Started adding ScrollViewer.

Currently works so far as to scroll an image in the Images tab of the
test app. Hiding the scrollbars is currently disabled as it requires a
layout pass to be triggered during a layout pass.  Need to work out a
way around that...

Perspex.Base/PerspexObject.cs

@@ -593,7 +593,7 @@ namespace Perspex
         {
             Contract.Requires<NullReferenceException>(property != null);
 
-            return this.Bind((PerspexProperty)property, (IObservable<object>)source, priority);
+            return this.Bind((PerspexProperty)property, source.Select(x => (object)x), priority);
         }
 
         /// <summary>

Perspex.Controls/Perspex.Controls.csproj

@@ -41,6 +41,7 @@
     <Compile Include="ColumnDefinitions.cs" />
     <Compile Include="ContentControl.cs" />
     <Compile Include="GridSplitter.cs" />
+    <Compile Include="Presenters\ScrollContentPresenter.cs" />
     <Compile Include="Presenters\ContentPresenter.cs" />
     <Compile Include="Control.cs" />
     <Compile Include="ControlExtensions.cs" />
@@ -71,6 +72,7 @@
     <Compile Include="RowDefinition.cs" />
     <Compile Include="RowDefinitions.cs" />
     <Compile Include="Primitives\SelectingItemsControl.cs" />
+    <Compile Include="ScrollViewer.cs" />
     <Compile Include="Shapes\Path.cs" />
     <Compile Include="Shapes\Rectangle.cs" />
     <Compile Include="Shapes\Shape.cs" />

Perspex.Controls/Presenters/ScrollContentPresenter.cs

@@ -0,0 +1,78 @@
+// -----------------------------------------------------------------------
+// <copyright file="ScrollContentPresenter.cs" company="Steven Kirk">
+// Copyright 2014 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Controls.Presenters
+{
+    using System.Linq;
+    using Perspex.Layout;
+
+    public class ScrollContentPresenter :  ContentPresenter
+    {
+        public static PerspexProperty<Size> ExtentProperty =
+            ScrollViewer.ExtentProperty.AddOwner<ScrollContentPresenter>();
+
+        public static PerspexProperty<Vector> OffsetProperty =
+            ScrollViewer.OffsetProperty.AddOwner<ScrollContentPresenter>();
+
+        public static PerspexProperty<Size> ViewportProperty =
+            ScrollViewer.ViewportProperty.AddOwner<ScrollContentPresenter>();
+
+        public ScrollContentPresenter()
+        {
+            AffectsRender(OffsetProperty);
+        }
+
+        public Size Extent
+        {
+            get { return this.GetValue(ExtentProperty); }
+            private set { this.SetValue(ExtentProperty, value); }
+        }
+
+        public Vector Offset
+        {
+            get { return this.GetValue(OffsetProperty); }
+            set { this.SetValue(OffsetProperty, value); }
+        }
+
+        public Size Viewport
+        {
+            get { return this.GetValue(ViewportProperty); }
+            private set { this.SetValue(ViewportProperty, value); }
+        }
+
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            var content = this.Content as ILayoutable;
+
+            if (content != null)
+            {
+                content.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
+                var size = content.DesiredSize.Value;
+                this.Extent = size;
+                return size.Constrain(availableSize);
+            }
+            else
+            {
+                return this.Extent = new Size();
+            }
+        }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            var child = this.GetVisualChildren().SingleOrDefault() as ILayoutable;
+
+            this.Viewport = finalSize;
+
+            if (child != null)
+            {
+                child.Arrange(new Rect((Point)(-this.Offset), child.DesiredSize.Value));
+                return finalSize;
+            }
+
+            return new Size();
+        }
+    }
+}

Perspex.Controls/Primitives/TemplatedControl.cs

@@ -71,6 +71,26 @@ namespace Perspex.Controls.Primitives
             }
         }
 
