diff --git a/src/Windows/Avalonia.Win32/NonPumpingSyncContext.cs b/src/Windows/Avalonia.Win32/NonPumpingSyncContext.cs
index 0c02f643b2..2c4d2c9468 100644
--- a/src/Windows/Avalonia.Win32/NonPumpingSyncContext.cs
+++ b/src/Windows/Avalonia.Win32/NonPumpingSyncContext.cs
@@ -8,17 +8,42 @@ namespace Avalonia.Win32
 {
     internal class NonPumpingSyncContext : SynchronizationContext, IDisposable
     {
-        private readonly SynchronizationContext _inner;
+        private readonly SynchronizationContext? _inner;
 
-        private NonPumpingSyncContext(SynchronizationContext inner)
+        private NonPumpingSyncContext(SynchronizationContext? inner)
         {
             _inner = inner;
             SetWaitNotificationRequired();
             SetSynchronizationContext(this);
         }
 
-        public override void Post(SendOrPostCallback d, object? state) => _inner.Post(d, state);
-        public override void Send(SendOrPostCallback d, object? state) => _inner.Send(d, state);
+        public override void Post(SendOrPostCallback d, object? state)
+        {
+            if (_inner is null)
+            {
+#if NET6_0_OR_GREATER
+                ThreadPool.QueueUserWorkItem(static x => x.d(x.state), (d, state), false);
+#else
+                ThreadPool.QueueUserWorkItem(_ => d(state));
+#endif
+            }
+            else
+            {
+                _inner.Post(d, state);
+            }
+        }
+
+        public override void Send(SendOrPostCallback d, object? state)
+        {
+            if (_inner is null)
+            {
+                d(state);
+            }
+            else
+            {
+                _inner.Send(d, state);
+            }
+        }
 
 #if !NET6_0_OR_GREATER
         [PrePrepareMethod]
@@ -34,7 +59,15 @@ namespace Avalonia.Win32
         public static IDisposable? Use()
         {
             var current = Current;
-            return current is null or NonPumpingSyncContext ? null : new NonPumpingSyncContext(current);
+            if (current == null)
+            {
+                if (Thread.CurrentThread.GetApartmentState() != ApartmentState.STA)
+                    return null;
+            }
+            if (current is NonPumpingSyncContext)
+                return null;
+
+            return new NonPumpingSyncContext(current);
         }
 
         internal class HelperImpl : NonPumpingLockHelper.IHelperImpl
diff --git a/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs b/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs
index 288bdf2448..ed80f88b53 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs
@@ -137,12 +137,12 @@ namespace Avalonia.Win32
                     {
                         var key = KeyInterop.KeyFromVirtualKey(ToInt32(wParam), ToInt32(lParam));
 
-                        if (key != Key.None && _owner is not null)
+                        if (key != Key.None)
                         {
                             e = new RawKeyEventArgs(
                                 WindowsKeyboardDevice.Instance,
                                 timestamp,
-                                _owner,
+                                Owner,
                                 RawKeyEventType.KeyDown,
                                 key,
                                 WindowsKeyboardDevice.Instance.Modifiers);
@@ -167,12 +167,12 @@ namespace Avalonia.Win32
                     {
                         var key = KeyInterop.KeyFromVirtualKey(ToInt32(wParam), ToInt32(lParam));
 
-                        if (key != Key.None && _owner is not null)
+                        if (key != Key.None)
                         {
                             e = new RawKeyEventArgs(
                             WindowsKeyboardDevice.Instance,
                             timestamp,
-                            _owner,
+                            Owner,
                             RawKeyEventType.KeyUp,
                             key,
                             WindowsKeyboardDevice.Instance.Modifiers);
@@ -182,9 +182,9 @@ namespace Avalonia.Win32
                 case WindowsMessage.WM_CHAR:
                     {
                         // Ignore control chars and chars that were handled in WM_KEYDOWN.
-                        if (ToInt32(wParam) >= 32 && !_ignoreWmChar && _owner is not null)
+                        if (ToInt32(wParam) >= 32 && !_ignoreWmChar)
                         {
-                            e = new RawTextInputEventArgs(WindowsKeyboardDevice.Instance, timestamp, _owner,
+                            e = new RawTextInputEventArgs(WindowsKeyboardDevice.Instance, timestamp, Owner,
                                 new string((char)ToInt32(wParam), 1));
                         }
 
