Add [RequireNode] attribute to graphs (#254)

Scripts/Editor/NodeEditor.cs

@@ -67,7 +67,7 @@ namespace XNodeEditor {
             serializedObject.ApplyModifiedProperties();
 
 #if ODIN_INSPECTOR
-            // Call repaint so that the graph window elements respond properly to layout changes coming from Odin    
+            // Call repaint so that the graph window elements respond properly to layout changes coming from Odin
             if (GUIHelper.RepaintRequested) {
                 GUIHelper.ClearRepaintRequest();
                 window.Repaint();
@@ -106,17 +106,22 @@ namespace XNodeEditor {
 
         /// <summary> Add items for the context menu when right-clicking this node. Override to add custom menu items. </summary>
         public virtual void AddContextMenuItems(GenericMenu menu) {
+            bool canRemove = true;
             // Actions if only one node is selected
             if (Selection.objects.Length == 1 && Selection.activeObject is XNode.Node) {
                 XNode.Node node = Selection.activeObject as XNode.Node;
                 menu.AddItem(new GUIContent("Move To Top"), false, () => NodeEditorWindow.current.MoveNodeToTop(node));
                 menu.AddItem(new GUIContent("Rename"), false, NodeEditorWindow.current.RenameSelectedNode);
+
+                canRemove = NodeGraphEditor.GetEditor(node.graph, NodeEditorWindow.current).CanRemove(node);
             }
 
             // Add actions to any number of selected nodes
             menu.AddItem(new GUIContent("Copy"), false, NodeEditorWindow.current.CopySelectedNodes);
             menu.AddItem(new GUIContent("Duplicate"), false, NodeEditorWindow.current.DuplicateSelectedNodes);
-            menu.AddItem(new GUIContent("Remove"), false, NodeEditorWindow.current.RemoveSelectedNodes);
+
+            if (canRemove) menu.AddItem(new GUIContent("Remove"), false, NodeEditorWindow.current.RemoveSelectedNodes);
+            else menu.AddItem(new GUIContent("Remove"), false, null);
 
             // Custom sctions if only one node is selected
             if (Selection.objects.Length == 1 && Selection.activeObject is XNode.Node) {
@@ -132,11 +137,10 @@ namespace XNodeEditor {
             OnRename();
             AssetDatabase.ImportAsset(AssetDatabase.GetAssetPath(target));
         }
-        
+
         /// <summary> Called after this node's name has changed. </summary>
         public virtual void OnRename() { }
-        
-        
+
         [AttributeUsage(AttributeTargets.Class)]
         public class CustomNodeEditorAttribute : Attribute,
         XNodeEditor.Internal.NodeEditorBase<NodeEditor, NodeEditor.CustomNodeEditorAttribute, XNode.Node>.INodeEditorAttrib {
@@ -152,4 +156,4 @@ namespace XNodeEditor {
             }
         }
     }
-}
+}

Scripts/Editor/NodeGraphEditor.cs

@@ -187,8 +187,25 @@ namespace XNodeEditor {
             return node;
         }
 
+        /// <summary> Return false for nodes that can't be removed </summary>
+        public virtual bool CanRemove(XNode.Node node) {
+            // Check graph attributes to see if this node is required
+            Type graphType = target.GetType();
+            XNode.NodeGraph.RequireNodeAttribute[] attribs = Array.ConvertAll(
+                graphType.GetCustomAttributes(typeof(XNode.NodeGraph.RequireNodeAttribute), true), x => x as XNode.NodeGraph.RequireNodeAttribute);
+            if (attribs.Any(x => x.Requires(node.GetType()))) {
+                if (target.nodes.Count(x => x.GetType() == node.GetType()) <= 1) {
+                    return false;
+                }
+            }
+            return true;
+        }
+
         /// <summary> Safely remove a node and all its connections. </summary>
         public virtual void RemoveNode(XNode.Node node) {
+            if (!CanRemove(node)) return;
+
+            // Remove the node
             Undo.RecordObject(node, "Delete Node");
             Undo.RecordObject(target, "Delete Node");
             foreach (var port in node.Ports)

