Merge branch 'editor-list-dragging' of https://github.com/MineBill/FlaxEngine into MineBill-editor-list-dragging

Source/Editor/CustomEditors/Editors/AssetRefEditor.cs

@@ -71,7 +71,7 @@ namespace FlaxEditor.CustomEditors.Editors
                 {
                     // Generic file picker
                     assetType = ScriptType.Null;
-                    Picker.FileExtension = assetReference.TypeName;
+                    Picker.Validator.FileExtension = assetReference.TypeName;
                 }
                 else
                 {
@@ -85,7 +85,7 @@ namespace FlaxEditor.CustomEditors.Editors
                 }
             }
 
-            Picker.AssetType = assetType;
+            Picker.Validator.AssetType = assetType;
             Picker.Height = height;
             Picker.SelectedItemChanged += OnSelectedItemChanged;
         }
@@ -95,15 +95,15 @@ namespace FlaxEditor.CustomEditors.Editors
             if (_isRefreshing)
                 return;
             if (typeof(AssetItem).IsAssignableFrom(_valueType.Type))
-                SetValue(Picker.SelectedItem);
+                SetValue(Picker.Validator.SelectedItem);
             else if (_valueType.Type == typeof(Guid))
-                SetValue(Picker.SelectedID);
+                SetValue(Picker.Validator.SelectedID);
             else if (_valueType.Type == typeof(SceneReference))
-                SetValue(new SceneReference(Picker.SelectedID));
+                SetValue(new SceneReference(Picker.Validator.SelectedID));
             else if (_valueType.Type == typeof(string))
-                SetValue(Picker.SelectedPath);
+                SetValue(Picker.Validator.SelectedPath);
             else
-                SetValue(Picker.SelectedAsset);
+                SetValue(Picker.Validator.SelectedAsset);
         }
 
         /// <inheritdoc />
@@ -115,15 +115,15 @@ namespace FlaxEditor.CustomEditors.Editors
             {
                 _isRefreshing = true;
                 if (Values[0] is AssetItem assetItem)
-                    Picker.SelectedItem = assetItem;
+                    Picker.Validator.SelectedItem = assetItem;
                 else if (Values[0] is Guid guid)
-                    Picker.SelectedID = guid;
+                    Picker.Validator.SelectedID = guid;
                 else if (Values[0] is SceneReference sceneAsset)
-                    Picker.SelectedItem = Editor.Instance.ContentDatabase.FindAsset(sceneAsset.ID);
+                    Picker.Validator.SelectedItem = Editor.Instance.ContentDatabase.FindAsset(sceneAsset.ID);
                 else if (Values[0] is string path)
-                    Picker.SelectedPath = path;
+                    Picker.Validator.SelectedPath = path;
                 else
-                    Picker.SelectedAsset = Values[0] as Asset;
+                    Picker.Validator.SelectedAsset = Values[0] as Asset;
                 _isRefreshing = false;
             }
         }

Source/Editor/CustomEditors/Editors/CollectionEditor.cs

@@ -2,11 +2,17 @@
 
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.Linq;
+using FlaxEditor.Content;
 using FlaxEditor.CustomEditors.Elements;
 using FlaxEditor.CustomEditors.GUI;
 using FlaxEditor.GUI.ContextMenu;
+using FlaxEditor.GUI.Drag;
+using FlaxEditor.Options;
+using FlaxEditor.SceneGraph;
 using FlaxEditor.Scripting;
+using FlaxEditor.Utilities;
 using FlaxEngine;
 using FlaxEngine.GUI;
 using FlaxEngine.Utilities;
@@ -134,15 +140,44 @@ namespace FlaxEditor.CustomEditors.Editors
                 overrideEditorType = TypeUtils.GetType(collection.OverrideEditorTypeName).Type;
                 spacing = collection.Spacing;
             }
+            
+            var dragArea = layout.CustomContainer<DragAreaControl>();
+            dragArea.CustomControl.Editor = this;
+            dragArea.CustomControl.ElementType = ElementType;
+            
+            // Check for the AssetReferenceAttribute. In JSON assets, it can be used to filter
+            // which scripts can be dragged over and dropped on this collection editor.
+            var assetReference = (AssetReferenceAttribute)attributes?.FirstOrDefault(x => x is AssetReferenceAttribute);
+            if (assetReference != null)
+            {
+                if (string.IsNullOrEmpty(assetReference.TypeName))
+                {
+                }
+                else if (assetReference.TypeName.Length > 1 && assetReference.TypeName[0] == '.')
+                {
+                    dragArea.CustomControl.ElementType = ScriptType.Null;
+                    dragArea.CustomControl.FileExtension = assetReference.TypeName;
+                }
+                else
+                {
+                    var customType = TypeUtils.GetType(assetReference.TypeName);
+                    if (customType != ScriptType.Null)
+                        dragArea.CustomControl.ElementType = customType;
+                    else if (!Content.Settings.GameSettings.OptionalPlatformSettings.Contains(assetReference.TypeName))
+                        Debug.LogWarning(string.Format("Unknown asset type '{0}' to use for drag and drop filter.", assetReference.TypeName));
+                    else
+                        dragArea.CustomControl.ElementType = ScriptType.Void;
+                }
+            }
 
             // Size
             if (_readOnly || (NotNullItems && size == 0))
             {
-                layout.Label("Size", size.ToString());
+                dragArea.Label("Size", size.ToString());
             }
             else
             {
-                _size = layout.IntegerValue("Size");
+                _size = dragArea.IntegerValue("Size");
                 _size.IntValue.MinValue = 0;
                 _size.IntValue.MaxValue = ushort.MaxValue;
                 _size.IntValue.Value = size;
@@ -152,7 +187,7 @@ namespace FlaxEditor.CustomEditors.Editors
             // Elements
             if (size > 0)
             {
-                var panel = layout.VerticalPanel();
+                var panel = dragArea.VerticalPanel();
                 panel.Panel.BackgroundColor = _background;
                 var elementType = ElementType;
 