+        protected T FindTemplateChild<T>(string id) where T : Control
+        {
+            return this.GetTemplateControls().OfType<T>().FirstOrDefault(x => x.Id == id);
+        }
+
+        protected T GetTemplateChild<T>(string id) where T : Control
+        {
+            var result = this.FindTemplateChild<T>(id);
+
+            if (result == null)
+            {
+                throw new InvalidOperationException(string.Format(
+                    "Could not find template child '{0}' in template for '{1}'.",
+                    id,
+                    this.GetType().FullName));
+            }
+
+            return result;
+        }
+
         protected virtual void OnTemplateApplied()
         {
         }

Perspex.Controls/ScrollViewer.cs

@@ -0,0 +1,95 @@
+// -----------------------------------------------------------------------
+// <copyright file="DefinitionBase.cs" company="Steven Kirk">
+// Copyright 2014 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+using System.Reactive.Linq;
+using Perspex.Controls.Presenters;
+using Perspex.Controls.Primitives;
+
+namespace Perspex.Controls
+{
+    public class ScrollViewer : ContentControl
+    {
+        public static PerspexProperty<Size> ExtentProperty =
+            PerspexProperty.Register<ScrollViewer, Size>("Extent");
+
+        public static PerspexProperty<Vector> OffsetProperty =
+            PerspexProperty.Register<ScrollViewer, Vector>("Offset");
+
+        public static PerspexProperty<Size> ViewportProperty =
+            PerspexProperty.Register<ScrollViewer, Size>("Viewport");
+
+        private ScrollContentPresenter presenter;
+
+        private ScrollBar horizontalScrollBar;
+
+        private ScrollBar verticalScrollBar;
+
+        public Size Extent
+        {
+            get { return this.GetValue(ExtentProperty); }
+            private set { this.SetValue(ExtentProperty, value); }
+        }
+
+        public Vector Offset
+        {
+            get { return this.GetValue(OffsetProperty); }
+            set { this.SetValue(OffsetProperty, value); }
+        }
+
+        public Size Viewport
+        {
+            get { return this.GetValue(ViewportProperty); }
+            private set { this.SetValue(ViewportProperty, value); }
+        }
+
+        protected override void OnTemplateApplied()
+        {
+            this.presenter = this.GetTemplateChild<ScrollContentPresenter>("presenter");
+            this.horizontalScrollBar = this.GetTemplateChild<ScrollBar>("horizontalScrollBar");
+            this.verticalScrollBar = this.GetTemplateChild<ScrollBar>("verticalScrollBar");
+
+            this[!ExtentProperty] = this.presenter[!ExtentProperty];
+            this[!ViewportProperty] = this.presenter[!ViewportProperty];
+            this.presenter[!OffsetProperty] = this[!OffsetProperty];
+
+            var extentAndViewport = Observable.CombineLatest(
+                this.GetObservable(ExtentProperty).StartWith(this.Extent),
+                this.GetObservable(ViewportProperty).StartWith(this.Viewport))
+                .Select(x => new { Extent = x[0], Viewport = x[1] });
+
+            //this.horizontalScrollBar.Bind(
+            //    IsVisibleProperty,
+            //    extentAndViewport.Select(x => x.Extent.Width > x.Viewport.Width));
+
+            this.horizontalScrollBar.Bind(
+                ScrollBar.MaximumProperty,
+                extentAndViewport.Select(x => x.Extent.Width));
+
+            this.horizontalScrollBar.Bind(
+                ScrollBar.ViewportSizeProperty,
+                extentAndViewport.Select(x => x.Viewport.Width));
+
+            //this.verticalScrollBar.Bind(
+            //    IsVisibleProperty,
+            //    extentAndViewport.Select(x => x.Extent.Height > x.Viewport.Height));
+
+            this.verticalScrollBar.Bind(
+                ScrollBar.MaximumProperty,
+                extentAndViewport.Select(x => x.Extent.Height));
+
+            this.verticalScrollBar.Bind(
+                ScrollBar.ViewportSizeProperty,
+                extentAndViewport.Select(x => x.Viewport.Height));
+
+            var offset = Observable.CombineLatest(
+                this.horizontalScrollBar.GetObservable(ScrollBar.ValueProperty),
+                this.verticalScrollBar.GetObservable(ScrollBar.ValueProperty))
+                .Select(x => new Vector(x[0], x[1]));
+
+            this.Bind(OffsetProperty, offset);
+        }
+    }
+}

