Use multimedia timer on Win32 for render loop.

src/Avalonia.SceneGraph/Rendering/DefaultRenderLoop.cs

@@ -65,24 +65,25 @@ namespace Avalonia.Rendering
         /// </summary>
         protected void Start()
         {
-            _subscription = StartCore();
+            _subscription = StartCore(InternalTick);
         }
 
         /// <summary>
         /// Provides the implementation of starting the timer.
         /// </summary>
+        /// <param name="tick">The method to call on each tick.</param>
         /// <remarks>
         /// This can be overridden by platform implementations to use a specialized timer
         /// implementation.
         /// </remarks>
-        protected virtual IDisposable StartCore()
+        protected virtual IDisposable StartCore(Action tick)
         {
             if (_threading == null)
             {
                 _threading = AvaloniaLocator.Current.GetService<IPlatformThreadingInterface>();
             }
 
-            return _threading.StartTimer(TimeSpan.FromSeconds(1.0 / FramesPerSecond), InternalTick);
+            return _threading.StartTimer(TimeSpan.FromSeconds(1.0 / FramesPerSecond), tick);
         }
 
         /// <summary>

src/Avalonia.SceneGraph/Rendering/Renderer.cs

@@ -13,6 +13,7 @@ namespace Avalonia.Rendering
         private IRenderRoot _root;
         private IRenderTarget _renderTarget;
         private bool _dirty;
+        private bool _rendering;
 
         public void Attach(IRenderRoot root, IRenderLoop renderLoop)
         {
@@ -35,6 +36,11 @@ namespace Avalonia.Rendering
 
         public void Render(Rect rect)
         {
+            if (_rendering)
+            {
+                return;
+            }
+
             if (_renderTarget == null)
             {
                 _renderTarget = _root.CreateRenderTarget();
@@ -42,6 +48,7 @@ namespace Avalonia.Rendering
 
             try
             {
+                _rendering = true;
                 _renderTarget.Render(_root);
             }
             catch (RenderTargetCorruptedException ex)
@@ -50,6 +57,11 @@ namespace Avalonia.Rendering
                 _renderTarget.Dispose();
                 _renderTarget = null;
             }
+            finally
+            {
+                _rendering = false;
+                _dirty = false;
+            }
         }
 
         private void OnRenderLoopTick(object sender, EventArgs e)

src/Windows/Avalonia.Win32/Avalonia.Win32.csproj

@@ -70,6 +70,7 @@
     </Compile>
     <Compile Include="Embedding\WpfAvaloniaControlHost.cs" />
     <Compile Include="IconImpl.cs" />
+    <Compile Include="RenderLoop.cs" />
     <Compile Include="SystemDialogImpl.cs" />
     <Compile Include="CursorFactory.cs" />
     <Compile Include="Input\KeyInterop.cs" />

src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs

@@ -23,6 +23,8 @@ namespace Avalonia.Win32.Interop
 
         public delegate void TimerProc(IntPtr hWnd, uint uMsg, IntPtr nIDEvent, uint dwTime);
 
+        public delegate void TimeCallback(uint uTimerID, uint uMsg, UIntPtr dwUser, UIntPtr dw1, UIntPtr dw2);
+
         public delegate IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);
 
         public enum Cursor
@@ -705,8 +707,6 @@ namespace Avalonia.Win32.Interop
         [DllImport("user32.dll")]
         public static extern IntPtr LoadCursor(IntPtr hInstance, IntPtr lpCursorName);
 
-
-
         [DllImport("user32.dll")]
         public static extern bool PeekMessage(out MSG lpMsg, IntPtr hWnd, uint wMsgFilterMin, uint wMsgFilterMax, uint wRemoveMsg);
         
@@ -738,6 +738,12 @@ namespace Avalonia.Win32.Interop
         [DllImport("user32.dll")]
         public static extern bool ShowWindow(IntPtr hWnd, ShowWindowCommand nCmdShow);
 
+        [DllImport("Winmm.dll")]
+        public static extern uint timeKillEvent(uint uTimerID);
+
+        [DllImport("Winmm.dll")]
+        public static extern uint timeSetEvent(uint uDelay, uint uResolution, TimeCallback lpTimeProc, UIntPtr dwUser, uint fuEvent);
+
         [DllImport("user32.dll")]
         public static extern int ToUnicode(
             uint virtualKeyCode,

src/Windows/Avalonia.Win32/RenderLoop.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Reactive.Disposables;
+using Avalonia.Rendering;
+using Avalonia.Win32.Interop;
+
+namespace Avalonia.Win32
+{
+    internal class RenderLoop : DefaultRenderLoop
+    {
+        private UnmanagedMethods.TimeCallback timerDelegate;
+
+        public RenderLoop(int framesPerSecond)
+            : base(framesPerSecond)
+        {
+        }
+
+        protected override IDisposable StartCore(Action tick)
+        {
+            timerDelegate = (id, uMsg, user, dw1, dw2) => tick();
+
+            var handle = UnmanagedMethods.timeSetEvent(
+                (uint)(1000 / FramesPerSecond),
+                0,
+                timerDelegate,
+                UIntPtr.Zero,
+                1);
+
+            return Disposable.Create(() =>
+            {
+                timerDelegate = null;
+                UnmanagedMethods.timeKillEvent(handle);
+            });
+        }
+    }
+}

src/Windows/Avalonia.Win32/Win32Platform.cs

@@ -66,7 +66,7 @@ namespace Avalonia.Win32
                 .Bind<IMouseDevice>().ToConstant(WindowsMouseDevice.Instance)
                 .Bind<IPlatformSettings>().ToConstant(s_instance)
                 .Bind<IPlatformThreadingInterface>().ToConstant(s_instance)
-                .Bind<IRenderLoop>().ToConstant(new DefaultRenderLoop(60))
+                .Bind<IRenderLoop>().ToConstant(new RenderLoop(60))
                 .Bind<ISystemDialogImpl>().ToSingleton<SystemDialogImpl>()
                 .Bind<IWindowingPlatform>().ToConstant(s_instance)
                 .Bind<IPlatformIconLoader>().ToConstant(s_instance);