Merge branch 'master' into fixes/Warnings/XML-Comment

.editorconfig

@@ -152,6 +152,8 @@ dotnet_diagnostic.CA1820.severity = warning
 dotnet_diagnostic.CA1821.severity = warning
 # CA1822: Mark members as static
 dotnet_diagnostic.CA1822.severity = suggestion
+# CA1823: Avoid unused private fields
+dotnet_diagnostic.CA1823.severity = warning
 dotnet_code_quality.CA1822.api_surface = private, internal
 # CA1825: Avoid zero-length array allocations
 dotnet_diagnostic.CA1825.severity = warning

samples/ControlCatalog/Pages/ImagePage.xaml.cs

@@ -70,7 +70,7 @@ namespace ControlCatalog.Pages
                 3 => new PixelRect(new PixelPoint(bitmapWidth - cropSize.Width, 0), cropSize),
                 4 => new PixelRect(new PixelPoint(0, bitmapHeight - cropSize.Height), cropSize),
                 5 => new PixelRect(new PixelPoint(bitmapWidth - cropSize.Width, bitmapHeight - cropSize.Height), cropSize),
-                _ => PixelRect.Empty
+                _ => default
             };
             
         }

src/Android/Avalonia.Android/Platform/SkiaPlatform/AndroidFramebuffer.cs

@@ -96,12 +96,14 @@ namespace Avalonia.Android.Platform.SkiaPlatform
             public IntPtr bits;
 
             // Do not touch.
+#pragma warning disable CA1823 // Avoid unused private fields
             uint reserved1;
             uint reserved2;
             uint reserved3;
             uint reserved4;
             uint reserved5;
             uint reserved6;
+#pragma warning restore CA1823 // Avoid unused private fields
         }
     }
 }

src/Avalonia.Base/CornerRadius.cs

@@ -61,9 +61,13 @@ namespace Avalonia
         public double BottomLeft { get; }
 
         /// <summary>
-        /// Gets a value indicating whether all corner radii are set to 0.
+        /// Gets a value indicating whether the instance has default values (all corner radii are set to 0).
         /// </summary>
-        public bool IsEmpty => TopLeft.Equals(0) && IsUniform;
+        public bool IsDefault => TopLeft == 0 && TopRight == 0 && BottomLeft == 0 && BottomRight == 0;
+
+        /// <inheritdoc cref="IsDefault"/>
+        [Obsolete("Use IsDefault instead.")]
+        public bool IsEmpty => IsDefault;
 
         /// <summary>
         /// Gets a value indicating whether all corner radii are equal.
@@ -79,7 +83,6 @@ namespace Avalonia
         {
             // ReSharper disable CompareOfFloatsByEqualityOperator
             return TopLeft == other.TopLeft &&
-                   
                    TopRight == other.TopRight &&
                    BottomRight == other.BottomRight &&
                    BottomLeft == other.BottomLeft;

src/Avalonia.Base/Data/Core/ExpressionNode.cs

@@ -4,8 +4,6 @@ namespace Avalonia.Data.Core
 {
     public abstract class ExpressionNode
     {
-        private static readonly object CacheInvalid = new object();
-
         protected static readonly WeakReference<object?> UnsetReference = 
             new WeakReference<object?>(AvaloniaProperty.UnsetValue);
 

src/Avalonia.Base/Data/Core/ExpressionObserver.cs

@@ -49,8 +49,6 @@ namespace Avalonia.Data.Core
                 new TaskStreamPlugin(),
                 new ObservableStreamPlugin(),
             };
-
-        private static readonly object UninitializedValue = new object();
         private readonly ExpressionNode _node;
         private object? _root;
         private Func<object?>? _rootGetter;

src/Avalonia.Base/Media/BoxShadow.cs

@@ -45,7 +45,14 @@ namespace Avalonia.Media
             }
         }
 
-        public bool IsEmpty => OffsetX == 0 && OffsetY == 0 && Blur == 0 && Spread == 0;
+        /// <summary>
+        /// Gets a value indicating whether the instance has default values.
+        /// </summary>
+        public bool IsDefault => OffsetX == 0 && OffsetY == 0 && Blur == 0 && Spread == 0;
+
+        /// <inheritdoc cref="IsDefault"/>
+        [Obsolete("Use IsDefault instead.")]
+        public bool IsEmpty => IsDefault;
 
         private readonly static char[] s_Separator = new char[] { ' ', '\t' };
 
@@ -82,7 +89,7 @@ namespace Avalonia.Media
         {
             var sb = StringBuilderCache.Acquire();
 
-            if (IsEmpty)
+            if (IsDefault)
             {
                 return "none";
             }

src/Avalonia.Base/Media/BoxShadows.cs

@@ -21,7 +21,7 @@ namespace Avalonia.Media
         {
             _first = shadow;
             _list = null;
-            Count = _first.IsEmpty ? 0 : 1;
+            Count = _first.IsDefault ? 0 : 1;
         }
 
         public BoxShadows(BoxShadow first, BoxShadow[] rest)
@@ -120,7 +120,7 @@ namespace Avalonia.Media
             get
             {
                 foreach(var boxShadow in this)
-                    if (!boxShadow.IsEmpty && boxShadow.IsInset)
+                    if (!boxShadow.IsDefault && boxShadow.IsInset)
                         return true;
                 return false;
             }

src/Avalonia.Base/Media/FormattedText.cs

@@ -1379,7 +1379,7 @@ namespace Avalonia.Media
                 }
             }
 
-            if (accumulatedBounds?.PlatformImpl == null || accumulatedBounds.PlatformImpl.Bounds.IsEmpty)
+            if (accumulatedBounds?.PlatformImpl == null || accumulatedBounds.PlatformImpl.Bounds.IsDefault)
             {
                 return null;
             }            

src/Avalonia.Base/Media/Geometry.cs

@@ -30,7 +30,7 @@ namespace Avalonia.Media
         /// <summary>
         /// Gets the geometry's bounding rectangle.
         /// </summary>
-        public Rect Bounds => PlatformImpl?.Bounds ?? Rect.Empty;
+        public Rect Bounds => PlatformImpl?.Bounds ?? default;
 
