Re-measure/render when window resized.

Perspex.Windows/Window.cs

@@ -5,11 +5,10 @@
     using System.Diagnostics.CodeAnalysis;
     using System.Runtime.InteropServices;
     using Perspex.Controls;
+    using Perspex.Layout;
     using Perspex.Windows.Interop;
-    using SharpDX.Direct2D1;
-    using SharpDX.DXGI;
 
-    public class Window : ContentControl
+    public class Window : ContentControl, ILayoutRoot
     {
         private UnmanagedMethods.WndProc wndProcDelegate;
 
@@ -20,9 +19,15 @@
         public Window()
         {
             this.CreateWindow();
-
             Size clientSize = this.ClientSize;
+            this.LayoutManager = new LayoutManager();
             this.renderer = new Renderer(this.Handle, (int)clientSize.Width, (int)clientSize.Height);
+
+            this.LayoutManager.LayoutNeeded.Subscribe(x => 
+            {
+                this.LayoutManager.ExecuteLayoutPass();
+                this.renderer.Render(this);
+            });
         }
 
         public Size ClientSize
@@ -41,12 +46,15 @@
             private set;
         }
 
+        public ILayoutManager LayoutManager
+        {
+            get;
+            private set;
+        }
+
         public void Show()
         {
             UnmanagedMethods.ShowWindow(this.Handle, 4);
-            this.Measure(this.ClientSize);
-            this.Arrange(new Rect(this.ClientSize));
-            this.renderer.Render(this);
         }
 
         protected override Visual DefaultTemplate()
@@ -133,14 +141,10 @@
                 ////    InputManager.Current.ProcessInput(new RawMouseEventArgs(mouse, RawMouseEventType.Move));
                 ////    break;
 
-                ////case UnmanagedMethods.WindowsMessage.WM_SIZE:
-                ////    if (this.renderTarget != null)
-                ////    {
-                ////        this.renderTarget.Resize(new SharpDX.DrawingSize((int)lParam & 0xffff, (int)lParam >> 16));
-                ////    }
-
-                ////    this.OnResized();
-                ////    return IntPtr.Zero;
+                case UnmanagedMethods.WindowsMessage.WM_SIZE:
+                    this.renderer.Resize((int)lParam & 0xffff, (int)lParam >> 16);
+                    this.InvalidateMeasure();
+                    return IntPtr.Zero;
             }
 
             return UnmanagedMethods.DefWindowProc(hWnd, msg, wParam, lParam);

Perspex/Controls/Control.cs

@@ -1,6 +1,8 @@
 namespace Perspex.Controls
 {
+    using System;
     using System.Diagnostics.Contracts;
+    using Perspex.Layout;
 
     public enum HorizontalAlignment
     {
@@ -18,7 +20,7 @@
         Bottom,
     }
 
-    public abstract class Control : Visual
+    public abstract class Control : Visual, ILayoutable
     {
         public static readonly PerspexProperty<HorizontalAlignment> HorizontalAlignmentProperty =
             PerspexProperty.Register<Control, HorizontalAlignment>("HorizontalAlignment");
@@ -53,6 +55,24 @@
             set { this.SetValue(MarginProperty, value); }
         }
 
+        public Control Parent
+        {
+            get;
+            internal set;
+        }
+
+        public ILayoutRoot GetLayoutRoot()
+        {
+            Control c = this;
+
+            while (c != null && !(c is ILayoutRoot))
+            {
+                c = c.Parent;
+            }
+
+            return (ILayoutRoot)c;
+        }
+
         public void Arrange(Rect rect)
         {
             this.Bounds = new Rect(
@@ -66,6 +86,16 @@
             this.DesiredSize = this.MeasureContent(availableSize).Constrain(availableSize);
         }
 
+        public void InvalidateArrange()
+        {
+            this.GetLayoutRoot().LayoutManager.InvalidateArrange(this);
+        }
+
+        public void InvalidateMeasure()
+        {
+            this.GetLayoutRoot().LayoutManager.InvalidateMeasure(this);
+        }
+
         protected virtual Size ArrangeContent(Size finalSize)
         {
             return finalSize;

