Version: 2018.1
public bool useGUILayout ;

Description

Disabling this lets you skip the GUI layout phase.

It can only be used if you do not use GUI.Window and GUILayout inside of this OnGUI call.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour { public void Start() { //Disabling this lets you skip the GUI layout phase. useGUILayout = false; } }