Merge pull request AvaloniaUI#7605 from AvaloniaUI/feature/skia-layering-extensions

Add Skia Helper Methods to allow applying Skia Filter Effects (Blur, DropShadow, Lighting) to DC content

Author: danwalmsley

src/Skia/Avalonia.Skia/Helpers/DrawingContextHelper.cs

@@ -1,10 +1,11 @@
-using Avalonia.Platform;
+using System;
+using Avalonia.Platform;
 using Avalonia.Rendering;
 using SkiaSharp;
 
 namespace Avalonia.Skia.Helpers
 {
-    public class DrawingContextHelper
+    public static class DrawingContextHelper
     {
         /// <summary>
         /// Wrap Skia canvas in drawing context so we can use Avalonia api to render to external skia canvas
@@ -27,5 +28,71 @@ public static IDrawingContextImpl WrapSkiaCanvas(SKCanvas canvas, Vector dpi, IV
 
             return new DrawingContextImpl(createInfo);
         }
+        
+        /// <summary>
+        /// Unsupported - Wraps a GPU Backed SkiaSurface in an Avalonia DrawingContext.
+        /// </summary>
+        [Obsolete]
+        public static ISkiaDrawingContextImpl WrapSkiaSurface(this SKSurface surface, GRContext grContext, Vector dpi, params IDisposable[] disposables)
+        {
+            var createInfo = new DrawingContextImpl.CreateInfo
+            {
+                GrContext = grContext,
+                Surface = surface,
+                Dpi = dpi,
+                DisableTextLcdRendering = false,
+            };
+
+            return new DrawingContextImpl(createInfo, disposables);
+        }
+        
+        /// <summary>
+        /// Unsupported - Wraps a non-GPU Backed SkiaSurface in an Avalonia DrawingContext.
+        /// </summary>
+        [Obsolete]
+        public static ISkiaDrawingContextImpl WrapSkiaSurface(this SKSurface surface, Vector dpi, params IDisposable[] disposables)
+        {
+            var createInfo = new DrawingContextImpl.CreateInfo
+            {
+                Surface = surface,
+                Dpi = dpi,
+                DisableTextLcdRendering = false,
+            };
+
+            return new DrawingContextImpl(createInfo, disposables);
+        }
+
+        [Obsolete]
+        public static ISkiaDrawingContextImpl CreateDrawingContext(Size size, Vector dpi, GRContext grContext = null)
+        {
+            if (grContext is null)
+            {
+                var surface = SKSurface.Create(
+                    new SKImageInfo(
+                        (int)Math.Ceiling(size.Width),
+                        (int)Math.Ceiling(size.Height),
+                        SKImageInfo.PlatformColorType,
+                        SKAlphaType.Premul));
+
+                return WrapSkiaSurface(surface, dpi, surface);
+            }
+            else
+            {
+                var surface = SKSurface.Create(grContext, false,
+                    new SKImageInfo(
+                        (int)Math.Ceiling(size.Width),
+                        (int)Math.Ceiling(size.Height),
+                        SKImageInfo.PlatformColorType,
+                        SKAlphaType.Premul));
+
+                return WrapSkiaSurface(surface, grContext, dpi, surface);
+            }
+        }
+        
+        [Obsolete]
+        public static void DrawTo(this ISkiaDrawingContextImpl source, ISkiaDrawingContextImpl destination, SKPaint paint = null)
+        {
+            destination.SkCanvas.DrawSurface(source.SkSurface, new SKPoint(0, 0), paint);
+        }
     }
 }