implement keyboard input.

src/Avalonia.Windowing/Bindings/EventNotifier.cs

@@ -5,6 +5,7 @@ namespace Avalonia.Windowing.Bindings
 {
     public delegate void MouseEventCallback(IntPtr windowId, MouseEvent mouseEvent);
     public delegate void ResizeEventCallback(IntPtr windowId, ResizeEvent resizeEvent);
+    public delegate void KeyboardEventCallback(IntPtr windowId, KeyboardEvent keyboardEvent);
     public delegate void AwakenedEventCallback();
 
     [StructLayout(LayoutKind.Sequential)]
@@ -13,5 +14,6 @@ namespace Avalonia.Windowing.Bindings
         public MouseEventCallback OnMouseEvent;
         public AwakenedEventCallback OnAwakened;
         public ResizeEventCallback OnResized;
+        public KeyboardEventCallback OnKeyboardEvent;
     }
 }

src/Avalonia.Windowing/Bindings/Events.cs

@@ -24,6 +24,17 @@ namespace Avalonia.Windowing.Bindings
         public LogicalPosition Position { get; set; }
     }
 
+    [StructLayout(LayoutKind.Sequential)]
+    public struct KeyboardEvent
+    {
+        public bool Pressed { get; set; }
+        public bool Shift { get; set; }
+        public bool Control { get; set; }
+        public bool Alt { get; set; }
+        public bool Logo { get; set; }
+        UInt32 VirtualKeyCode { get; set; }
+    }
+
     [StructLayout(LayoutKind.Sequential)]
     public struct ResizeEvent
     {

src/Avalonia.Windowing/Bindings/EventsLoop.cs

@@ -31,6 +31,7 @@ namespace Avalonia.Windowing.Bindings
         private readonly EventsLoopProxy _eventsLoopProxy;
         private readonly EventNotifier _notifier;
 
+        public event KeyboardEventCallback OnKeyboardEvent;
         public event MouseEventCallback OnMouseEvent;
         public event AwakenedEventCallback OnAwakened;
         public event ResizeEventCallback OnResized;
@@ -42,6 +43,7 @@ namespace Avalonia.Windowing.Bindings
             _notifier = new EventNotifier()
             {
                 OnMouseEvent = (IntPtr windowId, MouseEvent mouseEvent) => OnMouseEvent?.Invoke(windowId, mouseEvent),
+                OnKeyboardEvent = (IntPtr windowId, KeyboardEvent keyboardEvent) => OnKeyboardEvent?.Invoke(windowId, keyboardEvent),
                 OnResized = (IntPtr windowId, ResizeEvent resizeEvent) => OnResized?.Invoke(windowId, resizeEvent),
                 OnAwakened = () => OnAwakened?.Invoke()
             };

src/Avalonia.Windowing/WIndowingPlatform.cs

@@ -37,6 +37,7 @@ namespace Avalonia.Windowing
         {
             _eventsLoop = new EventsLoop();
             _eventsLoop.OnMouseEvent += _eventsLoop_MouseEvent;
+            _eventsLoop.OnKeyboardEvent += _eventsLoop_OnKeyboardEvent;
             _eventsLoop.OnAwakened += _eventsLoop_Awakened;
             _eventsLoop.OnResized += _eventsLoop_Resized;
             _windows = new Dictionary<IntPtr, WindowImpl>();
@@ -60,6 +61,14 @@ namespace Avalonia.Windowing
             }
         }
 
+        void _eventsLoop_OnKeyboardEvent(IntPtr windowId, KeyboardEvent keyboardEvent)
+        {
+            if(_windows.ContainsKey(windowId))
+            {
+                _windows[windowId].OnKeyboardEvent(keyboardEvent);
+            }
+        }
+
         private void _eventsLoop_Awakened()
         {
             Signaled?.Invoke(DispatcherPriority.Input);

src/Avalonia.Windowing/WindowImpl.cs

@@ -168,6 +168,11 @@ namespace Avalonia.Windowing
         {
         }
 
+        public void OnKeyboardEvent (KeyboardEvent evt)
+        {
+
+        }
+
         public void OnMouseEvent(MouseEvent evt)
         {
             Dispatcher.UIThread.RunJobs(DispatcherPriority.Input);