         /// <summary>
         /// Gets the platform-specific implementation of the geometry.
@@ -84,7 +84,7 @@ namespace Avalonia.Media
         /// </summary>
         /// <param name="pen">The stroke thickness.</param>
         /// <returns>The bounding rectangle.</returns>
-        public Rect GetRenderBounds(IPen pen) => PlatformImpl?.GetRenderBounds(pen) ?? Rect.Empty;
+        public Rect GetRenderBounds(IPen pen) => PlatformImpl?.GetRenderBounds(pen) ?? default;
 
         /// <summary>
         /// Indicates whether the geometry's fill contains the specified point.

src/Avalonia.Base/Media/GeometryDrawing.cs

@@ -69,7 +69,7 @@ namespace Avalonia.Media
         public override Rect GetBounds()
         {
             IPen pen = Pen ?? s_boundsPen;
-			return Geometry?.GetRenderBounds(pen) ?? Rect.Empty;
+			return Geometry?.GetRenderBounds(pen) ?? default;
         }
     }
 }

src/Avalonia.Base/Media/GlyphRunDrawing.cs

@@ -32,7 +32,7 @@
 
         public override Rect GetBounds()
         {
-            return GlyphRun != null ? new Rect(GlyphRun.Size) : Rect.Empty;
+            return GlyphRun != null ? new Rect(GlyphRun.Size) : default;
         }
     }
 }

src/Avalonia.Base/Media/ImageDrawing.cs

@@ -42,7 +42,7 @@ namespace Avalonia.Media
             var imageSource = ImageSource;
             var rect = Rect;
 
-            if (imageSource is object && !rect.IsEmpty)
+            if (imageSource is object && !rect.IsDefault)
             {
                 context.DrawImage(imageSource, rect);
             }

src/Avalonia.Base/Media/Imaging/CroppedBitmap.cs

@@ -78,8 +78,8 @@ namespace Avalonia.Media.Imaging
             get
             {
                 if (Source is not IBitmap bmp)
-                    return Size.Empty;
-                if (SourceRect.IsEmpty)
+                    return default;
+                if (SourceRect.IsDefault)
                     return Source.Size;
                 return SourceRect.Size.ToSizeWithDpi(bmp.Dpi);
             }

src/Avalonia.Base/Media/TextFormatting/FormattedTextSource.cs

@@ -8,7 +8,6 @@ namespace Avalonia.Media.TextFormatting
     internal readonly struct FormattedTextSource : ITextSource
     {
         private readonly CharacterBufferRange _text;
-        private readonly int length;
         private readonly TextRunProperties _defaultProperties;
         private readonly IReadOnlyList<ValueSpan<TextRunProperties>>? _textModifier;
 

src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs

@@ -532,7 +532,7 @@ namespace Avalonia.Media.TextFormatting
 
             var startX = Start;
             double currentWidth = 0;
-            var currentRect = Rect.Empty;
+            var currentRect = default(Rect);
 
             TextRunBounds lastRunBounds = default;
 
@@ -748,7 +748,7 @@ namespace Avalonia.Media.TextFormatting
 
             var startX = WidthIncludingTrailingWhitespace;
             double currentWidth = 0;
-            var currentRect = Rect.Empty;
+            var currentRect = default(Rect);
 
             for (var index = TextRuns.Count - 1; index >= 0; index--)
             {

src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs

@@ -5,7 +5,6 @@ namespace Avalonia.Media.TextFormatting.Unicode
     public ref struct CodepointEnumerator
     {
         private CharacterBufferRange _text;
-        private int _pos;
 
         public CodepointEnumerator(CharacterBufferRange text)
         {

src/Avalonia.Base/PixelRect.cs

@@ -12,6 +12,7 @@ namespace Avalonia
         /// <summary>
         /// An empty rectangle.
         /// </summary>
+        [Obsolete("Use the default keyword instead.")]
         public static readonly PixelRect Empty = default;
 
         /// <summary>
@@ -133,9 +134,13 @@ namespace Avalonia
         public PixelPoint Center => new PixelPoint(X + (Width / 2), Y + (Height / 2));
 
         /// <summary>
-        /// Gets a value that indicates whether the rectangle is empty.
+        /// Gets a value indicating whether the instance has default values (the rectangle is empty).
         /// </summary>
-        public bool IsEmpty => Width == 0 && Height == 0;
+        public bool IsDefault => Width == 0 && Height == 0;
+
+        /// <inheritdoc cref="IsDefault"/>
+        [Obsolete("Use IsDefault instead.")]
+        public bool IsEmpty => IsDefault;
 
         /// <summary>
         /// Checks for equality between two <see cref="PixelRect"/>s.
@@ -257,7 +262,7 @@ namespace Avalonia
             }
             else
             {
-                return Empty;
+                return default;
             }
         }
 
@@ -290,11 +295,11 @@ namespace Avalonia
         /// <returns>The union.</returns>
         public PixelRect Union(PixelRect rect)
         {
-            if (IsEmpty)
+            if (IsDefault)
             {
                 return rect;
             }
-            else if (rect.IsEmpty)
+            else if (rect.IsDefault)
             {
                 return this;
             }

src/Avalonia.Base/Rect.cs

@@ -18,7 +18,8 @@ namespace Avalonia
         /// <summary>
         /// An empty rectangle.
         /// </summary>
-        public static readonly Rect Empty = default(Rect);
+        [Obsolete("Use the default keyword instead.")]
+        public static readonly Rect Empty = default;
 
         /// <summary>
         /// The X position.
@@ -169,12 +170,16 @@ namespace Avalonia
         public Point Center => new Point(_x + (_width / 2), _y + (_height / 2));
 
         /// <summary>
-        /// Gets a value that indicates whether the rectangle is empty.
+        /// Gets a value indicating whether the instance has default values (the rectangle is empty).
         /// </summary>
         // ReSharper disable CompareOfFloatsByEqualityOperator
-        public bool IsEmpty => _width == 0 && _height == 0;
+        public bool IsDefault => _width == 0 && _height == 0;
         // ReSharper restore CompareOfFloatsByEqualityOperator
 
