing to do if past end of play interval
          if (getLen > 0) {
             if (backwards) {
-               auto results = cache.Get(floatSample, *pos - (getLen - 1), getLen);
+               auto results = cache.Get(floatSample, *pos - (getLen - 1), getLen, mMayThrow);
                if (results)
                   memcpy(&queue[*queueLen], results, sizeof(float) * getLen);
                else
@@ -446,7 +451,7 @@ size_t Mixer::MixVariableRates(int *channelFlags, WaveTrackCache &cache,
                *pos -= getLen;
             }
             else {
-               auto results = cache.Get(floatSample, *pos, getLen);
+               auto results = cache.Get(floatSample, *pos, getLen, mMayThrow);
                if (results)
                   memcpy(&queue[*queueLen], results, sizeof(float) * getLen);
                else
@@ -554,7 +559,7 @@ size_t Mixer::MixSameRate(int *channelFlags, WaveTrackCache &cache,
    slen = std::min(slen, mMaxOut);
 
    if (backwards) {
-      auto results = cache.Get(floatSample, *pos - (slen - 1), slen);
+      auto results = cache.Get(floatSample, *pos - (slen - 1), slen, mMayThrow);
       if (results)
          memcpy(mFloatBuffer.get(), results, sizeof(float) * slen);
       else
@@ -567,7 +572,7 @@ size_t Mixer::MixSameRate(int *channelFlags, WaveTrackCache &cache,
       *pos -= slen;
    }
    else {
-      auto results = cache.Get(floatSample, *pos, slen);
+      auto results = cache.Get(floatSample, *pos, slen, mMayThrow);
       if (results)
          memcpy(mFloatBuffer.get(), results, sizeof(float) * slen);
       else

src/Mix.h

@@ -91,7 +91,7 @@ class AUDACITY_DLL_API Mixer {
    // Constructor / Destructor
    //
 
-   Mixer(const WaveTrackConstArray &inputTracks,
+   Mixer(const WaveTrackConstArray &inputTracks, bool mayThrow,
          const WarpOptions &warpOptions,
          double startTime, double stopTime,
          unsigned numOutChannels, size_t outBufferSize, bool outInterleaved,
@@ -183,6 +183,8 @@ class AUDACITY_DLL_API Mixer {
    double           mRate;
    double           mSpeed;
    bool             mHighQuality;
+
+   bool             mMayThrow;
 };
 
 #endif

src/WaveClip.cpp

@@ -901,7 +901,9 @@ bool SpecCache::CalculateOneSpectrum
                floatSample, sampleCount(
                   floor(0.5 + from.as_double() + offset * rate)
                ),
-               myLen)
+               myLen,
+               // Don't throw in this drawing operation
+               false)
             );
 
             if (copy) {

src/WaveTrack.cpp

@@ -2621,7 +2621,7 @@ void WaveTrackCache::SetTrack(const WaveTrack *pTrack)
 }
 
 constSamplePtr WaveTrackCache::Get(sampleFormat format,
-   sampleCount start, size_t len)
+   sampleCount start, size_t len, bool mayThrow)
 {
    if (format == floatSample && len > 0) {
       const auto end = start + len;
@@ -2671,7 +2671,9 @@ constSamplePtr WaveTrackCache::Get(sampleFormat format,
          if (start0 >= 0) {
             const auto len0 = mPTrack->GetBestBlockSize(start0);
             wxASSERT(len0 <= mBufferSize);
-            if (!mPTrack->Get(samplePtr(mBuffers[0].data.get()), floatSample, start0, len0))
+            if (!mPTrack->Get(
+                  samplePtr(mBuffers[0].data.get()), floatSample, start0, len0,
+                  fillZero, mayThrow))
                return 0;
             mBuffers[0].start = start0;
             mBuffers[0].len = len0;

src/WaveTrack.h

@@ -648,7 +648,8 @@ public:
    // Returns null on failure
    // Returned pointer may be invalidated if Get is called again
    // Do not DELETE[] the pointer
-   constSamplePtr Get(sampleFormat format, sampleCount start, size_t len);
+   constSamplePtr Get(
+      sampleFormat format, sampleCount start, size_t len, bool mayThrow);
 
 private:
    void Free();

src/export/Export.cpp

@@ -246,6 +246,8 @@ std::unique_ptr<Mixer> ExportPlugin::CreateMixer(const WaveTrackConstArray &inpu
 {
    // MB: the stop time should not be warped, this was a bug.
    return std::make_unique<Mixer>(inputTracks,
+                  // Throw, to stop exporting, if read fails:
+                  true,
                   Mixer::WarpOptions(timeTrack),
                   startTime, stopTime,
                   numOutChannels, outBufferSize, outInterleaved,