Merge pull request #10390 from MrJul/skia-nullable

Nullable annotations for Avalonia.Skia

src/Avalonia.Base/Media/IImageBrush.cs

@@ -12,6 +12,6 @@ namespace Avalonia.Media
         /// <summary>
         /// Gets the image to draw.
         /// </summary>
-        IBitmap Source { get; }
+        IBitmap? Source { get; }
     }
 }

src/Avalonia.Base/Media/ImageBrush.cs

@@ -11,8 +11,8 @@ namespace Avalonia.Media
         /// <summary>
         /// Defines the <see cref="Visual"/> property.
         /// </summary>
-        public static readonly StyledProperty<IBitmap> SourceProperty =
+        public static readonly StyledProperty<IBitmap?> SourceProperty =
-            AvaloniaProperty.Register<ImageBrush, IBitmap>(nameof(Source));
+            AvaloniaProperty.Register<ImageBrush, IBitmap?>(nameof(Source));
 
         static ImageBrush()
         {
@@ -30,7 +30,7 @@ namespace Avalonia.Media
         /// Initializes a new instance of the <see cref="ImageBrush"/> class.
         /// </summary>
         /// <param name="source">The image to draw.</param>
-        public ImageBrush(IBitmap source)
+        public ImageBrush(IBitmap? source)
         {
             Source = source;
         }
@@ -38,7 +38,7 @@ namespace Avalonia.Media
         /// <summary>
         /// Gets or sets the image to draw.
         /// </summary>
-        public IBitmap Source
+        public IBitmap? Source
         {
             get { return GetValue(SourceProperty); }
             set { SetValue(SourceProperty, value); }

src/Avalonia.Base/Media/Immutable/ImmutableImageBrush.cs

@@ -24,13 +24,13 @@ namespace Avalonia.Media.Immutable
         /// <param name="tileMode">The tile mode.</param>
         /// <param name="bitmapInterpolationMode">The bitmap interpolation mode.</param>
         public ImmutableImageBrush(
-            IBitmap source,
+            IBitmap? source,
             AlignmentX alignmentX = AlignmentX.Center,
             AlignmentY alignmentY = AlignmentY.Center,
             RelativeRect? destinationRect = null,
             double opacity = 1,
             ImmutableTransform? transform = null,
-            RelativePoint transformOrigin = new RelativePoint(),
+            RelativePoint transformOrigin = default,
             RelativeRect? sourceRect = null,
             Stretch stretch = Stretch.Uniform,
             TileMode tileMode = TileMode.None,
@@ -61,6 +61,6 @@ namespace Avalonia.Media.Immutable
         }
 
         /// <inheritdoc/>
-        public IBitmap Source { get; }
+        public IBitmap? Source { get; }
     }
 }

src/Avalonia.Base/Media/Immutable/ImmutableVisualBrush.cs

@@ -24,7 +24,7 @@ namespace Avalonia.Media.Immutable
         /// <param name="tileMode">The tile mode.</param>
         /// <param name="bitmapInterpolationMode">Controls the quality of interpolation.</param>
         public ImmutableVisualBrush(
-            Visual visual,
+            Visual? visual,
             AlignmentX alignmentX = AlignmentX.Center,
             AlignmentY alignmentY = AlignmentY.Center,
             RelativeRect? destinationRect = null,

src/Avalonia.Base/Platform/IGeometryImpl.cs

@@ -1,3 +1,4 @@
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Media;
 using Avalonia.Metadata;
 
@@ -47,7 +48,7 @@ namespace Avalonia.Platform
         /// <param name="pen">The stroke to use.</param>
         /// <param name="point">The point.</param>
         /// <returns><c>true</c> if the geometry contains the point; otherwise, <c>false</c>.</returns>
-        bool StrokeContains(IPen pen, Point point);
+        bool StrokeContains(IPen? pen, Point point);
 
         /// <summary>
         /// Makes a clone of the geometry with the specified transform.
@@ -87,6 +88,7 @@ namespace Avalonia.Platform
         /// <param name="startOnBeginFigure">If ture, the resulting snipped path will start with a BeginFigure call.</param>
         /// <param name="segmentGeometry">The resulting snipped path.</param>
         /// <returns>If the snipping operation is successful.</returns>
-        bool TryGetSegment(double startDistance, double stopDistance, bool startOnBeginFigure, out IGeometryImpl segmentGeometry);
+        bool TryGetSegment(double startDistance, double stopDistance, bool startOnBeginFigure,
+            [NotNullWhen(true)] out IGeometryImpl? segmentGeometry);
     }
 }

src/Browser/Avalonia.Browser/Skia/BrowserSkiaGpu.cs

@@ -21,7 +21,7 @@ namespace Avalonia.Browser.Skia
             return null;
         }
 
-        public ISkiaSurface? TryCreateSurface(PixelSize size, ISkiaGpuRenderSession session)
+        public ISkiaSurface? TryCreateSurface(PixelSize size, ISkiaGpuRenderSession? session)
         {
             return null;
         }

src/Skia/Avalonia.Skia/Avalonia.Skia.csproj

@@ -19,6 +19,7 @@
   <Import Project="..\..\..\build\HarfBuzzSharp.props" />
   <Import Project="..\..\..\build\DevAnalyzers.props" />
   <Import Project="..\..\..\build\TrimmingEnable.props" />
+  <Import Project="..\..\..\build\NullableEnable.props" />
 
   <ItemGroup Label="InternalsVisibleTo">
     <InternalsVisibleTo Include="Avalonia.Skia.RenderTests, PublicKey=$(AvaloniaPublicKey)" />

src/Skia/Avalonia.Skia/CombinedGeometryImpl.cs

@@ -1,9 +1,6 @@
-using System.Collections.Generic;
 using Avalonia.Media;
 using SkiaSharp;
 
-#nullable enable
-
 namespace Avalonia.Skia
 {
     /// <summary>
@@ -13,23 +10,24 @@ namespace Avalonia.Skia
     {
         public CombinedGeometryImpl(GeometryCombineMode combineMode, Geometry g1, Geometry g2)
         {
-            var path1 = ((GeometryImpl)g1.PlatformImpl).EffectivePath;
+            var path1 = (g1.PlatformImpl as GeometryImpl)?.EffectivePath;
-            var path2 = ((GeometryImpl)g2.PlatformImpl).EffectivePath;
+            var path2 = (g2.PlatformImpl as GeometryImpl)?.EffectivePath;
+
             var op = combineMode switch
             {
                 GeometryCombineMode.Intersect => SKPathOp.Intersect,
                 GeometryCombineMode.Xor => SKPathOp.Xor,
                 GeometryCombineMode.Exclude => SKPathOp.Difference,
-                _ => SKPathOp.Union,
+                _ => SKPathOp.Union
             };
 
-            var path = path1.Op(path2, op);
+            var path = path1?.Op(path2, op);
 
