Compute LayoutConstraints on new *StackLayout

Author: albyrock87

src/Controls/src/Core/Layout/HorizontalStackLayout.cs

@@ -7,5 +7,17 @@ namespace Microsoft.Maui.Controls
 	public class HorizontalStackLayout : StackBase
 	{
 		protected override ILayoutManager CreateLayoutManager() => new HorizontalStackLayoutManager(this);
+
+		internal override void ComputeConstraintForView(View view)
+		{
+			if ((Constraint & LayoutConstraint.VerticallyFixed) != 0 && view.VerticalOptions.Alignment == LayoutAlignment.Fill)
+			{
+				view.ComputedConstraint = LayoutConstraint.VerticallyFixed;
+			}
+			else
+			{
+				view.ComputedConstraint = LayoutConstraint.None;
+			}
+		}
 	}
 }

src/Controls/src/Core/Layout/StackLayout.cs

@@ -36,5 +36,31 @@ protected override ILayoutManager CreateLayoutManager()
 		{
 			return new StackLayoutManager(this);
 		}
+
+		internal override void ComputeConstraintForView(View view)
+		{
+			if (Orientation == StackOrientation.Horizontal)
+			{
+				if ((Constraint & LayoutConstraint.VerticallyFixed) != 0 && view.VerticalOptions.Alignment == LayoutAlignment.Fill)
+				{
+					view.ComputedConstraint = LayoutConstraint.VerticallyFixed;
+				}
+				else
+				{
+					view.ComputedConstraint = LayoutConstraint.None;
+				}
+			}
+			else
+			{
+				if ((Constraint & LayoutConstraint.HorizontallyFixed) != 0 && view.HorizontalOptions.Alignment == LayoutAlignment.Fill)
+				{
+					view.ComputedConstraint = LayoutConstraint.HorizontallyFixed;
+				}
+				else
+				{
+					view.ComputedConstraint = LayoutConstraint.None;
+				}
+			}
+		}
 	}
 }

src/Controls/src/Core/Layout/VerticalStackLayout.cs

@@ -7,5 +7,17 @@ namespace Microsoft.Maui.Controls
 	public class VerticalStackLayout : StackBase
 	{
 		protected override ILayoutManager CreateLayoutManager() => new VerticalStackLayoutManager(this);
+
+		internal override void ComputeConstraintForView(View view)
+		{
+			if ((Constraint & LayoutConstraint.HorizontallyFixed) != 0 && view.HorizontalOptions.Alignment == LayoutAlignment.Fill)
+			{
+				view.ComputedConstraint = LayoutConstraint.HorizontallyFixed;
+			}
+			else
+			{
+				view.ComputedConstraint = LayoutConstraint.None;
+			}
+		}
 	}
 }

src/Controls/src/Core/Properties/AssemblyInfo.cs

@@ -13,6 +13,7 @@
 [assembly: InternalsVisibleTo("Microsoft.Maui.Controls.Compatibility.Tizen")]
 [assembly: InternalsVisibleTo("Microsoft.Maui.Controls.Core.Design")]
 [assembly: InternalsVisibleTo("Microsoft.Maui.Controls.Core.UnitTests")]
+[assembly: InternalsVisibleTo("Microsoft.Maui.UnitTests")]
 [assembly: InternalsVisibleTo("Microsoft.Maui.Controls.Android.UnitTests")]
 [assembly: InternalsVisibleTo("Microsoft.Maui.Controls.Compatibility.Android.UnitTests")]
 [assembly: InternalsVisibleTo("Microsoft.Maui.Controls.Compatibility.UAP.UnitTests")]

src/Core/tests/UnitTests/Layouts/HorizontalStackLayoutTests.cs

@@ -0,0 +1,25 @@
+using Microsoft.Maui.Controls;
+using Xunit;
+
+namespace Microsoft.Maui.UnitTests.Layouts
+{
+	[Category(TestCategory.Core, TestCategory.Layout)]
+	public class HorizontalStackLayoutTests
+	{
+		[Fact]
+		public void ConstrainsViewsVerticallyWhenConstrained()
+		{
+			var layout = new HorizontalStackLayout();
+			var child = new ContentView();
+			layout.Add(child);
+
+			Assert.Equal(LayoutConstraint.None, child.Constraint);
+
+			layout.HeightRequest = 100;
+			Assert.Equal(LayoutConstraint.VerticallyFixed, child.Constraint);
+
+			child.WidthRequest = 50;
+			Assert.Equal(LayoutConstraint.Fixed, child.Constraint);
+		}
+	}
+}

src/Core/tests/UnitTests/Layouts/StackLayoutTests.cs

@@ -0,0 +1,41 @@
+using Microsoft.Maui.Controls;
+using Xunit;
+
+namespace Microsoft.Maui.UnitTests.Layouts
+{
+	[Category(TestCategory.Core, TestCategory.Layout)]
+	public class StackLayoutTests
+	{
+		[Fact]
+		public void VerticalOrientationConstrainsViewsHorizontallyWhenConstrained()
+		{
+			var layout = new StackLayout { Orientation = StackOrientation.Vertical };
+			var child = new ContentView();
+			layout.Add(child);
+
+			Assert.Equal(LayoutConstraint.None, child.Constraint);
+
+			layout.WidthRequest = 100;
+			Assert.Equal(LayoutConstraint.HorizontallyFixed, child.Constraint);
+
+			child.HeightRequest = 50;
+			Assert.Equal(LayoutConstraint.Fixed, child.Constraint);
+		}
+
+		[Fact]
+		public void HorizontalOrientationConstrainsViewsVerticallyWhenConstrained()
+		{
+			var layout = new StackLayout { Orientation = StackOrientation.Horizontal };
+			var child = new ContentView();
+			layout.Add(child);
+
+			Assert.Equal(LayoutConstraint.None, child.Constraint);
+
+			layout.HeightRequest = 100;
+			Assert.Equal(LayoutConstraint.VerticallyFixed, child.Constraint);
+
+			child.WidthRequest = 50;
+			Assert.Equal(LayoutConstraint.Fixed, child.Constraint);
+		}
+	}
+}

src/Core/tests/UnitTests/Layouts/VerticalStackLayoutTests.cs

@@ -0,0 +1,25 @@
+using Microsoft.Maui.Controls;
+using Xunit;
+
+namespace Microsoft.Maui.UnitTests.Layouts
+{
+	[Category(TestCategory.Core, TestCategory.Layout)]
+	public class VerticalStackLayoutTests
+	{
+		[Fact]
+		public void ConstrainsViewsHorizontallyWhenConstrained()
+		{
+			var layout = new VerticalStackLayout();
+			var child = new ContentView();
+			layout.Add(child);
+
+			Assert.Equal(LayoutConstraint.None, child.Constraint);
+
+			layout.WidthRequest = 100;
+			Assert.Equal(LayoutConstraint.HorizontallyFixed, child.Constraint);
+
+			child.HeightRequest = 50;
+			Assert.Equal(LayoutConstraint.Fixed, child.Constraint);
+		}
+	}
+}