Added IPanel interface.

Tests/Perspex.Controls.UnitTests/Presenters/DeckPresenterTests.cs

@@ -18,7 +18,7 @@ namespace Perspex.Controls.UnitTests.Presenters
         {
             var target = new DeckPresenter
             {
-                ItemsPanel = new FuncTemplate<Panel>(() => new Panel()),
+                ItemsPanel = new FuncTemplate<IPanel>(() => new Panel()),
             };
 
             target.ApplyTemplate();

Tests/Perspex.Controls.UnitTests/Presenters/ItemsPresenterTests.cs

@@ -137,7 +137,7 @@ namespace Perspex.Controls.UnitTests.Presenters
             var panel = new Panel();
             var target = new ItemsPresenter
             {
-                ItemsPanel = new FuncTemplate<Panel>(() => panel),
+                ItemsPanel = new FuncTemplate<IPanel>(() => panel),
             };
 
             target.ApplyTemplate();
@@ -152,7 +152,7 @@ namespace Perspex.Controls.UnitTests.Presenters
 
             target.ApplyTemplate();
 
-            Assert.Equal(KeyboardNavigationMode.Once, KeyboardNavigation.GetTabNavigation(target.Panel));
+            Assert.Equal(KeyboardNavigationMode.Once, KeyboardNavigation.GetTabNavigation((InputElement)target.Panel));
         }
 
         [Fact]
@@ -163,7 +163,7 @@ namespace Perspex.Controls.UnitTests.Presenters
             KeyboardNavigation.SetTabNavigation(target, KeyboardNavigationMode.Cycle);
             target.ApplyTemplate();
 
-            Assert.Equal(KeyboardNavigationMode.Cycle, KeyboardNavigation.GetTabNavigation(target.Panel));
+            Assert.Equal(KeyboardNavigationMode.Cycle, KeyboardNavigation.GetTabNavigation((InputElement)target.Panel));
         }
 
         [Fact]

src/Perspex.Controls/Deck.cs

@@ -26,8 +26,8 @@ namespace Perspex.Controls
         /// <summary>
         /// The default value of <see cref="IReparentingControl"/> for <see cref="Deck"/>.
         /// </summary>
-        private static readonly ITemplate<Panel> PanelTemplate =
-            new FuncTemplate<Panel>(() => new Panel());
+        private static readonly ITemplate<IPanel> PanelTemplate =
+            new FuncTemplate<IPanel>(() => new Panel());
 
         /// <summary>
         /// Initializes static members of the <see cref="Deck"/> class.

src/Perspex.Controls/IPanel.cs

@@ -0,0 +1,19 @@
+// -----------------------------------------------------------------------
+// <copyright file="IPanel.cs" company="Steven Kirk">
+// Copyright 2015 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Controls
+{
+    /// <summary>
+    /// Interface for controls that can contain multiple children.
+    /// </summary>
+    public interface IPanel : IControl
+    {
+        /// <summary>
+        /// Gets or sets the children of the <see cref="Panel"/>.
+        /// </summary>
+        Controls Children { get; set; }
+    }
+}

src/Perspex.Controls/ItemsControl.cs

@@ -29,8 +29,8 @@ namespace Perspex.Controls
         /// The default value for the <see cref="ItemsPanel"/> property.
         /// </summary>
         [SuppressMessage("Microsoft.StyleCop.CSharp.NamingRules", "SA1202:ElementsMustBeOrderedByAccess", Justification = "Needs to be before or a NullReferenceException is thrown.")]
-        private static readonly FuncTemplate<Panel> DefaultPanel =
-            new FuncTemplate<Panel>(() => new StackPanel());
+        private static readonly FuncTemplate<IPanel> DefaultPanel =
+            new FuncTemplate<IPanel>(() => new StackPanel());
 
         /// <summary>
         /// Defines the <see cref="Items"/> property.
@@ -41,8 +41,8 @@ namespace Perspex.Controls
         /// <summary>
         /// Defines the <see cref="ItemsPanel"/> property.
         /// </summary>
-        public static readonly PerspexProperty<ITemplate<Panel>> ItemsPanelProperty =
-            PerspexProperty.Register<ItemsControl, ITemplate<Panel>>("ItemsPanel", defaultValue: DefaultPanel);
+        public static readonly PerspexProperty<ITemplate<IPanel>> ItemsPanelProperty =
+            PerspexProperty.Register<ItemsControl, ITemplate<IPanel>>("ItemsPanel", defaultValue: DefaultPanel);
 
         private IItemContainerGenerator itemContainerGenerator;
 