             EffectivePath = path;
-            Bounds = path.Bounds.ToAvaloniaRect();
+            Bounds = path?.Bounds.ToAvaloniaRect() ?? default;
         }
 
         public override Rect Bounds { get; }
-        public override SKPath EffectivePath { get; }
+        public override SKPath? EffectivePath { get; }
     }
 }

src/Skia/Avalonia.Skia/DrawingContextImpl.cs

@@ -19,27 +19,27 @@ namespace Avalonia.Skia
     /// </summary>
     internal class DrawingContextImpl : IDrawingContextImpl, IDrawingContextWithAcrylicLikeSupport
     {
-        private IDisposable[] _disposables;
+        private IDisposable?[]? _disposables;
         private readonly Vector _dpi;
-        private readonly Stack<PaintWrapper> _maskStack = new Stack<PaintWrapper>();
+        private readonly Stack<PaintWrapper> _maskStack = new();
-        private readonly Stack<double> _opacityStack = new Stack<double>();
+        private readonly Stack<double> _opacityStack = new();
-        private readonly Stack<BitmapBlendingMode> _blendingModeStack = new Stack<BitmapBlendingMode>();
+        private readonly Stack<BitmapBlendingMode> _blendingModeStack = new();
         private readonly Matrix? _postTransform;
-        private readonly IVisualBrushRenderer _visualBrushRenderer;
+        private readonly IVisualBrushRenderer? _visualBrushRenderer;
         private double _currentOpacity = 1.0f;
         private BitmapBlendingMode _currentBlendingMode = BitmapBlendingMode.SourceOver;
         private readonly bool _canTextUseLcdRendering;
         private Matrix _currentTransform;
         private bool _disposed;
-        private GRContext _grContext;
+        private GRContext? _grContext;
-        public GRContext GrContext => _grContext;
+        public GRContext? GrContext => _grContext;
-        private ISkiaGpu _gpu;
+        private readonly ISkiaGpu? _gpu;
         private readonly SKPaint _strokePaint = SKPaintCache.Shared.Get();
         private readonly SKPaint _fillPaint = SKPaintCache.Shared.Get();
         private readonly SKPaint _boxShadowPaint = SKPaintCache.Shared.Get();
-        private static SKShader s_acrylicNoiseShader;
+        private static SKShader? s_acrylicNoiseShader;
-        private readonly ISkiaGpuRenderSession _session;
+        private readonly ISkiaGpuRenderSession? _session;
-        private bool _leased = false;
+        private bool _leased;
 
         /// <summary>
         /// Context create info.
@@ -49,12 +49,12 @@ namespace Avalonia.Skia
             /// <summary>
             /// Canvas to draw to.
             /// </summary>
-            public SKCanvas Canvas;
+            public SKCanvas? Canvas;
 
             /// <summary>
             /// Surface to draw to.
             /// </summary>
-            public SKSurface Surface;
+            public SKSurface? Surface;
 
             /// <summary>
             /// Dpi of drawings.
@@ -64,7 +64,7 @@ namespace Avalonia.Skia
             /// <summary>
             /// Visual brush renderer.
             /// </summary>
-            public IVisualBrushRenderer VisualBrushRenderer;
+            public IVisualBrushRenderer? VisualBrushRenderer;
 
             /// <summary>
             /// Render text without Lcd rendering.
@@ -74,17 +74,17 @@ namespace Avalonia.Skia
             /// <summary>
             /// GPU-accelerated context (optional)
             /// </summary>
-            public GRContext GrContext;
+            public GRContext? GrContext;
 
             /// <summary>
             /// Skia GPU provider context (optional)
             /// </summary>
-            public ISkiaGpu Gpu;
+            public ISkiaGpu? Gpu;
 
-            public ISkiaGpuRenderSession CurrentSession;
+            public ISkiaGpuRenderSession? CurrentSession;
         }
 
-        class SkiaLeaseFeature : ISkiaSharpApiLeaseFeature
+        private class SkiaLeaseFeature : ISkiaSharpApiLeaseFeature
         {
             private readonly DrawingContextImpl _context;
 
@@ -99,10 +99,11 @@ namespace Avalonia.Skia
                 return new ApiLease(_context);
             }
 
-            class ApiLease : ISkiaSharpApiLease
+            private class ApiLease : ISkiaSharpApiLease
             {
-                private DrawingContextImpl _context;
+                private readonly DrawingContextImpl _context;
                 private readonly SKMatrix _revertTransform;
+                private bool _isDisposed;
 
                 public ApiLease(DrawingContextImpl context)
                 {
@@ -112,15 +113,18 @@ namespace Avalonia.Skia
                 }
 
                 public SKCanvas SkCanvas => _context.Canvas;
-                public GRContext GrContext => _context.GrContext;
+                public GRContext? GrContext => _context.GrContext;
-                public SKSurface SkSurface => _context.Surface;
+                public SKSurface? SkSurface => _context.Surface;
                 public double CurrentOpacity => _context._currentOpacity;
                 
                 public void Dispose()
                 {
-                    _context.Canvas.SetMatrix(_revertTransform);
+                    if (!_isDisposed)
-                    _context._leased = false;
+                    {
-                    _context = null;
+                        _context.Canvas.SetMatrix(_revertTransform);
+                        _context._leased = false;
+                        _isDisposed = true;
+                    }
                 }
             }
         }
@@ -130,8 +134,11 @@ namespace Avalonia.Skia
         /// </summary>
         /// <param name="createInfo">Create info.</param>
         /// <param name="disposables">Array of elements to dispose after drawing has finished.</param>
-        public DrawingContextImpl(CreateInfo createInfo, params IDisposable[] disposables)
+        public DrawingContextImpl(CreateInfo createInfo, params IDisposable?[]? disposables)
         {
+            Canvas = createInfo.Canvas ?? createInfo.Surface?.Canvas
+                ?? throw new ArgumentException("Invalid create info - no Canvas provided", nameof(createInfo));
+
             _dpi = createInfo.Dpi;
             _visualBrushRenderer = createInfo.VisualBrushRenderer;
             _disposables = disposables;
@@ -141,15 +148,9 @@ namespace Avalonia.Skia
             if (_grContext != null)
                 Monitor.Enter(_grContext);
             Surface = createInfo.Surface;
-            Canvas = createInfo.Canvas ?? createInfo.Surface?.Canvas;
 
             _session = createInfo.CurrentSession;
 
-            if (Canvas == null)
-            {
-                throw new ArgumentException("Invalid create info - no Canvas provided", nameof(createInfo));
-            }
-
             if (!_dpi.NearlyEquals(SkiaPlatform.DefaultDpi))
             {
                 _postTransform =
@@ -163,7 +164,7 @@ namespace Avalonia.Skia
         /// Skia canvas.
         /// </summary>
         public SKCanvas Canvas { get; }
-        public SKSurface Surface { get; }
+        public SKSurface? Surface { get; }
 
         private void CheckLease()
         {
@@ -205,87 +206,89 @@ namespace Avalonia.Skia
         }
 
         /// <inheritdoc />
-        public void DrawLine(IPen pen, Point p1, Point p2)
+        public void DrawLine(IPen? pen, Point p1, Point p2)
         {
             CheckLease();
 
-            if (pen is null)
+            if (pen is not null
-            {
+                && TryCreatePaint(_strokePaint, pen, new Size(Math.Abs(p2.X - p1.X), Math.Abs(p2.Y - p1.Y))) is { } stroke)
-                return;
-            }
-
-            using (var paint = CreatePaint(_strokePaint, pen, new Size(Math.Abs(p2.X - p1.X), Math.Abs(p2.Y - p1.Y))))
             {
-                if (paint.Paint is object)
+                using (stroke)
                 {
-                    Canvas.DrawLine((float)p1.X, (float)p1.Y, (float)p2.X, (float)p2.Y, paint.Paint);
+                    Canvas.DrawLine((float)p1.X, (float)p1.Y, (float)p2.X, (float)p2.Y, stroke.Paint);
                 }
             }
         }
 
         /// <inheritdoc />
-        public void DrawGeometry(IBrush brush, IPen pen, IGeometryImpl geometry)
+        public void DrawGeometry(IBrush? brush, IPen? pen, IGeometryImpl geometry)
         {
             CheckLease();
             var impl = (GeometryImpl) geometry;
             var size = geometry.Bounds.Size;
 
-            using (var fill = brush != null ? CreatePaint(_fillPaint, brush, size) : default)
+            if (brush is not null)
-            using (var stroke = pen?.Brush != null ? CreatePaint(_strokePaint, pen, 
-                size.Inflate(new Thickness(pen?.Thickness / 2 ?? 0))) : default)
             {
-                if (fill.Paint != null)
+                using (var fill = CreatePaint(_fillPaint, brush, size))
                 {
                     Canvas.DrawPath(impl.EffectivePath, fill.Paint);
                 }
+            }
 
