UIUtils.cs

#if UNITY_EDITOR
using UnityEditor;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public static class UIUtils {

    public static void SetHideFlags(this GameObject go, HideFlags value, bool includeChildren = true, bool includeComponent = false)
    {
        go.hideFlags = value;
        if (includeComponent)
        {
            foreach (var comp in go.GetComponents<Component>())
            {
                comp.hideFlags = value;
            }
        }

        if (includeChildren)
        {
            for (int i = 0; i < go.transform.childCount; i++)
            {
                go.transform.GetChild(i).gameObject.SetHideFlags(value, true, includeComponent);
            }
        }
    }

    #region copy from source code of uGUI
    private const string kUILayerName = "UI";

    private const string kStandardSpritePath = "UI/Skin/UISprite.psd";
    private const string kBackgroundSpritePath = "UI/Skin/Background.psd";
    private const string kInputFieldBackgroundPath = "UI/Skin/InputFieldBackground.psd";
    private const string kKnobPath = "UI/Skin/Knob.psd";
    private const string kCheckmarkPath = "UI/Skin/Checkmark.psd";
    private const string kDropdownArrowPath = "UI/Skin/DropdownArrow.psd";
    private const string kMaskPath = "UI/Skin/UIMask.psd";

    static private DefaultControls.Resources s_StandardResources;

    static public DefaultControls.Resources GetStandardResources()
    {
        if (s_StandardResources.standard == null)
        {
            s_StandardResources.standard = AssetDatabase.GetBuiltinExtraResource<Sprite>(kStandardSpritePath);
            s_StandardResources.background = AssetDatabase.GetBuiltinExtraResource<Sprite>(kBackgroundSpritePath);
            s_StandardResources.inputField = AssetDatabase.GetBuiltinExtraResource<Sprite>(kInputFieldBackgroundPath);
            s_StandardResources.knob = AssetDatabase.GetBuiltinExtraResource<Sprite>(kKnobPath);
            s_StandardResources.checkmark = AssetDatabase.GetBuiltinExtraResource<Sprite>(kCheckmarkPath);
            s_StandardResources.dropdown = AssetDatabase.GetBuiltinExtraResource<Sprite>(kDropdownArrowPath);
            s_StandardResources.mask = AssetDatabase.GetBuiltinExtraResource<Sprite>(kMaskPath);
        }
        return s_StandardResources;
    }



    public static void PlaceUIElementRoot(GameObject element, MenuCommand menuCommand)
    {
        GameObject parent = menuCommand.context as GameObject;
        if (parent == null || parent.GetComponentInParent<Canvas>() == null)
        {
            parent = GetOrCreateCanvasGameObject();
        }

        string uniqueName = GameObjectUtility.GetUniqueNameForSibling(parent.transform, element.name);
        element.name = uniqueName;
        Undo.RegisterCreatedObjectUndo(element, "Create " + element.name);
        Undo.SetTransformParent(element.transform, parent.transform, "Parent " + element.name);
        GameObjectUtility.SetParentAndAlign(element, parent);
        if (parent != menuCommand.context) // not a context click, so center in sceneview
            SetPositionVisibleinSceneView(parent.GetComponent<RectTransform>(), element.GetComponent<RectTransform>());

        Selection.activeGameObject = element;
    }

    private static void SetPositionVisibleinSceneView(RectTransform canvasRTransform, RectTransform itemTransform)
    {
        // Find the best scene view
        SceneView sceneView = SceneView.lastActiveSceneView;
        if (sceneView == null && SceneView.sceneViews.Count > 0)
            sceneView = SceneView.sceneViews[0] as SceneView;

        // Couldn't find a SceneView. Don't set position.
        if (sceneView == null || sceneView.camera == null)
            return;

        // Create world space Plane from canvas position.
        Vector2 localPlanePosition;
        Camera camera = sceneView.camera;
        Vector3 position = Vector3.zero;
        if (RectTransformUtility.ScreenPointToLocalPointInRectangle(canvasRTransform, new Vector2(camera.pixelWidth / 2, camera.pixelHeight / 2), camera, out localPlanePosition))
        {
            // Adjust for canvas pivot
            localPlanePosition.x = localPlanePosition.x + canvasRTransform.sizeDelta.x * canvasRTransform.pivot.x;
            localPlanePosition.y = localPlanePosition.y + canvasRTransform.sizeDelta.y * canvasRTransform.pivot.y;

            localPlanePosition.x = Mathf.Clamp(localPlanePosition.x, 0, canvasRTransform.sizeDelta.x);
            localPlanePosition.y = Mathf.Clamp(localPlanePosition.y, 0, canvasRTransform.sizeDelta.y);