@@ -201,7 +201,7 @@ namespace Avalonia.Win32
                             break;
                         }
                         shouldTakeFocus = ShouldTakeFocusOnClick;
-                        if (ShouldIgnoreTouchEmulatedMessage() || _owner is null)
+                        if (ShouldIgnoreTouchEmulatedMessage())
                         {
                             break;
                         }
@@ -209,7 +209,7 @@ namespace Avalonia.Win32
                         e = new RawPointerEventArgs(
                             _mouseDevice,
                             timestamp,
-                            _owner,
+                            Owner,
 #pragma warning disable CS8509
                             message switch
 #pragma warning restore CS8509
@@ -235,7 +235,7 @@ namespace Avalonia.Win32
                         {
                             break;
                         }
-                        if (ShouldIgnoreTouchEmulatedMessage() || _owner is null)
+                        if (ShouldIgnoreTouchEmulatedMessage())
                         {
                             break;
                         }
@@ -243,7 +243,7 @@ namespace Avalonia.Win32
                         e = new RawPointerEventArgs(
                             _mouseDevice,
                             timestamp,
-                            _owner,
+                            Owner,
 #pragma warning disable CS8509
                             message switch
 #pragma warning restore CS8509
@@ -310,15 +310,10 @@ namespace Avalonia.Win32
                         var prevPoint = _lastWmMousePoint;
                         _lastWmMousePoint = currPoint;
 
-                        if (_owner is null)
-                        {
-                            break;
-                        }
-
                         e = new RawPointerEventArgs(
                             _mouseDevice,
                             timestamp,
-                            _owner,
+                            Owner,
                             RawPointerEventType.Move,
                             point,
                             GetMouseModifiers(wParam))
@@ -331,14 +326,14 @@ namespace Avalonia.Win32
 
                 case WindowsMessage.WM_MOUSEWHEEL:
                     {
-                        if (IsMouseInPointerEnabled || _owner is null)
+                        if (IsMouseInPointerEnabled)
                         {
                             break;
                         }
                         e = new RawMouseWheelEventArgs(
                             _mouseDevice,
                             timestamp,
-                            _owner,
+                            Owner,
                             PointToClient(PointFromLParam(lParam)),
                             new Vector(0, (ToInt32(wParam) >> 16) / wheelDelta),
                             GetMouseModifiers(wParam));
@@ -347,14 +342,14 @@ namespace Avalonia.Win32
 
                 case WindowsMessage.WM_MOUSEHWHEEL:
                     {
-                        if (IsMouseInPointerEnabled || _owner is null)
+                        if (IsMouseInPointerEnabled)
                         {
                             break;
                         }
                         e = new RawMouseWheelEventArgs(
                             _mouseDevice,
                             timestamp,
-                            _owner,
+                            Owner,
                             PointToClient(PointFromLParam(lParam)),
                             new Vector(-(ToInt32(wParam) >> 16) / wheelDelta, 0),
                             GetMouseModifiers(wParam));
@@ -368,14 +363,10 @@ namespace Avalonia.Win32
                             break;
                         }
                         _trackingMouse = false;
-                        if (_owner is null)
-                        {
-                            break;
-                        }
                         e = new RawPointerEventArgs(
                             _mouseDevice,
                             timestamp,
-                            _owner,
+                            Owner,
                             RawPointerEventType.LeaveWindow,
                             new Point(-1, -1),
                             WindowsKeyboardDevice.Instance.Modifiers);
@@ -387,14 +378,14 @@ namespace Avalonia.Win32
                 case WindowsMessage.WM_NCMBUTTONDOWN:
                 case WindowsMessage.WM_NCXBUTTONDOWN:
                     {
-                        if (IsMouseInPointerEnabled || _owner is null)
+                        if (IsMouseInPointerEnabled)
                         {
                             break;
                         }
                         e = new RawPointerEventArgs(
                             _mouseDevice,
                             timestamp,
-                            _owner,
+                            Owner,
 #pragma warning disable CS8509
                             message switch
 #pragma warning restore CS8509
@@ -413,7 +404,7 @@ namespace Avalonia.Win32
                     }
                 case WindowsMessage.WM_TOUCH:
                     {
-                        if (_wmPointerEnabled || _owner is null || Input is not { } input)
+                        if (_wmPointerEnabled || Input is not { } input)
                         {
                             break;
                         }
@@ -427,7 +418,7 @@ namespace Avalonia.Win32
                             foreach (var touchInput in touchInputs)
                             {
                                 input.Invoke(new RawTouchEventArgs(_touchDevice, touchInput.Time,
-                                    _owner,
+                                    Owner,
                                     touchInput.Flags.HasAllFlags(TouchInputFlags.TOUCHEVENTF_UP) ?
                                         RawPointerEventType.TouchEnd :
                                         touchInput.Flags.HasAllFlags(TouchInputFlags.TOUCHEVENTF_DOWN) ?
@@ -450,14 +441,14 @@ namespace Avalonia.Win32
                 case WindowsMessage.WM_POINTERUP:
                 case WindowsMessage.WM_POINTERUPDATE:
                     {
-                        if (!_wmPointerEnabled || _owner is null)
+                        if (!_wmPointerEnabled)
                         {
                             break;
                         }
                         GetDevicePointerInfo(wParam, out var device, out var info, out var point, out var modifiers, ref timestamp);
                         var eventType = GetEventType(message, info);
 