-                if (stroke.Paint != null)
+            if (pen is not null
+                && TryCreatePaint(_strokePaint, pen, size.Inflate(new Thickness(pen.Thickness / 2))) is { } stroke)
+            {
+                using (stroke)
                 {
                     Canvas.DrawPath(impl.EffectivePath, stroke.Paint);
                 }
             }
         }
 
-        struct BoxShadowFilter : IDisposable
+        private struct BoxShadowFilter : IDisposable
         {
-            public SKPaint Paint;
+            public readonly SKPaint Paint;
-            private SKImageFilter _filter;
+            private readonly SKImageFilter? _filter;
-            public SKClipOperation ClipOperation;
+            public readonly SKClipOperation ClipOperation;
+
+            private BoxShadowFilter(SKPaint paint, SKImageFilter? filter, SKClipOperation clipOperation)
+            {
+                Paint = paint;
+                _filter = filter;
+                ClipOperation = clipOperation;
+            }
 
-            static float SkBlurRadiusToSigma(double radius) {
+            private static float SkBlurRadiusToSigma(double radius) {
                 if (radius <= 0)
                     return 0.0f;
                 return 0.288675f * (float)radius + 0.5f;
             }
+
             public static BoxShadowFilter Create(SKPaint paint, BoxShadow shadow, double opacity)
             {
                 var ac = shadow.Color;
 
-                SKImageFilter filter = null;
+                var filter = SKImageFilter.CreateBlur(SkBlurRadiusToSigma(shadow.Blur), SkBlurRadiusToSigma(shadow.Blur));
-                filter = SKImageFilter.CreateBlur(SkBlurRadiusToSigma(shadow.Blur), SkBlurRadiusToSigma(shadow.Blur));
                 var color = new SKColor(ac.R, ac.G, ac.B, (byte)(ac.A * opacity));
 
                 paint.Reset();
                 paint.IsAntialias = true;
                 paint.Color = color;
                 paint.ImageFilter = filter;
-                
+
-                return new BoxShadowFilter
+                var clipOperation = shadow.IsInset ? SKClipOperation.Intersect : SKClipOperation.Difference;
-                {
+
-                    Paint = paint, _filter = filter,
+                return new BoxShadowFilter(paint, filter, clipOperation);
-                    ClipOperation = shadow.IsInset ? SKClipOperation.Intersect : SKClipOperation.Difference
-                };
             }
 
             public void Dispose()
             {
-                Paint.Reset();
+                Paint?.Reset();
-                Paint = null;
                 _filter?.Dispose();
             }
         }
 
-        static SKRect AreaCastingShadowInHole(
+        private static SKRect AreaCastingShadowInHole(
             SKRect hole_rect,
             float shadow_blur,
             float shadow_spread,
@@ -306,18 +309,16 @@ namespace Avalonia.Skia
         }
 
         /// <inheritdoc />
-        public void DrawRectangle(IExperimentalAcrylicMaterial material, RoundedRect rect)
+        public void DrawRectangle(IExperimentalAcrylicMaterial? material, RoundedRect rect)
         {
             if (rect.Rect.Height <= 0 || rect.Rect.Width <= 0)
                 return;
             CheckLease();
             
             var rc = rect.Rect.ToSKRect();
-            var isRounded = rect.IsRounded;
+            SKRoundRect? skRoundRect = null;
-            var needRoundRect = rect.IsRounded;
-            SKRoundRect skRoundRect = null;
 
-            if (needRoundRect)
+            if (rect.IsRounded)
             {
                 skRoundRect = SKRoundRectCache.Shared.Get();
                 skRoundRect.SetRectRadii(rc,
@@ -334,7 +335,7 @@ namespace Avalonia.Skia
             {
                 using (var paint = CreateAcrylicPaint(_fillPaint, material))
                 {
-                    if (isRounded)
+                    if (skRoundRect is not null)
                     {
                         Canvas.DrawRoundRect(skRoundRect, paint.Paint);
                         SKRoundRectCache.Shared.Return(skRoundRect);
@@ -349,7 +350,7 @@ namespace Avalonia.Skia
         }
 
         /// <inheritdoc />
-        public void DrawRectangle(IBrush brush, IPen pen, RoundedRect rect, BoxShadows boxShadows = default)
+        public void DrawRectangle(IBrush? brush, IPen? pen, RoundedRect rect, BoxShadows boxShadows = default)
         {
             if (rect.Rect.Height <= 0 || rect.Rect.Width <= 0)
                 return;
@@ -362,7 +363,7 @@ namespace Avalonia.Skia
             var rc = rect.Rect.ToSKRect();
             var isRounded = rect.IsRounded;
             var needRoundRect = rect.IsRounded || (boxShadows.HasInsetShadows);
-            SKRoundRect skRoundRect = null;
+            SKRoundRect? skRoundRect = null;
             if (needRoundRect)
             {
                 skRoundRect = SKRoundRectCache.Shared.GetAndSetRadii(rc, rect);
@@ -412,15 +413,15 @@ namespace Avalonia.Skia
 
             if (brush != null)
             {
-                using (var paint = CreatePaint(_fillPaint, brush, rect.Rect.Size))
+                using (var fill = CreatePaint(_fillPaint, brush, rect.Rect.Size))
                 {
                     if (isRounded)
                     {
-                        Canvas.DrawRoundRect(skRoundRect, paint.Paint);
+                        Canvas.DrawRoundRect(skRoundRect, fill.Paint);
                     }
                     else
                     {
-                        Canvas.DrawRect(rc, paint.Paint);
+                        Canvas.DrawRect(rc, fill.Paint);
                     }
                 }
             }
@@ -454,30 +455,28 @@ namespace Avalonia.Skia
                 }
             }
 
-            if (pen?.Brush != null)
+            if (pen is not null
+                && TryCreatePaint(_strokePaint, pen, rect.Rect.Size.Inflate(new Thickness(pen.Thickness / 2))) is { } stroke)
             {
-                using (var paint = CreatePaint(_strokePaint, pen, rect.Rect.Size.Inflate(new Thickness(pen?.Thickness / 2 ?? 0))))
+                using (stroke)
                 {
-                    if (paint.Paint is object)
+                    if (isRounded)
                     {
-                        if (isRounded)
+                        Canvas.DrawRoundRect(skRoundRect, stroke.Paint);
-                        {
+                    }
-                            Canvas.DrawRoundRect(skRoundRect, paint.Paint);
+                    else
-                        }
+                    {
-                        else
+                        Canvas.DrawRect(rc, stroke.Paint);
-                        {
-                            Canvas.DrawRect(rc, paint.Paint);
-                        }
                     }
                 }
             }
 
-            if(isRounded)
+            if (skRoundRect is not null)
                 SKRoundRectCache.Shared.Return(skRoundRect);
         }
 
         /// <inheritdoc />
-        public void DrawEllipse(IBrush brush, IPen pen, Rect rect)
+        public void DrawEllipse(IBrush? brush, IPen? pen, Rect rect)
         {
             if (rect.Height <= 0 || rect.Width <= 0)
                 return;
@@ -487,26 +486,24 @@ namespace Avalonia.Skia
 
             if (brush != null)
             {
-                using (var paint = CreatePaint(_fillPaint, brush, rect.Size))
+                using (var fill = CreatePaint(_fillPaint, brush, rect.Size))
                 {
-                    Canvas.DrawOval(rc, paint.Paint);
+                    Canvas.DrawOval(rc, fill.Paint);
                 }
             }
 
-            if (pen?.Brush != null)
+            if (pen is not null
+                && TryCreatePaint(_strokePaint, pen, rect.Size.Inflate(new Thickness(pen.Thickness / 2))) is { } stroke)
             {
-                using (var paint = CreatePaint(_strokePaint, pen, rect.Size.Inflate(new Thickness(pen?.Thickness / 2 ?? 0))))
+                using (stroke)
                 {
-                    if (paint.Paint is object)
+                    Canvas.DrawOval(rc, stroke.Paint);
-                    {
-                        Canvas.DrawOval(rc, paint.Paint);
-                    }
                 }
             }
         }
        
