audio renderer/timeline: pass through channel count of waveform visualizations

app/audio/sumsamples.cpp

@@ -79,3 +79,8 @@ void SampleSummer::ClampMinMax(SampleSummer::Sum &sum, T value)
     sum.max = value;
   }
 }
+
+SampleSummer::Info::Info()
+{
+  channels = 0;
+}

app/audio/sumsamples.h

@@ -24,6 +24,12 @@ public:
 
   static QVector<Sum> ReSumSamples(const SampleSummer::Sum* samples, int nb_samples, int nb_channels);
 
+  struct Info {
+    Info();
+
+    int channels;
+  };
+
 private:
   template <typename T>
   static QVector<Sum> SumSamplesInternal(const T* samples, int nb_samples, int nb_channels);

app/render/backend/audiorenderworker.cpp

@@ -80,9 +80,10 @@ NodeValueTable AudioRenderWorker::RenderBlock(const TrackOutput *track, const Ti
       // Save waveform to file
       Block* src_block = static_cast<Block*>(copy_map_->value(b));
       QDir local_appdata_dir(Config::Current()["DiskCachePath"].toString());
-      QDir waveform_loc = local_appdata_dir.filePath("waveform");
+      QDir waveform_loc = local_appdata_dir.filePath(QStringLiteral("waveform"));
       waveform_loc.mkpath(".");
-      QFile wave_file(waveform_loc.filePath(QString::number(reinterpret_cast<quintptr>(src_block))));
+      QString wave_fn(waveform_loc.filePath(QString::number(reinterpret_cast<quintptr>(src_block))));
+      QFile wave_file(wave_fn);
 
       if (wave_file.open(QFile::ReadWrite)) {
         // We use S32 as a size-compatible substitute for SampleSummer::Sum which is 4 bytes in size
@@ -110,6 +111,17 @@ NodeValueTable AudioRenderWorker::RenderBlock(const TrackOutput *track, const Ti
 
         wave_file.close();
 
+        // Write metadata about this waveform file
+        QFile wave_metadata(wave_fn.append(QStringLiteral(".meta")));
+        if (wave_metadata.open(QFile::WriteOnly)) {
+          SampleSummer::Info info;
+          info.channels = audio_params_.channel_count();
+
+          wave_metadata.write(reinterpret_cast<char*>(&info), sizeof(SampleSummer::Info));
+
+          wave_metadata.close();
+        }
+
         if (src_block->type() == Block::kClip) {
           emit static_cast<ClipBlock*>(src_block)->PreviewUpdated();
         }

app/widget/timelinewidget/view/timelineviewblockitem.cpp

@@ -87,21 +87,32 @@ void TimelineViewBlockItem::paint(QPainter *painter, const QStyleOptionGraphicsI
     }
 
     // Draw waveform if one is available
-    QFile wave_file(QDir(QDir(Config::Current()["DiskCachePath"].toString()).filePath("waveform")).filePath(QString::number(reinterpret_cast<quintptr>(block_))));
+    QString wave_fn = QDir(QDir(Config::Current()["DiskCachePath"].toString()).filePath("waveform")).filePath(QString::number(reinterpret_cast<quintptr>(block_)));
+    QFile wave_file(wave_fn);
     if (wave_file.open(QFile::ReadOnly)){
       painter->setPen(QColor(64, 64, 64));
 
       QByteArray w = wave_file.readAll();
 
-      // FIXME: Hardcoded channel count
-      AudioWaveformView::DrawWaveform(painter,
-                                      rect().toRect(),
-                                      this->GetScale(),
-                                      reinterpret_cast<const SampleSummer::Sum*>(w.constData()),
-                                      w.size() / sizeof(SampleSummer::Sum),
-                                      2);
-
       wave_file.close();
+
+      // Read metadata
+      SampleSummer::Info info;
+      QFile wave_meta(wave_fn.append(QStringLiteral(".meta")));
+      if (wave_meta.open(QFile::ReadOnly)) {
+        wave_meta.read(reinterpret_cast<char*>(&info), sizeof(SampleSummer::Info));
+        wave_meta.close();
+      }
+
+      // Prevent divide by zero
+      if (info.channels) {
+        AudioWaveformView::DrawWaveform(painter,
+                                        rect().toRect(),
+                                        this->GetScale(),
+                                        reinterpret_cast<const SampleSummer::Sum*>(w.constData()),
+                                        w.size() / sizeof(SampleSummer::Sum),
+                                        info.channels);
+      }
     }
 
     painter->setPen(Qt::white);