Track mouse leave events.

*Actually* fixes #15.

Perspex.Input/IInputManager.cs

@@ -14,6 +14,8 @@ namespace Perspex.Input
     {
         IObservable<RawInputEventArgs> RawEventReceived { get; }
 
+        void ClearPointerOver(IPointerDevice device);
+
         void Process(RawInputEventArgs e);
 
         void SetPointerOver(IPointerDevice device, IVisual visual, Point p);

Perspex.Input/InputManager.cs

@@ -23,6 +23,23 @@ namespace Perspex.Input
             get { return this.rawEventReceived; }
         }
 
+        public void ClearPointerOver(IPointerDevice device)
+        {
+            foreach (var control in this.pointerOvers.ToList())
+            {
+                PointerEventArgs e = new PointerEventArgs
+                {
+                    RoutedEvent = InputElement.PointerLeaveEvent,
+                    Device = device,
+                    OriginalSource = control,
+                    Source = control,
+                };
+
+                this.pointerOvers.Remove(control);
+                control.RaiseEvent(e);
+            }
+        }
+
         public void Process(RawInputEventArgs e)
         {
             this.rawEventReceived.OnNext(e);

Perspex.Input/MouseDevice.cs

@@ -76,8 +76,8 @@ namespace Perspex.Input
 
             switch (e.Type)
             {
-                case RawMouseEventType.Move:
+                case RawMouseEventType.LeaveWindow:
-                    this.MouseMove(mouse, e.Root, e.Position);
+                    this.LeaveWindow(mouse, e.Root);
                     break;
                 case RawMouseEventType.LeftButtonDown:
                     this.MouseDown(mouse, e.Timestamp, e.Root, e.Position);
@@ -85,44 +85,18 @@ namespace Perspex.Input
                 case RawMouseEventType.LeftButtonUp:
                     this.MouseUp(mouse, e.Root, e.Position);
                     break;
+                case RawMouseEventType.Move:
+                    this.MouseMove(mouse, e.Root, e.Position);
+                    break;
                 case RawMouseEventType.Wheel:
                     this.MouseWheel(mouse, e.Root, e.Position, ((RawMouseWheelEventArgs)e).Delta);
                     break;
             }
         }
 
-        private void MouseMove(IMouseDevice device, IInputElement root, Point p)
+        private void LeaveWindow(IMouseDevice device, IInputElement root)
         {
-            IInteractive source;
+            this.InputManager.ClearPointerOver(this);
-
-            if (this.Captured == null)
-            {
-                this.InputManager.SetPointerOver(this, root, p);
-                source = root as IInteractive;
-            }
-            else
-            {
-                Point offset = new Point();
-
-                foreach (IVisual ancestor in this.Captured.GetVisualAncestors())
-                {
-                    offset += ancestor.Bounds.Position;
-                }
-
-                this.InputManager.SetPointerOver(this, this.Captured, p - offset);
-                source = this.Captured as IInteractive;
-            }
-
-            if (source != null)
-            {
-                source.RaiseEvent(new PointerEventArgs
-                {
-                    Device = this,
-                    RoutedEvent = InputElement.PointerMovedEvent,
-                    OriginalSource = source,
-                    Source = source,
-                });
-            }
         }
 
         private void MouseDown(IMouseDevice device, uint timestamp, IInputElement root, Point p)
@@ -167,6 +141,40 @@ namespace Perspex.Input
             }
         }
 
+        private void MouseMove(IMouseDevice device, IInputElement root, Point p)
+        {
+            IInteractive source;
+
+            if (this.Captured == null)
+            {
+                this.InputManager.SetPointerOver(this, root, p);
+                source = root as IInteractive;
+            }
+            else
+            {
+                Point offset = new Point();
+
+                foreach (IVisual ancestor in this.Captured.GetVisualAncestors())
+                {
+                    offset += ancestor.Bounds.Position;
+                }
+
+                this.InputManager.SetPointerOver(this, this.Captured, p - offset);
+                source = this.Captured as IInteractive;
+            }
+
+            if (source != null)
+            {
+                source.RaiseEvent(new PointerEventArgs
+                {
+                    Device = this,
+                    RoutedEvent = InputElement.PointerMovedEvent,
+                    OriginalSource = source,
+                    Source = source,
+                });
+            }
+        }
+
         private void MouseUp(IMouseDevice device, IInputElement root, Point p)
         {
             var hit = this.HitTest(root, p);

Perspex.Input/Raw/RawMouseEventArgs.cs

@@ -7,13 +7,13 @@
 namespace Perspex.Input.Raw
 {
     using System;
-    using Perspex.Layout;
 
     public enum RawMouseEventType
     {
-        Move,
+        LeaveWindow,
         LeftButtonDown,
         LeftButtonUp,
+        Move,
         Wheel,
     }
 

Windows/Perspex.Win32/Interop/UnmanagedMethods.cs

@@ -548,6 +548,9 @@ namespace Perspex.Win32.Interop
             int bufferSize, 
             uint flags);
 
+        [DllImport("user32.dll", SetLastError = true)]
+        public static extern bool TrackMouseEvent(ref TRACKMOUSEEVENT lpEventTrack);
+
         [DllImport("user32.dll")]
         public static extern bool TranslateMessage(ref MSG lpMsg);
 
@@ -608,6 +611,14 @@ namespace Perspex.Win32.Interop
             public int bottom;
         }
 
+        public struct TRACKMOUSEEVENT
+        {
+            public int cbSize;
+            public uint dwFlags;
+            public IntPtr hwndTrack;
+            public int dwHoverTime;
+        }
+
         [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
         public struct WNDCLASSEX
         {

Windows/Perspex.Win32/WindowImpl.cs

@@ -26,6 +26,8 @@ namespace Perspex.Win32
 
         private Window owner;
 
+        private bool trackingMouse;
+
         public WindowImpl()
         {
             this.CreateWindow();
@@ -188,6 +190,19 @@ namespace Perspex.Win32
                     break;
 
                 case UnmanagedMethods.WindowsMessage.WM_MOUSEMOVE:
+                    if (!this.trackingMouse)
+                    {
+                        var tm = new UnmanagedMethods.TRACKMOUSEEVENT
+                        {
+                            cbSize = Marshal.SizeOf(typeof(UnmanagedMethods.TRACKMOUSEEVENT)),
+                            dwFlags = 2,
+                            hwndTrack = this.hwnd,
+                            dwHoverTime = 0,
+                        };
+
+                        UnmanagedMethods.TrackMouseEvent(ref tm);
+                    }
+
                     e = new RawMouseEventArgs(
                         WindowsMouseDevice.Instance,
                         timestamp,
@@ -205,6 +220,16 @@ namespace Perspex.Win32
                         new Vector(0, ((int)wParam >> 16) / WheelDelta));
                     break;
 
+                case UnmanagedMethods.WindowsMessage.WM_MOUSELEAVE:
+                    this.trackingMouse = false;
+                    e = new RawMouseEventArgs(
+                        WindowsMouseDevice.Instance,
+                        timestamp,
+                        this.owner,
+                        RawMouseEventType.LeaveWindow,
+                        new Point());
+                    break;
+
                 case UnmanagedMethods.WindowsMessage.WM_PAINT:
                     UnmanagedMethods.PAINTSTRUCT ps;