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Source/Editor/GUI/Drag/DragItems.cs

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+// Copyright (c) 2012-2020 Wojciech Figat. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using FlaxEditor.Content;
+using FlaxEngine.GUI;
+
+namespace FlaxEditor.GUI.Drag
+{
+    /// <summary>
+    /// Drag content items handler.
+    /// </summary>
+    public sealed class DragItems : DragItems<DragEventArgs>
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DragItems"/> class.
+        /// </summary>
+        /// <param name="validateFunction">The validation function</param>
+        public DragItems(Func<ContentItem, bool> validateFunction)
+        : base(validateFunction)
+        {
+        }
+    }
+
+    /// <summary>
+    /// Helper class for handling <see cref="ContentItem"/> drag and drop.
+    /// </summary>
+    /// <seealso cref="ContentItem" />
+    public class DragItems<U> : DragHelper<ContentItem, U> where U : DragEventArgs
+    {
+        /// <summary>
+        /// The default prefix for drag data used for <see cref="ContentItem"/>.
+        /// </summary>
+        public const string DragPrefix = "ASSET!?";
+
+        /// <summary>
+        /// Creates a new DragHelper
+        /// </summary>
+        /// <param name="validateFunction">The validation function</param>
+        public DragItems(Func<ContentItem, bool> validateFunction)
+        : base(validateFunction)
+        {
+        }
+
+        /// <summary>
+        /// Gets the drag data for the given file.
+        /// </summary>
+        /// <param name="path">The path.</param>
+        /// <returns>The data.</returns>
+        public DragData ToDragData(string path) => GetDragData(path);
+
+        /// <inheritdoc/>
+        public override DragData ToDragData(ContentItem item) => GetDragData(item);
+
+        /// <inheritdoc/>
+        public override DragData ToDragData(IEnumerable<ContentItem> items) => GetDragData(items);
+
+        /// <summary>
+        /// Gets the drag data.
+        /// </summary>
+        /// <param name="path">The path.</param>
+        /// <returns>The data.</returns>
+        public static DragData GetDragData(string path)
+        {
+            if (path == null)
+                throw new ArgumentNullException();
+
+            return new DragDataText(DragPrefix + path);
+        }
+
+        /// <summary>
+        /// Gets the drag data.
+        /// </summary>
+        /// <param name="item">The item.</param>
+        /// <returns>The data.</returns>
+        public static DragDataText GetDragData(ContentItem item)
+        {
+            if (item == null)
+                throw new ArgumentNullException();
+
+            return new DragDataText(DragPrefix + item.Path);
+        }
+
+        /// <summary>
+        /// Gets the drag data.
+        /// </summary>
+        /// <param name="items">The items.</param>
+        /// <returns>The data.</returns>
+        public static DragData GetDragData(IEnumerable<ContentItem> items)
+        {
+            if (items == null)
+                throw new ArgumentNullException();
+
+            string text = DragPrefix;
+            foreach (var item in items)
+                text += item.Path + '\n';
+            return new DragDataText(text);
+        }
+
+        /// <inheritdoc/>
+        public override IEnumerable<ContentItem> FromDragData(DragData data)
+        {
+            if (data is DragDataText dataText)
+            {
+                if (dataText.Text.StartsWith(DragPrefix))
+                {
+                    // Remove prefix and parse spitted names
+                    var paths = dataText.Text.Remove(0, DragPrefix.Length).Split('\n');
+                    var results = new List<ContentItem>(paths.Length);
+                    for (int i = 0; i < paths.Length; i++)
+                    {
+                        // Find element
+                        var obj = Editor.Instance.ContentDatabase.Find(paths[i]);
+
+                        // Check it
+                        if (obj != null)
+                            results.Add(obj);
+                    }
+
+                    return results.ToArray();
+                }
+            }
+            return new ContentItem[0];
+        }
+    }
+}