Added StackPanel.

Perspex/Controls/ContentPresenter.cs

@@ -21,6 +21,24 @@ namespace Perspex.Controls
 
         private Visual visualChild;
 
+        public ContentPresenter()
+        {
+            this.GetObservableWithHistory(ContentProperty).Subscribe(x =>
+            {
+                if (x.Item1 is Control)
+                {
+                    ((IVisual)x.Item1).VisualParent = null;
+                    ((ILogical)x.Item1).LogicalParent = null;
+                }
+
+                if (x.Item2 is Control)
+                {
+                    ((IVisual)x.Item2).VisualParent = this;
+                    ((ILogical)x.Item2).LogicalParent = this;
+                }
+            });
+        }
+
         public object Content
         {
             get { return this.GetValue(ContentProperty); }

Perspex/Controls/Control.cs

@@ -47,8 +47,11 @@ namespace Perspex.Controls
         public static readonly PerspexProperty<Brush> ForegroundProperty =
             PerspexProperty.Register<Control, Brush>("Foreground", new SolidColorBrush(0xff000000), true);
 
+        public static readonly PerspexProperty<double> HeightProperty =
+            PerspexProperty.Register<Control, double>("Height", double.NaN);
+
         public static readonly PerspexProperty<bool> IsMouseOverProperty =
-            PerspexProperty.Register<Visual, bool>("IsMouseOver");
+            PerspexProperty.Register<Control, bool>("IsMouseOver");
 
         public static readonly PerspexProperty<HorizontalAlignment> HorizontalAlignmentProperty =
             PerspexProperty.Register<Control, HorizontalAlignment>("HorizontalAlignment");
@@ -56,12 +59,27 @@ namespace Perspex.Controls
         public static readonly PerspexProperty<Thickness> MarginProperty =
             PerspexProperty.Register<Control, Thickness>("Margin");
 
+        public static readonly PerspexProperty<double> MaxHeightProperty =
+            PerspexProperty.Register<Control, double>("MaxHeight", double.PositiveInfinity);
+
+        public static readonly PerspexProperty<double> MaxWidthProperty =
+            PerspexProperty.Register<Control, double>("MaxWidth", double.PositiveInfinity);
+
+        public static readonly PerspexProperty<double> MinHeightProperty =
+            PerspexProperty.Register<Control, double>("MinHeight");
+
+        public static readonly PerspexProperty<double> MinWidthProperty =
+            PerspexProperty.Register<Control, double>("MinWidth");
+
         public static readonly ReadOnlyPerspexProperty<Control> ParentProperty =
             new ReadOnlyPerspexProperty<Control>(ParentPropertyRW);
 
         public static readonly PerspexProperty<VerticalAlignment> VerticalAlignmentProperty =
             PerspexProperty.Register<Control, VerticalAlignment>("VerticalAlignment");
 
+        public static readonly PerspexProperty<double> WidthProperty =
+            PerspexProperty.Register<Control, double>("Width", double.NaN);
+
         public static readonly RoutedEvent<MouseEventArgs> MouseLeftButtonDownEvent =
             RoutedEvent.Register<Control, MouseEventArgs>("MouseLeftButtonDown", RoutingStrategy.Bubble);
 
@@ -196,6 +214,12 @@ namespace Perspex.Controls
             }
         }
 
+        public double Height
+        {
+            get { return this.GetValue(HeightProperty); }
+            set { this.SetValue(HeightProperty, value); }
+        }
+
         public bool IsMouseOver
         {
             get { return this.GetValue(IsMouseOverProperty); }
@@ -214,6 +238,30 @@ namespace Perspex.Controls
             set { this.SetValue(MarginProperty, value); }
         }
 