@@ -212,37 +247,33 @@ namespace FlaxEditor.CustomEditors.Editors
             // Add/Remove buttons
             if (!_readOnly)
             {
-                var area = layout.Space(20);
+                var panel = dragArea.HorizontalPanel();
-                var addButton = new Button(area.ContainerControl.Width - (16 + 16 + 2 + 2), 2, 16, 16)
+                panel.Panel.Size = new Float2(0, 20);
-                {
+                panel.Panel.Margin = new Margin(2);
-                    Text = "+",
+                
-                    TooltipText = "Add new item",
+                var removeButton = panel.Button("-", "Remove last item");
-                    AnchorPreset = AnchorPresets.TopRight,
+                removeButton.Button.Size = new Float2(16, 16);
-                    Parent = area.ContainerControl,
+                removeButton.Button.Enabled = size > 0;
-                    Enabled = !NotNullItems || size > 0,
+                removeButton.Button.AnchorPreset = AnchorPresets.TopRight;
-                };
+                removeButton.Button.Clicked += () =>
-                addButton.Clicked += () =>
-                {
-                    if (IsSetBlocked)
-                        return;
-
-                    Resize(Count + 1);
-                };
-                var removeButton = new Button(addButton.Right + 2, addButton.Y, 16, 16)
-                {
-                    Text = "-",
-                    TooltipText = "Remove last item",
-                    AnchorPreset = AnchorPresets.TopRight,
-                    Parent = area.ContainerControl,
-                    Enabled = size > 0,
-                };
-                removeButton.Clicked += () =>
                 {
                     if (IsSetBlocked)
                         return;
 
                     Resize(Count - 1);
                 };
+                
+                var addButton = panel.Button("+", "Add new item");
+                addButton.Button.Size = new Float2(16, 16);
+                addButton.Button.Enabled = !NotNullItems || size > 0;
+                addButton.Button.AnchorPreset = AnchorPresets.TopRight;
+                addButton.Button.Clicked += () =>
+                {
+                    if (IsSetBlocked)
+                        return;
+
+                    Resize(Count + 1);
+                };
             }
         }
 
@@ -369,5 +400,241 @@ namespace FlaxEditor.CustomEditors.Editors
             }
             return base.OnDirty(editor, value, token);
         }
+        
+        private class DragAreaControl : VerticalPanel
+        {
+            // private DragHandlers _dragHandlers;
+            // private DragAssets _dragAssets;
+            // private DragActors _dragActors;
+            private DragItems _dragItems;
+            private DragActors _dragActors;
+            private DragHandlers _dragHandlers;
+
+            private AssetPickerValidator _pickerValidator;
+            private ScriptType _elementType;
+            
+            public ScriptType ElementType
+            {
+                get => _elementType;
+                set
+                {
+                    _pickerValidator = new AssetPickerValidator(value);
+                    _elementType = value;
+                }
+            }
+
+            public CollectionEditor Editor { get; set; }
+
+            public string FileExtension
+            {
+                set => _pickerValidator.FileExtension = value;
+            }
+
+            /// <inheritdoc />
+            public override void Draw()
+            {
+                if (_dragHandlers is {HasValidDrag: true})
+                {
+                    var area = new Rectangle(Float2.Zero, Size);
+                    Render2D.FillRectangle(area, Color.Orange * 0.5f);
+                    Render2D.DrawRectangle(area, Color.Black);
+                }
+                base.Draw();
+            }
+
+            public override void OnDestroy()
+            {
+                _pickerValidator.OnDestroy();
+            }
+
+            private bool ValidateActors(ActorNode node)
+            {
+                return node.Actor.GetScript(ElementType.Type) || ElementType.Type.IsAssignableTo(typeof(Actor));
+            }
+
+            /// <inheritdoc />
+            public override DragDropEffect OnDragEnter(ref Float2 location, DragData data)
+            {
+                var result = base.OnDragEnter(ref location, data);
+                if (result != DragDropEffect.None)
+                    return result;
+
+                if (_dragHandlers == null)
+                {
+                    _dragItems = new DragItems(_pickerValidator.IsValid);
+                    _dragActors = new DragActors(ValidateActors);
+                    _dragHandlers = new DragHandlers
+                    {
+                        _dragActors,
+                        _dragItems
+                    };
+                }
+                return _dragHandlers.OnDragEnter(data);
+            }
+
+            /// <inheritdoc />
+            public override DragDropEffect OnDragMove(ref Float2 location, DragData data)
+            {
+                var result = base.OnDragMove(ref location, data);
+                if (result != DragDropEffect.None)
+                    return result;
+
+                return _dragHandlers.Effect;
+            }
+
+            /// <inheritdoc />
+            public override void OnDragLeave()
+            {
+                _dragHandlers.OnDragLeave();
+
+                base.OnDragLeave();
+            }
+
+            /// <inheritdoc />
+            public override DragDropEffect OnDragDrop(ref Float2 location, DragData data)
+            {
+                var result = base.OnDragDrop(ref location, data);
+                if (result != DragDropEffect.None)
+                {
+                    _dragHandlers.OnDragDrop(null);
+                    return result;
+                }
+
+                if (_dragHandlers.HasValidDrag)
+                {
+                    if (_dragItems.HasValidDrag)
+                    {
+                        var list = Editor.CloneValues();
+                        if (list == null)
+                        {
+                            if (Editor.Values.Type.IsArray)
+                            {
+                                list = TypeUtils.CreateArrayInstance(Editor.Values.Type.GetElementType(), 0);
+                            }
+                            else
+                            {
+                                list = Editor.Values.Type.CreateInstance() as IList;
+                            }
+                        }
+                        if (list.IsFixedSize)
+                        {
+                            var oldSize = list.Count;
+                            var newSize = list.Count + _dragItems.Objects.Count;
+                            var type = Editor.Values.Type.GetElementType();
+                            var array = TypeUtils.CreateArrayInstance(type, newSize);
+                            list.CopyTo(array, 0);
+                            
+                            for (var i = oldSize; i < newSize; i++)
+                            {
+                                var validator = new AssetPickerValidator
+                                {
+                                    FileExtension = _pickerValidator.FileExtension,
+                                    AssetType = _pickerValidator.AssetType,
+                                    SelectedItem = _dragItems.Objects[i - oldSize],
+                                };
+
+                                if (typeof(AssetItem).IsAssignableFrom(ElementType.Type))
+                                    array.SetValue(validator.SelectedItem, i);
+                                else if (ElementType.Type == typeof(Guid))
+                                    array.SetValue(validator.SelectedID, i);
+                                else if (ElementType.Type == typeof(SceneReference))
+                                    array.SetValue(new SceneReference(validator.SelectedID), i);
+                                else if (ElementType.Type == typeof(string))
+                                    array.SetValue(validator.SelectedPath, i);
+                                else
+                                    array.SetValue(validator.SelectedAsset, i);
+                                
+                                validator.OnDestroy();
+                            }
+                            Editor.SetValue(array);
+                        }
+                        else
+                        {
+                            foreach (var item in _dragItems.Objects)
+                            {
+                                var validator = new AssetPickerValidator
+                                {
+                                    FileExtension = _pickerValidator.FileExtension,
+                                    AssetType = _pickerValidator.AssetType,
+                                    SelectedItem = item,
+                                };
+                                
+                                if (typeof(AssetItem).IsAssignableFrom(ElementType.Type))
+                                    list.Add(validator.SelectedItem);
+                                else if (ElementType.Type == typeof(Guid))
+                                    list.Add(validator.SelectedID);
+                                else if (ElementType.Type == typeof(SceneReference))
+                                    list.Add(new SceneReference(validator.SelectedID));
+                                else if (ElementType.Type == typeof(string))
+                                    list.Add(validator.SelectedPath);
+                                else
+                                    list.Add(validator.SelectedAsset);
+                                
+                                validator.OnDestroy();
+                            }
+                            Editor.SetValue(list);
+                        }
+                    }
+                    else if (_dragActors.HasValidDrag)
+                    {
+                        var list = Editor.CloneValues();
+                        if (list == null)
+                        {
+                            if (Editor.Values.Type.IsArray)
+                            {
+                                list = TypeUtils.CreateArrayInstance(Editor.Values.Type.GetElementType(), 0);
+                            }
+                            else
+                            {
+                                list = Editor.Values.Type.CreateInstance() as IList;
+                            }
+                        }
+                        
+                        if (list.IsFixedSize)
+                        {
+                            var oldSize = list.Count;
+                            var newSize = list.Count + _dragActors.Objects.Count;
+                            var type = Editor.Values.Type.GetElementType();
+                            var array = TypeUtils.CreateArrayInstance(type, newSize);
+                            list.CopyTo(array, 0);
+                            
+                            for (var i = oldSize; i < newSize; i++)
+                            {
+                                var actor = _dragActors.Objects[i - oldSize].Actor;
+                                if (ElementType.Type.IsAssignableTo(typeof(Actor)))
+                                {
+                                    array.SetValue(actor, i);
+                                }
+                                else
+                                {
+                                    array.SetValue(actor.GetScript(ElementType.Type), i);
+                                }
+                            }
+                            Editor.SetValue(array);
+                        }
+                        else
+                        {
+                            foreach (var actorNode in _dragActors.Objects)
+                            {
+                                if (ElementType.Type.IsAssignableTo(typeof(Actor)))
+                                {
+                                    list.Add(actorNode.Actor);
+                                }
+                                else
+                                {
+                                    list.Add(actorNode.Actor.GetScript(ElementType.Type));
+                                }
+                            }
+                            Editor.SetValue(list);
+                        }
+                    }
+                    
+                    _dragHandlers.OnDragDrop(null);
+                }
+
+                return result;
+            }
+        }
     }
+
 }