         /// <inheritdoc />
-        public void DrawGlyphRun(IBrush foreground, IRef<IGlyphRunImpl> glyphRun)
+        public void DrawGlyphRun(IBrush? foreground, IRef<IGlyphRunImpl> glyphRun)
         {
             CheckLease();
 
@@ -711,14 +708,12 @@ namespace Avalonia.Skia
             }
         }
 
-#nullable enable
         public object? GetFeature(Type t)
         {
             if (t == typeof(ISkiaSharpApiLeaseFeature))
                 return new SkiaLeaseFeature(this);
             return null;
         }
-#nullable restore
 
         /// <summary>
         /// Configure paint wrapper for using gradient brush.
@@ -957,9 +952,10 @@ namespace Avalonia.Skia
         /// <param name="visualBrush">Visual brush.</param>
         /// <param name="visualBrushRenderer">Visual brush renderer.</param>
         /// <param name="tileBrushImage">Tile brush image.</param>
-        private void ConfigureVisualBrush(ref PaintWrapper paintWrapper, IVisualBrush visualBrush, IVisualBrushRenderer visualBrushRenderer, ref IDrawableBitmapImpl tileBrushImage)
+        private void ConfigureVisualBrush(ref PaintWrapper paintWrapper, IVisualBrush visualBrush,
+            IVisualBrushRenderer? visualBrushRenderer, ref IDrawableBitmapImpl? tileBrushImage)
         {
-            if (_visualBrushRenderer == null)
+            if (visualBrushRenderer == null)
             {
                 throw new NotSupportedException("No IVisualBrushRenderer was supplied to DrawingContextImpl.");
             }
@@ -982,7 +978,7 @@ namespace Avalonia.Skia
             }
         }
 
-        static SKColorFilter CreateAlphaColorFilter(double opacity)
+        private static SKColorFilter CreateAlphaColorFilter(double opacity)
         {
             if (opacity > 1)
                 opacity = 1;
@@ -997,7 +993,7 @@ namespace Avalonia.Skia
             return SKColorFilter.CreateTable(a, c, c, c);
         }
 
-        static byte Blend(byte leftColor, byte leftAlpha, byte rightColor, byte rightAlpha)
+        private static byte Blend(byte leftColor, byte leftAlpha, byte rightColor, byte rightAlpha)
         {
             var ca = leftColor / 255d;
             var aa = leftAlpha / 255d;
@@ -1007,7 +1003,7 @@ namespace Avalonia.Skia
             return (byte)(r * 255);
         }
 
-        static Color Blend(Color left, Color right)
+        private static Color Blend(Color left, Color right)
         {
             var aa = left.A / 255d;
             var ab = right.A / 255d;
@@ -1103,7 +1099,7 @@ namespace Avalonia.Skia
             }
             else
             {
-                tileBrushImage = (IDrawableBitmapImpl)(tileBrush as IImageBrush)?.Source?.PlatformImpl.Item;
+                tileBrushImage = (tileBrush as IImageBrush)?.Source?.PlatformImpl.Item as IDrawableBitmapImpl;
             }
 
             if (tileBrush != null && tileBrushImage != null)
@@ -1125,16 +1121,16 @@ namespace Avalonia.Skia
         /// <param name="pen">Source pen.</param>
         /// <param name="targetSize">Target size.</param>
         /// <returns></returns>
-        private PaintWrapper CreatePaint(SKPaint paint, IPen pen, Size targetSize)
+        private PaintWrapper? TryCreatePaint(SKPaint paint, IPen pen, Size targetSize)
         {
             // In Skia 0 thickness means - use hairline rendering
             // and for us it means - there is nothing rendered.
-            if (pen.Thickness == 0d)
+            if (pen.Brush is not { } brush || pen.Thickness == 0d)
             {
-                return default;
+                return null;
             }
 
-            var rv = CreatePaint(paint, pen.Brush, targetSize);
+            var rv = CreatePaint(paint, brush, targetSize);
 
             paint.IsStroke = true;
             paint.StrokeWidth = (float) pen.Thickness;
@@ -1253,9 +1249,9 @@ namespace Avalonia.Skia
             //We are saving memory allocations there
             public readonly SKPaint Paint;
 
-            private IDisposable _disposable1;
+            private IDisposable? _disposable1;
-            private IDisposable _disposable2;
+            private IDisposable? _disposable2;
-            private IDisposable _disposable3;
+            private IDisposable? _disposable3;
 
             public PaintWrapper(SKPaint paint)
             {

src/Skia/Avalonia.Skia/FontManagerImpl.cs

@@ -26,11 +26,11 @@ namespace Avalonia.Skia
             return _skFontManager.FontFamilies;
         }
 
-        [ThreadStatic] private static string[] t_languageTagBuffer;
+        [ThreadStatic] private static string[]? t_languageTagBuffer;
 
         public bool TryMatchCharacter(int codepoint, FontStyle fontStyle,
             FontWeight fontWeight, FontStretch fontStretch,
-            FontFamily fontFamily, CultureInfo culture, out Typeface fontKey)
+            FontFamily? fontFamily, CultureInfo? culture, out Typeface fontKey)
         {
             SKFontStyle skFontStyle;
 
@@ -53,20 +53,13 @@ namespace Avalonia.Skia
                     break;
             }
 
-            if (culture == null)
+            culture ??= CultureInfo.CurrentUICulture;
-            {
-                culture = CultureInfo.CurrentUICulture;
-            }
-
-            if (t_languageTagBuffer == null)
-            {
-                t_languageTagBuffer = new string[2];
-            }
 
+            t_languageTagBuffer ??= new string[2];
             t_languageTagBuffer[0] = culture.TwoLetterISOLanguageName;
             t_languageTagBuffer[1] = culture.ThreeLetterISOLanguageName;
 
-            if (fontFamily != null && fontFamily.FamilyNames.HasFallbacks)
+            if (fontFamily is not null && fontFamily.FamilyNames.HasFallbacks)
             {
                 var familyNames = fontFamily.FamilyNames;
 
@@ -104,9 +97,9 @@ namespace Avalonia.Skia
 
         public IGlyphTypeface CreateGlyphTypeface(Typeface typeface)
         {
-            SKTypeface skTypeface = null;
+            SKTypeface? skTypeface = null;
 
-            if (typeface.FontFamily.Key == null)
+            if (typeface.FontFamily.Key is null)
             {
                 var defaultName = SKTypeface.Default.FamilyName;
 

src/Skia/Avalonia.Skia/FramebufferRenderTarget.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Reactive;
 using Avalonia.Controls.Platform.Surfaces;
 using Avalonia.Platform;
@@ -15,9 +16,9 @@ namespace Avalonia.Skia
         private readonly IFramebufferPlatformSurface _platformSurface;
         private SKImageInfo _currentImageInfo;
         private IntPtr _currentFramebufferAddress;
-        private SKSurface _framebufferSurface;
+        private SKSurface? _framebufferSurface;
-        private PixelFormatConversionShim _conversionShim;
+        private PixelFormatConversionShim? _conversionShim;
-        private IDisposable _preFramebufferCopyHandler;
+        private IDisposable? _preFramebufferCopyHandler;
 
         /// <summary>
         /// Create new framebuffer render target using a target surface.
@@ -35,7 +36,7 @@ namespace Avalonia.Skia
         }
 
         /// <inheritdoc />
-        public IDrawingContextImpl CreateDrawingContext(IVisualBrushRenderer visualBrushRenderer)
+        public IDrawingContextImpl CreateDrawingContext(IVisualBrushRenderer? visualBrushRenderer)
         {
             var framebuffer = _platformSurface.Lock();
             var framebufferImageInfo = new SKImageInfo(framebuffer.Size.Width, framebuffer.Size.Height,
@@ -81,6 +82,7 @@ namespace Avalonia.Skia
         /// </summary>
         /// <param name="desiredImageInfo">Desired image info.</param>
         /// <param name="framebuffer">Backing framebuffer.</param>
+        [MemberNotNull(nameof(_framebufferSurface))]
         private void CreateSurface(SKImageInfo desiredImageInfo, ILockedFramebuffer framebuffer)
         {
             if (_framebufferSurface != null && AreImageInfosCompatible(_currentImageInfo, desiredImageInfo) && _currentFramebufferAddress == framebuffer.Address)

src/Skia/Avalonia.Skia/GeometryGroupImpl.cs

@@ -2,8 +2,6 @@ using System.Collections.Generic;
 using Avalonia.Media;
 using SkiaSharp;
 
