From 15c3ef499bca1c57b09a7b6b291382cf5633e38d Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 26 May 2017 00:47:34 +0200
Subject: [PATCH 1/2] Added failing test for #993.

---
 .../Avalonia.Layout.UnitTests/MeasureTests.cs | 53 +++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/tests/Avalonia.Layout.UnitTests/MeasureTests.cs b/tests/Avalonia.Layout.UnitTests/MeasureTests.cs
index b5a3539da9..570628b5b7 100644
--- a/tests/Avalonia.Layout.UnitTests/MeasureTests.cs
+++ b/tests/Avalonia.Layout.UnitTests/MeasureTests.cs
@@ -100,5 +100,58 @@ namespace Avalonia.Layout.UnitTests
 
             Assert.Equal(0, target.DesiredSize.Height);
         }
+
+        [Fact]
+        public void Margin_Should_Affect_AvailableSize()
+        {
+            MeasureTest target;
+
+            var outer = new Decorator
+            {
+                Width = 100,
+                Height = 100,
+                Child = target = new MeasureTest
+                {
+                    Margin = new Thickness(10),
+                }
+            };
+
+            outer.Measure(Size.Infinity);
+
+            Assert.Equal(new Size(80, 80), target.AvailableSize);
+        }
+
+        [Fact]
+        public void Margin_Should_Be_Applied_Before_Width_Height()
+        {
+            MeasureTest target;
+
+            var outer = new Decorator
+            {
+                Width = 100,
+                Height = 100,
+                Child = target = new MeasureTest
+                {
+                    Width = 80,
+                    Height = 80,
+                    Margin = new Thickness(10),
+                }
+            };
+
+            outer.Measure(Size.Infinity);
+
+            Assert.Equal(new Size(80, 80), target.AvailableSize);
+        }
+
+        class MeasureTest : Control
+        {
+            public Size? AvailableSize { get; private set; }
+
+            protected override Size MeasureOverride(Size availableSize)
+            {
+                AvailableSize = availableSize;
+                return availableSize;
+            }
+        }
     }
 }

From 16a47dac6150c4a78045c46f562cb93dcc2edc9f Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 26 May 2017 00:49:28 +0200
Subject: [PATCH 2/2] Apply margin before width/height.

Fixes #993.
---
 src/Avalonia.Layout/Layoutable.cs | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Layout/Layoutable.cs b/src/Avalonia.Layout/Layoutable.cs
index 5abd6c52f7..95a0dd625c 100644
--- a/src/Avalonia.Layout/Layoutable.cs
+++ b/src/Avalonia.Layout/Layoutable.cs
@@ -456,10 +456,9 @@ namespace Avalonia.Layout
 
                 ApplyTemplate();
 
-                var constrained = LayoutHelper
-                    .ApplyLayoutConstraints(this, availableSize)
-                    .Deflate(margin);
-
+                var constrained = LayoutHelper.ApplyLayoutConstraints(
+                    this,
+                    availableSize.Deflate(margin));
                 var measured = MeasureOverride(constrained);
 
                 var width = measured.Width;