+        public double MaxHeight
+        {
+            get { return this.GetValue(MaxHeightProperty); }
+            set { this.SetValue(MaxHeightProperty, value); }
+        }
+
+        public double MaxWidth
+        {
+            get { return this.GetValue(MaxWidthProperty); }
+            set { this.SetValue(MaxWidthProperty, value); }
+        }
+
+        public double MinHeight
+        {
+            get { return this.GetValue(MinHeightProperty); }
+            set { this.SetValue(MinHeightProperty, value); }
+        }
+
+        public double MinWidth
+        {
+            get { return this.GetValue(MinWidthProperty); }
+            set { this.SetValue(MinWidthProperty, value); }
+        }
+
         public Control Parent
         {
             get { return this.GetValue(ParentPropertyRW); }
@@ -250,6 +298,12 @@ namespace Perspex.Controls
             set { this.SetValue(VerticalAlignmentProperty, value); }
         }
 
+        public double Width
+        {
+            get { return this.GetValue(WidthProperty); }
+            set { this.SetValue(WidthProperty, value); }
+        }
+
         ILogical ILogical.LogicalParent
         {
             get { return this.Parent; }

Perspex/Controls/LogicalChildren.cs

@@ -26,12 +26,25 @@ namespace Perspex.Controls
     {
         private T parent;
 
+        private PerspexList<T> childrenCollection;
+
         private List<T> inner = new List<T>();
 
-        public LogicalChildren(T parent, INotifyCollectionChanged childrenCollection)
+        public LogicalChildren(T parent, PerspexList<T> childrenCollection)
         {
             this.parent = parent;
-            childrenCollection.CollectionChanged += CollectionChanged;
+            this.childrenCollection = childrenCollection;
+            this.Add(childrenCollection);
+            childrenCollection.CollectionChanged += this.CollectionChanged;
+        }
+
+        public void Change(PerspexList<T> childrenCollection)
+        {
+            this.childrenCollection.CollectionChanged -= this.CollectionChanged;
+            this.Remove(inner.ToList());
+            this.childrenCollection = childrenCollection;
+            this.Add(childrenCollection);
+            childrenCollection.CollectionChanged += this.CollectionChanged;
         }
 
         private void Add(IEnumerable<T> items)

Perspex/Controls/Panel.cs

@@ -17,20 +17,43 @@ namespace Perspex.Controls
     /// <summary>
     /// Base class for controls that can contain multiple children.
     /// </summary>
-    public class Panel : Control
+    public class Panel : Control, IVisual
     {
+        private PerspexList<Control> children;
+
         private LogicalChildren<Control> logicalChildren;
 
-        public Panel()
+        public PerspexList<Control> Children
         {
-            this.Children = new ObservableCollection<Control>();
-            this.logicalChildren = new LogicalChildren<Control>(this, this.Children);
+            get
+            {
+                if (this.children == null)
+                {
+                    this.children = new PerspexList<Control>();
+                    this.logicalChildren = new LogicalChildren<Control>(this, this.children);
+                }
+
+                return this.children;
+            }
+            
+            set
+            {
+                this.children = value;
+
+                if (this.logicalChildren != null)
+                {
+                    this.logicalChildren.Change(this.children);
+                }
+                else
+                {
+                    this.logicalChildren = new LogicalChildren<Control>(this, this.children);
+                }
+            }
         }
 
-        public ObservableCollection<Control> Children
+        IEnumerable<IVisual> IVisual.VisualChildren
         {
-            get;
-            private set;
+            get { return this.children; }
         }
     }
 }

