Standardize Default members in Size

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

@@ -78,7 +78,7 @@ namespace Avalonia.Media.Imaging
             get
             {
                 if (Source is not IBitmap bmp)
-                    return Size.Empty;
+                    return default;
                 if (SourceRect.IsDefault)
                     return Source.Size;
                 return SourceRect.Size.ToSizeWithDpi(bmp.Dpi);

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/DeferredRenderer.cs

@@ -277,7 +277,7 @@ namespace Avalonia.Rendering
         /// <inheritdoc/>
         Size IVisualBrushRenderer.GetRenderTargetSize(IVisualBrush brush)
         {
-            return TryGetChildScene(_currentDraw)?.Size ?? Size.Empty;
+            return TryGetChildScene(_currentDraw)?.Size ?? default;
         }
 
         /// <inheritdoc/>

src/Avalonia.Base/Rendering/ImmediateRenderer.cs

@@ -189,7 +189,7 @@ 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/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.Controls.DataGrid/DataGrid.cs

@@ -1124,7 +1124,7 @@ namespace Avalonia.Controls
                     EnsureColumnHeadersVisibility();
                     if (!newValueCols)
                     {
-                        _columnHeadersPresenter.Measure(Size.Empty);
+                        _columnHeadersPresenter.Measure(default(Size));
                     }
                     else
                     {
@@ -1165,7 +1165,7 @@ namespace Avalonia.Controls
                 _topLeftCornerHeader.IsVisible = newValueRows && newValueCols;
                 if (_topLeftCornerHeader.IsVisible)
                 {
-                    _topLeftCornerHeader.Measure(Size.Empty);
+                    _topLeftCornerHeader.Measure(default(Size));
                 }
             }
 

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());

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/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/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)

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

@@ -569,7 +569,7 @@ namespace Avalonia.Controls.UnitTests.Presenters
                 var target = CreateTarget(itemCount: 10);
                 var items = (IList<string>)target.Items;
                 target.ApplyTemplate();
-                target.Measure(Size.Empty);
+                target.Measure(default(Size));
                 target.Arrange(default);
 
                 // Check for issue #591: this should not throw.