-                        var args = CreatePointerArgs(device, timestamp, _owner, eventType, point, modifiers, info.pointerId);
+                        var args = CreatePointerArgs(device, timestamp, eventType, point, modifiers, info.pointerId);
                         args.IntermediatePoints = CreateLazyIntermediatePoints(info);
                         e = args;
                         break;
@@ -466,19 +457,19 @@ namespace Avalonia.Win32
                 case WindowsMessage.WM_POINTERLEAVE:
                 case WindowsMessage.WM_POINTERCAPTURECHANGED:
                     {
-                        if (!_wmPointerEnabled || _owner is null)
+                        if (!_wmPointerEnabled)
                         {
                             break;
                         }
                         GetDevicePointerInfo(wParam, out var device, out var info, out var point, out var modifiers, ref timestamp);
                         var eventType = device is TouchDevice ? RawPointerEventType.TouchCancel : RawPointerEventType.LeaveWindow;
-                        e = CreatePointerArgs(device, timestamp, _owner, eventType, point, modifiers, info.pointerId);
+                        e = CreatePointerArgs(device, timestamp, eventType, point, modifiers, info.pointerId);
                         break;
                     }
                 case WindowsMessage.WM_POINTERWHEEL:
                 case WindowsMessage.WM_POINTERHWHEEL:
                     {
-                        if (!_wmPointerEnabled || _owner is null)
+                        if (!_wmPointerEnabled)
                         {
                             break;
                         }
@@ -486,7 +477,7 @@ namespace Avalonia.Win32
 
                         var val = (ToInt32(wParam) >> 16) / wheelDelta;
                         var delta = message == WindowsMessage.WM_POINTERWHEEL ? new Vector(0, val) : new Vector(val, 0);
-                        e = new RawMouseWheelEventArgs(device, timestamp, _owner, point.Position, delta, modifiers)
+                        e = new RawMouseWheelEventArgs(device, timestamp, Owner, point.Position, delta, modifiers)
                         {
                             RawPointerId = info.pointerId
                         };
@@ -900,11 +891,11 @@ namespace Avalonia.Win32
             }
         }
 
-        private RawPointerEventArgs CreatePointerArgs(IInputDevice device, ulong timestamp, IInputRoot owner, RawPointerEventType eventType, RawPointerPoint point, RawInputModifiers modifiers, uint rawPointerId)
+        private RawPointerEventArgs CreatePointerArgs(IInputDevice device, ulong timestamp, RawPointerEventType eventType, RawPointerPoint point, RawInputModifiers modifiers, uint rawPointerId)
         {
             return device is TouchDevice
-                ? new RawTouchEventArgs(device, timestamp, owner, eventType, point, modifiers, rawPointerId)
-                : new RawPointerEventArgs(device, timestamp, owner, eventType, point, modifiers)
+                ? new RawTouchEventArgs(device, timestamp, Owner, eventType, point, modifiers, rawPointerId)
+                : new RawPointerEventArgs(device, timestamp, Owner, eventType, point, modifiers)
                 {
                     RawPointerId = rawPointerId
                 };
diff --git a/src/Windows/Avalonia.Win32/WindowImpl.cs b/src/Windows/Avalonia.Win32/WindowImpl.cs
index 57407b5f34..812c72fd3c 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.cs
@@ -180,40 +180,31 @@ namespace Avalonia.Win32
             s_instances.Add(this);
         }
 
-        /// <inheritdoc />
+        private IInputRoot Owner
+            => _owner ?? throw new InvalidOperationException($"{nameof(SetInputRoot)} must have been called");
+
         public Action? Activated { get; set; }
 
-        /// <inheritdoc />
         public Func<WindowCloseReason, bool>? Closing { get; set; }
 
-        /// <inheritdoc />
         public Action? Closed { get; set; }
 
-        /// <inheritdoc />
         public Action? Deactivated { get; set; }
 
-        /// <inheritdoc />
         public Action<RawInputEventArgs>? Input { get; set; }
 
-        /// <inheritdoc />
         public Action<Rect>? Paint { get; set; }
 
-        /// <inheritdoc />
         public Action<Size, PlatformResizeReason>? Resized { get; set; }
 
