public static void GetWindow(System.Type type, CustomObjectPickerAttribute attr, System.Action <Object> callback)
        {
            GetWindow <CustomObjectPickerEditorWindow>(false, "Select Object", true);

            _callback = callback;
            FilterAssets(type, attr);
        }
        private static void FilterAssets(System.Type type, CustomObjectPickerAttribute attr)
        {
            _allMatchingObjects = Resources.FindObjectsOfTypeAll(type);

            if (typeof(GameObject).IsAssignableFrom(type))
            {
                if (attr.resultObjectType != CustomObjectPickerAttribute.ResultObjectType.SceneOrAsset)
                {
                    if (attr.resultObjectType == CustomObjectPickerAttribute.ResultObjectType.Scene)
                    {
                        _allMatchingObjects = _allMatchingObjects.Where(t => PrefabUtility.GetPrefabType(t as GameObject) != PrefabType.Prefab);
                    }

                    if (attr.resultObjectType == CustomObjectPickerAttribute.ResultObjectType.Asset)
                    {
                        _allMatchingObjects = _allMatchingObjects.Where(t => PrefabUtility.GetPrefabType(t as GameObject) == PrefabType.Prefab);
                    }
                }

                // if we're dealing with GameObject references, then we'll restrict outrselves to any
                // GameObject with components attached that possess all type limitations collectively
                foreach (var restrictionType in attr.typeRestrictions)
                {
                    _allMatchingObjects = _allMatchingObjects.Where(t => (t as GameObject).GetComponent(restrictionType) != null).ToList();
                }
            }
            else if (typeof(Component).IsAssignableFrom(type))
            {
                if (attr.resultObjectType != CustomObjectPickerAttribute.ResultObjectType.SceneOrAsset)
                {
                    if (attr.resultObjectType == CustomObjectPickerAttribute.ResultObjectType.Scene)
                    {
                        _allMatchingObjects = _allMatchingObjects.Where(t => PrefabUtility.GetPrefabType((t as Component).gameObject) != PrefabType.Prefab);
                    }

                    if (attr.resultObjectType == CustomObjectPickerAttribute.ResultObjectType.Asset)
                    {
                        _allMatchingObjects = _allMatchingObjects.Where(t => PrefabUtility.GetPrefabType((t as Component).gameObject) == PrefabType.Prefab);
                    }
                }

                // if we're dealing with components, then we limit ourselves to components that derive
                // or implement all restriction type
                foreach (var restrictionType in attr.typeRestrictions)
                {
                    _allMatchingObjects = _allMatchingObjects.Where(t => restrictionType.IsAssignableFrom(t.GetType()));
                }
            }
            else if (typeof(ScriptableObject).IsAssignableFrom(type))
            {
                // ScriptableObjects are assets only, so we can skip the asset/scene object check
                foreach (var restrictionType in attr.typeRestrictions)
                {
                    _allMatchingObjects = _allMatchingObjects.Where(t => restrictionType.IsAssignableFrom(t.GetType()));
                }
            }
        }
        private static void RenderObjectPicker(Rect rect, string fieldName, SerializedProperty prop, Type reqObjType,
                                               CustomObjectPickerAttribute attr)
        {
            GUIContent content = GetContentFromObject(prop.objectReferenceValue, reqObjType);

            ObjectField(rect, rect, new GUIContent(fieldName), 1, prop.objectReferenceValue, reqObjType, attr, (val) =>
            {
                prop.objectReferenceValue = val;

                prop.serializedObject.ApplyModifiedProperties();
                prop.serializedObject.Update();
            });
        }
        private static bool ValidateObject(Object obj, Type reqObjType, CustomObjectPickerAttribute attr,
                                           bool includeGOComponents = false)
        {
            if (obj == null)
            {
                return(false);
            }

            Type objType = obj.GetType();

            if (GameObjectType.IsAssignableFrom(reqObjType))
            {
                if (GameObjectType.IsAssignableFrom(objType))
                {
                    foreach (var restriction in attr.typeRestrictions)
                    {
                        if ((obj as GameObject).GetComponent(restriction) == null)
                        {
                            return(false);
                        }
                    }

                    return(true);
                }
            }
            else if (ComponentType.IsAssignableFrom(reqObjType))
            {
                if (includeGOComponents && GameObjectType.IsAssignableFrom(objType))
                {
                    Object[] objs = (obj as GameObject).GetComponents(reqObjType);
                    foreach (var @object in objs)
                    {
                        bool success = true;
                        foreach (var restriction in attr.typeRestrictions)
                        {
                            if (!restriction.IsAssignableFrom(@object.GetType()))
                            {
                                success = false;
                            }
                        }