Perspex/Controls/StackPanel.cs

@@ -0,0 +1,154 @@
+// -----------------------------------------------------------------------
+// <copyright file="StackPanel.cs" company="Tricycle">
+// Copyright 2014 Tricycle. All rights reserved.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Controls
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Text;
+    using System.Threading.Tasks;
+
+    public enum Orientation
+    {
+        Horizontal,
+        Vertical,
+    }
+
+    public class StackPanel : Panel
+    {
+        public static readonly PerspexProperty<Orientation> OrientationProperty =
+            PerspexProperty.Register<StackPanel, Orientation>("Orientation");
+
+        public Orientation Orientation
+        {
+            get { return this.GetValue(OrientationProperty); }
+            set { this.SetValue(OrientationProperty, value); }
+        }
+
+        protected override Size MeasureContent(Size availableSize)
+        {
+            double childAvailableWidth = double.PositiveInfinity;
+            double childAvailableHeight = double.PositiveInfinity;
+
+            if (this.Orientation == Orientation.Vertical)
+            {
+                childAvailableWidth = availableSize.Width;
+
+                if (!double.IsNaN(this.Width))
+                {
+                    childAvailableWidth = this.Width;
+                }
+
+                childAvailableWidth = Math.Min(childAvailableWidth, this.MaxWidth);
+                childAvailableWidth = Math.Max(childAvailableWidth, this.MinWidth);
+            }
+            else
+            {
+                childAvailableHeight = availableSize.Height;
+
+                if (!double.IsNaN(this.Height))
+                {
+                    childAvailableHeight = this.Height;
+                }
+
+                childAvailableHeight = Math.Min(childAvailableHeight, this.MaxHeight);
+                childAvailableHeight = Math.Max(childAvailableHeight, this.MinHeight);
+            }
+
+            double measuredWidth = 0;
+            double measuredHeight = 0;
+
+            foreach (Control child in this.Children)
+            {
+                child.Measure(new Size(childAvailableWidth, childAvailableHeight));
+                Size size = child.DesiredSize.Value;
+
+                if (Orientation == Orientation.Vertical)
+                {
+                    measuredHeight += size.Height;
+                    measuredWidth = Math.Max(measuredWidth, size.Width);
+                }
+                else
+                {
+                    measuredWidth += size.Width;
+                    measuredHeight = Math.Max(measuredHeight, size.Height);
+                }
+            }
+
+            return new Size(measuredWidth, measuredHeight);
+        }
+
+        protected override Size ArrangeContent(Size finalSize)
+        {
+            double arrangedWidth = finalSize.Width;
+            double arrangedHeight = finalSize.Height;
+
+            if (Orientation == Orientation.Vertical)
+            {
+                arrangedHeight = 0;
+            }
+            else
+            {
+                arrangedWidth = 0;
+            }
+
+            foreach (Control child in this.Children)
+            {
+                double childWidth = child.DesiredSize.Value.Width;
+                double childHeight = child.DesiredSize.Value.Height;
+
+                if (Orientation == Orientation.Vertical)
+                {
+                    childWidth = finalSize.Width;
+
+                    Rect childFinal = new Rect(0, arrangedHeight, childWidth, childHeight);
+
+                    if (childFinal.IsEmpty)
+                    {
+                        child.Arrange(new Rect());
+                    }
+                    else
+                    {
+                        child.Arrange(childFinal);
+                    }
+
+                    arrangedWidth = Math.Max(arrangedWidth, childWidth);
+                    arrangedHeight += childHeight;
+                }
+                else
+                {
+                    childHeight = finalSize.Height;
+
+                    Rect childFinal = new Rect(arrangedWidth, 0, childWidth, childHeight);
+
+                    if (childFinal.IsEmpty)
+                    {
+                        child.Arrange(new Rect());
+                    }
+                    else
+                    {
+                        child.Arrange(childFinal);
+                    }
+
+                    arrangedWidth += childWidth;
+                    arrangedHeight = Math.Max(arrangedHeight, childHeight);
+                }
+            }
+
+            if (Orientation == Orientation.Vertical)
+            {
+                arrangedHeight = Math.Max(arrangedHeight, finalSize.Height);
+            }
+            else
+            {
+                arrangedWidth = Math.Max(arrangedWidth, finalSize.Width);
+            }
+
+            return new Size(arrangedWidth, arrangedHeight);
+        }
+    }
+}

