More work on layout.

Mostly works but Test_ScrollViewer_With_TextBlock is failing again.

Perspex.Layout.UnitTests/FullLayoutTests.cs

@@ -4,6 +4,7 @@
 // </copyright>
 // -----------------------------------------------------------------------
 
+using Microsoft.VisualStudio.TestTools.UnitTesting;
 namespace Perspex.Layout.UnitTests
 {
     using System.Linq;
@@ -24,6 +25,44 @@ namespace Perspex.Layout.UnitTests
     [TestClass]
     public class FullLayoutTests
     {
+        [TestMethod]
+        public void Grandchild_Size_Changed()
+        {
+            using (var context = Locator.CurrentMutable.WithResolver())
+            {
+                this.RegisterServices();
+
+                Border border;
+                TextBlock textBlock;
+
+                var window = new Window()
+                {
+                    Content = (border = new Border
+                    {
+                        HorizontalAlignment = HorizontalAlignment.Center,
+                        VerticalAlignment = VerticalAlignment.Center,
+                        Content = new Border
+                        {
+                            Content = (textBlock = new TextBlock
+                            {
+                                Width = 400,
+                                Height = 400,
+                                Text = "Hello World!",
+                            }),
+                        }
+                    })
+                };
+
+                window.LayoutManager.ExecuteLayoutPass();
+
+                Assert.AreEqual(new Size(400, 400), border.ActualSize);
+                textBlock.Width = 200;
+                window.LayoutManager.ExecuteLayoutPass();
+
+                Assert.AreEqual(new Size(200, 400), border.ActualSize);
+            }
+        }
+
         [TestMethod]
         public void Test_ScrollViewer_With_TextBlock()
         {
@@ -38,7 +77,6 @@ namespace Perspex.Layout.UnitTests
                 {
                     Content = (scrollViewer = new ScrollViewer
                     {
-                        Id = "scrollViewer",
                         Width = 200,
                         Height = 200,
                         HorizontalAlignment = HorizontalAlignment.Center,

Perspex.Layout/LayoutManager.cs

@@ -207,14 +207,14 @@ namespace Perspex.Layout
                     {
                         if (!item.Control.IsArrangeValid)
                         {
-                            var parent = item.Control.GetVisualParent<ILayoutable>();
+                            var control = item.Control;
 
-                            while (parent.PreviousArrange == null)
+                            while (control.PreviousArrange == null)
                             {
-                                parent = parent.GetVisualParent<ILayoutable>();
+                                control = control.GetVisualParent<ILayoutable>();
                             }
 
-                            parent.Arrange(parent.PreviousArrange.Value, true);
+                            control.Arrange(control.PreviousArrange.Value, true);
                         }
                     }
                 }

Perspex.Layout/Layoutable.cs

@@ -222,29 +222,44 @@ namespace Perspex.Layout
 
         public void InvalidateMeasure()
         {
-            var root = this.GetLayoutRoot();
+            if (this.IsMeasureValid)
+            {
+                var parent = this.GetVisualParent<ILayoutable>();
 
-            this.IsMeasureValid = false;
-            this.IsArrangeValid = false;
-            this.previousMeasure = null;
-            this.previousArrange = null;
+                this.IsMeasureValid = false;
+                this.IsArrangeValid = false;
+                this.previousMeasure = null;
+                this.previousArrange = null;
 
-            if (root != null && root.Item1.LayoutManager != null)
-            {
-                root.Item1.LayoutManager.InvalidateMeasure(this, root.Item2);
+                if (parent != null && IsResizable(parent))
+                {
+                    parent.InvalidateMeasure();
+                }
+                else
+                {
+                    var root = this.GetLayoutRoot();
+
+                    if (root != null && root.Item1.LayoutManager != null)
+                    {
+                        root.Item1.LayoutManager.InvalidateMeasure(this, root.Item2);
+                    }
+                }
             }
         }
 
         public void InvalidateArrange()
         {
-            var root = this.GetLayoutRoot();
+            if (this.IsArrangeValid)
+            {
+                var root = this.GetLayoutRoot();
 
-            this.IsArrangeValid = false;
-            this.previousArrange = null;
+                this.IsArrangeValid = false;
+                this.previousArrange = null;
 
-            if (root != null && root.Item1.LayoutManager != null)
-            {
-                root.Item1.LayoutManager.InvalidateArrange(this, root.Item2);
+                if (root != null && root.Item1.LayoutManager != null)
+                {
+                    root.Item1.LayoutManager.InvalidateArrange(this, root.Item2);
+                }
             }
         }
 
@@ -407,5 +422,10 @@ namespace Perspex.Layout
 
             return control != null ? Tuple.Create((ILayoutRoot)control, distance) : null;
         }
+
+        private static bool IsResizable(ILayoutable control)
+        {
+            return double.IsNaN(control.Width) || double.IsNaN(control.Height);
+        }
     }
 }