rendertask: return errors and respond appropriately

Fixes #1348

app/task/export/export.cpp

@@ -156,7 +156,7 @@ bool ExportTask::Run()
   return success;
 }
 
-void ExportTask::FrameDownloaded(FramePtr f, const QByteArray &hash, const QVector<rational> &times)
+bool ExportTask::FrameDownloaded(FramePtr f, const QByteArray &hash, const QVector<rational> &times)
 {
   Q_UNUSED(hash)
 
@@ -180,14 +180,19 @@ void ExportTask::FrameDownloaded(FramePtr f, const QByteArray &hash, const QVect
 
     // Unfortunately this can't be done in another thread since the frames need to be sent
     // one after the other chronologically.
-    encoder_->WriteFrame(time_map_.take(real_time), real_time);
+    if (!encoder_->WriteFrame(time_map_.take(real_time), real_time)) {
+      SetError(encoder_->GetError());
+      return false;
+    }
 
     frame_time_++;
     emit ProgressChanged(double(frame_time_) / double(GetTotalNumberOfFrames()));
   }
+
+  return true;
 }
 
-void ExportTask::AudioDownloaded(const TimeRange &range, SampleBufferPtr samples)
+bool ExportTask::AudioDownloaded(const TimeRange &range, SampleBufferPtr samples)
 {
   TimeRange adjusted_range = range;
 
@@ -196,20 +201,33 @@ void ExportTask::AudioDownloaded(const TimeRange &range, SampleBufferPtr samples
   }
 
   if (adjusted_range.in() == audio_time_) {
-    WriteAudioLoop(adjusted_range, samples);
+    if (!WriteAudioLoop(adjusted_range, samples)) {
+      return false;
+    }
   } else {
     audio_map_.insert(adjusted_range, samples);
   }
+
+  return true;
 }
 
-void ExportTask::EncodeSubtitle(const SubtitleBlock *sub)
+bool ExportTask::EncodeSubtitle(const SubtitleBlock *sub)
 {
-  encoder_->WriteSubtitle(sub);
+  if (!encoder_->WriteSubtitle(sub)) {
+    SetError(encoder_->GetError());
+    return false;
+  } else {
+    return true;
+  }
 }
 
-void ExportTask::WriteAudioLoop(const TimeRange& time, SampleBufferPtr samples)
+bool ExportTask::WriteAudioLoop(const TimeRange& time, SampleBufferPtr samples)
 {
-  encoder_->WriteAudio(samples);
+  if (!encoder_->WriteAudio(samples)) {
+    SetError(encoder_->GetError());
+    return false;
+  }
+
   audio_time_ = time.out();
 
   for (auto it=audio_map_.begin(); it!=audio_map_.end(); it++) {
@@ -221,12 +239,16 @@ void ExportTask::WriteAudioLoop(const TimeRange& time, SampleBufferPtr samples)
       audio_map_.erase(it);
 
       // Call recursively to write the next sample buffer
-      WriteAudioLoop(t, s);
+      if (!WriteAudioLoop(t, s)) {
+        return false;
+      }
 
       // Break out of loop
       break;
     }
   }
+
+  return true;
 }
 
 }