-#nullable enable
-
 namespace Avalonia.Skia
 {
     /// <summary>
@@ -22,8 +20,10 @@ namespace Avalonia.Skia
             
             for (var i = 0; i < count; ++i)
             {
-                if (children[i]?.PlatformImpl is GeometryImpl child)
+                if (children[i].PlatformImpl is GeometryImpl { EffectivePath: { } effectivePath })
-                    path.AddPath(child.EffectivePath);
+                {
+                    path.AddPath(effectivePath);
+                }
             }
 
             EffectivePath = path;

src/Skia/Avalonia.Skia/GeometryImpl.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Media;
 using Avalonia.Platform;
 using SkiaSharp;
@@ -11,20 +12,9 @@ namespace Avalonia.Skia
     internal abstract class GeometryImpl : IGeometryImpl
     {
         private PathCache _pathCache;
-        private SKPathMeasure _pathMeasureCache;
+        private SKPathMeasure? _cachedPathMeasure;
 
-        private SKPathMeasure CachedPathMeasure
+        private SKPathMeasure CachedPathMeasure => _cachedPathMeasure ??= new SKPathMeasure(EffectivePath!);
-        {
-            get
-            {
-                if (_pathMeasureCache is null)
-                {
-                    _pathMeasureCache = new SKPathMeasure(EffectivePath);
-                }
-
-                return _pathMeasureCache;
-            }
-        }
 
         /// <inheritdoc />
         public abstract Rect Bounds { get; }
@@ -37,11 +27,11 @@ namespace Avalonia.Skia
                 if (EffectivePath is null)
                     return 0;
 
-                return (double)CachedPathMeasure?.Length;
+                return CachedPathMeasure.Length;
             }
         }
 
-        public abstract SKPath EffectivePath { get; }
+        public abstract SKPath? EffectivePath { get; }
 
         /// <inheritdoc />
         public bool FillContains(Point point)
@@ -50,7 +40,7 @@ namespace Avalonia.Skia
         }
 
         /// <inheritdoc />
-        public bool StrokeContains(IPen pen, Point point)
+        public bool StrokeContains(IPen? pen, Point point)
         {
             // Skia requires to compute stroke path to check for point containment.
             // Due to that we are caching using stroke width.
@@ -98,21 +88,26 @@ namespace Avalonia.Skia
         /// <param name="path">Path to check.</param>
         /// <param name="point">Point.</param>
         /// <returns>True, if point is contained in a path.</returns>
-        private static bool PathContainsCore(SKPath path, Point point)
+        private static bool PathContainsCore(SKPath? path, Point point)
         {
-            return path.Contains((float)point.X, (float)point.Y);
+            return path is not null && path.Contains((float)point.X, (float)point.Y);
         }
 
         /// <inheritdoc />
-        public IGeometryImpl Intersect(IGeometryImpl geometry)
+        public IGeometryImpl? Intersect(IGeometryImpl geometry)
         {
-            var result = EffectivePath.Op(((GeometryImpl)geometry).EffectivePath, SKPathOp.Intersect);
+            if (EffectivePath is { } path
+                && (geometry as GeometryImpl)?.EffectivePath is { } otherPath
+                && path.Op(otherPath, SKPathOp.Intersect) is { } result)
+            {
+                return new StreamGeometryImpl(result);
+            }
 
-            return result == null ? null : new StreamGeometryImpl(result);
+            return null;
         }
 
         /// <inheritdoc />
-        public Rect GetRenderBounds(IPen pen)
+        public Rect GetRenderBounds(IPen? pen)
         {
             var strokeWidth = (float)(pen?.Thickness ?? 0);
 
@@ -161,7 +156,7 @@ namespace Avalonia.Skia
         }
 
         public bool TryGetSegment(double startDistance, double stopDistance, bool startOnBeginFigure,
-            out IGeometryImpl segmentGeometry)
+            [NotNullWhen(true)] out IGeometryImpl? segmentGeometry)
         {
             if (EffectivePath is null)
             {
@@ -203,7 +198,7 @@ namespace Avalonia.Skia
             /// <summary>
             /// Cached contour path.
             /// </summary>
-            public SKPath CachedStrokePath { get; private set; }
+            public SKPath? CachedStrokePath { get; private set; }
 
             /// <summary>
             /// Cached geometry render bounds.
@@ -244,6 +239,7 @@ namespace Avalonia.Skia
             public void Invalidate()
             {
                 CachedStrokePath?.Dispose();
+                CachedStrokePath = null;
                 CachedGeometryRenderBounds = default;
                 _cachedStrokeWidth = default;
             }

src/Skia/Avalonia.Skia/GlyphRunImpl.cs

@@ -2,7 +2,6 @@
 using System.Collections.Generic;
 using Avalonia.Platform;
 using SkiaSharp;
-#nullable enable
 
 namespace Avalonia.Skia
 {
@@ -10,7 +9,7 @@ namespace Avalonia.Skia
     {
         public GlyphRunImpl(SKTextBlob textBlob, Size size, Point baselineOrigin)
         {
-            TextBlob = textBlob ?? throw new ArgumentNullException (nameof (textBlob));
+            TextBlob = textBlob ?? throw new ArgumentNullException(nameof(textBlob));
 
             Size = size;
 

src/Skia/Avalonia.Skia/GlyphTypefaceImpl.cs

@@ -140,7 +140,7 @@ namespace Avalonia.Skia
             return Font.GetHorizontalGlyphAdvances(glyphIndices);
         }
 
-        private Blob GetTable(Face face, Tag tag)
+        private Blob? GetTable(Face face, Tag tag)
         {
             var size = Typeface.GetTableSize(tag);
 
@@ -166,8 +166,8 @@ namespace Avalonia.Skia
                 return;
             }
 
-            Font?.Dispose();
+            Font.Dispose();
-            Face?.Dispose();
+            Face.Dispose();
         }
 
         public void Dispose()

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

@@ -15,14 +15,14 @@ namespace Avalonia.Skia
         /// </summary>
         /// <param name="surfaces">Surfaces.</param>
         /// <returns>Created render target or <see langword="null"/> if it fails.</returns>
-        ISkiaGpuRenderTarget TryCreateRenderTarget(IEnumerable<object> surfaces);
+        ISkiaGpuRenderTarget? TryCreateRenderTarget(IEnumerable<object> surfaces);
 
