pass surfaceorigin to FboSkiaSurface.

src/Skia/Avalonia.Skia/DrawingContextImpl.cs

@@ -36,6 +36,7 @@ namespace Avalonia.Skia
         private readonly SKPaint _fillPaint = new SKPaint();
         private readonly SKPaint _boxShadowPaint = new SKPaint();
         private static SKShader s_acrylicNoiseShader;
+        private readonly GRSurfaceOrigin _surfaceOrigin; 
 
         /// <summary>
         /// Context create info.
@@ -76,6 +77,8 @@ namespace Avalonia.Skia
             /// Skia GPU provider context (optional)
             /// </summary>
             public ISkiaGpu Gpu;
+
+            public ISkiaGpuRenderSession CurrentSession;
         }
 
         /// <summary>
@@ -96,6 +99,8 @@ namespace Avalonia.Skia
             Surface = createInfo.Surface;
             Canvas = createInfo.Canvas ?? createInfo.Surface?.Canvas;
 
+            _surfaceOrigin = createInfo.CurrentSession?.SurfaceOrigin ?? GRSurfaceOrigin.TopLeft;
+
             if (Canvas == null)
             {
                 throw new ArgumentException("Invalid create info - no Canvas provided", nameof(createInfo));
@@ -972,7 +977,7 @@ namespace Avalonia.Skia
                 Gpu = _gpu
             };
 
-            return new SurfaceRenderTarget(createInfo);
+            return new SurfaceRenderTarget(createInfo, _surfaceOrigin);
         }        
 
         /// <summary>

src/Skia/Avalonia.Skia/Gpu/ISkiaGpu.cs

@@ -21,7 +21,7 @@ namespace Avalonia.Skia
         /// Creates an offscreen render target surface
         /// </summary>
         /// <param name="size">size in pixels</param>
-        ISkiaSurface TryCreateSurface(PixelSize size);
+        ISkiaSurface TryCreateSurface(PixelSize size, GRSurfaceOrigin surfaceOrigin);
     }
     
     public interface ISkiaSurface : IDisposable

src/Skia/Avalonia.Skia/Gpu/ISkiaGpuRenderSession.cs

@@ -22,5 +22,7 @@ namespace Avalonia.Skia
         /// Scaling factor.
         /// </summary>
         double ScaleFactor { get; }
+        
+        GRSurfaceOrigin SurfaceOrigin { get; }
     }
 }

src/Skia/Avalonia.Skia/Gpu/OpenGl/FboSkiaSurface.cs

@@ -14,7 +14,7 @@ namespace Avalonia.Skia
         private int _texture;
 
         private static readonly bool[] TrueFalse = new[] { true, false };
-        public FboSkiaSurface(GRContext grContext, IGlContext glContext, PixelSize pixelSize)
+        public FboSkiaSurface(GRContext grContext, IGlContext glContext, PixelSize pixelSize, GRSurfaceOrigin surfaceOrigin)
         {
             _grContext = grContext;
             _glContext = glContext;
@@ -93,7 +93,7 @@ namespace Avalonia.Skia
             var target = new GRBackendRenderTarget(pixelSize.Width, pixelSize.Height, 0, 8,
                 new GRGlFramebufferInfo((uint)_fbo, SKColorType.Rgba8888.ToGlSizedFormat()));
             Surface = SKSurface.Create(_grContext, target,
-                GRSurfaceOrigin.TopLeft, SKColorType.Rgba8888);
+                surfaceOrigin, SKColorType.Rgba8888);
             CanBlit = gl.BlitFramebuffer != null;
         }
         

src/Skia/Avalonia.Skia/Gpu/OpenGl/GlRenderTarget.cs

@@ -39,6 +39,8 @@ namespace Avalonia.Skia
                 _backendRenderTarget = backendRenderTarget;
                 _surface = surface;
                 _glSession = glSession;
+                
+                SurfaceOrigin = glSession.IsYFlipped ? GRSurfaceOrigin.TopLeft : GRSurfaceOrigin.BottomLeft;
             }
             public void Dispose()
             {
@@ -48,6 +50,8 @@ namespace Avalonia.Skia
                 GrContext.Flush();
                 _glSession.Dispose();
             }
+            
+            public GRSurfaceOrigin SurfaceOrigin { get; }
 
             public GRContext GrContext { get; }
             public SKSurface SkSurface => _surface;

src/Skia/Avalonia.Skia/Gpu/OpenGl/GlSkiaGpu.cs

@@ -47,7 +47,7 @@ namespace Avalonia.Skia
             return null;
         }
 
-        public ISkiaSurface TryCreateSurface(PixelSize size)
+        public ISkiaSurface TryCreateSurface(PixelSize size, GRSurfaceOrigin surfaceOrigin)
         {
             // Only windows platform needs our FBO trickery
             if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
@@ -62,7 +62,7 @@ namespace Avalonia.Skia
                 return null;
             try
             {
-                var surface = new FboSkiaSurface(_grContext, _glContext, size);
+                var surface = new FboSkiaSurface(_grContext, _glContext, size, surfaceOrigin);
                 _canCreateSurfaces = true;
                 return surface;
             }

src/Skia/Avalonia.Skia/Gpu/SkiaGpuRenderTarget.cs

@@ -33,7 +33,8 @@ namespace Avalonia.Skia
                 Dpi = SkiaPlatform.DefaultDpi * session.ScaleFactor,
                 VisualBrushRenderer = visualBrushRenderer,
                 DisableTextLcdRendering = true,
-                Gpu = _skiaGpu
+                Gpu = _skiaGpu,
+                CurrentSession =  session
             };
 
             return new DrawingContextImpl(nfo, session);

src/Skia/Avalonia.Skia/PlatformRenderInterface.cs

@@ -127,7 +127,7 @@ namespace Avalonia.Skia
                 DisableTextLcdRendering = false
             };
 
-            return new SurfaceRenderTarget(createInfo);
+            return new SurfaceRenderTarget(createInfo, GRSurfaceOrigin.TopLeft);
         }
 
         /// <inheritdoc />

src/Skia/Avalonia.Skia/SurfaceRenderTarget.cs

@@ -42,7 +42,7 @@ namespace Avalonia.Skia
         /// Create new surface render target.
         /// </summary>
         /// <param name="createInfo">Create info.</param>
-        public SurfaceRenderTarget(CreateInfo createInfo)
+        public SurfaceRenderTarget(CreateInfo createInfo, GRSurfaceOrigin surfaceOrigin)
         {
             PixelSize = new PixelSize(createInfo.Width, createInfo.Height);
             Dpi = createInfo.Dpi;
@@ -51,7 +51,7 @@ namespace Avalonia.Skia
             _grContext = createInfo.GrContext;
             _gpu = createInfo.Gpu;
 
-            _surface = _gpu?.TryCreateSurface(PixelSize);
+            _surface = _gpu?.TryCreateSurface(PixelSize, surfaceOrigin);
             if (_surface == null)
                 _surface = new SkiaSurfaceWrapper(CreateSurface(createInfo.GrContext, PixelSize.Width, PixelSize.Height,
                     createInfo.Format));
@@ -100,7 +100,7 @@ namespace Avalonia.Skia
                 VisualBrushRenderer = visualBrushRenderer,
                 DisableTextLcdRendering = _disableLcdRendering,
                 GrContext = _grContext,
-                Gpu = _gpu
+                Gpu = _gpu,
             };
 
             return new DrawingContextImpl(createInfo, Disposable.Create(() => Version++));