+        /// <inheritdoc cref="IsDefault"/>
+        [Obsolete("Use IsDefault instead.")]
+        public bool IsEmpty => IsDefault;
+
         /// <summary>
         /// Checks for equality between two <see cref="Rect"/>s.
         /// </summary>
@@ -390,7 +395,7 @@ namespace Avalonia
             }
             else
             {
-                return Empty;
+                return default;
             }
         }
 
@@ -457,13 +462,13 @@ namespace Avalonia
 		/// </remarks>
 		public Rect Normalize()
         {
-            Rect rect = this;            
+            Rect rect = this;
 
             if(double.IsNaN(rect.Right) || double.IsNaN(rect.Bottom) || 
                 double.IsNaN(rect.X) || double.IsNaN(rect.Y) || 
                 double.IsNaN(Height) || double.IsNaN(Width))
             {
-                return Rect.Empty;
+                return default;
             }
 
             if (rect.Width < 0)
@@ -493,11 +498,11 @@ namespace Avalonia
             /// <returns>The union.</returns>
             public Rect Union(Rect rect)
         {
-            if (IsEmpty)
+            if (IsDefault)
             {
                 return rect;
             }
-            else if (rect.IsEmpty)
+            else if (rect.IsDefault)
             {
                 return this;
             }

src/Avalonia.Base/Rendering/Composition/Server/DrawingContextProxy.cs

@@ -163,7 +163,7 @@ internal class CompositorDrawingContextProxy : IDrawingContextImpl, IDrawingCont
         public CompositionDrawList? VisualBrushDrawList { get; set; }
         public Size GetRenderTargetSize(IVisualBrush brush)
         {
-            return VisualBrushDrawList?.Size ?? Size.Empty;
+            return VisualBrushDrawList?.Size ?? default;
         }
 
         public void RenderVisualBrush(IDrawingContextImpl context, IVisualBrush brush)

src/Avalonia.Base/Rendering/Composition/Server/ServerCompositionDrawListVisual.cs

@@ -37,7 +37,7 @@ internal class ServerCompositionDrawListVisual : ServerCompositionContainerVisua
         {
             if (_contentBounds == null)
             {
-                var rect = Rect.Empty;
+                var rect = default(Rect);
                 if(_renderCommands!=null)
                     foreach (var cmd in _renderCommands)
                         rect = rect.Union(cmd.Item.Bounds);

src/Avalonia.Base/Rendering/Composition/Server/ServerCompositionTarget.cs

@@ -90,7 +90,7 @@ namespace Avalonia.Rendering.Composition.Server
 
             Compositor.UpdateServerTime();
             
-            if(_dirtyRect.IsEmpty && !_redrawRequested)
+            if(_dirtyRect.IsDefault && !_redrawRequested)
                 return;
 
             Revision++;
@@ -119,7 +119,7 @@ namespace Avalonia.Rendering.Composition.Server
                     _dirtyRect = new Rect(0, 0, layerSize.Width, layerSize.Height);
                 }
 
-                if (!_dirtyRect.IsEmpty)
+                if (!_dirtyRect.IsDefault)
                 {
                     var visualBrushHelper = new CompositorDrawingContextProxy.VisualBrushRenderer();
                     using (var context = _layer.CreateDrawingContext(visualBrushHelper))
@@ -162,7 +162,7 @@ namespace Avalonia.Rendering.Composition.Server
                 }
                 RenderedVisuals = 0;
 
-                _dirtyRect = Rect.Empty;
+                _dirtyRect = default;
             }
         }
 
@@ -181,7 +181,7 @@ namespace Avalonia.Rendering.Composition.Server
         
         public void AddDirtyRect(Rect rect)
         {
-            if(rect.IsEmpty)
+            if(rect.IsDefault)
                 return;
             var snapped = SnapToDevicePixels(rect, Scaling);
             DebugEvents?.RectInvalidated(rect);

src/Avalonia.Base/Rendering/Composition/Server/ServerCompositionVisual.cs

@@ -37,7 +37,7 @@ namespace Avalonia.Rendering.Composition.Server
                 return;
 
             currentTransformedClip = currentTransformedClip.Intersect(_combinedTransformedClipBounds);
-            if(currentTransformedClip.IsEmpty)
+            if(currentTransformedClip.IsDefault)
                 return;
 
             Root!.RenderedVisuals++;
@@ -139,7 +139,7 @@ namespace Avalonia.Rendering.Composition.Server
             if (ownBounds != _oldOwnContentBounds || positionChanged)
             {
                 _oldOwnContentBounds = ownBounds;
-                if (ownBounds.IsEmpty)
+                if (ownBounds.IsDefault)
                     TransformedOwnContentBounds = default;
                 else
                     TransformedOwnContentBounds =
@@ -163,7 +163,7 @@ namespace Avalonia.Rendering.Composition.Server
             EffectiveOpacity = Opacity * (Parent?.EffectiveOpacity ?? 1);
 
             IsVisibleInFrame = _parent?.IsVisibleInFrame != false && Visible && EffectiveOpacity > 0.04 && !_isBackface &&
-                               !_combinedTransformedClipBounds.IsEmpty;
+                               !_combinedTransformedClipBounds.IsDefault;
 
             if (wasVisible != IsVisibleInFrame || positionChanged)
             {
@@ -192,7 +192,7 @@ namespace Avalonia.Rendering.Composition.Server
 
         void AddDirtyRect(Rect rc)
         {
-            if(rc == Rect.Empty)
+            if(rc == default)
                 return;
             Root?.AddDirtyRect(rc);
         }

src/Avalonia.Base/Rendering/DeferredRenderer.cs

@@ -311,7 +311,7 @@ namespace Avalonia.Rendering
         /// <inheritdoc/>
         Size IVisualBrushRenderer.GetRenderTargetSize(IVisualBrush brush)
         {
-            return TryGetChildScene(_currentDraw)?.Size ?? Size.Empty;
+            return TryGetChildScene(_currentDraw)?.Size ?? default;
         }
 
         /// <inheritdoc/>
@@ -463,7 +463,7 @@ namespace Avalonia.Rendering
             {
                 clipBounds = node.ClipBounds.Intersect(clipBounds);
 
