Use ReadOnlySpan<HwndWrapperHook> instead of a temporary heap array

src/Microsoft.DotNet.Wpf/src/Common/Graphics/wgx_render.cs

@@ -721,13 +721,7 @@ internal struct BitmapTransformCaps
         // TRUE if the effect supports multi-resolution
 
         [MarshalAs(UnmanagedType.Bool)] bool fSupportMultiResolution;
-};
-
-    [StructLayout(LayoutKind.Sequential)]
-    internal struct HWND
-    {
-        public int hwnd;
-    }
+    };
 
     [StructLayout(LayoutKind.Sequential)]
     internal struct MILAVInstruction

src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/InterOp/HwndSource.cs

@@ -234,18 +234,23 @@ private void Initialize(HwndSourceParameters parameters)
             // list. If this is done the other way around, first HwndTarget resize will
             // force re-render, then layout will be updated according to the new size,
             // scheduling another render.
-            HwndWrapperHook[] wrapperHooks = { _hwndTargetHook, _layoutHook, _inputHook, null };
 
-            if (null != parameters.HwndSourceHook)
+            ReadOnlySpan<HwndWrapperHook> wrapperHooks = [_hwndTargetHook, _layoutHook, _inputHook, _publicHook];
+
+            if (parameters.HwndSourceHook is not null)
             {
                 // In case there's more than one delegate, add these to the event storage backwards
                 // so they'll get invoked in the expected order.
                 Delegate[] handlers = parameters.HwndSourceHook.GetInvocationList();
-                for (int i = handlers.Length -1; i >= 0; --i)
+                for (int i = handlers.Length - 1; i >= 0; --i)
                 {
                     EventHelper.AddHandler(ref _hooks, (HwndSourceHook)handlers[i]);
                 }
-                wrapperHooks[3] = _publicHook;
+            }
+            else
+            {
+                // In this case, we do not need the _publicHook
+                wrapperHooks = wrapperHooks.Slice(0, 3);
             }
 
             _restoreFocusMode = parameters.RestoreFocusMode;
@@ -260,27 +265,19 @@ private void Initialize(HwndSourceParameters parameters)
                 parameters.ExtendedWindowStyle &= (~NativeMethods.WS_EX_LAYERED);
             }
 
-
             _constructionParameters = parameters;
-            _hwndWrapper = new HwndWrapper(parameters.WindowClassStyle,
-                                       parameters.WindowStyle,
-                                       parameters.ExtendedWindowStyle,
-                                       parameters.PositionX,
-                                       parameters.PositionY,
-                                       parameters.Width,
-                                       parameters.Height,
-                                       parameters.WindowName,
-                                       parameters.ParentWindow,
-                                       wrapperHooks);
-
-            _hwndTarget = new HwndTarget(_hwndWrapper.Handle);
-            _hwndTarget.UsesPerPixelOpacity = parameters.EffectivePerPixelOpacity;
-            if(_hwndTarget.UsesPerPixelOpacity)
+
+            _hwndWrapper = new HwndWrapper(parameters.WindowClassStyle, parameters.WindowStyle, parameters.ExtendedWindowStyle,
+                                           parameters.PositionX, parameters.PositionY, parameters.Width, parameters.Height,
+                                           parameters.WindowName, parameters.ParentWindow, wrapperHooks);
+
+            _hwndTarget = new HwndTarget(_hwndWrapper.Handle) { UsesPerPixelOpacity = parameters.EffectivePerPixelOpacity };
+            if (_hwndTarget.UsesPerPixelOpacity)
             {
                 _hwndTarget.BackgroundColor = Colors.Transparent;
 
                 // Prevent this window from being themed.
-                UnsafeNativeMethods.CriticalSetWindowTheme(new HandleRef(this, _hwndWrapper.Handle), "", "");
+                UnsafeNativeMethods.CriticalSetWindowTheme(new HandleRef(this, _hwndWrapper.Handle), string.Empty, string.Empty);
             }
             _constructionParameters = null;
 

src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/InterOp/HwndTarget.cs

@@ -2567,19 +2567,7 @@ public NotificationWindowHelper()
                     // (HwndWrapper keeps a WeakReference to the hook)
 
                     _notificationHook = new HwndWrapperHook(NotificationFilterMessage);
-                    HwndWrapperHook[] wrapperHooks = { _notificationHook };
-
-                    _notificationHwnd = new HwndWrapper(
-                                                0,
-                                                0,
-                                                0,
-                                                0,
-                                                0,
-                                                0,
-                                                0,
-                                                "",
-                                                IntPtr.Zero,
-                                                wrapperHooks);
+                    _notificationHwnd = new HwndWrapper(0, 0, 0, 0, 0, 0, 0, string.Empty, IntPtr.Zero, _notificationHook);
 
                     Guid monitorGuid = new Guid(NativeMethods.GUID_MONITOR_POWER_ON.ToByteArray());
                     unsafe

src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/MediaContextNotificationWindow.cs

@@ -66,12 +66,9 @@ internal MediaContextNotificationWindow(MediaContext ownerMediaContext)
 
             // Create a top-level, invisible window so we can get the WM_DWMCOMPOSITIONCHANGED
             // and other DWM notifications that are broadcasted to top-level windows only.
-            HwndWrapper hwndNotification;
-            hwndNotification = new HwndWrapper(0, NativeMethods.WS_POPUP, 0, 0, 0, 0, 0, "MediaContextNotificationWindow", IntPtr.Zero, null);
-
             _hwndNotificationHook = new HwndWrapperHook(MessageFilter);
 
-            _hwndNotification = hwndNotification;
+            _hwndNotification = new HwndWrapper(0, NativeMethods.WS_POPUP, 0, 0, 0, 0, 0, "MediaContextNotificationWindow", parent: IntPtr.Zero);
             _hwndNotification.AddHook(_hwndNotificationHook);
 