Source/Editor/CustomEditors/Editors/ModelInstanceEntryEditor.cs

@@ -72,14 +72,14 @@ namespace FlaxEditor.CustomEditors.Editors
                 return;
             _isRefreshing = true;
             var slots = _modelInstance.MaterialSlots;
-            var material = _materialEditor.Picker.SelectedAsset as MaterialBase;
+            var material = _materialEditor.Picker.Validator.SelectedAsset as MaterialBase;
             var defaultMaterial = GPUDevice.Instance.DefaultMaterial;
             var value = (ModelInstanceEntry)Values[0];
             var prevMaterial = value.Material;
             if (!material)
             {
                 // Fallback to default material
-                _materialEditor.Picker.SelectedAsset = defaultMaterial;
+                _materialEditor.Picker.Validator.SelectedAsset = defaultMaterial;
                 value.Material = defaultMaterial;
             }
             else if (material == slots[_entryIndex].Material)

Source/Editor/GUI/AssetPicker.cs

@@ -5,6 +5,7 @@ using System.IO;
 using FlaxEditor.Content;
 using FlaxEditor.GUI.Drag;
 using FlaxEditor.Scripting;
+using FlaxEditor.Utilities;
 using FlaxEngine;
 using FlaxEngine.GUI;
 using FlaxEngine.Utilities;
@@ -17,189 +18,21 @@ namespace FlaxEditor.GUI
     /// <seealso cref="Control" />
     /// <seealso cref="IContentItemOwner" />
     [HideInEditor]
-    public class AssetPicker : Control, IContentItemOwner
+    public class AssetPicker : Control
     {
         private const float DefaultIconSize = 64;
         private const float ButtonsOffset = 2;
         private const float ButtonsSize = 12;
 
-        private Asset _selected;
-        private ContentItem _selectedItem;
-        private ScriptType _type;
-        private string _fileExtension;
-
         private bool _isMouseDown;
         private Float2 _mouseDownPos;
         private Float2 _mousePos;
         private DragItems _dragOverElement;
 