Perspex/Layout/ILayoutManager.cs

@@ -0,0 +1,23 @@
+// -----------------------------------------------------------------------
+// <copyright file="ILayoutManager.cs" company="Steven Kirk">
+// Copyright 2013 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Layout
+{
+    using System;
+    using System.Reactive;
+    using Perspex.Controls;
+
+    public interface ILayoutManager
+    {
+        IObservable<Unit> LayoutNeeded { get; }
+
+        void ExecuteLayoutPass();
+
+        void InvalidateMeasure(ILayoutable item);
+
+        void InvalidateArrange(ILayoutable item);
+    }
+}

Perspex/Layout/ILayoutRoot.cs

@@ -0,0 +1,15 @@
+// -----------------------------------------------------------------------
+// <copyright file="ILayoutRoot.cs" company="Steven Kirk">
+// Copyright 2013 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Layout
+{
+    public interface ILayoutRoot : ILayoutable
+    {
+        Size ClientSize { get; }
+
+        ILayoutManager LayoutManager { get; }
+    }
+}

Perspex/Layout/ILayoutable.cs

@@ -0,0 +1,23 @@
+// -----------------------------------------------------------------------
+// <copyright file="ILayoutable.cs" company="Steven Kirk">
+// Copyright 2013 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Layout
+{
+    public interface ILayoutable
+    {
+        Size? DesiredSize { get; }
+
+        ILayoutRoot GetLayoutRoot();
+
+        void Arrange(Rect rect);
+
+        void Measure(Size availableSize);
+
+        void InvalidateArrange();
+
+        void InvalidateMeasure();
+    }
+}

Perspex/Layout/LayoutManager.cs

@@ -0,0 +1,48 @@
+namespace Perspex.Layout
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Reactive;
+    using System.Reactive.Subjects;
+    using Perspex.Controls;
+
+    public class LayoutManager : ILayoutManager
+    {
+        private ILayoutRoot root;
+
+        private Subject<Unit> layoutNeeded;
+
+        public LayoutManager()
+        {
+            this.layoutNeeded = new Subject<Unit>();
+        }
+
+        public IObservable<Unit> LayoutNeeded
+        {
+            get { return this.layoutNeeded; }
+        }
+
+        public void ExecuteLayoutPass()
+        {
+            if (root != null)
+            {
+                root.Measure(root.ClientSize);
+                root.Arrange(new Rect(root.ClientSize));
+            }
+
+            root = null;
+        }
+
+        public void InvalidateMeasure(ILayoutable item)
+        {
+            this.root = item.GetLayoutRoot();
+            this.layoutNeeded.OnNext(Unit.Default);
+        }
+
+        public void InvalidateArrange(ILayoutable item)
+        {
+            this.root = item.GetLayoutRoot();
+            this.layoutNeeded.OnNext(Unit.Default);
+        }
+    }
+}

Perspex/Perspex.csproj

@@ -74,6 +74,10 @@
     <Compile Include="Controls\ContentControl.cs" />
     <Compile Include="Controls\Control.cs" />
     <Compile Include="Controls\TextBlock.cs" />
+    <Compile Include="Layout\ILayoutable.cs" />
+    <Compile Include="Layout\ILayoutManager.cs" />
+    <Compile Include="Layout\ILayoutRoot.cs" />
+    <Compile Include="Layout\LayoutManager.cs" />
     <Compile Include="Media\FormattedText.cs" />
     <Compile Include="Media\IDrawingContext.cs" />
     <Compile Include="Media\Brush.cs" />

TestApplication/Program.cs

@@ -9,6 +9,7 @@ using Perspex.Media;
 using Perspex.Windows;
 using Perspex.Windows.Media;
 using Perspex.Windows.Threading;
+
 namespace TestApplication
 {
     class Program