-        /// <inheritdoc />
         public Action<double>? ScalingChanged { get; set; }
 
-        /// <inheritdoc />
         public Action<PixelPoint>? PositionChanged { get; set; }
 
-        /// <inheritdoc />
         public Action<WindowState>? WindowStateChanged { get; set; }
 
-        /// <inheritdoc />
         public Action? LostFocus { get; set; }
 
-        /// <inheritdoc />
         public Action<WindowTransparencyLevel>? TransparencyLevelChanged { get; set; }
 
         public Thickness BorderThickness
@@ -245,13 +236,10 @@ namespace Avalonia.Win32
 
         private double PrimaryScreenRenderScaling => Screen.AllScreens.FirstOrDefault(screen => screen.IsPrimary)?.Scaling ?? 1;
 
-        /// <inheritdoc />
         public double RenderScaling => _scaling;
 
-        /// <inheritdoc />
         public double DesktopScaling => RenderScaling;
 
-        /// <inheritdoc />
         public Size ClientSize
         {
             get
@@ -262,7 +250,6 @@ namespace Avalonia.Win32
             }
         }
 
-        /// <inheritdoc />
         public Size? FrameSize
         {
             get
@@ -278,18 +265,14 @@ namespace Avalonia.Win32
             }
         }
 
-        /// <inheritdoc />
         public IScreenImpl Screen { get; }
 
-        /// <inheritdoc />
         public IPlatformHandle Handle { get; private set; }
 
-        /// <inheritdoc />
         public virtual Size MaxAutoSizeHint => new Size(_maxTrackSize.X / RenderScaling, _maxTrackSize.Y / RenderScaling);
 
         public IMouseDevice MouseDevice => _mouseDevice;
 
-        /// <inheritdoc />
         public WindowState WindowState
         {
             get
@@ -327,14 +310,12 @@ namespace Avalonia.Win32
             }
         }
 
-        /// <inheritdoc />
         public WindowTransparencyLevel TransparencyLevel { get; private set; }
 
         protected IntPtr Hwnd => _hwnd;
 
         private bool IsMouseInPointerEnabled => _wmPointerEnabled && IsMouseInPointerEnabled();
 
-        /// <inheritdoc />
         public object? TryGetFeature(Type featureType)
         {
             if (featureType == typeof(ITextInputMethodImpl))
@@ -355,7 +336,6 @@ namespace Avalonia.Win32
             return null;
         }
 
-        /// <inheritdoc />
         public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel)
         {
             TransparencyLevel = EnableBlur(transparencyLevel);
@@ -537,13 +517,11 @@ namespace Avalonia.Win32
             }
         }
 
-        /// <inheritdoc />
         public IEnumerable<object> Surfaces
             => _gl is null ?
                 new object[] { Handle, _framebuffer } :
                 new object[] { Handle, _gl, _framebuffer };
 
-        /// <inheritdoc />
         public PixelPoint Position
         {
             get
@@ -589,21 +567,17 @@ namespace Avalonia.Win32
             }
         }
 
-        /// <inheritdoc />
         public void Move(PixelPoint point) => Position = point;
 
-        /// <inheritdoc />
         public void SetMinMaxSize(Size minSize, Size maxSize)
         {
             _minSize = minSize;
             _maxSize = maxSize;
         }
 
-        /// <inheritdoc />
         public IRenderer CreateRenderer(IRenderRoot root) =>
             new CompositingRenderer(root, Win32Platform.Compositor, () => Surfaces);
 
-        /// <inheritdoc />
         public void Resize(Size value, PlatformResizeReason reason)
         {
             if (WindowState != WindowState.Normal)
@@ -631,16 +605,13 @@ namespace Avalonia.Win32
             }
         }
 
-        /// <inheritdoc />
         public void Activate()
         {
             SetForegroundWindow(_hwnd);
         }
 
-        /// <inheritdoc />
         public IPopupImpl? CreatePopup() => Win32Platform.UseOverlayPopups ? null : new PopupImpl(this);
 
-        /// <inheritdoc />
         public void Dispose()
         {
             (_gl as IDisposable)?.Dispose();
@@ -682,7 +653,6 @@ namespace Avalonia.Win32
             InvalidateRect(_hwnd, ref r, false);
         }
 
-        /// <inheritdoc />
         public Point PointToClient(PixelPoint point)
         {
             var p = new POINT { X = point.X, Y = point.Y };
@@ -690,7 +660,6 @@ namespace Avalonia.Win32
             return new Point(p.X, p.Y) / RenderScaling;
         }
 