         /// <summary>
-        /// Gets or sets the selected item.
+        /// The asset validator. Used to ensure only appropriate items can be picked.
         /// </summary>
-        public ContentItem SelectedItem
+        public AssetPickerValidator Validator { get; }
-        {
-            get => _selectedItem;
-            set
-            {
-                if (_selectedItem == value)
-                    return;
-                if (value == null)
-                {
-                    if (_selected == null && _selectedItem is SceneItem)
-                    {
-                        // Deselect scene reference
-                        _selectedItem.RemoveReference(this);
-                        _selectedItem = null;
-                        _selected = null;
-                        OnSelectedItemChanged();
-                        return;
-                    }
-
-                    // Deselect
-                    _selectedItem?.RemoveReference(this);
-                    _selectedItem = null;
-                    _selected = null;
-                    OnSelectedItemChanged();
-                }
-                else if (value is SceneItem item)
-                {
-                    if (_selectedItem == item)
-                        return;
-                    if (!IsValid(item))
-                        item = null;
-
-                    // Change value to scene reference (cannot load asset because scene can be already loaded - duplicated ID issue)
-                    _selectedItem?.RemoveReference(this);
-                    _selectedItem = item;
-                    _selected = null;
-                    _selectedItem?.AddReference(this);
-                    OnSelectedItemChanged();
-                }
-                else if (value is AssetItem assetItem)
-                {
-                    SelectedAsset = FlaxEngine.Content.LoadAsync(assetItem.ID);
-                }
-                else
-                {
-                    // Change value
-                    _selectedItem?.RemoveReference(this);
-                    _selectedItem = value;
-                    _selected = null;
-                    OnSelectedItemChanged();
-                }
-            }
-        }
-
-        /// <summary>
-        /// Gets or sets the selected asset identifier.
-        /// </summary>
-        public Guid SelectedID
-        {
-            get
-            {
-                if (_selected != null)
-                    return _selected.ID;
-                if (_selectedItem is AssetItem assetItem)
-                    return assetItem.ID;
-                return Guid.Empty;
-            }
-            set => SelectedItem = Editor.Instance.ContentDatabase.FindAsset(value);
-        }
-
-        /// <summary>
-        /// Gets or sets the selected content item path.
-        /// </summary>
-        public string SelectedPath
-        {
-            get
-            {
-                string path = _selectedItem?.Path ?? _selected?.Path;
-                if (path != null)
-                {
-                    // Convert into path relative to the project (cross-platform)
-                    var projectFolder = Globals.ProjectFolder;
-                    if (path.StartsWith(projectFolder))
-                        path = path.Substring(projectFolder.Length + 1);
-                }
-                return path;
-            }
-            set
-            {
-                if (string.IsNullOrEmpty(value))
-                {
-                    SelectedItem = null;
-                }
-                else
-                {
-                    var path = StringUtils.IsRelative(value) ? Path.Combine(Globals.ProjectFolder, value) : value;
-                    SelectedItem = Editor.Instance.ContentDatabase.Find(path);
-                }
-            }
-        }
-
-        /// <summary>
-        /// Gets or sets the selected asset object.
-        /// </summary>
-        public Asset SelectedAsset
-        {
-            get => _selected;
-            set
-            {
-                // Check if value won't change
-                if (value == _selected)
-                    return;
-
-                // Find item from content database and check it
-                var item = value ? Editor.Instance.ContentDatabase.FindAsset(value.ID) : null;
-                if (item != null && !IsValid(item))
-                    item = null;
-
-                // Change value
-                _selectedItem?.RemoveReference(this);
-                _selectedItem = item;
-                _selected = value;
-                _selectedItem?.AddReference(this);
-                OnSelectedItemChanged();
-            }
-        }
-
-        /// <summary>
-        /// Gets or sets the assets types that this picker accepts (it supports types derived from the given type). Use <see cref="ScriptType.Null"/> for generic file picker.
-        /// </summary>
-        public ScriptType AssetType
-        {
-            get => _type;
-            set
-            {
-                if (_type != value)
-                {
-                    _type = value;
-
-                    // Auto deselect if the current value is invalid
-                    if (_selectedItem != null && !IsValid(_selectedItem))
-                        SelectedItem = null;
-                }
-            }
-        }
-
-        /// <summary>
-        /// Gets or sets the content items extensions filter. Null if unused.
-        /// </summary>
-        public string FileExtension
-        {
-            get => _fileExtension;
-            set
-            {
-                if (_fileExtension != value)
-                {
-                    _fileExtension = value;
-
-                    // Auto deselect if the current value is invalid
-                    if (_selectedItem != null && !IsValid(_selectedItem))
-                        SelectedItem = null;
-                }
-            }
-        }
 
         /// <summary>
         /// Occurs when selected item gets changed.
@@ -216,38 +49,6 @@ namespace FlaxEditor.GUI
         /// </summary>
         public bool CanEdit = true;
 
-        private bool IsValid(ContentItem item)
-        {
-            if (_fileExtension != null && !item.Path.EndsWith(_fileExtension))
-                return false;
-            if (CheckValid != null && !CheckValid(item))
-                return false;
-            if (_type == ScriptType.Null)
-                return true;
-
-            if (item is AssetItem assetItem)
-            {
-                // Faster path for binary items (in-built)
-                if (assetItem is BinaryAssetItem binaryItem)
-                    return _type.IsAssignableFrom(new ScriptType(binaryItem.Type));
-
-                // Type filter
-                var type = TypeUtils.GetType(assetItem.TypeName);
-                if (_type.IsAssignableFrom(type))
-                    return true;
-
-                // Json assets can contain any type of the object defined by the C# type (data oriented design)
-                if (assetItem is JsonAssetItem && (_type.Type == typeof(JsonAsset) || _type.Type == typeof(Asset)))
-                    return true;
-
-                // Special case for scene asset references
-                if (_type.Type == typeof(SceneReference) && assetItem is SceneItem)
-                    return true;
-            }
-
-            return false;
-        }
-
         /// <summary>
         /// Initializes a new instance of the <see cref="AssetPicker"/> class.
         /// </summary>
@@ -264,7 +65,8 @@ namespace FlaxEditor.GUI
         public AssetPicker(ScriptType assetType, Float2 location)
         : base(location, new Float2(DefaultIconSize + ButtonsOffset + ButtonsSize, DefaultIconSize))
         {
-            _type = assetType;
+            Validator = new AssetPickerValidator(assetType);
+            Validator.SelectedItemChanged += OnSelectedItemChanged;
             _mousePos = Float2.Minimum;
         }
 
@@ -275,10 +77,10 @@ namespace FlaxEditor.GUI
         {
             // Update tooltip
             string tooltip;
-            if (_selectedItem is AssetItem assetItem)
+            if (Validator.SelectedItem is AssetItem assetItem)
                 tooltip = assetItem.NamePath;
             else
-                tooltip = SelectedPath;
+                tooltip = Validator.SelectedPath;
             TooltipText = tooltip;
 