-                if (!clipBounds.IsEmpty && node.Opacity > 0)
+                if (!clipBounds.IsDefault && node.Opacity > 0)
                 {
                     var isLayerRoot = node.Visual == layer;
 

src/Avalonia.Base/Rendering/DirtyRects.cs

@@ -10,6 +10,9 @@ namespace Avalonia.Rendering
     {
         private List<Rect> _rects = new List<Rect>();
 
+        /// <summary>
+        /// Gets a value indicating whether the collection of dirty rectangles is empty.
+        /// </summary>
         public bool IsEmpty => _rects.Count == 0;
 
         /// <summary>
@@ -27,7 +30,7 @@ namespace Avalonia.Rendering
         /// </remarks>
         public void Add(Rect rect)
         {
-            if (!rect.IsEmpty)
+            if (!rect.IsDefault)
             {
                 for (var i = 0; i < _rects.Count; ++i)
                 {

src/Avalonia.Base/Rendering/ImmediateRenderer.cs

@@ -138,7 +138,7 @@ namespace Avalonia.Rendering
         /// <inheritdoc/>
         public void AddDirty(Visual visual)
         {
-            if (visual.Bounds != Rect.Empty)
+            if (!visual.Bounds.IsDefault)
             {
                 var m = visual.TransformToVisual(_root);
 
@@ -203,7 +203,7 @@ namespace Avalonia.Rendering
         Size IVisualBrushRenderer.GetRenderTargetSize(IVisualBrush brush)
         {
             (brush.Visual as IVisualBrushInitialize)?.EnsureInitialized();
-            return brush.Visual?.Bounds.Size ?? Size.Empty;
+            return brush.Visual?.Bounds.Size ?? default;
         }
 
         /// <inheritdoc/>

src/Avalonia.Base/Rendering/SceneGraph/BitmapBlendModeNode.cs

@@ -27,7 +27,7 @@ namespace Avalonia.Rendering.SceneGraph
         }
 
         /// <inheritdoc/>
-        public Rect Bounds => Rect.Empty;
+        public Rect Bounds => default;
 
         /// <summary>
         /// Gets the BitmapBlend to be pushed or null if the operation represents a pop.

src/Avalonia.Base/Rendering/SceneGraph/ClipNode.cs

@@ -40,7 +40,7 @@ namespace Avalonia.Rendering.SceneGraph
         }
 
         /// <inheritdoc/>
-        public Rect Bounds => Rect.Empty;
+        public Rect Bounds => default;
 
         /// <summary>
         /// Gets the clip to be pushed or null if the operation represents a pop.

src/Avalonia.Base/Rendering/SceneGraph/GeometryClipNode.cs

@@ -28,7 +28,7 @@ namespace Avalonia.Rendering.SceneGraph
         }
 
         /// <inheritdoc/>
-        public Rect Bounds => Rect.Empty;
+        public Rect Bounds => default;
 
         /// <summary>
         /// Gets the clip to be pushed or null if the operation represents a pop.

src/Avalonia.Base/Rendering/SceneGraph/OpacityMaskNode.cs

@@ -19,7 +19,7 @@ namespace Avalonia.Rendering.SceneGraph
         /// <param name="bounds">The bounds of the mask.</param>
         /// <param name="aux">Auxiliary data required to draw the brush.</param>
         public OpacityMaskNode(IBrush mask, Rect bounds, IDisposable? aux = null)
-            : base(Rect.Empty, Matrix.Identity, aux)
+            : base(default, Matrix.Identity, aux)
         {
             Mask = mask.ToImmutable();
             MaskBounds = bounds;
@@ -30,7 +30,7 @@ namespace Avalonia.Rendering.SceneGraph
         /// opacity mask pop.
         /// </summary>
         public OpacityMaskNode()
-            : base(Rect.Empty, Matrix.Identity, null)
+            : base(default, Matrix.Identity, null)
         {
         }
 

src/Avalonia.Base/Rendering/SceneGraph/OpacityNode.cs

@@ -26,7 +26,7 @@ namespace Avalonia.Rendering.SceneGraph
         }
 
         /// <inheritdoc/>
-        public Rect Bounds => Rect.Empty;
+        public Rect Bounds => default;
 
         /// <summary>
         /// Gets the opacity to be pushed or null if the operation represents a pop.

src/Avalonia.Base/Rendering/SceneGraph/SceneBuilder.cs

@@ -331,8 +331,8 @@ namespace Avalonia.Rendering.SceneGraph
 
                 scene.Size = newSize;
 
-                Rect horizontalDirtyRect = Rect.Empty;
-                Rect verticalDirtyRect = Rect.Empty;
+                Rect horizontalDirtyRect = default;
+                Rect verticalDirtyRect = default;
 
                 if (newSize.Width > oldSize.Width)
                 {
@@ -429,7 +429,7 @@ namespace Avalonia.Rendering.SceneGraph
             else
             {
                 layer.OpacityMask = null;
-                layer.OpacityMaskRect = Rect.Empty;
+                layer.OpacityMaskRect = default;
             }
 
             layer.GeometryClip = node.HasAncestorGeometryClip ?

src/Avalonia.Base/Size.cs

@@ -28,8 +28,9 @@ namespace Avalonia
         public static readonly Size Infinity = new Size(double.PositiveInfinity, double.PositiveInfinity);
 
         /// <summary>
-        /// A size representing zero
+        /// A size representing zero.
         /// </summary>
+        [Obsolete("Use the default keyword instead.")]
         public static readonly Size Empty = new Size(0, 0);
 
         /// <summary>
@@ -309,9 +310,6 @@ namespace Avalonia
         /// <summary>
         /// Gets a value indicating whether the Width and Height values are zero.
         /// </summary>
-        public bool IsDefault
-        {
-            get { return (_width == 0) && (_height == 0); }
-        }
+        public bool IsDefault => (_width == 0) && (_height == 0);
     }
 }

src/Avalonia.Base/Thickness.cs

@@ -97,10 +97,9 @@ namespace Avalonia
         /// </summary>
         public double Bottom => _bottom;
 
-        /// <summary>
-        /// Gets a value indicating whether all sides are set to 0.
-        /// </summary>
-        public bool IsEmpty => Left.Equals(0) && IsUniform;
+        /// <inheritdoc cref="IsDefault"/>
+        [Obsolete("Use IsDefault instead.")]
+        public bool IsEmpty => IsDefault;
 