@@ -91,7 +91,7 @@ namespace Perspex.Controls
         /// <summary>
         /// Gets or sets the panel used to display the items.
         /// </summary>
-        public ITemplate<Panel> ItemsPanel
+        public ITemplate<IPanel> ItemsPanel
         {
             get { return this.GetValue(ItemsPanelProperty); }
             set { this.SetValue(ItemsPanelProperty, value); }

src/Perspex.Controls/Menu.cs

@@ -24,8 +24,8 @@ namespace Perspex.Controls
         /// <summary>
         /// Defines the default items panel used by a <see cref="Menu"/>.
         /// </summary>
-        private static readonly ITemplate<Panel> DefaultPanel =
-            new FuncTemplate<Panel>(() => new StackPanel { Orientation = Orientation.Horizontal });
+        private static readonly ITemplate<IPanel> DefaultPanel =
+            new FuncTemplate<IPanel>(() => new StackPanel { Orientation = Orientation.Horizontal });
 
         /// <summary>
         /// Defines the <see cref="IsOpen"/> property.

src/Perspex.Controls/MenuItem.cs

@@ -77,8 +77,8 @@ namespace Perspex.Controls
         /// <summary>
         /// The default value for the <see cref="ItemsControl.ItemsPanel"/> property.
         /// </summary>
-        private static readonly ITemplate<Panel> DefaultPanel =
-            new FuncTemplate<Panel>(() => new StackPanel
+        private static readonly ITemplate<IPanel> DefaultPanel =
+            new FuncTemplate<IPanel>(() => new StackPanel
             {
                 [KeyboardNavigation.DirectionalNavigationProperty] = KeyboardNavigationMode.Cycle,
             });

src/Perspex.Controls/Panel.cs

@@ -19,7 +19,7 @@ namespace Perspex.Controls
     /// Controls can be added to a <see cref="Panel"/> by adding them to its <see cref="Children"/>
     /// collection. All children are layed out to fill the panel.
     /// </remarks>
-    public class Panel : Control, IReparentingControl
+    public class Panel : Control, IReparentingControl, IPanel
     {
         private Controls children = new Controls();
 

src/Perspex.Controls/Perspex.Controls.csproj

@@ -44,6 +44,7 @@
     <Compile Include="Generators\ITreeItemContainerGenerator.cs" />
     <Compile Include="Generators\ItemContainers.cs" />
     <Compile Include="IControl.cs" />
+    <Compile Include="IPanel.cs" />
     <Compile Include="IReparentingHost.cs" />
     <Compile Include="ISetLogicalParent.cs" />
     <Compile Include="MenuItemAccessKeyHandler.cs" />

src/Perspex.Controls/Presenters/DeckPresenter.cs

@@ -31,7 +31,7 @@ namespace Perspex.Controls.Presenters
         /// <summary>
         /// Defines the <see cref="ItemsPanel"/> property.
         /// </summary>
-        public static readonly PerspexProperty<ITemplate<Panel>> ItemsPanelProperty =
+        public static readonly PerspexProperty<ITemplate<IPanel>> ItemsPanelProperty =
             ItemsControl.ItemsPanelProperty.AddOwner<DeckPresenter>();
 
         /// <summary>
@@ -98,7 +98,7 @@ namespace Perspex.Controls.Presenters
         /// <summary>
         /// Gets or sets the panel used to display the pages.
         /// </summary>
-        public ITemplate<Panel> ItemsPanel
+        public ITemplate<IPanel> ItemsPanel
         {
             get { return this.GetValue(ItemsPanelProperty); }
             set { this.SetValue(ItemsPanelProperty, value); }
@@ -116,7 +116,7 @@ namespace Perspex.Controls.Presenters
         /// <summary>
         /// Gets the panel used to display the pages.
         /// </summary>
-        public Panel Panel
+        public IPanel Panel
         {
             get;
             private set;