             SelectedItemChanged?.Invoke();
@@ -289,37 +91,13 @@ namespace FlaxEditor.GUI
             // Do the drag drop operation if has selected element
             if (new Rectangle(Float2.Zero, Size).Contains(ref _mouseDownPos))
             {
-                if (_selected != null)
+                if (Validator.SelectedAsset != null)
-                    DoDragDrop(DragAssets.GetDragData(_selected));
+                    DoDragDrop(DragAssets.GetDragData(Validator.SelectedAsset));
-                else if (_selectedItem != null)
+                else if (Validator.SelectedItem != null)
-                    DoDragDrop(DragItems.GetDragData(_selectedItem));
+                    DoDragDrop(DragItems.GetDragData(Validator.SelectedItem));
             }
         }
 
-        /// <inheritdoc />
-        public void OnItemDeleted(ContentItem item)
-        {
-            // Deselect item
-            SelectedItem = null;
-        }
-
-        /// <inheritdoc />
-        public void OnItemRenamed(ContentItem item)
-        {
-        }
-
-        /// <inheritdoc />
-        public void OnItemReimported(ContentItem item)
-        {
-        }
-
-        /// <inheritdoc />
-        public void OnItemDispose(ContentItem item)
-        {
-            // Deselect item
-            SelectedItem = null;
-        }
-
         private Rectangle IconRect => new Rectangle(0, 0, Height, Height);
 
         private Rectangle Button1Rect => new Rectangle(Height + ButtonsOffset, 0, ButtonsSize, ButtonsSize);
@@ -341,10 +119,10 @@ namespace FlaxEditor.GUI
             if (CanEdit)
                 Render2D.DrawSprite(style.ArrowDown, button1Rect, button1Rect.Contains(_mousePos) ? style.Foreground : style.ForegroundGrey);
 
-            if (_selectedItem != null)
+            if (Validator.SelectedItem != null)
             {
                 // Draw item preview
-                _selectedItem.DrawThumbnail(ref iconRect);
+                Validator.SelectedItem.DrawThumbnail(ref iconRect);
 
                 // Draw buttons
                 if (CanEdit)
@@ -363,7 +141,7 @@ namespace FlaxEditor.GUI
                 {
                     Render2D.DrawText(
                                       style.FontSmall,
-                                      _selectedItem.ShortName,
+                                      Validator.SelectedItem.ShortName,
                                       new Rectangle(button1Rect.Right + 2, 0, sizeForTextLeft, ButtonsSize),
                                       style.Foreground,
                                       TextAlignment.Near,
@@ -371,7 +149,7 @@ namespace FlaxEditor.GUI
                 }
             }
             // Check if has no item but has an asset (eg. virtual asset)
-            else if (_selected)
+            else if (Validator.SelectedAsset)
             {
                 // Draw remove button
                 Render2D.DrawSprite(style.Cross, button3Rect, button3Rect.Contains(_mousePos) ? style.Foreground : style.ForegroundGrey);
@@ -380,8 +158,8 @@ namespace FlaxEditor.GUI
                 float sizeForTextLeft = Width - button1Rect.Right;
                 if (sizeForTextLeft > 30)
                 {
-                    var name = _selected.GetType().Name;
+                    var name = Validator.SelectedAsset.GetType().Name;
-                    if (_selected.IsVirtual)
+                    if (Validator.SelectedAsset.IsVirtual)
                         name += " (virtual)";
                     Render2D.DrawText(
                                       style.FontSmall,
@@ -407,9 +185,7 @@ namespace FlaxEditor.GUI
         /// <inheritdoc />
         public override void OnDestroy()
         {
-            _selectedItem?.RemoveReference(this);
+            Validator.OnDestroy();
-            _selectedItem = null;
-            _selected = null;
 
             base.OnDestroy();
         }
@@ -463,57 +239,57 @@ namespace FlaxEditor.GUI
                 // Buttons logic
                 if (!CanEdit)
                 {
-                    if (Button1Rect.Contains(location) && _selectedItem != null)
+                    if (Button1Rect.Contains(location) && Validator.SelectedItem != null)
                     {
                         // Select asset
-                        Editor.Instance.Windows.ContentWin.Select(_selectedItem);
+                        Editor.Instance.Windows.ContentWin.Select(Validator.SelectedItem);
                     }
                 }
                 else if (Button1Rect.Contains(location))
                 {
                     Focus();
-                    if (_type != ScriptType.Null)
+                    if (Validator.AssetType != ScriptType.Null)
                     {
                         // Show asset picker popup
-                        var popup = AssetSearchPopup.Show(this, Button1Rect.BottomLeft, IsValid, item =>
+                        var popup = AssetSearchPopup.Show(this, Button1Rect.BottomLeft, Validator.IsValid, item =>
                         {
-                            SelectedItem = item;
+                            Validator.SelectedItem = item;
                             RootWindow.Focus();
                             Focus();
                         });
-                        if (_selected != null)
+                        if (Validator.SelectedAsset != null)
                         {
-                            var selectedAssetName = Path.GetFileNameWithoutExtension(_selected.Path);
+                            var selectedAssetName = Path.GetFileNameWithoutExtension(Validator.SelectedAsset.Path);
                             popup.ScrollToAndHighlightItemByName(selectedAssetName);
                         }
                     }
                     else
                     {
                         // Show content item picker popup
-                        var popup = ContentSearchPopup.Show(this, Button1Rect.BottomLeft, IsValid, item =>
+                        var popup = ContentSearchPopup.Show(this, Button1Rect.BottomLeft, Validator.IsValid, item =>
                         {
-                            SelectedItem = item;
+                            Validator.SelectedItem = item;
                             RootWindow.Focus();
                             Focus();
                         });
-                        if (_selectedItem != null)
+                        if (Validator.SelectedItem != null)
                         {
-                            popup.ScrollToAndHighlightItemByName(_selectedItem.ShortName);
+                            popup.ScrollToAndHighlightItemByName(Validator.SelectedItem.ShortName);
                         }
                     }
                 }
-                else if (_selected != null || _selectedItem != null)
+                else if (Validator.SelectedAsset != null || Validator.SelectedItem != null)
                 {
-                    if (Button2Rect.Contains(location) && _selectedItem != null)
+                    if (Button2Rect.Contains(location) && Validator.SelectedItem != null)
                     {
                         // Select asset
-                        Editor.Instance.Windows.ContentWin.Select(_selectedItem);
+                        Editor.Instance.Windows.ContentWin.Select(Validator.SelectedItem);
                     }
                     else if (Button3Rect.Contains(location))
                     {
                         // Deselect asset
                         Focus();
-                        SelectedItem = null;
+                        Validator.SelectedItem = null;
                     }
                 }
             }
@@ -540,10 +316,10 @@ namespace FlaxEditor.GUI
         {
             Focus();
 