         /// <summary>
         /// Creates an offscreen render target surface
         /// </summary>
         /// <param name="size">size in pixels.</param>
         /// <param name="session">An optional custom render session.</param>
-        ISkiaSurface TryCreateSurface(PixelSize size, ISkiaGpuRenderSession session);
+        ISkiaSurface? TryCreateSurface(PixelSize size, ISkiaGpuRenderSession? session);
     }
     
     public interface ISkiaSurface : IDisposable

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

@@ -3,6 +3,7 @@ using Avalonia.OpenGL;
 using Avalonia.Platform;
 using SkiaSharp;
 using static Avalonia.OpenGL.GlConsts;
+
 namespace Avalonia.Skia
 {
     internal class FboSkiaSurface : ISkiaSurface
@@ -14,6 +15,7 @@ namespace Avalonia.Skia
         private int _fbo;
         private int _depthStencil;
         private int _texture;
+        private SKSurface? _surface;
 
         private static readonly bool[] TrueFalse = new[] { true, false };
         public FboSkiaSurface(GlSkiaGpu gpu, GRContext grContext, IGlContext glContext, PixelSize pixelSize, GRSurfaceOrigin surfaceOrigin)
@@ -89,7 +91,7 @@ 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,
+            _surface = SKSurface.Create(_grContext, target,
                 surfaceOrigin, SKColorType.Rgba8888, new SKSurfaceProperties(SKPixelGeometry.RgbHorizontal));
             CanBlit = gl.IsBlitFramebufferAvailable;
         }
@@ -100,8 +102,8 @@ namespace Avalonia.Skia
             {
                 using (_glContext.EnsureCurrent())
                 {
-                    Surface?.Dispose();
+                    _surface?.Dispose();
-                    Surface = null;
+                    _surface = null;
                     var gl = _glContext.GlInterface;
                     if (_fbo != 0)
                     {
@@ -113,11 +115,11 @@ namespace Avalonia.Skia
             }
             catch (PlatformGraphicsContextLostException)
             {
-                if (Surface != null)
+                if (_surface != null)
                     // We need to dispose SKSurface _after_ GRContext.Abandon was called,
                     // otherwise it will try to do OpenGL calls without a proper context 
-                    _gpu.AddPostDispose(Surface.Dispose);
+                    _gpu.AddPostDispose(_surface.Dispose);
-                Surface = null;
+                _surface = null;
             }
             finally
             {
@@ -125,8 +127,10 @@ namespace Avalonia.Skia
             }
         }
 
-        public SKSurface Surface { get; private set; }
+        public SKSurface Surface => _surface ?? throw new ObjectDisposedException(nameof(FboSkiaSurface));
+
         public bool CanBlit { get; }
+
         public void Blit(SKCanvas canvas)
         {
             // This should set the render target as the current FBO

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

@@ -1,4 +1,3 @@
-#nullable enable
 using System;
 using System.Collections.Generic;
 using Avalonia.OpenGL;
@@ -150,6 +149,11 @@ internal class GlSkiaImportedImage : IPlatformRenderInterfaceImportedImage
     
     public IBitmapImpl SnapshotWithKeyedMutex(uint acquireIndex, uint releaseIndex)
     {
+        if (_image is null)
+        {
+            throw new NotSupportedException("Only supported with an external image");
+        }
+
         using (_gpu.EnsureCurrent())
         {
             _image.AcquireKeyedMutex(acquireIndex);
@@ -167,6 +171,11 @@ internal class GlSkiaImportedImage : IPlatformRenderInterfaceImportedImage
     public IBitmapImpl SnapshotWithSemaphores(IPlatformRenderInterfaceImportedSemaphore waitForSemaphore,
         IPlatformRenderInterfaceImportedSemaphore signalSemaphore)
     {
+        if (_image is null)
+        {
+            throw new NotSupportedException("Only supported with an external image");
+        }
+
         var wait = (GlSkiaImportedSemaphore)waitForSemaphore;
         var signal = (GlSkiaImportedSemaphore)signalSemaphore;
         using (_gpu.EnsureCurrent())

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

@@ -10,15 +10,15 @@ using static Avalonia.OpenGL.GlConsts;
 
 namespace Avalonia.Skia
 {
-    class GlSkiaGpu : ISkiaGpu, IOpenGlTextureSharingRenderInterfaceContextFeature
+    internal class GlSkiaGpu : ISkiaGpu, IOpenGlTextureSharingRenderInterfaceContextFeature
     {
-        private GRContext _grContext;
+        private readonly GRContext _grContext;
-        private IGlContext _glContext;
+        private readonly IGlContext _glContext;
         public GRContext GrContext => _grContext;
         public IGlContext GlContext => _glContext;
-        private List<Action> _postDisposeCallbacks = new();
+        private readonly List<Action> _postDisposeCallbacks = new();
         private bool? _canCreateSurfaces;
-        private IExternalObjectsRenderInterfaceContextFeature? _externalObjectsFeature;
+        private readonly IExternalObjectsRenderInterfaceContextFeature? _externalObjectsFeature;
 
         public GlSkiaGpu(IGlContext context, long? maxResourceBytes)
         {
@@ -41,7 +41,7 @@ namespace Avalonia.Skia
             }
         }
 
-        class SurfaceWrapper : IGlPlatformSurface
+        private class SurfaceWrapper : IGlPlatformSurface
         {
             private readonly object _surface;
 
@@ -57,7 +57,7 @@ namespace Avalonia.Skia
             }
         }
 
-        public ISkiaGpuRenderTarget TryCreateRenderTarget(IEnumerable<object> surfaces)
+        public ISkiaGpuRenderTarget? TryCreateRenderTarget(IEnumerable<object> surfaces)
         {
             var customRenderTargetFactory = _glContext.TryGetFeature<IGlPlatformSurfaceRenderTargetFactory>();
             foreach (var surface in surfaces)
@@ -75,7 +75,7 @@ namespace Avalonia.Skia
             return null;
         }
 
-        public ISkiaSurface TryCreateSurface(PixelSize size, ISkiaGpuRenderSession session)
+        public ISkiaSurface? TryCreateSurface(PixelSize size, ISkiaGpuRenderSession? session)
         {
             // Only windows platform needs our FBO trickery
             if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
@@ -106,7 +106,7 @@ namespace Avalonia.Skia
 
         public bool CanCreateSharedContext => _glContext.CanCreateSharedContext;
 
-        public IGlContext CreateSharedContext(IEnumerable<GlVersion> preferredVersions = null) =>
+        public IGlContext? CreateSharedContext(IEnumerable<GlVersion>? preferredVersions = null) =>
             _glContext.CreateSharedContext(preferredVersions);
 
         public ICompositionImportableOpenGlSharedTexture CreateSharedTextureForComposition(IGlContext context, PixelSize size)
@@ -153,7 +153,7 @@ namespace Avalonia.Skia
         public bool IsLost => _glContext.IsLost;
         public IDisposable EnsureCurrent() => _glContext.EnsureCurrent();
 
-        public object TryGetFeature(Type featureType)
+        public object? TryGetFeature(Type featureType)
         {
             if (featureType == typeof(IOpenGlTextureSharingRenderInterfaceContextFeature))
                 return this;

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

@@ -22,7 +22,7 @@ namespace Avalonia.Skia
             _renderTarget.Dispose();
         }
 
-        public IDrawingContextImpl CreateDrawingContext(IVisualBrushRenderer visualBrushRenderer)
+        public IDrawingContextImpl CreateDrawingContext(IVisualBrushRenderer? visualBrushRenderer)
         {
             var session = _renderTarget.BeginRenderingSession();
 

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

@@ -15,7 +15,7 @@ namespace Avalonia.Skia.Helpers
         /// <param name="dpi"></param>
         /// <param name="visualBrushRenderer"></param>
         /// <returns>DrawingContext</returns>
-        public static IDrawingContextImpl WrapSkiaCanvas(SKCanvas canvas, Vector dpi, IVisualBrushRenderer visualBrushRenderer = null)
+        public static IDrawingContextImpl WrapSkiaCanvas(SKCanvas canvas, Vector dpi, IVisualBrushRenderer? visualBrushRenderer = null)
         {
             var createInfo = new DrawingContextImpl.CreateInfo
             {

src/Skia/Avalonia.Skia/ISkiaSharpApiLeaseFeature.cs

@@ -14,7 +14,7 @@ public interface ISkiaSharpApiLeaseFeature
 public interface ISkiaSharpApiLease : IDisposable
 {
     SKCanvas SkCanvas { get; }
-    GRContext GrContext { get; }
+    GRContext? GrContext { get; }
-    SKSurface SkSurface { get; }
+    SKSurface? SkSurface { get; }
     double CurrentOpacity { get; }
-}
+}

src/Skia/Avalonia.Skia/ImmutableBitmap.cs

@@ -100,7 +100,7 @@ namespace Avalonia.Skia
                     _bitmap = scaledBmp;
                 }
                 
-                _bitmap!.SetImmutable();
+                _bitmap.SetImmutable();
 
