nodes: optimize node graph changes by only updating from inputs that changed

A huge optimization that ensures only the parts of a node graph that have
changed get pushed to the renderer. For thread-safety, the node graph is
copied elsewhere so that users can make changes asynchronously and the graph
can update when its threads are ready. Up until now, if an input value changed,
every node's values would be re-copied, or worse, if a connection was changed,
the entire graph would be recopied. This has been negligible in testing since
we've been largely testing with small graphs, but for massive projects, it's
important that this be as optimized as possible.

app/node/node.h

@@ -29,7 +29,6 @@
 #include "codec/samplebuffer.h"
 #include "common/rational.h"
 #include "common/xmlutils.h"
-#include "node/dependency.h"
 #include "node/input.h"
 #include "node/inputarray.h"
 #include "node/output.h"
@@ -196,9 +195,14 @@ public:
   virtual void ProcessSamples(const NodeValueDatabase &values, const AudioRenderingParams& params, const SampleBufferPtr input, SampleBufferPtr output, int index) const;
 
   /**
-   * @brief Returns the parameter with the specified ID (or nullptr if it doesn't exist)
+   * @brief Returns the input with the specified ID (or nullptr if it doesn't exist)
    */
-  NodeParam* GetParameterWithID(const QString& id) const;
+  NodeInput* GetInputWithID(const QString& id) const;
+
+  /**
+   * @brief Returns the output with the specified ID (or nullptr if it doesn't exist)
+   */
+  NodeOutput* GetOutputWithID(const QString& id) const;
 
   /**
    * @brief Returns whether this Node outputs data to the Node `n` in any way
@@ -261,12 +265,12 @@ public:
    * the DAG. Even if the time needs to be transformed somehow (e.g. converting media time to sequence time), you can
    * call this function with transformed time and relay the signal that way.
    */
-  virtual void InvalidateCache(const rational& start_range, const rational& end_range, NodeInput* from = nullptr);
+  virtual void InvalidateCache(const TimeRange& range, NodeInput* from, NodeInput* source);
 
   /**
    * @brief Signal through node graph to only invalidate frames that are currently visible on a ViewerWidget
    */
-  virtual void InvalidateVisible(NodeInput *from);
+  virtual void InvalidateVisible(NodeInput *from, NodeInput* source);
 
   /**
    * @brief Adjusts time that should be sent to nodes connected to certain inputs.
@@ -288,11 +292,6 @@ public:
    */
   static void CopyInputs(Node* source, Node* destination, bool include_connections = true);
 
-  /**
-   * @brief For a list of copies nodes, this function will duplicate all the connections in the source list to the destination list
-   */
-  static void DuplicateConnectionsBetweenLists(const QList<Node*>& source, const QList<Node *> &destination);
-
   /**
    * @brief Return whether this Node can be deleted or not
    */
@@ -358,9 +357,7 @@ protected:
 
   void ClearCachedValuesInParameters(const rational& start_range, const rational& end_range);
 
-  void SendInvalidateCache(const rational& start_range, const rational& end_range);
-
-  virtual void DependentEdgeChanged(NodeInput* from);
+  void SendInvalidateCache(const TimeRange &range, NodeInput *source);
 
   virtual void LoadInternal(QXmlStreamReader* reader, XMLNodeData& xml_node_data);
 
@@ -403,9 +400,7 @@ private:
 
   void DisconnectInput(NodeInput* input);
 
-  static void TraverseInputInternal(QList<Node*>& list, NodeInput* input, bool traverse, bool exclusive_only);
-
-  static void GetDependenciesInternal(const Node* n, QList<Node*>& list, bool traverse, bool exclusive_only);
+  QList<Node *> GetDependenciesInternal(bool traverse, bool exclusive_only) const;
 
   QList<NodeParam *> params_;
 
@@ -425,7 +420,7 @@ private:
   QPointF position_;
 
 private slots:
-  void InputChanged(rational start, rational end);
+  void InputChanged(const TimeRange &range);
 
   void InputConnectionChanged(NodeEdgePtr edge);