                        if (success)
                        {
                            return(true);
                        }
                    }

                    return(false);
                }
                else
                {
                    if (ComponentType.IsAssignableFrom(objType))
                    {
                        foreach (var restriction in attr.typeRestrictions)
                        {
                            if (!restriction.IsAssignableFrom(objType))
                            {
                                return(false);
                            }
                        }

                        return(true);
                    }
                }
            }
            else if (ScriptableObjectType.IsAssignableFrom(reqObjType))
            {
                if (ScriptableObjectType.IsAssignableFrom(objType))
                {
                    foreach (var restriction in attr.typeRestrictions)
                    {
                        if (!restriction.IsAssignableFrom(objType))
                        {
                            return(false);
                        }
                    }

                    return(true);
                }
            }

            return(false);
        }
        private static void ObjectField(Rect position, Rect dropRect, GUIContent fieldName, int id, Object obj, Type reqObjType,
                                        CustomObjectPickerAttribute attr, Action <Object> callback)
        {
            Event     current   = Event.current;
            EventType eventType = current.type;

            if (!GUI.enabled && Event.current.rawType == EventType.MouseDown)
            {
                eventType = Event.current.rawType;
            }

            if (fieldName != null && string.IsNullOrEmpty(fieldName.text) == false)
            {
                var labelPos = position;
                labelPos.width = EditorGUIUtility.labelWidth;
                EditorGUI.PrefixLabel(labelPos, fieldName);

                position.x     += labelPos.width;
                position.width -= labelPos.width;
            }

            EditorGUI.LabelField(position, obj ? $"{obj.name} [{obj.GetType().Name}]" : $"None ({attr.typeRestrictions.JoinString(", ", a => a.GetSimpleAliasName())})", EditorStyles.objectField);
            position.width -= 32;

            if (Event.current.type == EventType.MouseDown || Event.current.type == EventType.MouseUp)
            {
                if (position.Contains(Event.current.mousePosition) && obj != null)
                {
                    Selection.objects = new[] { obj };
                    EditorGUIUtility.PingObject(obj);
                    Event.current.Use();
                    GUIUtility.ExitGUI();
                }

                position.x    += position.width;
                position.width = 32;

                if (position.Contains(Event.current.mousePosition))
                {
                    CustomObjectPickerEditorWindow.GetWindow(reqObjType, attr, (val) =>
                    {
                        if (callback != null)
                        {
                            callback(val);
                        }

                        GUI.changed = true;
                    });
                }
            }

            EventType eventType2 = eventType;

            switch (eventType2)
            {
            case EventType.KeyUp:
            case EventType.ScrollWheel:
            case EventType.Layout:
            case EventType.Ignore:
            case EventType.Used:
            case EventType.ValidateCommand:
            case EventType.Repaint:
            case EventType.ExecuteCommand:
                break;

            case EventType.DragUpdated:
            case EventType.DragPerform:
                if (dropRect.Contains(Event.current.mousePosition) && GUI.enabled)
                {
                    Object[] objectReferences = DragAndDrop.objectReferences;
                    var      obj2             = objectReferences.FirstOrDefault();

                    if (obj2 != null)
                    {
                        DragAndDrop.visualMode = DragAndDropVisualMode.Generic;
                        if (eventType == EventType.DragPerform && ValidateObject(obj2, reqObjType, attr, true))
                        {
                            obj         = obj2;
                            GUI.changed = true;

                            Type objType = obj.GetType();
                            if (GameObjectType.IsAssignableFrom(objType))
                            {
                                var objAsGameObject = obj as GameObject;

                                if (GameObjectType.IsAssignableFrom(reqObjType))
                                {
                                    callback(obj);
                                }
                                else if (ComponentType.IsAssignableFrom(reqObjType))
                                {
                                    Object[] objs = (obj as GameObject).GetComponents(reqObjType);
                                    foreach (var @object in objs)
                                    {
                                        bool success = true;
                                        foreach (var restriction in attr.typeRestrictions)
                                        {
                                            if (!restriction.IsAssignableFrom(@object.GetType()))
                                            {
                                                success = false;
                                            }
                                        }

                                        if (success)
                                        {
                                            callback(@object);
                                        }
                                    }
                                }
                            }
                            else
                            {
                                callback(obj);
                            }

                            DragAndDrop.AcceptDrag();
                            DragAndDrop.activeControlID = 0;
                        }
                        else
                        {
                            DragAndDrop.activeControlID = id;
                        }

                        Event.current.Use();
                    }
                }

                break;

            case EventType.DragExited:
                if (GUI.enabled)
                {
                    HandleUtility.Repaint();
                }
                break;
            }
        }