-            if (_selectedItem != null && IconRect.Contains(location))
+            if (Validator.SelectedItem != null && IconRect.Contains(location))
             {
                 // Open it
-                Editor.Instance.ContentEditing.Open(_selectedItem);
+                Editor.Instance.ContentEditing.Open(Validator.SelectedItem);
             }
 
             // Handled
@@ -557,7 +333,7 @@ namespace FlaxEditor.GUI
 
             // Check if drop asset
             if (_dragOverElement == null)
-                _dragOverElement = new DragItems(IsValid);
+                _dragOverElement = new DragItems(Validator.IsValid);
             if (CanEdit && _dragOverElement.OnDragEnter(data))
             {
             }
@@ -590,7 +366,7 @@ namespace FlaxEditor.GUI
             if (CanEdit && _dragOverElement.HasValidDrag)
             {
                 // Select element
-                SelectedItem = _dragOverElement.Objects[0];
+                Validator.SelectedItem = _dragOverElement.Objects[0];
             }
 
             // Clear cache

Source/Editor/GUI/Timeline/Tracks/SingleMediaAssetTrack.cs

@@ -39,7 +39,7 @@ namespace FlaxEditor.GUI.Timeline.Tracks
                 if (AssetID == value?.ID)
                     return;
                 AssetID = value?.ID ?? Guid.Empty;
-                _picker.SelectedAsset = value;
+                _picker.Validator.SelectedAsset = value;
                 OnAssetChanged();
                 Timeline?.MarkAsEdited();
             }
@@ -63,10 +63,10 @@ namespace FlaxEditor.GUI.Timeline.Tracks
 
         private void OnPickerSelectedItemChanged()
         {
-            if (Asset == (TAsset)_picker.SelectedAsset)
+            if (Asset == (TAsset)_picker.Validator.SelectedAsset)
                 return;
             using (new TrackUndoBlock(this))
-                Asset = (TAsset)_picker.SelectedAsset;
+                Asset = (TAsset)_picker.Validator.SelectedAsset;
         }
 
         /// <summary>

Source/Editor/Surface/Archetypes/Animation.MultiBlend.cs

@@ -465,7 +465,7 @@ namespace FlaxEditor.Surface.Archetypes
                 if (selectedIndex != -1)
                 {
                     var index = 5 + selectedIndex * 2;
-                    SetValue(index, _animationPicker.SelectedID);
+                    SetValue(index, _animationPicker.Validator.SelectedID);
                 }
             }
 
@@ -495,7 +495,7 @@ namespace FlaxEditor.Surface.Archetypes
             {
                 if (isValid)
                 {
-                    _animationPicker.SelectedID = data1;
+                    _animationPicker.Validator.SelectedID = data1;
                     _animationSpeed.Value = data0.W;
 
                     var path = string.Empty;
@@ -505,7 +505,7 @@ namespace FlaxEditor.Surface.Archetypes
                 }
                 else
                 {
-                    _animationPicker.SelectedID = Guid.Empty;
+                    _animationPicker.Validator.SelectedID = Guid.Empty;
                     _animationSpeed.Value = 1.0f;
                 }
                 _animationPicker.Enabled = isValid;

Source/Editor/Surface/Archetypes/Function.cs

@@ -95,7 +95,7 @@ namespace FlaxEditor.Surface.Archetypes
 
             private void OnAssetPickerSelectedItemChanged()
             {
-                SetValue(0, _assetPicker.SelectedID);
+                SetValue(0, _assetPicker.Validator.SelectedID);
             }
 
             private void TryRestoreConnections(Box box, Box[] prevBoxes, ref NodeElementArchetype arch)
@@ -133,7 +133,7 @@ namespace FlaxEditor.Surface.Archetypes
                 var prevOutputs = _outputs;
 
                 // Extract function signature parameters (inputs and outputs packed)
-                _asset = LoadSignature(_assetPicker.SelectedID, out var typeNames, out var names);
+                _asset = LoadSignature(_assetPicker.Validator.SelectedID, out var typeNames, out var names);
                 if (typeNames != null && names != null)
                 {
                     var types = new Type[typeNames.Length];
@@ -174,7 +174,7 @@ namespace FlaxEditor.Surface.Archetypes
                         _outputs[i] = box;
                     }
 
-                    Title = _assetPicker.SelectedItem.ShortName;
+                    Title = _assetPicker.Validator.SelectedItem.ShortName;
                 }
                 else
                 {

Source/Editor/Surface/Elements/AssetSelect.cs

@@ -38,13 +38,13 @@ namespace FlaxEditor.Surface.Elements
 
         private void OnNodeValuesChanged()
         {
-            SelectedID = (Guid)ParentNode.Values[Archetype.ValueIndex];
+            Validator.SelectedID = (Guid)ParentNode.Values[Archetype.ValueIndex];
         }
 
         /// <inheritdoc />
         protected override void OnSelectedItemChanged()
         {
-            var selectedId = SelectedID;
+            var selectedId = Validator.SelectedID;
             if (ParentNode != null && (Guid)ParentNode.Values[Archetype.ValueIndex] != selectedId)
             {
                 ParentNode.SetValue(Archetype.ValueIndex, selectedId);

