Make Rect.Deflate consistent with Rect.Inflate.

`Rect.Deflate` was halving the thickness passed into it whereas `Rect.Inflate` wasn't. Make both methods consistent and _not_ halve the thickness.

src/Avalonia.Controls/Shapes/Ellipse.cs

@@ -14,7 +14,7 @@ namespace Avalonia.Controls.Shapes
 
         protected override Geometry CreateDefiningGeometry()
         {
-            var rect = new Rect(Bounds.Size).Deflate(StrokeThickness);
+            var rect = new Rect(Bounds.Size).Deflate(StrokeThickness / 2);
             return new EllipseGeometry(rect);
         }
 

src/Avalonia.Controls/Shapes/Rectangle.cs

@@ -14,7 +14,7 @@ namespace Avalonia.Controls.Shapes
 
         protected override Geometry CreateDefiningGeometry()
         {
-            var rect = new Rect(Bounds.Size).Deflate(StrokeThickness);
+            var rect = new Rect(Bounds.Size).Deflate(StrokeThickness / 2);
             return new RectangleGeometry(rect);
         }
 

src/Avalonia.Visuals/Rect.cs

@@ -256,7 +256,7 @@ namespace Avalonia
         /// <summary>
         /// Inflates the rectangle.
         /// </summary>
-        /// <param name="thickness">The thickness.</param>
+        /// <param name="thickness">The thickness to be subtracted for each side of the rectangle.</param>
         /// <returns>The inflated rectangle.</returns>
         public Rect Inflate(double thickness)
         {
@@ -266,7 +266,7 @@ namespace Avalonia
         /// <summary>
         /// Inflates the rectangle.
         /// </summary>
-        /// <param name="thickness">The thickness.</param>
+        /// <param name="thickness">The thickness to be subtracted for each side of the rectangle.</param>
         /// <returns>The inflated rectangle.</returns>
         public Rect Inflate(Thickness thickness)
         {
@@ -278,20 +278,18 @@ namespace Avalonia
         /// <summary>
         /// Deflates the rectangle.
         /// </summary>
-        /// <param name="thickness">The thickness.</param>
+        /// <param name="thickness">The thickness to be subtracted for each side of the rectangle.</param>
         /// <returns>The deflated rectangle.</returns>
-        /// <remarks>The deflated rectangle size cannot be less than 0.</remarks>
         public Rect Deflate(double thickness)
         {
-            return Deflate(new Thickness(thickness / 2));
+            return Deflate(new Thickness(thickness));
         }
 
         /// <summary>
         /// Deflates the rectangle by a <see cref="Thickness"/>.
         /// </summary>
-        /// <param name="thickness">The thickness.</param>
+        /// <param name="thickness">The thickness to be subtracted for each side of the rectangle.</param>
         /// <returns>The deflated rectangle.</returns>
-        /// <remarks>The deflated rectangle size cannot be less than 0.</remarks>
         public Rect Deflate(Thickness thickness)
         {
             return new Rect(

tests/Avalonia.RenderTests/Controls/CustomRenderTests.cs

@@ -36,7 +36,7 @@ namespace Avalonia.Direct2D1.RenderTests.Controls
                         new Rect(control.Bounds.Size),
                         4);
 
-                    using (context.PushClip(new Rect(control.Bounds.Size).Deflate(20)))
+                    using (context.PushClip(new Rect(control.Bounds.Size).Deflate(10)))
                     {
                         context.FillRectangle(
                             Brushes.Blue,
@@ -100,7 +100,7 @@ namespace Avalonia.Direct2D1.RenderTests.Controls
                     {
                         context.FillRectangle(
                             Brushes.Blue,
-                            new Rect(control.Bounds.Size).Deflate(20),
+                            new Rect(control.Bounds.Size).Deflate(10),
                             4);
                     }
                 }),
@@ -140,7 +140,7 @@ namespace Avalonia.Direct2D1.RenderTests.Controls
                     {
                         context.FillRectangle(
                             Brushes.Blue,
-                            new Rect(control.Bounds.Size).Deflate(20),
+                            new Rect(control.Bounds.Size).Deflate(10),
                             4);
                     }
                 }),