                 _image = SKImage.FromBitmap(_bitmap);
 
@@ -134,7 +134,7 @@ namespace Avalonia.Skia
                     data);
                 _bitmap = tmp.Copy();
             }
-            _bitmap!.SetImmutable();
+            _bitmap.SetImmutable();
             _image = SKImage.FromBitmap(_bitmap);
 
             if (_image == null)
@@ -179,10 +179,13 @@ namespace Avalonia.Skia
         public PixelFormat? Format => _bitmap?.ColorType.ToAvalonia();
         public ILockedFramebuffer Lock()
         {
-            if (_bitmap == null)
+            if (_bitmap is null)
-                throw new NotSupportedException();
+                throw new NotSupportedException("A bitmap is needed for locking");
-            return new LockedFramebuffer(_bitmap.GetPixels(), PixelSize, _bitmap.RowBytes, Dpi,
+
-                _bitmap.ColorType.ToAvalonia().Value, null);
+            if (_bitmap.ColorType.ToAvalonia() is not { } format)
+                throw new NotSupportedException($"Unsupported format {_bitmap.ColorType}");
+
+            return new LockedFramebuffer(_bitmap.GetPixels(), PixelSize, _bitmap.RowBytes, Dpi, format, null);
         }
     }
 }

src/Skia/Avalonia.Skia/PlatformRenderInterface.cs

@@ -24,7 +24,7 @@ namespace Avalonia.Skia
         }
 
 
-        public IPlatformRenderInterfaceContext CreateBackendContext(IPlatformGraphicsContext graphicsContext)
+        public IPlatformRenderInterfaceContext CreateBackendContext(IPlatformGraphicsContext? graphicsContext)
         {
             if (graphicsContext == null)
                 return new SkiaContext(null);
@@ -225,7 +225,7 @@ namespace Avalonia.Skia
                 throw new ArgumentNullException(nameof(glyphInfos));
             }
 
-            var glyphTypefaceImpl = glyphTypeface as GlyphTypefaceImpl;
+            var glyphTypefaceImpl = (GlyphTypefaceImpl)glyphTypeface;
 
             var font = SKFontCache.Shared.Get();
 

src/Skia/Avalonia.Skia/SKTypefaceCollection.cs

@@ -1,4 +1,5 @@
 using System.Collections.Concurrent;
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Media;
 using SkiaSharp;
 
@@ -6,20 +7,19 @@ namespace Avalonia.Skia
 {
     internal class SKTypefaceCollection
     {
-        private readonly ConcurrentDictionary<Typeface, SKTypeface> _typefaces =
+        private readonly ConcurrentDictionary<Typeface, SKTypeface> _typefaces = new();
-            new ConcurrentDictionary<Typeface, SKTypeface>();
 
         public void AddTypeface(Typeface key, SKTypeface typeface)
         {
             _typefaces.TryAdd(key, typeface);
         }
 
-        public SKTypeface Get(Typeface typeface)
+        public SKTypeface? Get(Typeface typeface)
         {
             return GetNearestMatch(typeface);
         }
 
-        private SKTypeface GetNearestMatch(Typeface key)
+        private SKTypeface? GetNearestMatch(Typeface key)
         {
             if (_typefaces.Count == 0)
             {
@@ -70,7 +70,7 @@ namespace Avalonia.Skia
                 return typeface;
             }
 
-            SKTypeface skTypeface = null;
+            SKTypeface? skTypeface = null;
 
             foreach(var pair in _typefaces)
             {
@@ -85,7 +85,7 @@ namespace Avalonia.Skia
             return skTypeface;
         }
 
-        private bool TryFindStretchFallback(Typeface key, out SKTypeface typeface)
+        private bool TryFindStretchFallback(Typeface key, [NotNullWhen(true)] out SKTypeface? typeface)
         {
             typeface = null;
             var stretch = (int)key.Stretch;
@@ -114,7 +114,7 @@ namespace Avalonia.Skia
             return false;
         }
 
-        private bool TryFindWeightFallback(Typeface key, out SKTypeface typeface)
+        private bool TryFindWeightFallback(Typeface key, [NotNullWhen(true)] out SKTypeface? typeface)
         {
             typeface = null;
             var weight = (int)key.Weight;

src/Skia/Avalonia.Skia/SKTypefaceCollectionCache.cs

@@ -23,7 +23,7 @@ namespace Avalonia.Skia
         /// <returns></returns>
         public static SKTypefaceCollection GetOrAddTypefaceCollection(FontFamily fontFamily)
         {
-            return s_cachedCollections.GetOrAdd(fontFamily, x => CreateCustomFontCollection(fontFamily));
+            return s_cachedCollections.GetOrAdd(fontFamily, CreateCustomFontCollection);
         }
 
         /// <summary>
@@ -33,10 +33,15 @@ namespace Avalonia.Skia
         /// <returns></returns>
         private static SKTypefaceCollection CreateCustomFontCollection(FontFamily fontFamily)
         {
-            var fontAssets = FontFamilyLoader.LoadFontAssets(fontFamily.Key);
-
             var typeFaceCollection = new SKTypefaceCollection();
 
+            if (fontFamily.Key is not { } fontFamilyKey)
+            {
+                return typeFaceCollection;
+            }
+
+            var fontAssets = FontFamilyLoader.LoadFontAssets(fontFamilyKey);
+
             var assetLoader = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>();
 
             foreach (var asset in fontAssets)

src/Skia/Avalonia.Skia/SkiaBackendContext.cs

@@ -9,9 +9,9 @@ namespace Avalonia.Skia;
 
 internal class SkiaContext : IPlatformRenderInterfaceContext
 {
-    private ISkiaGpu _gpu;
+    private ISkiaGpu? _gpu;
 
-    public SkiaContext(ISkiaGpu gpu)
+    public SkiaContext(ISkiaGpu? gpu)
     {
         _gpu = gpu;
     }
@@ -25,10 +25,10 @@ internal class SkiaContext : IPlatformRenderInterfaceContext
     /// <inheritdoc />
     public IRenderTarget CreateRenderTarget(IEnumerable<object> surfaces)
     {
-        if (!(surfaces is IList))
+        if (surfaces is not IList)
             surfaces = surfaces.ToList();
-        var gpuRenderTarget = _gpu?.TryCreateRenderTarget(surfaces);
+
-        if (gpuRenderTarget != null)
+        if (_gpu?.TryCreateRenderTarget(surfaces) is { } gpuRenderTarget)
         {
             return new SkiaGpuRenderTarget(_gpu, gpuRenderTarget);
         }
@@ -43,7 +43,7 @@ internal class SkiaContext : IPlatformRenderInterfaceContext
             "Don't know how to create a Skia render target from any of provided surfaces");
     }
 
-    public bool IsLost => _gpu.IsLost;
+    public bool IsLost => _gpu?.IsLost ?? false;
 
-    public object TryGetFeature(Type featureType) => _gpu?.TryGetFeature(featureType);
+    public object? TryGetFeature(Type featureType) => _gpu?.TryGetFeature(featureType);
 }

src/Skia/Avalonia.Skia/SkiaSharpExtensions.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Media;
 using Avalonia.Platform;
 using Avalonia.Media.Imaging;
@@ -111,7 +112,7 @@ namespace Avalonia.Skia
             return sm;
         }
 
-        public static SKColor ToSKColor(this Media.Color c)
+        public static SKColor ToSKColor(this Color c)
         {
             return new SKColor(c.R, c.G, c.B, c.A);
         }
@@ -171,14 +172,14 @@ namespace Avalonia.Skia
             };
         }
 
