CmdPal: Prevent the main window from stealing focus (#45309)

## Summary of the Pull Request

This PR adds two fixes to prevent Command Palette’s main window from
stealing focus while or after it is being hidden.

1) GoBack was not forwarding the withAnimation and focusSearch
parameters when chaining to GoHome.

2) Page focus after load can be triggered too late—when the window is
already hidden—causing CmdPal to regain focus unexpectedly.

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## PR Checklist

- [x] Closes: #45301
<!-- - [ ] Closes: #yyy (add separate lines for additional resolved
issues) -->
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI/MainWindow.xaml

@@ -31,6 +31,6 @@
             TintIntensity="{x:Bind ViewModel.BackgroundImageTintIntensity, Mode=OneWay}"
             Visibility="{x:Bind ViewModel.ShowBackgroundImage, Mode=OneWay}" />
 
-        <pages:ShellPage />
+        <pages:ShellPage HostWindow="{x:Bind}" />
     </Grid>
 </winuiex:WindowEx>

src/modules/cmdpal/Microsoft.CmdPal.UI/MainWindow.xaml.cs

@@ -54,7 +54,8 @@ public sealed partial class MainWindow : WindowEx,
     IRecipient<ErrorOccurredMessage>,
     IRecipient<DragStartedMessage>,
     IRecipient<DragCompletedMessage>,
-    IDisposable
+    IDisposable,
+    IHostWindow
 {
     [System.Diagnostics.CodeAnalysis.SuppressMessage("StyleCop.CSharp.NamingRules", "SA1310:Field names should not contain underscore", Justification = "Stylistically, window messages are WM_")]
     [System.Diagnostics.CodeAnalysis.SuppressMessage("StyleCop.CSharp.NamingRules", "SA1306:Field names should begin with lower-case letter", Justification = "Stylistically, window messages are WM_")]
@@ -92,6 +93,8 @@ public sealed partial class MainWindow : WindowEx,
 
     private MainWindowViewModel ViewModel { get; }
 
+    public bool IsVisibleToUser { get; private set; } = true;
+
     public MainWindow()
     {
         InitializeComponent();
@@ -700,15 +703,12 @@ public sealed partial class MainWindow : WindowEx,
             {
                 Logger.LogWarning($"DWM cloaking of the main window failed. HRESULT: {hr.Value}.");
             }
-
-            wasCloaked = hr.Succeeded;
+            else
+            {
+                IsVisibleToUser = false;
             }
 
-        if (wasCloaked)
-        {
-            // Because we're only cloaking the window, bury it at the bottom in case something can
-            // see it - e.g. some accessibility helper (note: this also removes the top-most status).
-            PInvoke.SetWindowPos(_hwnd, HWND.HWND_BOTTOM, 0, 0, 0, 0, SET_WINDOW_POS_FLAGS.SWP_NOMOVE | SET_WINDOW_POS_FLAGS.SWP_NOSIZE);
+            wasCloaked = hr.Succeeded;
         }
 
         return wasCloaked;
@@ -720,6 +720,7 @@ public sealed partial class MainWindow : WindowEx,
         {
             BOOL value = false;
             PInvoke.DwmSetWindowAttribute(_hwnd, DWMWINDOWATTRIBUTE.DWMWA_CLOAK, &value, (uint)sizeof(BOOL));
+            IsVisibleToUser = true;
         }
     }
 

src/modules/cmdpal/Microsoft.CmdPal.UI/Pages/ShellPage.xaml.cs

@@ -13,6 +13,7 @@ using Microsoft.CmdPal.Core.ViewModels.Messages;
 using Microsoft.CmdPal.UI.Events;
 using Microsoft.CmdPal.UI.Helpers;
 using Microsoft.CmdPal.UI.Messages;
+using Microsoft.CmdPal.UI.Services;
 using Microsoft.CmdPal.UI.Settings;
 using Microsoft.CmdPal.UI.ViewModels;
 using Microsoft.CommandPalette.Extensions;
@@ -72,6 +73,8 @@ public sealed partial class ShellPage : Microsoft.UI.Xaml.Controls.Page,
 
     public event PropertyChangedEventHandler? PropertyChanged;
 
+    public IHostWindow? HostWindow { get; set; }
+
     public ShellPage()
     {
         this.InitializeComponent();
@@ -435,7 +438,7 @@ public sealed partial class ShellPage : Microsoft.UI.Xaml.Controls.Page,
 
         if (!RootFrame.CanGoBack)
         {
-            ViewModel.GoHome();
+            ViewModel.GoHome(withAnimation, focusSearch);
         }
 
         if (focusSearch)
@@ -531,6 +534,11 @@ public sealed partial class ShellPage : Microsoft.UI.Xaml.Controls.Page,
 
         if (shouldSearchBoxBeVisible || page is not ContentPage)
         {
+            if (HostWindow?.IsVisibleToUser != true)
+            {
+                return;
+            }
+
             ViewModel.IsSearchBoxVisible = shouldSearchBoxBeVisible;
             SearchBox.Focus(FocusState.Programmatic);
             SearchBox.SelectSearch();
@@ -547,6 +555,11 @@ public sealed partial class ShellPage : Microsoft.UI.Xaml.Controls.Page,
 
                     try
                     {
+                        if (HostWindow?.IsVisibleToUser != true)
+                        {
+                            return;
+                        }
+
                         await page.DispatcherQueue.EnqueueAsync(
                             async () =>
                             {
@@ -556,6 +569,11 @@ public sealed partial class ShellPage : Microsoft.UI.Xaml.Controls.Page,
                                 {
                                     token.ThrowIfCancellationRequested();
 
+                                    if (HostWindow?.IsVisibleToUser != true)
+                                    {
+                                        break;
+                                    }
+
                                     if (FocusManager.FindFirstFocusableElement(page) is FrameworkElement frameworkElement)
                                     {
                                         var set = frameworkElement.Focus(FocusState.Programmatic);

src/modules/cmdpal/Microsoft.CmdPal.UI/Services/IHostWindow.cs

@@ -0,0 +1,16 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.CmdPal.UI.Services;
+
+/// <summary>
+/// Represents abstract host window functionality.
+/// </summary>
+public interface IHostWindow
+{
+    /// <summary>
+    /// Gets a value indicating whether the window is visible to the user, taking account not only window visibility but also cloaking.
+    /// </summary>
+    bool IsVisibleToUser { get; }
+}