         /// <summary>
         /// Gets a value indicating whether all sides are equal.
@@ -292,15 +291,13 @@ namespace Avalonia
             left = this._left;
             top = this._top;
             right = this._right;
-            bottom = this._bottom;        
+            bottom = this._bottom;
         }
 
         /// <summary>
-        /// Gets a value indicating whether the left, top, right and bottom thickness values are zero.
+        /// Gets a value indicating whether the instance has default values
+        /// (the left, top, right and bottom values are zero).
         /// </summary>
-        public bool IsDefault
-        {
-            get { return (_left == 0) && (_top == 0) && (_right == 0) && (_bottom == 0); }
-        }
+        public bool IsDefault => (_left == 0) && (_top == 0) && (_right == 0) && (_bottom == 0);
     }
 }

src/Avalonia.Controls.DataGrid/DataGrid.cs

@@ -48,7 +48,6 @@ namespace Avalonia.Controls
         private const string DATAGRID_elementColumnHeadersPresenterName = "PART_ColumnHeadersPresenter";
         private const string DATAGRID_elementFrozenColumnScrollBarSpacerName = "PART_FrozenColumnScrollBarSpacer";
         private const string DATAGRID_elementHorizontalScrollbarName = "PART_HorizontalScrollbar";
-        private const string DATAGRID_elementRowHeadersPresenterName = "PART_RowHeadersPresenter";
         private const string DATAGRID_elementTopLeftCornerHeaderName = "PART_TopLeftCornerHeader";
         private const string DATAGRID_elementTopRightCornerHeaderName = "PART_TopRightCornerHeader";
         private const string DATAGRID_elementBottomRightCornerHeaderName = "PART_BottomRightCorner";
@@ -1124,7 +1123,7 @@ namespace Avalonia.Controls
                     EnsureColumnHeadersVisibility();
                     if (!newValueCols)
                     {
-                        _columnHeadersPresenter.Measure(Size.Empty);
+                        _columnHeadersPresenter.Measure(default(Size));
                     }
                     else
                     {
@@ -1165,7 +1164,7 @@ namespace Avalonia.Controls
                 _topLeftCornerHeader.IsVisible = newValueRows && newValueCols;
                 if (_topLeftCornerHeader.IsVisible)
                 {
-                    _topLeftCornerHeader.Measure(Size.Empty);
+                    _topLeftCornerHeader.Measure(default(Size));
                 }
             }
 

src/Avalonia.Controls.DataGrid/DataGridCheckBoxColumn.cs

@@ -192,14 +192,14 @@ namespace Avalonia.Controls
                     
                     void OnLayoutUpdated(object sender, EventArgs e)
                     {
-                        if(!editingCheckBox.Bounds.IsEmpty)
+                        if(!editingCheckBox.Bounds.IsDefault)
                         {
                             editingCheckBox.LayoutUpdated -= OnLayoutUpdated;
                             ProcessPointerArgs();
                         }
                     }
 
-                    if(editingCheckBox.Bounds.IsEmpty)
+                    if(editingCheckBox.Bounds.IsDefault)
                     {
                         editingCheckBox.LayoutUpdated += OnLayoutUpdated;
                     }

src/Avalonia.Controls.DataGrid/DataGridColumnHeader.cs

@@ -34,7 +34,6 @@ namespace Avalonia.Controls
         }
 
         private const int DATAGRIDCOLUMNHEADER_resizeRegionWidth = 5;
-        private const double DATAGRIDCOLUMNHEADER_separatorThickness = 1;
         private const int DATAGRIDCOLUMNHEADER_columnsDragTreshold = 5;
 
         private bool _areHandlersSuspended;

src/Avalonia.Controls.DataGrid/DataGridRowHeader.cs

@@ -18,8 +18,6 @@ namespace Avalonia.Controls.Primitives
     public class DataGridRowHeader : ContentControl
     {
         private const string DATAGRIDROWHEADER_elementRootName = "PART_Root";
-        private const double DATAGRIDROWHEADER_separatorThickness = 1;
-
         private Control _rootElement;
 
         public static readonly StyledProperty<IBrush> SeparatorBrushProperty =

src/Avalonia.Controls.DataGrid/Primitives/DataGridCellsPresenter.cs

@@ -161,7 +161,7 @@ namespace Avalonia.Controls.Primitives
                 {
                     // Clip
                     RectangleGeometry rg = new RectangleGeometry();
-                    rg.Rect = Rect.Empty;
+                    rg.Rect = default;
                     cell.Clip = rg;
                 }
             }

src/Avalonia.Controls.DataGrid/Primitives/DataGridColumnHeadersPresenter.cs

@@ -305,7 +305,7 @@ namespace Avalonia.Controls.Primitives
             }
             if (!OwningGrid.AreColumnHeadersVisible)
             {
-                return Size.Empty;
+                return default;
             }
             double height = OwningGrid.ColumnHeaderHeight;
             bool autoSizeHeight;

src/Avalonia.Controls.DataGrid/Primitives/DataGridDetailsPresenter.cs

@@ -112,7 +112,7 @@ namespace Avalonia.Controls.Primitives
         {
             if (OwningGrid == null || Children.Count == 0)
             {
-                return Size.Empty;
+                return default;
             }
 
             double desiredWidth = OwningGrid.AreRowDetailsFrozen ?

src/Avalonia.Controls/Flyouts/FlyoutBase.cs

@@ -435,7 +435,7 @@ namespace Avalonia.Controls.Primitives
         {
             Size sz;
             // Popup.Child can't be null here, it was set in ShowAtCore.
-            if (Popup.Child!.DesiredSize == Size.Empty)
+            if (Popup.Child!.DesiredSize.IsDefault)
             {
                 // Popup may not have been shown yet. Measure content
                 sz = LayoutHelper.MeasureChild(Popup.Child, Size.Infinity, new Thickness());
@@ -457,7 +457,7 @@ namespace Avalonia.Controls.Primitives
                     PopupPositioning.PopupPositionerConstraintAdjustment.SlideY;
             }
 