-        public static SKShaderTileMode ToSKShaderTileMode(this Media.GradientSpreadMethod m)
+        public static SKShaderTileMode ToSKShaderTileMode(this GradientSpreadMethod m)
         {
             switch (m)
             {
                 default:
-                case Media.GradientSpreadMethod.Pad: return SKShaderTileMode.Clamp;
+                case GradientSpreadMethod.Pad: return SKShaderTileMode.Clamp;
-                case Media.GradientSpreadMethod.Reflect: return SKShaderTileMode.Mirror;
+                case GradientSpreadMethod.Reflect: return SKShaderTileMode.Mirror;
-                case Media.GradientSpreadMethod.Repeat: return SKShaderTileMode.Repeat;
+                case GradientSpreadMethod.Repeat: return SKShaderTileMode.Repeat;
             }
         }
 
@@ -215,7 +216,8 @@ namespace Avalonia.Skia
             };
         }
 
-        public static SKPath Clone(this SKPath src)
+        [return: NotNullIfNotNull(nameof(src))]
+        public static SKPath? Clone(this SKPath? src)
         {
             return src != null ? new SKPath(src) : null;
         }

src/Skia/Avalonia.Skia/StreamGeometryImpl.cs

@@ -47,7 +47,7 @@ namespace Avalonia.Skia
         /// <inheritdoc />
         public IStreamGeometryImpl Clone()
         {
-            return new StreamGeometryImpl(_effectivePath?.Clone(), Bounds);
+            return new StreamGeometryImpl(_effectivePath.Clone(), Bounds);
         }
 
         /// <inheritdoc />

src/Skia/Avalonia.Skia/SurfaceRenderTarget.cs

@@ -1,7 +1,6 @@
 using System;
 using System.IO;
 using Avalonia.Reactive;
-using Avalonia.Media;
 using Avalonia.Platform;
 using Avalonia.Rendering;
 using Avalonia.Skia.Helpers;
@@ -17,24 +16,26 @@ namespace Avalonia.Skia
         private readonly ISkiaSurface _surface;
         private readonly SKCanvas _canvas;
         private readonly bool _disableLcdRendering;
-        private readonly GRContext _grContext;
+        private readonly GRContext? _grContext;
-        private readonly ISkiaGpu _gpu;
+        private readonly ISkiaGpu? _gpu;
 
-        class SkiaSurfaceWrapper : ISkiaSurface
+        private class SkiaSurfaceWrapper : ISkiaSurface
         {
-            public SKSurface Surface { get; private set; }
+            private SKSurface? _surface;
+
+            public SKSurface Surface => _surface ?? throw new ObjectDisposedException(nameof(SkiaSurfaceWrapper));
             public bool CanBlit => false;
             public void Blit(SKCanvas canvas) => throw new NotSupportedException();
 
             public SkiaSurfaceWrapper(SKSurface surface)
             {
-                Surface = surface;
+                _surface = surface;
             }
 
             public void Dispose()
             {
-                Surface?.Dispose();
+                _surface?.Dispose();
-                Surface = null;
+                _surface = null;
             }
         }
         
@@ -51,18 +52,25 @@ namespace Avalonia.Skia
             _grContext = createInfo.GrContext;
             _gpu = createInfo.Gpu;
 
-            if (!createInfo.DisableManualFbo)
+            ISkiaSurface? surface = null;
-                _surface = _gpu?.TryCreateSurface(PixelSize, createInfo.Session);
-            if (_surface == null)
-                _surface = new SkiaSurfaceWrapper(CreateSurface(createInfo.GrContext, PixelSize.Width, PixelSize.Height,
-                    createInfo.Format));
 
-            _canvas = _surface?.Surface.Canvas;
+            if (!createInfo.DisableManualFbo)
+                surface = _gpu?.TryCreateSurface(PixelSize, createInfo.Session);
 
-            if (_surface == null || _canvas == null)
+            if (surface is null)
             {
-                throw new InvalidOperationException("Failed to create Skia render target surface");
+                if (CreateSurface(createInfo.GrContext, PixelSize.Width, PixelSize.Height, createInfo.Format)
+                    is { } skSurface)
+                {
+                    surface = new SkiaSurfaceWrapper(skSurface);
+                }
             }
+
+            if (surface?.Surface.Canvas is not { } canvas)
+                throw new InvalidOperationException("Failed to create Skia render target surface");
+
+            _surface = surface;
+            _canvas = canvas;
         }
 
         /// <summary>
@@ -73,7 +81,7 @@ namespace Avalonia.Skia
         /// <param name="height">Height.</param>
         /// <param name="format">Format.</param>
         /// <returns></returns>
-        private static SKSurface CreateSurface(GRContext gpu, int width, int height, PixelFormat? format)
+        private static SKSurface? CreateSurface(GRContext? gpu, int width, int height, PixelFormat? format)
         {
             var imageInfo = MakeImageInfo(width, height, format);
             if (gpu != null)
@@ -89,7 +97,7 @@ namespace Avalonia.Skia
         }
 
         /// <inheritdoc />
-        public IDrawingContextImpl CreateDrawingContext(IVisualBrushRenderer visualBrushRenderer)
+        public IDrawingContextImpl CreateDrawingContext(IVisualBrushRenderer? visualBrushRenderer)
         {
             _canvas.RestoreToCount(-1);
             _canvas.ResetMatrix();
@@ -218,11 +226,11 @@ namespace Avalonia.Skia
             /// <summary>
             /// GPU-accelerated context (optional)
             /// </summary>
-            public GRContext GrContext;
+            public GRContext? GrContext;
 
-            public ISkiaGpu Gpu;
+            public ISkiaGpu? Gpu;
 
-            public ISkiaGpuRenderSession Session;
+            public ISkiaGpuRenderSession? Session;
 
             public bool DisableManualFbo;
         }

src/Skia/Avalonia.Skia/TextShaperImpl.cs

@@ -37,7 +37,7 @@ namespace Avalonia.Skia
 
                 var usedCulture = culture ?? CultureInfo.CurrentCulture;
 
-                buffer.Language = s_cachedLanguage.GetOrAdd(usedCulture.LCID, i => new Language(usedCulture));
+                buffer.Language = s_cachedLanguage.GetOrAdd(usedCulture.LCID, _ => new Language(usedCulture));
 
                 var font = ((GlyphTypefaceImpl)typeface).Font;
 
@@ -170,7 +170,7 @@ namespace Avalonia.Skia
                 return segment.Array.AsMemory();
             }
 
-            if (MemoryMarshal.TryGetMemoryManager(memory, out MemoryManager<char> memoryManager, out start, out length))
+            if (MemoryMarshal.TryGetMemoryManager(memory, out MemoryManager<char>? memoryManager, out start, out length))
             {
                 return memoryManager.Memory;
             }

src/Skia/Avalonia.Skia/TransformedGeometryImpl.cs

@@ -19,14 +19,14 @@ namespace Avalonia.Skia
             Transform = transform;
 
             var transformedPath = source.EffectivePath.Clone();
-            transformedPath.Transform(transform.ToSKMatrix());
+            transformedPath?.Transform(transform.ToSKMatrix());
 
             EffectivePath = transformedPath;
-            Bounds = transformedPath.TightBounds.ToAvaloniaRect();
+            Bounds = transformedPath?.TightBounds.ToAvaloniaRect() ?? default;
         }
 
         /// <inheritdoc />
-        public override SKPath EffectivePath { get; }
+        public override SKPath? EffectivePath { get; }
 
         /// <inheritdoc />
         public IGeometryImpl SourceGeometry { get; }

src/Skia/Avalonia.Skia/WriteableBitmapImpl.cs

@@ -15,7 +15,7 @@ namespace Avalonia.Skia
     {
         private static readonly SKBitmapReleaseDelegate s_releaseDelegate = ReleaseProc;
         private readonly SKBitmap _bitmap;
-        private readonly object _lock = new object();
+        private readonly object _lock = new();
         
         /// <summary>
         /// Create a WriteableBitmap from given stream.
@@ -205,8 +205,8 @@ namespace Avalonia.Skia
                 _bitmap.NotifyPixelsChanged();
                 _parent.Version++;
                 Monitor.Exit(_parent._lock);
-                _bitmap = null;
+                _bitmap = null!;
-                _parent = null;
+                _parent = null!;
             }
             
             /// <inheritdoc />