CmdPal: fix alt+f4 handling (#49708)

As I threw in
https://github.com/microsoft/PowerToys/issues/49572#issuecomment-5195807441:

Our alt+f4 handling is wack. We shouldn't close the dock when you press
alt+f4 on it, just like you can't close the taskbar with alt+f4.

But also some folks want alt+f4 to quit cmdpal, and some folks don't. So
there's a setting for what happens when you alt+f4 cmdpal.

Closes #38333
Closes #40277
Closes #49572

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/SettingsModel.cs

@@ -46,6 +46,8 @@ public record SettingsModel
 
     public bool AllowExternalReload { get; init; }
 
+    public bool AllowAltF4 { get; init; }
+
     public bool CompactMode { get; set; }
 
     // When compact mode is on and the palette is centered on launch, this is the relative

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/SettingsViewModel.cs

@@ -69,6 +69,15 @@ public partial class SettingsViewModel : INotifyPropertyChanged,
         }
     }
 
+    public bool AllowAltF4
+    {
+        get => _settingsService.Settings.AllowAltF4;
+        set
+        {
+            _settingsService.UpdateSettings(s => s with { AllowAltF4 = value });
+        }
+    }
+
     public bool ShowAppDetails
     {
         get => _settingsService.Settings.ShowAppDetails;

src/modules/cmdpal/Microsoft.CmdPal.UI/Dock/DockWindow.xaml.cs

@@ -1351,13 +1351,12 @@ public sealed partial class DockWindow : WindowEx,
             HandleDeactivationForAutoHide();
         }
 
-        // Intercept WM_SYSCOMMAND to prevent minimize and maximize
+        // Prevent close, minimize, and maximize system commands.
         else if (msg == PInvoke.WM_SYSCOMMAND)
         {
             var command = (int)(wParam.Value & 0xFFF0);
-            if (command == PInvoke.SC_MINIMIZE || command == PInvoke.SC_MAXIMIZE)
+            if (command == PInvoke.SC_CLOSE || command == PInvoke.SC_MINIMIZE || command == PInvoke.SC_MAXIMIZE)
             {
-                // Block minimize and maximize commands
                 return new LRESULT(0);
             }
         }

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

@@ -1700,6 +1700,23 @@ public sealed partial class MainWindow : WindowEx,
             case PInvoke.WM_NCACTIVATE when _hwndFrameVisible != true:
                 return PInvoke.CallWindowProc(_originalWndProc, hwnd, uMsg, wParam, new LPARAM(-1));
 
+            case PInvoke.WM_SYSCOMMAND:
+                {
+                    var command = (int)(wParam.Value & 0xFFF0);
+                    if (command == PInvoke.SC_CLOSE)
+                    {
+                        var settings = App.Current.Services.GetRequiredService<ISettingsService>().Settings;
+                        if (settings.AllowAltF4)
+                        {
+                            WeakReferenceMessenger.Default.Send<QuitMessage>();
+                        }
+
+                        return (LRESULT)IntPtr.Zero;
+                    }
+
+                    break;
+                }
+
             case PInvoke.WM_HOTKEY:
                 {
                     var hotkeyIndex = (int)wParam.Value;

src/modules/cmdpal/Microsoft.CmdPal.UI/NativeMethods.txt

@@ -115,6 +115,7 @@ WM_GETMINMAXINFO
 MINMAXINFO
 SetWinEventHook
 WINDOW_STYLE
+SC_CLOSE
 SC_MINIMIZE
 SC_MAXIMIZE
 SET_WINDOW_POS_FLAGS

src/modules/cmdpal/Microsoft.CmdPal.UI/Settings/GeneralPage.xaml

@@ -172,6 +172,10 @@
                         <ToggleSwitch AutomationProperties.AutomationId="CmdPal_GeneralPage_ShowSystemTrayIcon" IsOn="{x:Bind viewModel.ShowSystemTrayIcon, Mode=TwoWay}" />
                     </controls:SettingsCard>
 
+                    <controls:SettingsCard x:Uid="Settings_GeneralPage_AllowAltF4_SettingsCard" HeaderIcon="{ui:FontIcon Glyph=&#xE7E8;}">
+                        <ToggleSwitch AutomationProperties.AutomationId="CmdPal_GeneralPage_AllowAltF4" IsOn="{x:Bind viewModel.AllowAltF4, Mode=TwoWay}" />
+                    </controls:SettingsCard>
+
                     <!--  'For Developers' section  -->
 
                     <TextBlock x:Uid="ForDevelopersSettingsHeader" Style="{StaticResource SettingsSectionHeaderTextBlockStyle}" />

src/modules/cmdpal/Microsoft.CmdPal.UI/Strings/en-us/Resources.resw

@@ -495,6 +495,12 @@ Right-click to remove the key combination, thereby deactivating the shortcut.</v
   <data name="Settings_GeneralPage_ShowSystemTrayIcon_SettingsCard.Description" xml:space="preserve">
     <value>Choose if Command Palette is visible in the system tray</value>
   </data>
+  <data name="Settings_GeneralPage_AllowAltF4_SettingsCard.Header" xml:space="preserve">
+    <value>Quit Command Palette with Alt+F4</value>
+  </data>
+  <data name="Settings_GeneralPage_AllowAltF4_SettingsCard.Description" xml:space="preserve">
+    <value>If this setting is on, pressing Alt+F4 will quit Command Palette</value>
+  </data>
   <data name="Settings_GeneralPage_DisableAnimations_SettingsCard.Header" xml:space="preserve">
     <value>Disable animations</value>
   </data>