overhauled render classes to support video AND audio

Major refactoring work to try sharing as much code as possible between the
video renderers and audio renderers, as well as make them as
platform-independent as possible.

app/render/backend/videorenderbackend.cpp

@@ -36,11 +36,6 @@ VideoRenderBackend::VideoRenderBackend(QObject *parent) :
   SetCacheName("Test");
 }
 
-VideoRenderBackend::~VideoRenderBackend()
-{
-  Close();
-}
-
 void VideoRenderBackend::InvalidateCache(const rational &start_range, const rational &end_range)
 {
   if (!params_.is_valid()) {
@@ -51,10 +46,10 @@ void VideoRenderBackend::InvalidateCache(const rational &start_range, const rati
   rational start_range_adj = qMax(rational(0), start_range);
   rational end_range_adj = qMin(viewer_node()->Length(), end_range);
 
-  qDebug() << "Cache invalidated between"
+  /*qDebug() << "Cache invalidated between"
            << start_range_adj.toDouble()
            << "and"
-           << end_range_adj.toDouble();
+           << end_range_adj.toDouble();*/
 
   // Snap start_range to timebase
   double start_range_dbl = start_range_adj.toDouble();
@@ -100,6 +95,9 @@ void VideoRenderBackend::InvalidateCache(const rational &start_range, const rati
     }
   }
 
+  // Remove frames after this time code if it's changed
+  frame_cache_.Truncate(viewer_node()->Length());
+
   CacheNext();
 }
 
@@ -160,6 +158,14 @@ void VideoRenderBackend::CacheIDChangedEvent(const QString &id)
   frame_cache_.SetCacheID(id);
 }
 
+void VideoRenderBackend::ConnectWorkerToThis(RenderWorker *processor)
+{
+  connect(processor, SIGNAL(CompletedFrame(NodeDependency, QByteArray)), this, SLOT(ThreadCompletedFrame(NodeDependency, QByteArray)));
+  connect(processor, SIGNAL(HashAlreadyBeingCached()), this, SLOT(ThreadSkippedFrame()));
+  connect(processor, SIGNAL(CompletedDownload(NodeDependency, QByteArray)), this, SLOT(ThreadCompletedDownload(NodeDependency, QByteArray)));
+  connect(processor, SIGNAL(HashAlreadyExists(NodeDependency, QByteArray)), this, SLOT(ThreadHashAlreadyExists(NodeDependency, QByteArray)));
+}
+
 VideoRenderFrameCache *VideoRenderBackend::frame_cache()
 {
   return &frame_cache_;
@@ -207,3 +213,8 @@ const char *VideoRenderBackend::GetCachedFrame(const rational &time)
 
   return nullptr;
 }
+
+NodeInput *VideoRenderBackend::GetDependentInput()
+{
+  return viewer_node()->texture_input();
+}