xNode/Scripts/Editor/NodeEditorGUI.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;
using System;

/// <summary> Contains GUI methods </summary>
public partial class NodeEditorWindow {

    private void OnGUI() {
        Event e = Event.current;
        Matrix4x4 m = GUI.matrix;
        Controls();

        if (e.type != EventType.MouseMove && e.type != EventType.MouseDrag) {
            DrawGrid(position, zoom, panOffset);
            DrawNodes();
            DrawConnections();
            DrawDraggedConnection();
            DrawToolbar();
        }

        GUI.matrix = m;
    }

    public static void DrawConnection(Vector2 from, Vector2 to, Color col) {
        Handles.DrawBezier(from, to, from, to, col, new Texture2D(2, 2), 2);
    }

    public static void BeginZoomed(Rect rect, float zoom) {
        GUI.EndClip();
            
        GUIUtility.ScaleAroundPivot(Vector2.one / zoom, rect.size * 0.5f);
        Vector4 padding = new Vector4(0, 22, 0, 0);
        padding *= zoom;
        GUI.BeginClip(new Rect(
            -((rect.width * zoom) - rect.width) * 0.5f,
            -(((rect.height * zoom) - rect.height) * 0.5f) + (22 * zoom),
            rect.width * zoom,
            rect.height * zoom));
    }

    public static void EndZoomed(Rect rect, float zoom) {
        GUIUtility.ScaleAroundPivot(Vector2.one * zoom, rect.size * 0.5f);
        Vector3 offset = new Vector3(
            (((rect.width * zoom) - rect.width) * 0.5f),
            (((rect.height * zoom) - rect.height) * 0.5f) + (-22 * zoom)+22,
            0);
        GUI.matrix = Matrix4x4.TRS(offset, Quaternion.identity, Vector3.one);
    }

    public static void DrawGrid(Rect rect, float zoom, Vector2 panOffset) {

        rect.position = Vector2.zero;

        Vector2 center = rect.size / 2f;
        Texture2D gridTex = gridTexture;
        Texture2D crossTex = crossTexture;
            
        // Offset from origin in tile units
        float xOffset = -(center.x * zoom + panOffset.x) / gridTex.width;
        float yOffset = ((center.y - rect.size.y) * zoom + panOffset.y) / gridTex.height;

        Vector2 tileOffset = new Vector2(xOffset, yOffset);

        // Amount of tiles
        float tileAmountX = Mathf.Round(rect.size.x * zoom) / gridTex.width;
        float tileAmountY = Mathf.Round(rect.size.y * zoom) / gridTex.height;

        Vector2 tileAmount = new Vector2(tileAmountX, tileAmountY);

        // Draw tiled background
        GUI.DrawTextureWithTexCoords(rect, gridTex, new Rect(tileOffset, tileAmount));
        GUI.DrawTextureWithTexCoords(rect, crossTex, new Rect(tileOffset + new Vector2(0.5f,0.5f), tileAmount));
    }

    public void DrawToolbar() {
        EditorGUILayout.BeginHorizontal("Toolbar");

        if (DropdownButton("File", 50)) FileContextMenu();
        if (DropdownButton("Edit", 50)) EditContextMenu();
        if (DropdownButton("View", 50)) { }
        if (DropdownButton("Settings", 70)) { }
        if (DropdownButton("Tools", 50)) { }
        if (IsHoveringNode) {
            GUILayout.Space(20);
            string hoverInfo = hoveredNode.GetType().ToString();
            if (IsHoveringPort) hoverInfo += " > "+hoveredPort.name;
            GUILayout.Label(hoverInfo);
        }

        // Make the toolbar extend all throughout the window extension.
        GUILayout.FlexibleSpace();

        EditorGUILayout.EndHorizontal();
    }

    public static bool DropdownButton(string name, float width) {
        return GUILayout.Button(name, EditorStyles.toolbarDropDown, GUILayout.Width(width));
    }

    public void RightClickContextMenu() {
        GenericMenu contextMenu = new GenericMenu();

        if (hoveredNode != null) {
            Node node = hoveredNode;
            contextMenu.AddItem(new GUIContent("Remove"), false, () => graph.RemoveNode(node));
        }
        else {
            Vector2 pos = WindowToGridPosition(Event.current.mousePosition);
            for (int i = 0; i < nodeTypes.Length; i++) {
                Type type = nodeTypes[i];
                contextMenu.AddItem(new GUIContent(nodeTypes[i].ToString()), false, () => {
                    CreateNode(type, pos);
                });
            }
        }
        contextMenu.DropDown(new Rect(Event.current.mousePosition, Vector2.zero));
    }

    public static void FileContextMenu() {
        GenericMenu contextMenu = new GenericMenu();
        contextMenu.AddItem(new GUIContent("Create New"), false, null);
        contextMenu.AddItem(new GUIContent("Load"), false, null);

        contextMenu.AddSeparator("");
        contextMenu.AddItem(new GUIContent("Save"), false, null);
        contextMenu.AddItem(new GUIContent("Save As"), false, null);

        contextMenu.DropDown(new Rect(5f, 17f, 0f, 0f));
    }

    public void EditContextMenu() {
        GenericMenu contextMenu = new GenericMenu();
        contextMenu.AddItem(new GUIContent("Clear"), false, () => graph.Clear());

        contextMenu.DropDown(new Rect(5f, 17f, 0f, 0f));
    }

    public  void DrawConnection(Vector2 startPoint, Vector2 endPoint) {
        startPoint = GridToWindowPosition(startPoint);
        endPoint = GridToWindowPosition(endPoint);

        Vector2 startTangent = startPoint;
        if (startPoint.x < endPoint.x) startTangent.x = Mathf.LerpUnclamped(startPoint.x, endPoint.x, 0.7f);
        else startTangent.x = Mathf.LerpUnclamped(startPoint.x, endPoint.x, -0.7f);

        Vector2 endTangent = endPoint;
        if (startPoint.x > endPoint.x) endTangent.x = Mathf.LerpUnclamped(endPoint.x, startPoint.x, -0.7f);
        else endTangent.x = Mathf.LerpUnclamped(endPoint.x, startPoint.x, 0.7f);

        Handles.DrawBezier(startPoint, endPoint, startTangent, endTangent, Color.gray, null, 4);
        Handles.DrawBezier(startPoint, endPoint, startTangent, endTangent, Color.white, null, 2);
    }
}