Added mousewheel support to ScrollViewer.

Perspex.Controls/Presenters/ScrollContentPresenter.cs

@@ -6,7 +6,9 @@
 
 namespace Perspex.Controls.Presenters
 {
+    using System;
     using System.Linq;
+    using Perspex.Input;
     using Perspex.Layout;
 
     public class ScrollContentPresenter : ContentPresenter
@@ -20,9 +22,9 @@ namespace Perspex.Controls.Presenters
         public static readonly PerspexProperty<Size> ViewportProperty =
             ScrollViewer.ViewportProperty.AddOwner<ScrollContentPresenter>();
 
-        public ScrollContentPresenter()
+        static ScrollContentPresenter()
         {
-            Control.AffectsRender(OffsetProperty);
+            Control.AffectsArrange(OffsetProperty);
         }
 
         public Size Extent
@@ -74,5 +76,17 @@ namespace Perspex.Controls.Presenters
 
             return new Size();
         }
+
+        protected override void OnPointerWheelChanged(PointerWheelEventArgs e)
+        {
+            if (this.Extent.Height > this.Viewport.Height)
+            {
+                var y = this.Offset.Y + (-e.Delta.Y * 50);
+                y = Math.Max(y, 0);
+                y = Math.Min(y, Extent.Height - Viewport.Height);
+                this.Offset = new Vector(this.Offset.X, y);
+                e.Handled = true;
+            }
+        }
     }
 }

Perspex.Controls/ScrollViewer.cs

@@ -6,6 +6,7 @@
 
 namespace Perspex.Controls
 {
+    using System;
     using System.Reactive.Linq;
     using Perspex.Controls.Presenters;
     using Perspex.Controls.Primitives;
@@ -89,6 +90,12 @@ namespace Perspex.Controls
                 this.verticalScrollBar.GetObservable(ScrollBar.ValueProperty))
                 .Select(x => new Vector(x[0], x[1]));
 
+            this.presenter.GetObservable(ScrollContentPresenter.OffsetProperty).Subscribe(x =>
+            {
+                this.horizontalScrollBar.Value = x.X;
+                this.verticalScrollBar.Value = x.Y;
+            });
+
             this.Bind(OffsetProperty, offset);
         }
     }

Perspex.Input/InputElement.cs

@@ -48,6 +48,9 @@ namespace Perspex.Input
         public static readonly RoutedEvent<PointerEventArgs> PointerReleasedEvent =
             RoutedEvent.Register<InputElement, PointerEventArgs>("PointerReleased", RoutingStrategy.Bubble);
 
+        public static readonly RoutedEvent<PointerEventArgs> PointerWheelChangedEvent =
+            RoutedEvent.Register<InputElement, PointerEventArgs>("PointerWheelChanged", RoutingStrategy.Bubble);
+
         public InputElement()
         {
             this.GotFocus += (_, e) => this.OnGotFocus(e);
@@ -59,6 +62,7 @@ namespace Perspex.Input
             this.PointerMoved += (_, e) => this.OnPointerMoved(e);
             this.PointerPressed += (_, e) => this.OnPointerPressed(e);
             this.PointerReleased += (_, e) => this.OnPointerReleased(e);
+            this.PointerWheelChanged += (_, e) => this.OnPointerWheelChanged(e);
         }
 
         public event EventHandler<RoutedEventArgs> GotFocus
@@ -115,6 +119,12 @@ namespace Perspex.Input
             remove { this.RemoveHandler(PointerReleasedEvent, value); }
         }
 
+        public event EventHandler<PointerWheelEventArgs> PointerWheelChanged
+        {
+            add { this.AddHandler(PointerWheelChangedEvent, value); }
+            remove { this.RemoveHandler(PointerWheelChangedEvent, value); }
+        }
+
         public bool Focusable
         {
             get { return this.GetValue(FocusableProperty); }
@@ -177,5 +187,9 @@ namespace Perspex.Input
         protected virtual void OnPointerReleased(PointerEventArgs e)
         {
         }
+
+        protected virtual void OnPointerWheelChanged(PointerWheelEventArgs e)
+        {
+        }
     }
 }

Perspex.Input/MouseDevice.cs

@@ -76,6 +76,13 @@ namespace Perspex.Input
                 case RawMouseEventType.LeftButtonUp:
                     this.MouseUp((IMouseDevice)e.Device, (IVisual)e.Root, e.Position);
                     break;
+                case RawMouseEventType.Wheel:
+                    this.MouseWheel(
+                        (IMouseDevice)e.Device, 
+                        (IVisual)e.Root, 
+                        e.Position,
+                        ((RawMouseWheelEventArgs)e).Delta);
+                    break;
             }
         }
 
