export: use viewer params not export params

Fixes #1703

app/task/render/render.cpp

@@ -26,10 +26,7 @@
 
 namespace olive {
 
-RenderTask::RenderTask(ViewerOutput *viewer, const VideoParams &vparams, const AudioParams &aparams) :
-  viewer_(viewer),
-  video_params_(vparams),
-  audio_params_(aparams),
+RenderTask::RenderTask() :
   running_tickets_(0),
   native_progress_signalling_(true)
 {

app/task/render/render.h

@@ -36,7 +36,7 @@ class RenderTask : public Task
 {
   Q_OBJECT
 public:
-  RenderTask(ViewerOutput* viewer, const VideoParams &vparams, const AudioParams &aparams);
+  RenderTask();
 
   virtual ~RenderTask() override;
 
@@ -62,16 +62,31 @@ protected:
     return viewer_;
   }
 
+  void set_viewer(ViewerOutput *v)
+  {
+    viewer_ = v;
+  }
+
   const VideoParams& video_params() const
   {
     return video_params_;
   }
 
+  void set_video_params(const VideoParams& video_params)
+  {
+    video_params_ = video_params;
+  }
+
   const AudioParams& audio_params() const
   {
     return audio_params_;
   }
 
+  void set_audio_params(const AudioParams& audio_params)
+  {
+    audio_params_ = audio_params;
+  }
+
   virtual void CancelEvent() override
   {
     finished_watcher_mutex_.lock();