Merge pull request #1186 from AvaloniaUI/fixes/1185-stackpanel-gap-property-last-child

[StackPanel] Gap value is not added to the measured width or height a…

src/Avalonia.Controls/StackPanel.cs

@@ -170,6 +170,15 @@ namespace Avalonia.Controls
                 }
             }
 
+            if (Orientation == Orientation.Vertical)
+            {
+                measuredHeight -= gap;
+            }
+            else
+            {
+                measuredWidth -= gap;
+            }
+
             return new Size(measuredWidth, measuredHeight);
         }
 

tests/Avalonia.Controls.UnitTests/StackPanelTests.cs

@@ -70,7 +70,7 @@ namespace Avalonia.Controls.UnitTests
             target.Measure(Size.Infinity);
             target.Arrange(new Rect(target.DesiredSize));
 
-            Assert.Equal(new Size(120, 130), target.Bounds.Size);
+            Assert.Equal(new Size(120, 120), target.Bounds.Size);
             Assert.Equal(new Rect(0, 0, 120, 20), target.Children[0].Bounds);
             Assert.Equal(new Rect(0, 30, 120, 30), target.Children[1].Bounds);
             Assert.Equal(new Rect(0, 70, 120, 50), target.Children[2].Bounds);
@@ -94,7 +94,7 @@ namespace Avalonia.Controls.UnitTests
             target.Measure(Size.Infinity);
             target.Arrange(new Rect(target.DesiredSize));
 
-            Assert.Equal(new Size(130, 120), target.Bounds.Size);
+            Assert.Equal(new Size(120, 120), target.Bounds.Size);
             Assert.Equal(new Rect(0, 0, 20, 120), target.Children[0].Bounds);
             Assert.Equal(new Rect(30, 0, 30, 120), target.Children[1].Bounds);
             Assert.Equal(new Rect(70, 0, 50, 120), target.Children[2].Bounds);