-            var trgtBnds = Target?.Bounds ?? Rect.Empty;
+            var trgtBnds = Target?.Bounds ?? default;
 
             switch (Placement)
             {

src/Avalonia.Controls/LayoutTransformControl.cs

@@ -91,7 +91,7 @@ namespace Avalonia.Controls
             arrangedsize = TransformRoot.Bounds.Size;
 
             // This is the first opportunity under Silverlight to find out the Child's true DesiredSize
-            if (IsSizeSmaller(finalSizeTransformed, arrangedsize) && (Size.Empty == _childActualSize))
+            if (IsSizeSmaller(finalSizeTransformed, arrangedsize) && _childActualSize.IsDefault)
             {
                 //// Unfortunately, all the work so far is invalid because the wrong DesiredSize was used
                 //// Make a note of the actual DesiredSize
@@ -102,7 +102,7 @@ namespace Avalonia.Controls
             else
             {
                 // Clear the "need to measure/arrange again" flag
-                _childActualSize = Size.Empty;
+                _childActualSize = default;
             }
 
             // Return result to perform the transformation
@@ -122,7 +122,7 @@ namespace Avalonia.Controls
             }
 
             Size measureSize;
-            if (_childActualSize == Size.Empty)
+            if (_childActualSize.IsDefault)
             {
                 // Determine the largest size after the transformation
                 measureSize = ComputeLargestTransformedSize(availableSize);
@@ -206,7 +206,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Actual DesiredSize of Child element (the value it returned from its MeasureOverride method).
         /// </summary>
-        private Size _childActualSize = Size.Empty;
+        private Size _childActualSize = default;
 
         /// <summary>
         /// RenderTransform/MatrixTransform applied to TransformRoot.
@@ -281,7 +281,7 @@ namespace Avalonia.Controls
         private Size ComputeLargestTransformedSize(Size arrangeBounds)
         {
             // Computed largest transformed size
-            Size computedSize = Size.Empty;
+            Size computedSize = default;
 
             // Detect infinite bounds and constrain the scenario
             bool infiniteWidth = double.IsInfinity(arrangeBounds.Width);

src/Avalonia.Controls/NativeControlHost.cs

@@ -145,7 +145,7 @@ namespace Avalonia.Controls
 
             if (IsEffectivelyVisible && bounds.HasValue)
             {
-                if (bounds.Value.IsEmpty)
+                if (bounds.Value.IsDefault)
                     return false;
                 _attachment?.ShowInBounds(bounds.Value);
             }

src/Avalonia.Controls/Presenters/ItemsPresenter.cs

@@ -77,7 +77,7 @@ namespace Avalonia.Controls.Presenters
         }
 
         /// <inheritdoc/>
-        Size IScrollable.Extent => Virtualizer?.Extent ?? Size.Empty;
+        Size IScrollable.Extent => Virtualizer?.Extent ?? default;
 
         /// <inheritdoc/>
         Vector IScrollable.Offset
@@ -136,12 +136,12 @@ namespace Avalonia.Controls.Presenters
         /// <inheritdoc/>
         protected override Size MeasureOverride(Size availableSize)
         {
-            return Virtualizer?.MeasureOverride(availableSize) ?? Size.Empty;
+            return Virtualizer?.MeasureOverride(availableSize) ?? default;
         }
 
         protected override Size ArrangeOverride(Size finalSize)
         {
-            return Virtualizer?.ArrangeOverride(finalSize) ?? Size.Empty;
+            return Virtualizer?.ArrangeOverride(finalSize) ?? default;
         }
 
         /// <inheritdoc/>

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -106,7 +106,6 @@ namespace Avalonia.Controls.Presenters
         private Rect _caretBounds;
         private Point _navigationPosition;
         private string? _preeditText;
-        private CharacterHit _compositionStartHit = new CharacterHit(-1);
 
         static TextPresenter()
         {

src/Avalonia.Controls/Primitives/PopupPositioning/ManagedPopupPositioner.cs

@@ -112,7 +112,7 @@ namespace Avalonia.Controls.Primitives.PopupPositioning
                                    ?? screens.FirstOrDefault(s => s.Bounds.Intersects(parentGeometry))
                                    ?? screens.FirstOrDefault();
 
-                if (targetScreen != null && targetScreen.WorkingArea.IsEmpty)
+                if (targetScreen != null && targetScreen.WorkingArea.IsDefault)
                 {
                     return targetScreen.Bounds;
                 }

src/Avalonia.Controls/Primitives/SelectingItemsControl.cs

@@ -119,8 +119,6 @@ namespace Avalonia.Controls.Primitives
         /// </summary>
         public static readonly StyledProperty<bool> WrapSelectionProperty =
             AvaloniaProperty.Register<SelectingItemsControl, bool>(nameof(WrapSelection), defaultValue: false);
-
-        private static readonly IList Empty = Array.Empty<object>();
         private string _textSearchTerm = string.Empty;
         private DispatcherTimer? _textSearchTimer;
         private ISelectionModel? _selection;

src/Avalonia.Controls/Repeater/ViewportManager.cs

@@ -465,7 +465,7 @@ namespace Avalonia.Controls
 
             _pendingViewportShift = default;
             _unshiftableShift = default;
-            if (_visibleWindow.IsEmpty)
+            if (_visibleWindow.IsDefault)
             {
                 // We got cleared.
                 _layoutExtent = default;
@@ -551,7 +551,7 @@ namespace Avalonia.Controls
         private void TryInvalidateMeasure()
         {
             // Don't invalidate measure if we have an invalid window.
-            if (!_visibleWindow.IsEmpty)
+            if (!_visibleWindow.IsDefault)
             {
                 // We invalidate measure instead of just invalidating arrange because
                 // we don't invalidate measure in UpdateViewport if the view is changing to

src/Avalonia.Controls/Shapes/Shape.cs

@@ -292,7 +292,7 @@ namespace Avalonia.Controls.Shapes
                 return finalSize;
             }
 
