SceneInformationsWidget

using UnityEngine;
using UnityEditor;
using System.Linq;
using UnityEngine.SceneManagement;
using System.Globalization;


namespace OddTales.Framework.Core.EditorExtension
{
    // InitializeOnLoad : force constructor call
    [InitializeOnLoad]
    public static class SceneInformationsWidget
    {
        private static bool enable = false;
        private static bool initialized = false;

        // Needed for bold (rich text) and font color
        private static GUIStyle textStyle;

        private static bool selectionChanged = false, hierarchyChanged = false;

        private static int numberOfSelected = 0, numberOfChildren = 0, numberOfChildrenRecursive = 0;
        private static int numberOfRootGameObjects = 0, numberOfGamesObjectsInScene = 0;
        private static int numberOfVerticesInChildren = 0, numberOfTrianglesInChildren = 0;

        // Needed to display numbers with good formatting
        private static NumberFormatInfo integerFormatInfo;

        // Construtor
        static SceneInformationsWidget()
        {
            enable = EditorPrefs.GetBool(SceneInformationsKey("Display"), false);
            if (enable) Init();
        }

        static void Init()
        {
            initialized = true;

            SceneView.onSceneGUIDelegate -= SceneInformationsWidget.OnSceneGUI;
            SceneView.onSceneGUIDelegate += SceneInformationsWidget.OnSceneGUI;

            Selection.selectionChanged -= OnSelectionChanged;
            Selection.selectionChanged += OnSelectionChanged;

            EditorApplication.hierarchyChanged -= OnHierarchyChanged;
            EditorApplication.hierarchyChanged += OnHierarchyChanged;

            selectionChanged = hierarchyChanged = true; 

            integerFormatInfo = new NumberFormatInfo();
            integerFormatInfo.NumberGroupSeparator = " ";

            SceneView.RepaintAll();
        }

        [MenuItem("Tools/Scene Widgets/Display Scene Informations")]
        public static void Enable()
        {
            enable = !enable;
            EditorPrefs.SetBool(SceneInformationsKey("Display"), enable);
            Menu.SetChecked("Tools/Display Scene Informations", enable);

            if (enable && !initialized) Init();
            else SceneView.RepaintAll();
        }

        // Menu.SetChecked doesn't work in constructor (Unity bug ?). Must use it in MenuItem validation method
        [MenuItem("Tools/Display Scene Informations", true)]
        public static bool EnableValidation()
        {
            Menu.SetChecked("Tools/Scene Widgets/Display Scene Informations", enable);
            return true;
        }

        private static string SceneInformationsKey(string key)
        {
            return "NyxFramework_ScenesInformationsWidget_" + key;
        }

        public static void OnSceneGUI(SceneView sceneView)
        {
            if (!enable) return;

            // Style must be initialized in GUI method (because it uses GUI method)
            if (textStyle == null)
            {
                textStyle = new GUIStyle(GUI.skin.label);
                textStyle.richText = true;
                textStyle.normal.textColor = Color.white;
            }

            // 2D Screen GUI
            Handles.BeginGUI();

            // Background to improve text visibility
            GUI.backgroundColor = Color.black;
            EditorGUI.HelpBox(new Rect(0, 0, 200, 210), "", MessageType.None);
            GUI.backgroundColor = Color.white;

            if (selectionChanged)
            {
                UpdateSelectionChildrenCount();
                UpdateChildenVerticesAndTrianglesNumbers();
                selectionChanged = false;
            }

            GUI.Label(new Rect(20, 10, 400, 20), "<b>Selection</b>", textStyle);
            GUI.Label(new Rect(20, 30, 400, 20), "GameObjects : " + numberOfSelected, textStyle);
            GUI.Label(new Rect(20, 50, 400, 20), "Direct children : " + numberOfChildren, textStyle);
            GUI.Label(new Rect(20, 70, 400, 100), "Recursive children : " + numberOfChildrenRecursive, textStyle);
            GUI.Label(new Rect(20, 90, 400, 100), "Vertices : " + numberOfVerticesInChildren.ToString("N0", integerFormatInfo), textStyle);
            GUI.Label(new Rect(20, 110, 400, 100), "Triangles : " + numberOfTrianglesInChildren.ToString("N0", integerFormatInfo), textStyle);

            if (hierarchyChanged)
            {
                UpdateSceneNumberOfobjectsCount();
                hierarchyChanged = false;
            }

            GUI.Label(new Rect(20, 140, 400, 20), "<b>Active scene</b>", textStyle);
            GUI.Label(new Rect(20, 160, 400, 20), "Root GameObjects : " + numberOfRootGameObjects, textStyle);
            GUI.Label(new Rect(20, 180, 400, 20), "GameObjects : " + numberOfGamesObjectsInScene, textStyle);

            Handles.EndGUI();
        }

        private static void OnHierarchyChanged()
        {
            hierarchyChanged = true;
        }

        private static void OnSelectionChanged()
        {
            selectionChanged = true;
        }

        private static void UpdateSelectionChildrenCount()
        {
            numberOfSelected = Selection.gameObjects.Length;
            numberOfChildren = numberOfChildrenRecursive = 0;

            for (int i = 0; i < Selection.gameObjects.Length; i++)
            {
                numberOfChildren += GetNumberOfChildren(Selection.gameObjects[i].transform, false);
                numberOfChildrenRecursive += GetNumberOfChildren(Selection.gameObjects[i].transform, true);
            }
        }

        private static void UpdateSceneNumberOfobjectsCount()
        {
            GameObject[] rootGameObjects = SceneManager.GetActiveScene().GetRootGameObjects();
            numberOfRootGameObjects = rootGameObjects.Length;

            numberOfGamesObjectsInScene = 0;
            for (int i = 0; i < rootGameObjects.Length; i++)
            {
                numberOfGamesObjectsInScene += 1 + GetNumberOfChildren(rootGameObjects[i].transform, true);
            }
        }

        private static int GetNumberOfChildren(Transform goTransform, bool recursive)
        {
            if (recursive)
            {
                int childrenNumber = 0;
                for (int i = 0; i < goTransform.childCount; i++)
                {
                    childrenNumber += 1 + GetNumberOfChildren(goTransform.GetChild(i), true);
                }

                return childrenNumber;
            }
            else return goTransform.childCount;
        }

        private static void UpdateChildenVerticesAndTrianglesNumbers()
        {
            numberOfVerticesInChildren = numberOfTrianglesInChildren = 0;

            for (int i = 0; i < Selection.gameObjects.Length; i++)
            {
                MeshFilter[] meshFilters = Selection.gameObjects[i].GetComponentsInChildren<MeshFilter>();
                numberOfVerticesInChildren += meshFilters.Where(x => x.sharedMesh != null).Sum(x => x.sharedMesh.vertexCount);
                numberOfTrianglesInChildren += meshFilters.Where(x => x.sharedMesh != null).Sum(x => x.sharedMesh.triangles.Length / 3);
            }
        }
    }
}