ShaderGroup.cs

using System;
using System.Linq;
using UnityEditor.Experimental.GraphView;
using UnityEditor.Graphing;
using UnityEngine;
using UnityEngine.UIElements;
using ContextualMenuManipulator = UnityEngine.UIElements.ContextualMenuManipulator;
using ContextualMenuPopulateEvent = UnityEngine.UIElements.ContextualMenuPopulateEvent;
using VisualElementExtensions = UnityEngine.UIElements.VisualElementExtensions;

namespace UnityEditor.ShaderGraph
{
    sealed class ShaderGroup : Group
    {
        GraphData m_Graph;
        public new GroupData userData
        {
            get => (GroupData)base.userData;
            set => base.userData = value;
        }

        public ShaderGroup()
        {
            VisualElementExtensions.AddManipulator(this, new ContextualMenuManipulator(BuildContextualMenu));
            style.backgroundColor = new StyleColor(new Color(25 / 255f, 25 / 255f, 25 / 255f, 25 / 255f));
            capabilities |= Capabilities.Ascendable;
        }

        public void BuildContextualMenu(ContextualMenuPopulateEvent evt)
        {
        }

        public override bool AcceptsElement(GraphElement element, ref string reasonWhyNotAccepted)
        {
            if (element is StackNode stackNode)
            {
                reasonWhyNotAccepted = "Vertex and Pixel Stacks cannot be grouped";
                return false;
            }

            var nodeView = element as IShaderNodeView;
            if (nodeView == null)
            {
                // sticky notes are not nodes, but still groupable
                return true;
            }

            if (nodeView.node is BlockNode)
            {
                reasonWhyNotAccepted = "Block Nodes cannot be grouped";
                return false;
            }

            return true;
        }

        protected override void SetScopePositionOnly(Rect newPos)
        {
            base.SetScopePositionOnly(newPos);

            userData.position = newPos.position;
        }

    }
}