            // Adjust for anchoring
            position.x = localPlanePosition.x - canvasRTransform.sizeDelta.x * itemTransform.anchorMin.x;
            position.y = localPlanePosition.y - canvasRTransform.sizeDelta.y * itemTransform.anchorMin.y;

            Vector3 minLocalPosition;
            minLocalPosition.x = canvasRTransform.sizeDelta.x * (0 - canvasRTransform.pivot.x) + itemTransform.sizeDelta.x * itemTransform.pivot.x;
            minLocalPosition.y = canvasRTransform.sizeDelta.y * (0 - canvasRTransform.pivot.y) + itemTransform.sizeDelta.y * itemTransform.pivot.y;

            Vector3 maxLocalPosition;
            maxLocalPosition.x = canvasRTransform.sizeDelta.x * (1 - canvasRTransform.pivot.x) - itemTransform.sizeDelta.x * itemTransform.pivot.x;
            maxLocalPosition.y = canvasRTransform.sizeDelta.y * (1 - canvasRTransform.pivot.y) - itemTransform.sizeDelta.y * itemTransform.pivot.y;

            position.x = Mathf.Clamp(position.x, minLocalPosition.x, maxLocalPosition.x);
            position.y = Mathf.Clamp(position.y, minLocalPosition.y, maxLocalPosition.y);
        }

        itemTransform.anchoredPosition = position;
        itemTransform.localRotation = Quaternion.identity;
        itemTransform.localScale = Vector3.one;
    }

    // Helper function that returns a Canvas GameObject; preferably a parent of the selection, or other existing Canvas.
    static public GameObject GetOrCreateCanvasGameObject()
    {
        GameObject selectedGo = Selection.activeGameObject;

        // Try to find a gameobject that is the selected GO or one if its parents.
        Canvas canvas = (selectedGo != null) ? selectedGo.GetComponentInParent<Canvas>() : null;
        if (canvas != null && canvas.gameObject.activeInHierarchy)
            return canvas.gameObject;

        // No canvas in selection or its parents? Then use just any canvas..
        canvas = UnityEngine.Object.FindObjectOfType(typeof(Canvas)) as Canvas;
        if (canvas != null && canvas.gameObject.activeInHierarchy)
            return canvas.gameObject;

        // No canvas in the scene at all? Then create a new one.
        return CreateNewUI();
    }

    static public GameObject CreateNewUI()
    {
        // Root for the UI
        var root = new GameObject("Canvas");
        root.layer = LayerMask.NameToLayer(kUILayerName);
        Canvas canvas = root.AddComponent<Canvas>();
        canvas.renderMode = RenderMode.ScreenSpaceOverlay;
        root.AddComponent<CanvasScaler>();
        root.AddComponent<GraphicRaycaster>();
        Undo.RegisterCreatedObjectUndo(root, "Create " + root.name);

        // if there is no event system add one...
        CreateEventSystem(false);
        return root;
    }

    public static void CreateEventSystem(MenuCommand menuCommand)
    {
        GameObject parent = menuCommand.context as GameObject;
        CreateEventSystem(true, parent);
    }

    private static void CreateEventSystem(bool select)
    {
        CreateEventSystem(select, null);
    }

    private static void CreateEventSystem(bool select, GameObject parent)
    {
        var esys = UnityEngine.Object.FindObjectOfType<EventSystem>();
        if (esys == null)
        {
            var eventSystem = new GameObject("EventSystem");
            GameObjectUtility.SetParentAndAlign(eventSystem, parent);
            esys = eventSystem.AddComponent<EventSystem>();
            eventSystem.AddComponent<StandaloneInputModule>();

            Undo.RegisterCreatedObjectUndo(eventSystem, "Create " + eventSystem.name);
        }

        if (select && esys != null)
        {
            Selection.activeGameObject = esys.gameObject;
        }
    }
    #endregion
}

#endif //end if UNITY_EDITOR