-            return Size.Empty;
+            return default;
         }
 
         internal static (Size size, Matrix transform) CalculateSizeAndTransform(Size availableSize, Rect shapeBounds, Stretch Stretch)

src/Avalonia.Controls/Window.cs

@@ -169,10 +169,6 @@ namespace Avalonia.Controls
         /// </summary>
         public static readonly RoutedEvent<RoutedEventArgs> WindowOpenedEvent =
             RoutedEvent.Register<Window, RoutedEventArgs>("WindowOpened", RoutingStrategies.Direct);
-
-
-
-        private readonly NameScope _nameScope = new NameScope();
         private object? _dialogResult;
         private readonly Size _maxPlatformClientSize;
         private WindowStartupLocation _windowStartupLocation;
@@ -235,7 +231,7 @@ namespace Avalonia.Controls
             impl.GotInputWhenDisabled = OnGotInputWhenDisabled;
             impl.WindowStateChanged = HandleWindowStateChanged;
             _maxPlatformClientSize = PlatformImpl?.MaxAutoSizeHint ?? default(Size);
-            impl.ExtendClientAreaToDecorationsChanged = ExtendClientAreaToDecorationsChanged;            
+            impl.ExtendClientAreaToDecorationsChanged = ExtendClientAreaToDecorationsChanged;
             this.GetObservable(ClientSizeProperty).Skip(1).Subscribe(x => PlatformImpl?.Resize(x, PlatformResizeReason.Application));
 
             PlatformImpl?.ShowTaskbarIcon(ShowInTaskbar);

src/Avalonia.Diagnostics/Diagnostics/Controls/Application.cs

@@ -10,8 +10,7 @@ namespace Avalonia.Diagnostics.Controls
 
     {
         private readonly App _application;
-        private static readonly Version s_version = typeof(AvaloniaObject).Assembly?.GetName()?.Version
-            ?? Version.Parse("0.0.00");
+
         public event EventHandler? Closed;
 
         public Application(App application)

src/Avalonia.Headless/HeadlessPlatformRenderInterface.cs

@@ -215,7 +215,7 @@ namespace Avalonia.Headless
 
         class HeadlessStreamingGeometryStub : HeadlessGeometryStub, IStreamGeometryImpl
         {
-            public HeadlessStreamingGeometryStub() : base(Rect.Empty)
+            public HeadlessStreamingGeometryStub() : base(default)
             {
             }
 

src/Avalonia.Native/ClipboardImpl.cs

@@ -15,8 +15,7 @@ namespace Avalonia.Native
         private IAvnClipboard _native;
         private const string NSPasteboardTypeString = "public.utf8-plain-text";
         private const string NSFilenamesPboardType = "NSFilenamesPboardType";
-        private const string NSPasteboardTypeFileUrl = "public.file-url";
-        
+
         public ClipboardImpl(IAvnClipboard native)
         {
             _native = native;

src/Avalonia.Native/IAvnMenu.cs

@@ -46,7 +46,6 @@ namespace Avalonia.Native.Interop.Impl
         private AvaloniaNativeMenuExporter _exporter;
         private List<__MicroComIAvnMenuItemProxy> _menuItems = new List<__MicroComIAvnMenuItemProxy>();
         private Dictionary<NativeMenuItemBase, __MicroComIAvnMenuItemProxy> _menuItemLookup = new Dictionary<NativeMenuItemBase, __MicroComIAvnMenuItemProxy>();
-        private CompositeDisposable _propertyDisposables = new CompositeDisposable();
 
         public void RaiseNeedsUpdate()
         {

src/Avalonia.Native/WindowImplBase.cs

@@ -63,7 +63,6 @@ namespace Avalonia.Native
         private double _savedScaling;
         private GlPlatformSurface _glSurface;
         private NativeControlHostImpl _nativeControlHost;
-        private IGlContext _glContext;
 
         internal WindowBaseImpl(IAvaloniaNativeFactory factory, AvaloniaNativePlatformOptions opts,
             AvaloniaNativeGlPlatformGraphics glFeature)

src/Avalonia.X11/X11Clipboard.cs

@@ -18,8 +18,6 @@ namespace Avalonia.X11
         private TaskCompletionSource<object> _requestedDataTcs;
         private readonly IntPtr[] _textAtoms;
         private readonly IntPtr _avaloniaSaveTargetsAtom;
-        private readonly Dictionary<string, IntPtr> _formatAtoms = new Dictionary<string, IntPtr>();
-        private readonly Dictionary<IntPtr, string> _atomFormats = new Dictionary<IntPtr, string>();
 
         public X11Clipboard(AvaloniaX11Platform platform)
         {

src/Browser/Avalonia.Browser/BrowserNativeControlHost.cs

@@ -55,12 +55,6 @@ namespace Avalonia.Browser
 
         private class Attachment : INativeControlHostControlTopLevelAttachment
         {
-            private const string InitializeWithChildHandleSymbol = "InitializeWithChildHandle";
-            private const string AttachToSymbol = "AttachTo";
-            private const string ShowInBoundsSymbol = "ShowInBounds";
-            private const string HideWithSizeSymbol = "HideWithSize";
-            private const string ReleaseChildSymbol = "ReleaseChild";
-
             private JSObject? _native;
             private BrowserNativeControlHost? _attachedTo;
 

src/Browser/Avalonia.Browser/WebEmbeddableControlRoot.cs

@@ -18,7 +18,7 @@ namespace Avalonia.Browser
                 _onFirstRender = onFirstRender;
             }
 
-            public Rect Bounds => Rect.Empty;
+            public Rect Bounds => default;
 
             public bool HasRendered => _hasRendered;
 

src/Linux/Avalonia.LinuxFramebuffer/Input/EvDev/EvDevBackend.cs

@@ -3,7 +3,6 @@ using System.Collections.Generic;
 using System.Threading;
 using Avalonia.Input;
 using Avalonia.Input.Raw;
-using Avalonia.Threading;
 using static Avalonia.LinuxFramebuffer.NativeUnsafeMethods;
 
 namespace Avalonia.LinuxFramebuffer.Input.EvDev
@@ -13,7 +12,6 @@ namespace Avalonia.LinuxFramebuffer.Input.EvDev
         private readonly EvDevDeviceDescription[] _deviceDescriptions;
         private readonly List<EvDevDeviceHandler> _handlers = new List<EvDevDeviceHandler>();
         private int _epoll;
-        private object _lock = new object();
         private Action<RawInputEventArgs> _onInput;
         private IInputRoot _inputRoot;
         private RawEventGroupingThreadingHelper _inputQueue;