             _isDisposed = false;

src/Microsoft.DotNet.Wpf/src/PresentationFramework/Microsoft/Win32/CommonDialog.cs

@@ -100,7 +100,7 @@ public virtual Nullable<bool> ShowDialog()
                 // prevent breaking UIAutomation.
                 if (hwndOwner == IntPtr.Zero)
                 {
-                    tempParentHwnd = new HwndWrapper(0, 0, 0, 0, 0, 0, 0, "", IntPtr.Zero, null);
+                    tempParentHwnd = new HwndWrapper(0, 0, 0, 0, 0, 0, 0, string.Empty, IntPtr.Zero);
                     hwndOwner = tempParentHwnd.Handle;
                 }
 

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Application.cs

@@ -2143,19 +2143,7 @@ private void EnsureHwndSource()
                 // (HwndWrapper keeps a WeakReference to the hook)
 
                 _appFilterHook = new HwndWrapperHook(AppFilterMessage);
-                HwndWrapperHook[] wrapperHooks = {_appFilterHook};
-
-                _parkingHwnd = new HwndWrapper(
-                                0,
-                                0,
-                                0,
-                                0,
-                                0,
-                                0,
-                                0,
-                                "",
-                                IntPtr.Zero,
-                                wrapperHooks);
+                _parkingHwnd = new HwndWrapper(0, 0, 0, 0, 0, 0, 0, string.Empty, IntPtr.Zero, _appFilterHook);
             }
         }
 

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/SystemResources.cs

@@ -1115,18 +1115,15 @@ private static DpiUtil.HwndDpiInfo CreateResourceChangeListenerWindow(DpiAwarene
             {
                 // Create a top-level, invisible window so we can get the WM_THEMECHANGE notification
                 // and for HwndHost to park non-visible HwndHosts.
-                var hwndNotify =
-                    new HwndWrapper(
-                    classStyle: 0,
-                    style: NativeMethods.WS_POPUP | NativeMethods.WS_DISABLED,
-                    exStyle: 0,
-                    x: x,
-                    y: y,
-                    width: 0,
-                    height: 0,
-                    name: "SystemResourceNotifyWindow",
-                    parent: IntPtr.Zero,
-                    hooks: null);
+                HwndWrapper hwndNotify = new(classStyle: 0,
+                                             style: NativeMethods.WS_POPUP | NativeMethods.WS_DISABLED,
+                                             exStyle: 0,
+                                             x: x,
+                                             y: y,
+                                             width: 0,
+                                             height: 0,
+                                             name: "SystemResourceNotifyWindow",
+                                             parent: IntPtr.Zero);
 
                 // Do not call into DpiUtil.GetExtendedDpiInfoForWindow()
                 // unless IsPerMonitorDpiscalingActive == true. DpiUtil.GetExtendedDpiInfoForWindow()

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Window.cs

@@ -6377,21 +6377,15 @@ private static void _OnClipToBoundsChanged(DependencyObject d, DependencyPropert
         /// </summary>
         private HwndWrapper EnsureHiddenWindow()
         {
-            if (_hiddenWindow == null)
-            {
-                _hiddenWindow = new HwndWrapper(
-                    0, // classStyle
-                    NativeMethods.WS_OVERLAPPEDWINDOW, // style
-                    0, // exStyle
-                    NativeMethods.CW_USEDEFAULT, // x
-                    NativeMethods.CW_USEDEFAULT, // y
-                    NativeMethods.CW_USEDEFAULT, // width
-                    NativeMethods.CW_USEDEFAULT, // height
-                    "Hidden Window", // name
-                    IntPtr.Zero,
-                    null
-                );
-            }
+            _hiddenWindow ??= new HwndWrapper(classStyle: 0,
+                                              NativeMethods.WS_OVERLAPPEDWINDOW, // style
+                                              exStyle: 0,
+                                              NativeMethods.CW_USEDEFAULT, // x
+                                              NativeMethods.CW_USEDEFAULT, // y
+                                              NativeMethods.CW_USEDEFAULT, // width
+                                              NativeMethods.CW_USEDEFAULT, // height
+                                              "Hidden Window", // name
+                                              IntPtr.Zero);
 
             return _hiddenWindow;
         }

src/Microsoft.DotNet.Wpf/src/Shared/MS/Win32/HwndSubclass.cs

@@ -2,29 +2,13 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Runtime.InteropServices;
-using MS.Internal;
-using MS.Internal.Interop;
-using MS.Utility;
-using System.Windows;
 using System.Windows.Threading;
-using System.Security;                       // CAS
-using System.Threading;                      // Thread
-
-// The SecurityHelper class differs between assemblies and could not actually be
-//  shared, so it is duplicated across namespaces to prevent name collision.
-#if WINDOWS_BASE
-    using MS.Internal.WindowsBase;
-#elif PRESENTATION_CORE
-    using MS.Internal.PresentationCore;
-#elif PRESENTATIONFRAMEWORK
-    using MS.Internal.PresentationFramework;
-#elif DRT
-    using MS.Internal.Drt;
-#else
-#error Attempt to use a class (duplicated across multiple namespaces) from an unknown assembly.
-#endif
+using MS.Internal.Interop;
+using System.Threading;
+using System;
+
+using SR = MS.Internal.WindowsBase.SR;
 
 namespace MS.Win32
 {
@@ -49,7 +33,6 @@ namespace MS.Win32
     ///     is not thread safe and will be operated on by the thread that owns
     ///     the window.
     /// </summary>
-    /// <remarks> Not available to partial trust callers</remarks>
     internal class HwndSubclass : IDisposable
     {
         static HwndSubclass()