src/Perspex.Controls/Presenters/IItemsPresenter.cs

@@ -8,6 +8,6 @@ namespace Perspex.Controls.Presenters
 {
     public interface IItemsPresenter : IPresenter
     {
-        Panel Panel { get; }
+        IPanel Panel { get; }
     }
 }

src/Perspex.Controls/Presenters/ItemsPresenter.cs

@@ -28,7 +28,7 @@ namespace Perspex.Controls.Presenters
         /// <summary>
         /// Defines the <see cref="ItemsPanel"/> property.
         /// </summary>
-        public static readonly PerspexProperty<ITemplate<Panel>> ItemsPanelProperty =
+        public static readonly PerspexProperty<ITemplate<IPanel>> ItemsPanelProperty =
             ItemsControl.ItemsPanelProperty.AddOwner<ItemsPresenter>();
 
         private bool createdPanel;
@@ -93,7 +93,7 @@ namespace Perspex.Controls.Presenters
         /// <summary>
         /// Gets or sets a template which creates the <see cref="Panel"/> used to display the items.
         /// </summary>
-        public ITemplate<Panel> ItemsPanel
+        public ITemplate<IPanel> ItemsPanel
         {
             get { return this.GetValue(ItemsPanelProperty); }
             set { this.SetValue(ItemsPanelProperty, value); }
@@ -102,7 +102,7 @@ namespace Perspex.Controls.Presenters
         /// <summary>
         /// Gets the panel used to display the items.
         /// </summary>
-        public Panel Panel
+        public IPanel Panel
         {
             get;
             private set;
@@ -143,7 +143,9 @@ namespace Perspex.Controls.Presenters
 
             if (!this.Panel.IsSet(KeyboardNavigation.DirectionalNavigationProperty))
             {
-                KeyboardNavigation.SetDirectionalNavigation(this.Panel, KeyboardNavigationMode.Contained);
+                KeyboardNavigation.SetDirectionalNavigation(
+                    (InputElement)this.Panel, 
+                    KeyboardNavigationMode.Contained);
             }
 
             this.AddVisualChild(this.Panel);
@@ -157,7 +159,9 @@ namespace Perspex.Controls.Presenters
                     logicalHost.LogicalChildren);
             }
 
-            KeyboardNavigation.SetTabNavigation(this.Panel, KeyboardNavigation.GetTabNavigation(this));
+            KeyboardNavigation.SetTabNavigation(
+                (InputElement)this.Panel, 
+                KeyboardNavigation.GetTabNavigation(this));
             this.createdPanel = true;
             this.CreateItemsAndListenForChanges(this.Items);
         }

src/Perspex.Controls/Primitives/SelectingItemsControl.cs

@@ -325,7 +325,9 @@ namespace Perspex.Controls.Primitives
                 var inputElement = container as IInputElement;
                 if (inputElement != null && this.Presenter != null && this.Presenter.Panel != null)
                 {
-                    KeyboardNavigation.SetTabOnceActiveElement(this.Presenter.Panel, inputElement);
+                    KeyboardNavigation.SetTabOnceActiveElement(
+                        (InputElement)this.Presenter.Panel, 
+                        inputElement);
                 }
             }
         }

src/Perspex.Controls/TreeView.cs

@@ -69,7 +69,9 @@ namespace Perspex.Controls
 
             if (this.Presenter != null && this.Presenter.Panel != null)
             {
-                KeyboardNavigation.SetTabOnceActiveElement(this.Presenter.Panel, selectedContainer);
+                KeyboardNavigation.SetTabOnceActiveElement(
+                    (InputElement)this.Presenter.Panel, 
+                    selectedContainer);
             }
 
             foreach (var item in containers)

src/Perspex.Controls/TreeViewItem.cs

@@ -33,8 +33,8 @@ namespace Perspex.Controls
         public static readonly PerspexProperty<bool> IsSelectedProperty =
             ListBoxItem.IsSelectedProperty.AddOwner<TreeViewItem>();
 
-        private static readonly ITemplate<Panel> DefaultPanel =
-            new FuncTemplate<Panel>(() => new StackPanel
+        private static readonly ITemplate<IPanel> DefaultPanel =
+            new FuncTemplate<IPanel>(() => new StackPanel
             {
                 [KeyboardNavigation.DirectionalNavigationProperty] = KeyboardNavigationMode.Continue,
             });