Source/Editor/Tools/Terrain/EditTab.cs

@@ -290,7 +290,7 @@ namespace FlaxEditor.Tools.Terrain
 
             var patchCoord = Gizmo.SelectedPatchCoord;
             var chunkCoord = Gizmo.SelectedChunkCoord;
-            var action = new EditChunkMaterialAction(CarveTab.SelectedTerrain, ref patchCoord, ref chunkCoord, _chunkOverrideMaterial.SelectedAsset as MaterialBase);
+            var action = new EditChunkMaterialAction(CarveTab.SelectedTerrain, ref patchCoord, ref chunkCoord, _chunkOverrideMaterial.Validator.SelectedAsset as MaterialBase);
             action.Do();
             CarveTab.Editor.Undo.AddAction(action);
         }
@@ -336,12 +336,12 @@ namespace FlaxEditor.Tools.Terrain
                     _isUpdatingUI = true;
                     if (terrain.HasPatch(ref patchCoord))
                     {
-                        _chunkOverrideMaterial.SelectedAsset = terrain.GetChunkOverrideMaterial(ref patchCoord, ref chunkCoord);
+                        _chunkOverrideMaterial.Validator.SelectedAsset = terrain.GetChunkOverrideMaterial(ref patchCoord, ref chunkCoord);
                         _chunkOverrideMaterial.Enabled = true;
                     }
                     else
                     {
-                        _chunkOverrideMaterial.SelectedAsset = null;
+                        _chunkOverrideMaterial.Validator.SelectedAsset = null;
                         _chunkOverrideMaterial.Enabled = false;
                     }
                     _isUpdatingUI = false;

Source/Editor/Utilities/AssetPickerValidator.cs

@@ -0,0 +1,293 @@
+using System;
+using System.IO;
+using FlaxEditor.Content;
+using FlaxEditor.Scripting;
+using FlaxEngine;
+using FlaxEngine.Utilities;
+
+namespace FlaxEditor.Utilities;
+
+/// <summary>
+/// Manages and converts the selected content item to the appropriate types. Useful for drag operations.
+/// </summary>
+public class AssetPickerValidator: IContentItemOwner
+{
+    private Asset _selected;
+    private ContentItem _selectedItem;
+    private ScriptType _type;
+    private string _fileExtension;
+
+    /// <summary>
+    /// Gets or sets the selected item.
+    /// </summary>
+    public ContentItem SelectedItem
+    {
+        get => _selectedItem;
+        set
+        {
+            if (_selectedItem == value)
+                return;
+            if (value == null)
+            {
+                if (_selected == null && _selectedItem is SceneItem)
+                {
+                    // Deselect scene reference
+                    _selectedItem.RemoveReference(this);
+                    _selectedItem = null;
+                    _selected = null;
+                    OnSelectedItemChanged();
+                    return;
+                }
+
+                // Deselect
+                _selectedItem?.RemoveReference(this);
+                _selectedItem = null;
+                _selected = null;
+                OnSelectedItemChanged();
+            }
+            else if (value is SceneItem item)
+            {
+                if (_selectedItem == item)
+                    return;
+                if (!IsValid(item))
+                    item = null;
+
+                // Change value to scene reference (cannot load asset because scene can be already loaded - duplicated ID issue)
+                _selectedItem?.RemoveReference(this);
+                _selectedItem = item;
+                _selected = null;
+                _selectedItem?.AddReference(this);
+                OnSelectedItemChanged();
+            }
+            else if (value is AssetItem assetItem)
+            {
+                SelectedAsset = FlaxEngine.Content.LoadAsync(assetItem.ID);
+            }
+            else
+            {
+                // Change value
+                _selectedItem?.RemoveReference(this);
+                _selectedItem = value;
+                _selected = null;
+                OnSelectedItemChanged();
+            }
+        }
+    }
+
+    /// <summary>
+    /// Gets or sets the selected asset identifier.
+    /// </summary>
+    public Guid SelectedID
+    {
+        get
+        {
+            if (_selected != null)
+                return _selected.ID;
+            if (_selectedItem is AssetItem assetItem)
+                return assetItem.ID;
+            return Guid.Empty;
+        }
+        set => SelectedItem = Editor.Instance.ContentDatabase.FindAsset(value);
+    }
+
+    /// <summary>
+    /// Gets or sets the selected content item path.
+    /// </summary>
+    public string SelectedPath
+    {
+        get
+        {
+            string path = _selectedItem?.Path ?? _selected?.Path;
+            if (path != null)
+            {
+                // Convert into path relative to the project (cross-platform)
+                var projectFolder = Globals.ProjectFolder;
+                if (path.StartsWith(projectFolder))
+                    path = path.Substring(projectFolder.Length + 1);
+            }
+            return path;
+        }
+        set
+        {
+            if (string.IsNullOrEmpty(value))
+            {
+                SelectedItem = null;
+            }
+            else
+            {
+                var path = StringUtils.IsRelative(value) ? Path.Combine(Globals.ProjectFolder, value) : value;
+                SelectedItem = Editor.Instance.ContentDatabase.Find(path);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Gets or sets the selected asset object.
+    /// </summary>
+    public Asset SelectedAsset
+    {
+        get => _selected;
+        set
+        {
+            // Check if value won't change
+            if (value == _selected)
+                return;
+
+            // Find item from content database and check it
+            var item = value ? Editor.Instance.ContentDatabase.FindAsset(value.ID) : null;
+            if (item != null && !IsValid(item))
+                item = null;
+
+            // Change value
+            _selectedItem?.RemoveReference(this);
+            _selectedItem = item;
+            _selected = value;
+            _selectedItem?.AddReference(this);
+            OnSelectedItemChanged();
+        }
+    }
+
+    /// <summary>
+    /// Gets or sets the assets types that this picker accepts (it supports types derived from the given type). Use <see cref="ScriptType.Null"/> for generic file picker.
+    /// </summary>
+    public ScriptType AssetType
+    {
+        get => _type;
+        set
+        {
+            if (_type != value)
+            {
+                _type = value;
+
+                // Auto deselect if the current value is invalid
+                if (_selectedItem != null && !IsValid(_selectedItem))
+                    SelectedItem = null;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Gets or sets the content items extensions filter. Null if unused.
+    /// </summary>
+    public string FileExtension
+    {
+        get => _fileExtension;
+        set
+        {
+            if (_fileExtension != value)
+            {
+                _fileExtension = value;
+
+                // Auto deselect if the current value is invalid
+                if (_selectedItem != null && !IsValid(_selectedItem))
+                    SelectedItem = null;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Occurs when selected item gets changed.
+    /// </summary>
+    public event Action SelectedItemChanged;
+
+    /// <summary>
+    /// The custom callback for assets validation. Cane be used to implement a rule for assets to pick.
+    /// </summary>
+    public Func<ContentItem, bool> CheckValid;
+
+    /// <summary>
+    /// Returns whether item is valid.
+    /// </summary>
+    /// <param name="item"></param>
+    /// <returns></returns>
+    public bool IsValid(ContentItem item)
+    {
+        if (_fileExtension != null && !item.Path.EndsWith(_fileExtension))
+            return false;
+        if (CheckValid != null && !CheckValid(item))
+            return false;
+        if (_type == ScriptType.Null)
+            return true;
+
+        if (item is AssetItem assetItem)
+        {
+            // Faster path for binary items (in-built)
+            if (assetItem is BinaryAssetItem binaryItem)
+                return _type.IsAssignableFrom(new ScriptType(binaryItem.Type));
+
+            // Type filter
+            var type = TypeUtils.GetType(assetItem.TypeName);
+            if (_type.IsAssignableFrom(type))
+                return true;
+
+            // Json assets can contain any type of the object defined by the C# type (data oriented design)
+            if (assetItem is JsonAssetItem && (_type.Type == typeof(JsonAsset) || _type.Type == typeof(Asset)))
+                return true;
+
+            // Special case for scene asset references
+            if (_type.Type == typeof(SceneReference) && assetItem is SceneItem)
+                return true;
+        }
+
+        return false;
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AssetPickerValidator"/> class.
+    /// </summary>
+    public AssetPickerValidator()
+    : this(new ScriptType(typeof(Asset)))
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AssetPickerValidator"/> class.
+    /// </summary>
+    /// <param name="assetType">The assets types that this picker accepts.</param>
+    public AssetPickerValidator(ScriptType assetType)
+    {
+        _type = assetType;
+    }
+
+    /// <summary>
+    /// Called when selected item gets changed.
+    /// </summary>
+    protected virtual void OnSelectedItemChanged()
+    {
+        SelectedItemChanged?.Invoke();
+    }
+
+    /// <inheritdoc />
+    public void OnItemDeleted(ContentItem item)
+    {
+        // Deselect item
+        SelectedItem = null;
+    }
+
+    /// <inheritdoc />
+    public void OnItemRenamed(ContentItem item)
+    {
+    }
+
+    /// <inheritdoc />
+    public void OnItemReimported(ContentItem item)
+    {
+    }
+
+    /// <inheritdoc />
+    public void OnItemDispose(ContentItem item)
+    {
+        // Deselect item
+        SelectedItem = null;
+    }
+
+    /// <summary>
+    /// Call to remove reference from the selected item.
+    /// </summary>
+    public void OnDestroy()
+    {
+        _selectedItem?.RemoveReference(this);
+        _selectedItem = null;
+        _selected = null;
+    }
+}