Scripts/Editor/NodeGraphImporter.cs

@@ -0,0 +1,45 @@
+using System;
+using System.IO;
+using System.Linq;
+using UnityEditor;
+using UnityEditor.Experimental.AssetImporters;
+using UnityEngine;
+using XNode;
+
+namespace XNodeEditor {
+    /// <summary> Deals with modified assets </summary>
+    class NodeGraphImporter : AssetPostprocessor {
+        private static void OnPostprocessAllAssets(string[] importedAssets, string[] deletedAssets, string[] movedAssets, string[] movedFromAssetPaths) {
+            foreach (string path in importedAssets) {
+                // Skip processing anything without the .asset extension
+                if (Path.GetExtension(path) != ".asset") continue;
+
+                // Get the object that is requested for deletion
+                NodeGraph graph = AssetDatabase.LoadAssetAtPath<NodeGraph>(path);
+                if (graph == null) continue;
+
+                // Get attributes
+                Type graphType = graph.GetType();
+                NodeGraph.RequireNodeAttribute[] attribs = Array.ConvertAll(
+                    graphType.GetCustomAttributes(typeof(NodeGraph.RequireNodeAttribute), true), x => x as NodeGraph.RequireNodeAttribute);
+
+                Vector2 position = Vector2.zero;
+                foreach (NodeGraph.RequireNodeAttribute attrib in attribs) {
+                    if (attrib.type0 != null) AddRequired(graph, attrib.type0, ref position);
+                    if (attrib.type1 != null) AddRequired(graph, attrib.type1, ref position);
+                    if (attrib.type2 != null) AddRequired(graph, attrib.type2, ref position);
+                }
+            }
+        }
+
+        private static void AddRequired(NodeGraph graph, Type type, ref Vector2 position) {
+            if (!graph.nodes.Any(x => x.GetType() == type)) {
+                XNode.Node node = graph.AddNode(type);
+                node.position = position;
+                position.x += 200;
+                if (node.name == null || node.name.Trim() == "") node.name = NodeEditorUtilities.NodeDefaultName(type);
+                if (!string.IsNullOrEmpty(AssetDatabase.GetAssetPath(graph))) AssetDatabase.AddObjectToAsset(node, graph);
+            }
+        }
+    }
+}

Scripts/Editor/NodeGraphImporter.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: 7a816f2790bf3da48a2d6d0035ebc9a0
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Scripts/NodeGraph.cs

@@ -81,5 +81,44 @@ namespace XNode {
             // Remove all nodes prior to graph destruction
             Clear();
         }
+
+#region Attributes
+        /// <summary> Automatically ensures the existance of a certain node type, and prevents it from being deleted. </summary>
+        [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
+        public class RequireNodeAttribute : Attribute {
+            public Type type0;
+            public Type type1;
+            public Type type2;
+
+            /// <summary> Automatically ensures the existance of a certain node type, and prevents it from being deleted </summary>
+            public RequireNodeAttribute(Type type) {
+                this.type0 = type;
+                this.type1 = null;
+                this.type2 = null;
+            }
+
+            /// <summary> Automatically ensures the existance of a certain node type, and prevents it from being deleted </summary>
+            public RequireNodeAttribute(Type type, Type type2) {
+                this.type0 = type;
+                this.type1 = type2;
+                this.type2 = null;
+            }
+
+            /// <summary> Automatically ensures the existance of a certain node type, and prevents it from being deleted </summary>
+            public RequireNodeAttribute(Type type, Type type2, Type type3) {
+                this.type0 = type;
+                this.type1 = type2;
+                this.type2 = type3;
+            }
+
+            public bool Requires(Type type) {
+                if (type == null) return false;
+                if (type == type0) return true;
+                else if (type == type1) return true;
+                else if (type == type2) return true;
+                return false;
+            }
+        }
+#endregion
     }
 }