Perspex/Controls/TemplatedControl.cs

@@ -10,6 +10,7 @@ namespace Perspex.Controls
     using System.Collections.Generic;
     using System.Linq;
     using Perspex.Media;
+    using Splat;
 
     public class TemplatedControl : Control, IVisual, ITemplatedControl
     {
@@ -37,6 +38,11 @@ namespace Perspex.Controls
 
                 if (this.visualChild == null && template != null)
                 {
+                    this.Log().Debug(string.Format(
+                        "Creating template for {0} (#{1:x8})",
+                        this.GetType().Name,
+                        this.GetHashCode()));
+
                     this.visualChild = template.Build(this);
                     this.visualChild.VisualParent = this;
                 }

Perspex/Controls/TextBlock.cs

@@ -14,6 +14,7 @@ namespace Perspex.Controls
         public static readonly PerspexProperty<double> FontSizeProperty =
             PerspexProperty.Register<TextBlock, double>(
                 "FontSize",
+                defaultValue: 12.0,
                 inherits: true);
 
         public static readonly PerspexProperty<string> TextProperty =

Perspex/Perspex.csproj

@@ -70,6 +70,9 @@
   <ItemGroup>
     <Compile Include="Application.cs" />
     <Compile Include="BindingExtensions.cs" />
+    <Compile Include="Controls\LogicalChildren.cs" />
+    <Compile Include="Controls\Panel.cs" />
+    <Compile Include="Controls\StackPanel.cs" />
     <Compile Include="Styling\StyleBinding.cs" />
     <Compile Include="Classes.cs" />
     <Compile Include="Contract.cs" />

Perspex/Rect.cs

@@ -122,6 +122,14 @@ namespace Perspex
             get { return new Size(this.width, this.height); }
         }
 
+        /// <summary>
+        /// Gets a value that indicates whether the rectangle is empty.
+        /// </summary>
+        public bool IsEmpty
+        {
+            get { return this.width == 0 && this.height == 0; }
+        }
+
         /// <summary>
         /// Determines whether a points in in the bounds of the rectangle.
         /// </summary>

Perspex/Size.cs

@@ -88,6 +88,26 @@ namespace Perspex
                 this.height + thickness.Top + thickness.Bottom);
         }
 
+        /// <summary>
+        /// Returns a new <see cref="Size"/> with the same height and the specified width.
+        /// </summary>
+        /// <param name="width">The width.</param>
+        /// <returns>The new <see cref="Size"/>.</returns>
+        public Size WithWidth(double width)
+        {
+            return new Size(width, this.height);
+        }
+
+        /// <summary>
+        /// Returns a new <see cref="Size"/> with the same width and the specified height.
+        /// </summary>
+        /// <param name="height">The height.</param>
+        /// <returns>The new <see cref="Size"/>.</returns>
+        public Size WithHeight(double height)
+        {
+            return new Size(this.width, height);
+        }
+
         /// <summary>
         /// Returns the string representation of the size.
         /// </summary>

Perspex/Styling/StyleActivator.cs

@@ -17,7 +17,7 @@ namespace Perspex.Styling
         Or,
     }
 
-    public class StyleActivator : IObservable<bool>
+    public class StyleActivator : IObservable<bool>, IDisposable
     {
         ActivatorMode mode;
 
@@ -62,6 +62,19 @@ namespace Perspex.Styling
             private set;
         }
 
+        public void Dispose()
+        {
+            foreach (IObserver<bool> observer in this.observers)
+            {
+                observer.OnCompleted();
+            }
+
+            foreach (IDisposable subscription in this.subscriptions)
+            {
+                subscription.Dispose();
+            }
+        }
+
         public IDisposable Subscribe(IObserver<bool> observer)
         {
             Contract.Requires<ArgumentNullException>(observer != null);