@@ -162,6 +169,28 @@ namespace Perspex.Input
             }
         }
 
+        private void MouseWheel(IMouseDevice device, IVisual visual, Point p,  Vector delta)
+        {
+            IVisual hit = visual.GetVisualAt(p);
+
+            if (hit != null)
+            {
+                IInteractive source = this.GetSource(hit);
+
+                if (source != null)
+                {
+                    source.RaiseEvent(new PointerWheelEventArgs
+                    {
+                        Device = this,
+                        RoutedEvent = InputElement.PointerWheelChangedEvent,
+                        OriginalSource = source,
+                        Source = source,
+                        Delta = delta,
+                    });
+                }
+            }
+        }
+
         private IInputElement GetFocusable(IVisual hit)
         {
             return this.Captured as IInputElement ?? 

Perspex.Input/Perspex.Input.csproj

@@ -68,6 +68,8 @@
     <Compile Include="IPointerDevice.cs" />
     <Compile Include="Key.cs" />
     <Compile Include="KeyboardDevice.cs" />
+    <Compile Include="PointerWheelEventArgs.cs" />
+    <Compile Include="Raw\RawMouseWheelEventArgs.cs" />
     <Compile Include="Raw\RawSizeEventArgs.cs" />
     <Compile Include="VectorEventArgs.cs" />
     <Compile Include="KeyEventArgs.cs" />

Perspex.Input/PointerWheelEventArgs.cs

@@ -0,0 +1,13 @@
+// -----------------------------------------------------------------------
+// <copyright file="PointerWheelEventArgs.cs" company="Steven Kirk">
+// Copyright 2013 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Input
+{
+    public class PointerWheelEventArgs : PointerEventArgs
+    {
+        public Vector Delta { get; set; }
+    }
+}

Perspex.Input/Raw/RawMouseEventArgs.cs

@@ -14,6 +14,7 @@ namespace Perspex.Input.Raw
         Move,
         LeftButtonDown,
         LeftButtonUp,
+        Wheel,
     }
 
     public class RawMouseEventArgs : RawInputEventArgs

Perspex.Input/Raw/RawMouseWheelEventArgs.cs

@@ -0,0 +1,26 @@
+// -----------------------------------------------------------------------
+// <copyright file="RawMouseEventArgs.cs" company="Steven Kirk">
+// Copyright 2013 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Input.Raw
+{
+    using System;
+    using Perspex.Layout;
+
+    public class RawMouseWheelEventArgs : RawMouseEventArgs
+    {
+        public RawMouseWheelEventArgs(
+            IInputDevice device,
+            ILayoutRoot root,
+            Point position,
+            Vector delta)
+            : base(device, root, RawMouseEventType.Wheel, position)
+        {
+            this.Delta = delta;
+        }
+
+        public Vector Delta { get; private set; }
+    }
+}

Windows/Perspex.Win32/WindowImpl.cs

@@ -134,9 +134,18 @@ namespace Perspex.Win32
             this.Handle = new PlatformHandle(this.hwnd, "HWND");
         }
 
+        private Point ScreenToClient(uint x, uint y)
+        {
+            var p = new UnmanagedMethods.POINT { X = (int)x, Y = (int)y };
+            UnmanagedMethods.ScreenToClient(this.hwnd, ref p);
+            return new Point(p.X, p.Y);
+        }
+
         [SuppressMessage("Microsoft.StyleCop.CSharp.NamingRules", "SA1305:FieldNamesMustNotUseHungarianNotation", Justification = "Using Win32 naming for consistency.")]
         private IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
         {
+            const double WheelDelta = 120.0;
+
             RawInputEventArgs e = null;
 
             WindowsMouseDevice.Instance.CurrentWindow = this;
@@ -184,6 +193,14 @@ namespace Perspex.Win32
                         new Point((uint)lParam & 0xffff, (uint)lParam >> 16));
                     break;
 
+                case UnmanagedMethods.WindowsMessage.WM_MOUSEWHEEL:
+                    e = new RawMouseWheelEventArgs(
+                        WindowsMouseDevice.Instance,
+                        this.owner,
+                        this.ScreenToClient((uint)lParam & 0xffff, (uint)lParam >> 16),
+                        new Vector(0, ((int)wParam >> 16) / WheelDelta));
+                    break;
+
                 case UnmanagedMethods.WindowsMessage.WM_PAINT:
                     UnmanagedMethods.PAINTSTRUCT ps;