Perspex.SceneGraph/Vector.cs

@@ -65,6 +65,11 @@ namespace Perspex
             return new Vector(a.x - b.x, a.y - b.y);
         }
 
+        public static explicit operator Point(Vector a)
+        {
+            return new Point(a.x, a.y);
+        }
+
         /// <summary>
         /// Returns the string representation of the point.
         /// </summary>

Perspex.Themes.Default/DefaultTheme.cs

@@ -18,6 +18,7 @@ namespace Perspex.Themes.Default
             this.Add(new GridSplitterStyle());
             this.Add(new ItemsControlStyle());
             this.Add(new ScrollBarStyle());
+            this.Add(new ScrollViewerStyle());
             this.Add(new TabControlStyle());
             this.Add(new TabItemStyle());
             this.Add(new TabStripStyle());

Perspex.Themes.Default/Perspex.Themes.Default.csproj

@@ -66,6 +66,7 @@
     </ProjectReference>
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="ScrollViewerStyle.cs" />
     <Compile Include="ScrollBarStyle.cs" />
     <Compile Include="GridSplitterStyle.cs" />
     <Compile Include="ButtonStyle.cs" />

Perspex.Themes.Default/ScrollViewerStyle.cs

@@ -0,0 +1,69 @@
+// -----------------------------------------------------------------------
+// <copyright file="ScrollViewerStyle.cs" company="Steven Kirk">
+// Copyright 2014 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Themes.Default
+{
+    using System.Linq;
+    using Perspex.Controls;
+    using Perspex.Controls.Presenters;
+    using Perspex.Controls.Primitives;
+    using Perspex.Media;
+    using Perspex.Styling;
+
+    public class ScrollViewerStyle : Styles
+    {
+        public ScrollViewerStyle()
+        {
+            this.AddRange(new[]
+            {
+                new Style(x => x.OfType<ScrollViewer>())
+                {
+                    Setters = new[]
+                    {
+                        new Setter(ScrollViewer.TemplateProperty, ControlTemplate.Create<ScrollViewer>(this.Template)),
+                    },
+                },
+            });
+        }
+
+        private Control Template(ScrollViewer control)
+        {
+            return new Grid
+            {
+                ColumnDefinitions = new ColumnDefinitions
+                {
+                    new ColumnDefinition(1, GridUnitType.Star),
+                    new ColumnDefinition(GridLength.Auto),
+                },
+                RowDefinitions = new RowDefinitions
+                {
+                    new RowDefinition(1, GridUnitType.Star),
+                    new RowDefinition(GridLength.Auto),
+                },
+                Children = new Controls
+                {
+                    new ScrollContentPresenter
+                    {
+                        Id = "presenter",
+                        [~ContentPresenter.ContentProperty] = control[~ScrollViewer.ContentProperty],
+                    },
+                    new ScrollBar
+                    {
+                        Id = "horizontalScrollBar",
+                        Orientation = Orientation.Horizontal,
+                        [Grid.RowProperty] = 1,
+                    },
+                    new ScrollBar
+                    {
+                        Id = "verticalScrollBar",
+                        Orientation = Orientation.Vertical,
+                        [Grid.ColumnProperty] = 1,
+                    },
+                },
+            };
+        }
+    }
+}

TestApplication/Program.cs

@@ -116,6 +116,7 @@ namespace TestApplication
                             {
                                 ButtonsTab(),
                                 TextTab(),
+                                ImagesTab(),
                                 ListsTab(),
                                 SlidersTab(),
                                 LayoutTab(),
@@ -211,14 +212,19 @@ namespace TestApplication
                     HorizontalAlignment = HorizontalAlignment.Center,
                     VerticalAlignment = VerticalAlignment.Center,
                     Gap = 8,
-                    Width = 120,
                     Children = new Controls
                     {
-                        new Image
+                        new ScrollViewer
                         {
-                            Source = new Bitmap("github_icon.png"),
                             Width = 200,
-                        },
+                            Height = 200,
+                            Content = new Image
+                            {
+                                Source = new Bitmap("github_icon.png"),
+                                Width = 400,
+                                Height = 400,
+                            },
+                        }
                     }
                 },
             };