timeline/various: implemented block copy/paste

Implemented the ability to copy/paste blocks/clips in the timeline. This did
require some large scale changes and reworking of the copy/paste system
introduced a few commits ago, but should be largely functional now.

app/common/xmlutils.cpp

@@ -1,16 +1,17 @@
 #include "xmlutils.h"
 
 #include "node/factory.h"
+#include "widget/nodeview/nodeviewundo.h"
 
 Node* XMLLoadNode(QXmlStreamReader* reader) {
   QString node_id;
+  quintptr node_ptr = 0;
 
   XMLAttributeLoop(reader, attr) {
-    if (attr.name() == "id") {
+    if (attr.name() == QStringLiteral("id")) {
       node_id = attr.value().toString();
-
-      // Currently the only thing we need
-      break;
+    } else if (attr.name() == QStringLiteral("ptr")) {
+      node_ptr = attr.value().toULongLong();
     }
   }
 
@@ -21,20 +22,26 @@ Node* XMLLoadNode(QXmlStreamReader* reader) {
 
   Node* node = NodeFactory::CreateFromID(node_id);
 
-  if (!node) {
+  if (node) {
+    node->setProperty("xml_ptr", node_ptr);
+  } else {
     qWarning() << "Failed to load" << node_id << "- no node with that ID is installed";
   }
 
   return node;
 }
 
-void XMLConnectNodes(const QHash<quintptr, NodeOutput*>& output_ptrs, const QList<NodeParam::SerializedConnection>& desired_connections)
+void XMLConnectNodes(const QHash<quintptr, NodeOutput*>& output_ptrs, const QList<XMLNodeData::SerializedConnection>& desired_connections, QUndoCommand *command)
 {
-  foreach (const NodeParam::SerializedConnection& con, desired_connections) {
+  foreach (const XMLNodeData::SerializedConnection& con, desired_connections) {
     NodeOutput* out = output_ptrs.value(con.output);
 
     if (out) {
-      NodeParam::ConnectEdge(out, con.input);
+      if (command) {
+        new NodeEdgeAddCommand(out, con.input, command);
+      } else {
+        NodeParam::ConnectEdge(out, con.input);
+      }
     }
   }
 }