Source/Editor/Windows/AssetReferencesGraphWindow.cs

@@ -46,14 +46,14 @@ namespace FlaxEditor.Windows
                 if (asset != null)
                 {
                     var path = asset.Path;
-                    picker.SelectedAsset = asset;
+                    picker.Validator.SelectedAsset = asset;
                     Title = System.IO.Path.GetFileNameWithoutExtension(path);
                     TooltipText = asset.TypeName + '\n' + path;
                 }
                 else
                 {
-                    picker.SelectedID = AssetId;
+                    picker.Validator.SelectedID = AssetId;
-                    var assetItem = picker.SelectedItem as AssetItem;
+                    var assetItem = picker.Validator.SelectedItem as AssetItem;
                     if (assetItem != null)
                     {
                         Title = assetItem.ShortName;

Source/Editor/Windows/Assets/SkinnedModelWindow.cs

@@ -837,7 +837,7 @@ namespace FlaxEditor.Windows.Assets
                         sourceAssetPicker.CheckValid = CheckSourceAssetValid;
                         sourceAssetPicker.SelectedItemChanged += () =>
                         {
-                            proxy.Setups.Add(sourceAssetPicker.SelectedAsset, new SetupProxy());
+                            proxy.Setups.Add(sourceAssetPicker.Validator.SelectedAsset, new SetupProxy());
                             proxy.Window.MarkAsEdited();
                             RebuildLayout();
                         };
@@ -856,7 +856,7 @@ namespace FlaxEditor.Windows.Assets
 
                         // Source asset picker
                         var sourceAssetPicker = setupGroup.AddPropertyItem("Source Asset").Custom<AssetPicker>().CustomControl;
-                        sourceAssetPicker.SelectedAsset = sourceAsset;
+                        sourceAssetPicker.Validator.SelectedAsset = sourceAsset;
                         sourceAssetPicker.CanEdit = false;
                         sourceAssetPicker.Height = 48;
 
@@ -916,12 +916,12 @@ namespace FlaxEditor.Windows.Assets
                         {
                             // Show skeleton asset picker
                             var sourceSkeletonPicker = setupGroup.AddPropertyItem("Skeleton", "Skinned model that contains a skeleton for this animation retargeting.").Custom<AssetPicker>().CustomControl;
-                            sourceSkeletonPicker.AssetType = new ScriptType(typeof(SkinnedModel));
+                            sourceSkeletonPicker.Validator.AssetType = new ScriptType(typeof(SkinnedModel));
-                            sourceSkeletonPicker.SelectedAsset = setup.Value.Skeleton;
+                            sourceSkeletonPicker.Validator.SelectedAsset = setup.Value.Skeleton;
                             sourceSkeletonPicker.Height = 48;
                             sourceSkeletonPicker.SelectedItemChanged += () =>
                             {
-                                setup.Value.Skeleton = (SkinnedModel)sourceSkeletonPicker.SelectedAsset;
+                                setup.Value.Skeleton = (SkinnedModel)sourceSkeletonPicker.Validator.SelectedAsset;
                                 proxy.Window.MarkAsEdited();
                             };
                         }