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/renderworker.h

@@ -3,6 +3,7 @@
 
 #include <QObject>
 
+#include "node/block/block.h"
 #include "node/node.h"
 #include "decodercache.h"
 
@@ -27,8 +28,36 @@ public slots:
 
   virtual void RenderAsSibling(NodeDependency dep) = 0;
 
+signals:
+  void RequestSibling(NodeDependency path);
+
+  void CompletedCache(NodeDependency dep);
+
 protected:
-  Node* ValidateBlock(Node* n, const rational& time);
+  /**
+   * @brief Returns the block in a sequence that is active at a given time
+   *
+   * Blocks are connected to each other previous/next to create a BlockList or a sequence of blocks. The block that
+   * is currently "active" depends on the time and only one block in a track can be active at any given time.
+   *
+   * Calling this function with a block and a time will traverse the provided block's track to find the block that will
+   * be active at that time. The block must be valid (non-null) and the time must be valid (>= 0).
+   *
+   * This function may return the same block that it was called with. It will never return nullptr.
+   */
+  Block *ValidateBlock(Block* block, const rational& time);
+
+  /**
+   * @brief Returns all the blocks that could be active within a range of time
+   *
+   * Similar to ValidateBlock() but rather than returning one block for a single time, this function returns a list of
+   * blocks that could be active within a range of time.
+   *
+   * The block must be valid (non-null) and the time must be valid (>= 0).
+   *
+   * The list will always contain at least one entry.
+   */
+  QList<Block*> ValidateBlockRange(Block* n, const TimeRange& range);
 
   virtual bool InitInternal() = 0;
 
@@ -36,11 +65,21 @@ protected:
 
   virtual void RenderInternal(const NodeDependency& path);
 
+  virtual bool OutputIsAccelerated(NodeOutput *output) = 0;
+
+  virtual QVariant RunNodeAccelerated(NodeOutput *output) = 0;
+
   StreamPtr ResolveStreamFromInput(NodeInput* input);
   DecoderPtr ResolveDecoderFromInput(NodeInput* input);
 
   QList<Node*> ListNodeAndAllDependencies(Node* n);
 
+  QList<NodeInput*> ProcessNodeInputsForTime(Node* n, const TimeRange& time);
+
+  virtual QVariant FrameToValue(FramePtr frame) = 0;
+
+  QVariant ProcessNodeNormally(const NodeDependency &dep);
+
   DecoderCache* decoder_cache();
 
   QAtomicInt working_;