DYN-6449 Graph Loading Performance Improving

Using Jetbrains dotTrace I noticed that creating the NodeView for Watch nodes was taking too much time when loading the Graph (due that was creating the PreviewControl), then due that Watch nodes doesn't have Preview I've added code for preventing the creation of the PreviewControl, this improved the Graph loading time.
Also I've noticed that the call nodeView.UpdateLayout() was consuming loading time so I've modified the code in a way that the method call will be executed asynchronous in background.

src/DynamoCoreWpf/NodeViewCustomization/NodeViewCustomizations/FunctionNodeViewCustomization.cs

@@ -1,4 +1,6 @@
+using System;
 using System.Windows.Controls;
+using System.Windows.Threading;
 using Dynamo.Controls;
 using Dynamo.Graph.Nodes.CustomNodes;
 using Dynamo.Graph.Workspaces;
@@ -60,7 +62,10 @@ public void CustomizeView(Function function, NodeView nodeView)
             publishCustomNodeItem.Command = nodeView.ViewModel.DynamoViewModel.PublishSelectedNodesCommand;
             publishCustomNodeItem.CommandParameter = functionNodeModel;
 
-            nodeView.UpdateLayout();
+            nodeView.Dispatcher.BeginInvoke(new Action(() =>
+            {
+                nodeView.UpdateLayout();
+            }), DispatcherPriority.Background);
         }
 
         private void EditCustomNodeProperties()
@@ -136,4 +141,4 @@ public void Dispose()
 
         }
     }
-}
+}

src/DynamoCoreWpf/Views/Core/NodeView.xaml.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics;
@@ -551,6 +551,9 @@ private void OnNodeViewMouseLeave(object sender, MouseEventArgs e)
         {
             ViewModel.ZIndex = oldZIndex;
 
+            //Watch nodes doesn't have Preview so we should avoid to use any method/property in PreviewControl class due that Preview is created automatically
+            if (ViewModel.NodeModel != null && ViewModel.NodeModel is CoreNodeModels.Watch) return;
+
             // If mouse in over node/preview control or preview control is pined, we can not hide preview control.
             if (IsMouseOver || PreviewControl.IsMouseOver || PreviewControl.StaysOpen || IsMouseInsidePreview(e) ||
                 (Mouse.Captured is DragCanvas && IsMouseInsideNodeOrPreview(e.GetPosition(this)))) return;
@@ -731,6 +734,9 @@ internal void TogglePreviewControlAllowance()
         {
             previewEnabled = !previewEnabled;
 
+            //Watch nodes doesn't have Preview so we should avoid to use any method/property in PreviewControl class due that Preview is created automatically
+            if (ViewModel.NodeModel != null && ViewModel.NodeModel is CoreNodeModels.Watch) return;
+
             if (previewEnabled == false && !PreviewControl.StaysOpen)
             {
                 if (PreviewControl.IsExpanded)

src/Libraries/PythonNodeModelsWpf/PythonNode.cs

@@ -7,6 +7,7 @@
 using System.Windows.Controls;
 using System.Windows.Data;
 using System.Windows.Input;
+using System.Windows.Threading;
 using Dynamo.Configuration;
 using Dynamo.Controls;
 using Dynamo.Graph.Nodes;
@@ -99,8 +100,11 @@ public void CustomizeView(PythonNode nodeModel, NodeView nodeView)
             PythonEngineManager.Instance.AvailableEngines.CollectionChanged += PythonEnginesChanged;
 
             nodeView.MainContextMenu.Items.Add(learnMoreItem);
-
-            nodeView.UpdateLayout();
+            nodeView.Dispatcher.BeginInvoke(new Action( () =>
+            {
+                nodeView.UpdateLayout();
+            }), DispatcherPriority.Background);
+
 
             nodeView.MouseDown += View_MouseDown;
             nodeModel.DeletionStarted += NodeModel_DeletionStarted;