Perspex/Visual.cs

@@ -12,6 +12,7 @@ namespace Perspex
     using Perspex.Controls;
     using Perspex.Layout;
     using Perspex.Media;
+    using Splat;
 
     public abstract class Visual : PerspexObject, IVisual
     {
@@ -25,7 +26,7 @@ namespace Perspex
 
         IEnumerable<IVisual> IVisual.ExistingVisualChildren
         {
-            get { return Enumerable.Empty<Visual>(); }
+            get { return ((IVisual)this).VisualChildren; }
         }
 
         IEnumerable<IVisual> IVisual.VisualChildren
@@ -51,6 +52,11 @@ namespace Perspex
 
                     if (this.GetVisualAncestor<ILayoutRoot>() != null)
                     {
+                        this.Log().Debug(string.Format(
+                            "Attached {0} (#{1:x8}) to visual tree",
+                            this.GetType().Name,
+                            this.GetHashCode()));
+
                         this.AttachedToVisualTree();
                     }
                 }

Perspex/VisualExtensions.cs

@@ -7,10 +7,29 @@
 namespace Perspex
 {
     using System;
+    using System.Collections.Generic;
     using System.Linq;
+    using Perspex.Styling;
 
     public static class VisualExtensions
     {
+        public static IEnumerable<IVisual> GetVisual(this IVisual visual, Func<Selector, Selector> selector)
+        {
+            Selector sel = selector(new Selector());
+            IEnumerable<IVisual> visuals = Enumerable.Repeat(visual, 1).Concat(visual.GetVisualDescendents());
+
+            foreach (IStyleable v in visuals.OfType<IStyleable>())
+            {
+                using (StyleActivator activator = sel.GetActivator(v))
+                {
+                    if (activator.CurrentValue)
+                    {
+                        yield return (IVisual)v;
+                    }
+                }
+            }
+        }
+
         public static T GetVisualAncestor<T>(this IVisual visual) where T : class
         {
             Contract.Requires<NullReferenceException>(visual != null);
@@ -67,5 +86,18 @@ namespace Perspex
 
             return null;
         }
+
+        public static IEnumerable<IVisual> GetVisualDescendents(this IVisual visual)
+        {
+            foreach (IVisual child in visual.VisualChildren)
+            {
+                yield return child;
+
+                foreach (IVisual descendent in child.GetVisualDescendents())
+                {
+                    yield return descendent;
+                }
+            }
+        }
     }
 }

TestApplication/Program.cs

@@ -36,7 +36,9 @@ namespace TestApplication
     {
         static void Main(string[] args)
         {
-            Locator.CurrentMutable.Register(() => new TextService(new SharpDX.DirectWrite.Factory()), typeof(ITextService));
+            TextService textService = new TextService(new SharpDX.DirectWrite.Factory());
+
+            Locator.CurrentMutable.Register(() => textService, typeof(ITextService));
             Locator.CurrentMutable.Register(() => new Styler(), typeof(IStyler));
             Locator.CurrentMutable.Register(() => new TestLogger(), typeof(ILogger));
 
@@ -50,15 +52,28 @@ namespace TestApplication
 
             Window window = new Window
             {
-                Content = new Button
-                {
-                    Background = new SolidColorBrush(0xff0000ff),
-                    Content = "Hello World",
+                Content = new StackPanel 
+                { 
                     HorizontalAlignment = HorizontalAlignment.Center,
                     VerticalAlignment = VerticalAlignment.Center,
-                },
+                    Orientation = Orientation.Vertical,
+                    Children = new PerspexList<Control> 
+                    { 
+                        new Button
+                        {
+                            Margin = new Thickness(2),
+                        },
+                        new Button
+                        {
+                            Content = "Explict Background",
+                            Background = new SolidColorBrush(0xffa0a0ff),
+                        }
+                    }
+                }
             };
 
+            var m = window.GetVisual(x => x.OfType<Button>().Template().Id("border"));
+
             window.Show();
             Dispatcher.Run();
         }