src/Linux/Avalonia.LinuxFramebuffer/Input/LibInput/LibInputBackend.cs

@@ -11,7 +11,6 @@ namespace Avalonia.LinuxFramebuffer.Input.LibInput
     {
         private IScreenInfoProvider _screen;
         private IInputRoot _inputRoot;
-        private readonly Queue<Action> _inputThreadActions = new Queue<Action>();
         private TouchDevice _touch = new TouchDevice();
         private const string LibInput = nameof(Avalonia.LinuxFramebuffer) + "/" + nameof(Avalonia.LinuxFramebuffer.Input) + "/" + nameof(LibInput);
         private readonly RawEventGroupingThreadingHelper _inputQueue;

src/Skia/Avalonia.Skia/DrawingContextImpl.cs

@@ -362,7 +362,7 @@ namespace Avalonia.Skia
 
             foreach (var boxShadow in boxShadows)
             {
-                if (!boxShadow.IsEmpty && !boxShadow.IsInset)
+                if (!boxShadow.IsDefault && !boxShadow.IsInset)
                 {
                     using (var shadow = BoxShadowFilter.Create(_boxShadowPaint, boxShadow, _currentOpacity))
                     {
@@ -418,7 +418,7 @@ namespace Avalonia.Skia
 
             foreach (var boxShadow in boxShadows)
             {
-                if (!boxShadow.IsEmpty && boxShadow.IsInset)
+                if (!boxShadow.IsDefault && boxShadow.IsInset)
                 {
                     using (var shadow = BoxShadowFilter.Create(_boxShadowPaint, boxShadow, _currentOpacity))
                     {

src/Skia/Avalonia.Skia/GeometryImpl.cs

@@ -244,7 +244,7 @@ namespace Avalonia.Skia
             public void Invalidate()
             {
                 CachedStrokePath?.Dispose();
-                CachedGeometryRenderBounds = Rect.Empty;
+                CachedGeometryRenderBounds = default;
                 _cachedStrokeWidth = default(float);
             }
         }

src/Skia/Avalonia.Skia/StreamGeometryImpl.cs

@@ -34,7 +34,7 @@ namespace Avalonia.Skia
         /// <summary>
         /// Initializes a new instance of the <see cref="StreamGeometryImpl"/> class.
         /// </summary>
-        public StreamGeometryImpl() : this(CreateEmptyPath(), Rect.Empty)
+        public StreamGeometryImpl() : this(CreateEmptyPath(), default)
         {
         }
         

src/Windows/Avalonia.Win32/Interop/Automation/UiaCoreTypesApi.cs

@@ -6,8 +6,6 @@ namespace Avalonia.Win32.Interop.Automation
 {
     internal static class UiaCoreTypesApi
     {
-        private const string StartListeningExportName = "SynchronizedInputPattern_StartListening";
-
         internal enum AutomationIdType
         {
             Property,

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -1343,8 +1343,6 @@ namespace Avalonia.Win32
         }
 
         private const int MF_BYCOMMAND = 0x0;
-        private const int MF_BYPOSITION = 0x400;
-        private const int MF_REMOVE = 0x1000;
         private const int MF_ENABLED = 0x0;
         private const int MF_GRAYED = 0x1;
         private const int MF_DISABLED = 0x2;

tests/Avalonia.Base.UnitTests/RectTests.cs

@@ -52,7 +52,7 @@ namespace Avalonia.Base.UnitTests
                 double.PositiveInfinity, double.PositiveInfinity)
                 .Normalize();
 
-            Assert.Equal(Rect.Empty, result);
+            Assert.Equal(default, result);
         }
     }
 }

tests/Avalonia.Base.UnitTests/Rendering/DeferredRendererTests_HitTesting.cs

@@ -403,7 +403,7 @@ namespace Avalonia.Base.UnitTests.Rendering
                 root.Measure(Size.Infinity);
                 root.Arrange(new Rect(container.DesiredSize));
                 
-                root.Renderer.Paint(Rect.Empty);
+                root.Renderer.Paint(default);
                 var result = root.Renderer.HitTest(new Point(50, 150), root, null).First();
 
                 Assert.Equal(item1, result);
@@ -419,7 +419,7 @@ namespace Avalonia.Base.UnitTests.Rendering
                 container.InvalidateArrange();
                 container.Arrange(new Rect(container.DesiredSize));
 
-                root.Renderer.Paint(Rect.Empty);
+                root.Renderer.Paint(default);
                 result = root.Renderer.HitTest(new Point(50, 150), root, null).First();
                 Assert.Equal(item2, result);
 

tests/Avalonia.Base.UnitTests/Rendering/SceneGraph/DrawOperationTests.cs

@@ -13,9 +13,9 @@ namespace Avalonia.Base.UnitTests.Rendering.SceneGraph
         [Fact]
         public void Empty_Bounds_Remain_Empty()
         {
-            var target = new TestDrawOperation(Rect.Empty, Matrix.Identity, null);
+            var target = new TestDrawOperation(default, Matrix.Identity, null);
 
-            Assert.Equal(Rect.Empty, target.Bounds);
+            Assert.Equal(default, target.Bounds);
         }
 
         [Theory]

tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs

@@ -569,8 +569,8 @@ namespace Avalonia.Controls.UnitTests.Presenters
                 var target = CreateTarget(itemCount: 10);
                 var items = (IList<string>)target.Items;
                 target.ApplyTemplate();
-                target.Measure(Size.Empty);
-                target.Arrange(Rect.Empty);
+                target.Measure(default(Size));
+                target.Arrange(default);
 
                 // Check for issue #591: this should not throw.
                 target.ScrollIntoView(0);

tests/Avalonia.Controls.UnitTests/Shapes/RectangleTests.cs

@@ -18,7 +18,7 @@ namespace Avalonia.Controls.UnitTests.Shapes
             target.Measure(new Size(100, 100));
 
             var geometry = Assert.IsType<RectangleGeometry>(target.RenderedGeometry);
-            Assert.Equal(Rect.Empty, geometry.Rect);
+            Assert.Equal(default, geometry.Rect);
         }
 
         [Fact]