-        /// <inheritdoc />
         public PixelPoint PointToScreen(Point point)
         {
             point *= RenderScaling;
@@ -699,31 +668,26 @@ namespace Avalonia.Win32
             return new PixelPoint(p.X, p.Y);
         }
 
-        /// <inheritdoc />
         public void SetInputRoot(IInputRoot inputRoot)
         {
             _owner = inputRoot;
             CreateDropTarget(inputRoot);
         }
 
-        /// <inheritdoc />
         public void Hide()
         {
             UnmanagedMethods.ShowWindow(_hwnd, ShowWindowCommand.Hide);
             _shown = false;
         }
 
-        /// <inheritdoc />
         public virtual void Show(bool activate, bool isDialog)
         {
             SetParent(_parent);
             ShowWindow(_showWindowState, activate);
         }
 
-        /// <inheritdoc />
         public Action? GotInputWhenDisabled { get; set; }
 
-        /// <inheritdoc />
         public void SetParent(IWindowImpl? parent)
         {
             _parent = parent as WindowImpl;
@@ -739,10 +703,8 @@ namespace Avalonia.Win32
             SetWindowLongPtr(_hwnd, (int)WindowLongParam.GWL_HWNDPARENT, parentHwnd);
         }
 
-        /// <inheritdoc />
         public void SetEnabled(bool enable) => EnableWindow(_hwnd, enable);
 
-        /// <inheritdoc />
         public void BeginMoveDrag(PointerPressedEventArgs e)
         {
             e.Pointer.Capture(null);
@@ -750,7 +712,6 @@ namespace Avalonia.Win32
                 new IntPtr((int)HitTestValues.HTCAPTION), IntPtr.Zero);
         }
 
-        /// <inheritdoc />
         public void BeginResizeDrag(WindowEdge edge, PointerPressedEventArgs e)
         {
             if (_windowProperties.IsResizable)
@@ -765,13 +726,11 @@ namespace Avalonia.Win32
             }
         }
 
-        /// <inheritdoc />
         public void SetTitle(string? title)
         {
             SetWindowText(_hwnd, title);
         }
 
-        /// <inheritdoc />
         public void SetCursor(ICursorImpl? cursor)
         {
             var impl = cursor as CursorImpl;
@@ -779,13 +738,12 @@ namespace Avalonia.Win32
             var hCursor = impl?.Handle ?? s_defaultCursor;
             SetClassLong(_hwnd, ClassLongIndex.GCLP_HCURSOR, hCursor);
 
-            if (_owner?.IsPointerOver == true)
+            if (Owner.IsPointerOver)
             {
                 UnmanagedMethods.SetCursor(hCursor);
             }
         }
 
-        /// <inheritdoc />
         public void SetIcon(IWindowIconImpl? icon)
         {
             var impl = icon as IconImpl;
@@ -795,7 +753,6 @@ namespace Avalonia.Win32
                 new IntPtr((int)Icons.ICON_BIG), hIcon);
         }
 
-        /// <inheritdoc />
         public void ShowTaskbarIcon(bool value)
         {
             var newWindowProperties = _windowProperties;
@@ -805,7 +762,6 @@ namespace Avalonia.Win32
             UpdateWindowProperties(newWindowProperties);
         }
 
-        /// <inheritdoc />
         public void CanResize(bool value)
         {
             var newWindowProperties = _windowProperties;
@@ -815,7 +771,6 @@ namespace Avalonia.Win32
             UpdateWindowProperties(newWindowProperties);
         }
 
-        /// <inheritdoc />
         public void SetSystemDecorations(SystemDecorations value)
         {
             var newWindowProperties = _windowProperties;
@@ -825,7 +780,6 @@ namespace Avalonia.Win32
             UpdateWindowProperties(newWindowProperties);
         }
 
-        /// <inheritdoc />
         public void SetTopmost(bool value)
         {
             if (value == _topmost)
@@ -842,7 +796,6 @@ namespace Avalonia.Win32
             _topmost = value;
         }
 
-        /// <inheritdoc />
         public unsafe void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
         {
             if (Win32Platform.WindowsVersion.Build >= 22000)
@@ -1457,7 +1410,6 @@ namespace Avalonia.Win32
 
         IntPtr EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo.Handle => Handle.Handle;
 
-        /// <inheritdoc />
         public void SetExtendClientAreaToDecorationsHint(bool hint)
         {
             _isClientAreaExtended = hint;
@@ -1465,7 +1417,6 @@ namespace Avalonia.Win32
             ExtendClientArea();
         }
 
-        /// <inheritdoc />
         public void SetExtendClientAreaChromeHints(ExtendClientAreaChromeHints hints)
         {
             _extendChromeHints = hints;