Added deletable bool API on the BaseNode

Author: alelievr

Assets/Examples/DefaultNodes/Nodes/OutputNode.cs

@@ -0,0 +1,21 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+using GraphProcessor;
+using System.Linq;
+
+[System.Serializable, NodeMenuItem("Custom/OutputNode")]
+public class OutputNode : BaseNode
+{
+	[Input(name = "In")]
+    public float                input;
+
+	public override string		name => "OutputNode";
+
+	public override bool		deletable => false;
+
+	protected override void Process()
+	{
+		// Do stuff
+	}
+}

Assets/Examples/DefaultNodes/Nodes/OutputNode.cs.meta

@@ -70,6 +70,9 @@ public void Initialize(BaseGraphView owner, BaseNode node)
 			nodeTarget = node;
 			this.owner = owner;
 
+			if (!node.deletable)
+				capabilities &= ~Capabilities.Deletable;
+
 			owner.computeOrderUpdated += ComputeOrderUpdatedCallback;
 			node.onMessageAdded += AddMessageView;
 			node.onMessageRemoved += RemoveMessageView;

Assets/com.alelievr.NodeGraphProcessor/Editor/Views/BaseNodeView.cs

@@ -47,6 +47,9 @@ public abstract class BaseNode
 		/// <summary>Show the node controlContainer only when the mouse is over the node</summary>
 		public virtual bool			showControlsOnHover => false;
 
+		/// <summary>True if the node can be deleted, false otherwise</summary>
+		public virtual bool			deletable => true;
+
 		/// <summary>
 		/// Container of input ports
 		/// </summary>