Improved node collapsing performance a lot

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Drawing/Drawer/NodeDrawer.cs

         {
             var headerData = nodeData.elements.OfType<HeaderDrawData>().FirstOrDefault();
 
-            if (headerData == m_HeaderData || headerData == null)
+            if (m_HeaderData == headerData)
-                return;
+                m_HeaderDrawer.Touch(ChangeType.Repaint);
-
-            if (m_HeaderData != null)
-                RemoveChild(m_HeaderDrawer);
-
-            m_HeaderDrawer = new HeaderDrawer(headerData);
-            InsertChild(0, m_HeaderDrawer);
-            m_HeaderData = headerData;
+            else if (m_HeaderData != null)
+            {
+                m_HeaderDrawer.dataProvider = headerData;
+                m_HeaderData = headerData;
+            }
+            else
+            {
+                m_HeaderDrawer = new HeaderDrawer(headerData);
+                InsertChild(0, m_HeaderDrawer);
+                m_HeaderData = headerData;
+            }
         }
 
         private void AddSlots(NodeDrawData nodeData)
                 ClearChildren();
                 AddContainers();
                 return;
+            }
+
+            if (!nodeData.expanded)
+            {
+                if (!classList.Contains("collapsed"))
+                    AddToClassList("collapsed");
+            }
+            else
+            {
+                if (classList.Contains("collapsed"))
+                    RemoveFromClassList("collapsed");
             }
 
             AddHeader(nodeData);

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Drawing/Manipulators/NodeExpander.cs

                     {
                         this.ReleaseCapture();
                         var withinInitialTarget = initialTarget != null && initialTarget.ContainsPoint(evt.mousePosition);
-                        if (true || withinInitialTarget)
+                        if (withinInitialTarget)
                         {
                             data.expanded = !data.expanded;
                         }

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Styles/MaterialGraph.uss

     position-type: absolute;
     position-top: 0;
     position-left: 5;
-    background-color: #000;
+	height: 14;
 }
 
 MaterialNodeDrawer #slots {