Add new UIBrush that uses UIBrushAsset json resource with a brush data

Source/Editor/CustomEditors/Editors/IBrushEditor.cs

@@ -26,6 +26,7 @@ namespace FlaxEditor.CustomEditors.Editors
             new OptionType("Texture 9-Slicing", typeof(Texture9SlicingBrush)),
             new OptionType("Sprite 9-Slicing", typeof(Sprite9SlicingBrush)),
             new OptionType("Video", typeof(VideoBrush)),
+            new OptionType("UI Brush", typeof(UIBrush)),
         };
     }
 }

Source/Engine/UI/GUI/Brushes/UIBrush.cs

@@ -0,0 +1,75 @@
+// Copyright (c) Wojciech Figat. All rights reserved.
+
+namespace FlaxEngine.GUI
+{
+    /// <summary>
+    /// Asset with <see cref="IBrush"/> that can be reused in different UI controls.
+    /// </summary>
+    /// <seealso cref="IBrush" />
+    /// <seealso cref="UIBrush" />
+    public class UIBrushAsset
+    {
+        /// <summary>
+        /// Brush object.
+        /// </summary>
+        public IBrush Brush;
+    }
+
+    /// <summary>
+    /// Implementation of <see cref="IBrush"/> for <see cref="FlaxEngine.VideoPlayer"/> frame displaying.
+    /// </summary>
+    /// <seealso cref="IBrush" />
+    /// <seealso cref="UIBrushAsset" />
+    public sealed class UIBrush : IBrush
+    {
+        /// <summary>
+        /// The UI Brush asset to use.
+        /// </summary>
+        public JsonAssetReference<UIBrushAsset> Asset;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UIBrush"/> class.
+        /// </summary>
+        public UIBrush()
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UIBrush"/> struct.
+        /// </summary>
+        /// <param name="asset">The UI Brush asset to use.</param>
+        public UIBrush(JsonAssetReference<UIBrushAsset> asset)
+        {
+            Asset = asset;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UIBrush"/> struct.
+        /// </summary>
+        /// <param name="asset">The UI Brush asset to use.</param>
+        public UIBrush(JsonAsset asset)
+        {
+            Asset = asset;
+        }
+
+        /// <inheritdoc />
+        public Float2 Size
+        {
+            get
+            {
+                var asset = (UIBrushAsset)Asset.Asset?.Instance;
+                if (asset != null && asset.Brush != null)
+                    return asset.Brush.Size;
+                return Float2.Zero;
+            }
+        }
+
+        /// <inheritdoc />
+        public void Draw(Rectangle rect, Color color)
+        {
+            var asset = (UIBrushAsset)Asset.Asset?.Instance;
+            if (asset != null && asset.Brush != null)
+                asset.Brush.Draw(rect, color);
+        }
+    }
+}