audiovisualwaveform: keep track of length

Useful to determine how long the visual waveform is.

app/audio/audiovisualwaveform.cpp

@@ -121,6 +121,9 @@ void AudioVisualWaveform::OverwriteSamples(SampleBufferPtr samples, int sample_r
                                input_start, input_length, start, current_mipmap->first.toDouble(),
                                current_mipmap->second);
   }
+
+  rational sample_length(samples->sample_count(), sample_rate);
+  length_ = qMax(length_, start + sample_length);
 }
 
 void AudioVisualWaveform::OverwriteSums(const AudioVisualWaveform &sums, const rational &dest, const rational& offset, const rational& length)
@@ -155,6 +158,8 @@ void AudioVisualWaveform::OverwriteSums(const AudioVisualWaveform &sums, const r
            reinterpret_cast<const char*>(their_arr.constData()) + their_start_index * sizeof(SamplePerChannel),
            copy_len * sizeof(SamplePerChannel));
   }
+
+  length_ = qMax(length_, dest + length);
 }
 
 void AudioVisualWaveform::Shift(const rational &from, const rational &to)
@@ -201,6 +206,8 @@ void AudioVisualWaveform::Shift(const rational &from, const rational &to)
       memset(reinterpret_cast<char*>(&data[from_index]), 0, distance * sizeof(SamplePerChannel));
     }
   }
+
+  length_ += (to-from);
 }
 
 AudioVisualWaveform::Sample AudioVisualWaveform::GetSummaryFromTime(const rational &start, const rational &length) const

app/audio/audiovisualwaveform.h

@@ -55,6 +55,11 @@ public:
     channels_ = channels;
   }
 
+  const rational& length() const
+  {
+    return length_;
+  }
+
   /**
    * @brief Writes samples into the visual waveform buffer
    *
@@ -112,6 +117,8 @@ private:
 
   std::map<rational, Sample> mipmapped_data_;
 
+  rational length_;
+
 };
 
 }