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/input.cpp

@@ -60,7 +60,7 @@ NodeInput::NodeInput(const QString &id, const NodeParam::DataType &type) :
   Init(type);
 }
 
-bool NodeInput::IsArray()
+bool NodeInput::IsArray() const
 {
   return false;
 }
@@ -273,7 +273,6 @@ void NodeInput::SaveConnections(QXmlStreamWriter *writer) const
   writer->writeEndElement(); // connections
 }
 
-
 const NodeParam::DataType &NodeInput::data_type() const
 {
   return data_type_;
@@ -363,6 +362,45 @@ QVariant NodeInput::StringToValue(const DataType& data_type, const QString &stri
   }
 }
 
+void NodeInput::GetDependencies(QList<Node *> &list, bool traverse, bool exclusive_only) const
+{
+  if (IsConnected()
+      && (get_connected_output()->edges().size() == 1 || !exclusive_only)) {
+    Node* connected = get_connected_node();
+
+    if (!list.contains(connected)) {
+      list.append(connected);
+
+      if (traverse) {
+        QList<NodeInput*> connected_inputs = connected->GetInputsIncludingArrays();
+
+        foreach (NodeInput* i, connected_inputs) {
+          i->GetDependencies(list, traverse, exclusive_only);
+        }
+      }
+    }
+  }
+}
+
+QList<Node *> NodeInput::GetDependencies(bool traverse, bool exclusive_only) const
+{
+  QList<Node *> list;
+
+  GetDependencies(list, traverse, exclusive_only);
+
+  return list;
+}
+
+QList<Node *> NodeInput::GetExclusiveDependencies() const
+{
+  return GetDependencies(true, true);
+}
+
+QList<Node *> NodeInput::GetImmediateDependencies() const
+{
+  return GetDependencies(false, false);
+}
+
 QVariant NodeInput::StringToValue(const QString &string, QList<XMLNodeData::FootageConnection>& footage_connections)
 {
   if (data_type_ == NodeParam::kFootage) {
@@ -757,7 +795,7 @@ void NodeInput::KeyframeBezierInChanged()
     start = keyframe_tracks_.at(key->track()).at(keyframe_index - 1)->time();
   }
 
-  emit ValueChanged(start, end);
+  emit ValueChanged(TimeRange(start, end));
 }
 
 void NodeInput::KeyframeBezierOutChanged()
@@ -772,7 +810,7 @@ void NodeInput::KeyframeBezierOutChanged()
     end = keyframe_tracks_.at(key->track()).at(keyframe_index + 1)->time();
   }
 
-  emit ValueChanged(start, end);
+  emit ValueChanged(TimeRange(start, end));
 }
 
 int NodeInput::FindIndexOfKeyframeFromRawPtr(NodeKeyframe *raw_ptr) const
@@ -855,7 +893,7 @@ TimeRange NodeInput::get_range_around_index(int index, int track) const
 
 void NodeInput::emit_time_range(const TimeRange &range)
 {
-  emit ValueChanged(range.in(), range.out());
+  emit ValueChanged(range);
 }
 
 void NodeInput::emit_range_affected_by_keyframe(NodeKeyframe *key)
@@ -915,7 +953,7 @@ void NodeInput::set_standard_value(const QVariant &value, int track)
 
   if (is_using_standard_value(track)) {
     // If this standard value is being used, we need to send a value changed signal
-    emit ValueChanged(RATIONAL_MIN, RATIONAL_MAX);
+    emit ValueChanged(TimeRange(RATIONAL_MIN, RATIONAL_MAX));
   }
 }
 
@@ -964,7 +1002,7 @@ void NodeInput::CopyValues(NodeInput *source, NodeInput *dest, bool include_conn
     }
   }
 
-  emit dest->ValueChanged(RATIONAL_MIN, RATIONAL_MAX);
+  emit dest->ValueChanged(TimeRange(RATIONAL_MIN, RATIONAL_MAX));
 }
 
 void NodeInput::set_property(const QString &key, const QVariant &value)