Immersive dark mode + Theme Listener (#18315)

* C++ impl of immersive dark mode

* Stop using the hardcoded value.

* Conjured up theme listener based on registry.

* Update MainWindow.xaml.cpp

* Update expect.txt

* Moved themehelpers to the common themes lib.

* Ported theme helpers back to .NET

* Update expect.txt

* Updated C# Theme Listening logic to mimic the one from Windows Community Toolkit.

* Replaced unmanaged code for RegisterForImmersiveDarkMode with unmanaged ThemeListener class.

* Fix upstream changes

* Update ThemeListener.h

* Update ThemeListener.h

* Proper formatting

* Added handler to Keyboard Manager.

* Update EditKeyboardWindow.cpp

* Added dwmapi.lib to runner, removed condition from additional dependencies.

* Update PowerRenameUI.vcxproj

* Added new deps for ManagedCommon to Product.wxs

* Crude attempts and understanding installer

* Removed Microsoft.Win32.Registry.dll from product.wxs.

* Updated dictionary

* Renamed ThemeListener class file for consistency, removed unused CheckImmersiveDarkMode in theme_helpers.

* Update Themes.vcxproj

* Update theme_listener.cpp

* Removed SupportsImmersiveDarkMode version check

* Removed SupportsImmersiveDarkMode version check

* Whoops

* Update expect.txt

src/common/ManagedCommon/ManagedCommon.csproj

@@ -17,6 +17,8 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
+    <PackageReference Include="Microsoft.Win32.Registry" Version="5.0.0" />
+    <PackageReference Include="System.Management" Version="6.0.0" />
   </ItemGroup>
 
   <ItemGroup>

src/common/ManagedCommon/Theme.cs

@@ -14,4 +14,10 @@ namespace ManagedCommon
         HighContrastBlack,
         HighContrastWhite,
     }
+
+    public enum AppTheme
+    {
+        Dark = 0,
+        Light = 1,
+    }
 }

src/common/ManagedCommon/ThemeHelpers.cs

@@ -0,0 +1,37 @@
+// 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.
+
+using System;
+using System.Linq;
+using System.Runtime.InteropServices;
+using Microsoft.Win32;
+
+namespace ManagedCommon
+{
+    // Based on https://stackoverflow.com/a/62811758/5001796
+    public static class ThemeHelpers
+    {
+        [DllImport("dwmapi.dll")]
+        private static extern int DwmSetWindowAttribute(IntPtr hwnd, int attr, ref int attrValue, int attrSize);
+
+        internal const string HKeyRoot = "HKEY_CURRENT_USER";
+        internal const string HkeyWindowsTheme = @"SOFTWARE\Microsoft\Windows\CurrentVersion\Themes";
+        internal const string HkeyWindowsPersonalizeTheme = $@"{HkeyWindowsTheme}\Personalize";
+        internal const string HValueAppTheme = "AppsUseLightTheme";
+        internal const int DWMWAImmersiveDarkMode = 20;
+
+        // based on https://stackoverflow.com/questions/51334674/how-to-detect-windows-10-light-dark-mode-in-win32-application
+        public static AppTheme GetAppTheme()
+        {
+            int value = (int)Registry.GetValue($"{HKeyRoot}\\{HkeyWindowsPersonalizeTheme}", HValueAppTheme, 1);
+            return (AppTheme)value;
+        }
+
+        public static void SetImmersiveDarkMode(IntPtr window, bool enabled)
+        {
+            int useImmersiveDarkMode = enabled ? 1 : 0;
+            _ = DwmSetWindowAttribute(window, DWMWAImmersiveDarkMode, ref useImmersiveDarkMode, sizeof(int));
+        }
+    }
+}

src/common/ManagedCommon/ThemeListener.cs

@@ -0,0 +1,62 @@
+// 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.
+
+using System;
+using System.Management;
+using System.Security.Principal;
+
+namespace ManagedCommon
+{
+    /// <summary>
+    /// The Delegate for a ThemeChanged Event.
+    /// </summary>
+    /// <param name="sender">Sender ThemeListener</param>
+    public delegate void ThemeChangedEvent(ThemeListener sender);
+
+    public class ThemeListener : IDisposable
+    {
+        /// <summary>
+        /// Gets the App Theme.
+        /// </summary>
+        public AppTheme AppTheme { get; private set; }
+
+        /// <summary>
+        /// An event that fires if the Theme changes.
+        /// </summary>
+        public event ThemeChangedEvent ThemeChanged;
+
+        private readonly ManagementEventWatcher watcher;
+
+        public ThemeListener()
+        {
+            var currentUser = WindowsIdentity.GetCurrent();
+            var query = new WqlEventQuery(
+                $"SELECT * FROM RegistryValueChangeEvent WHERE Hive='HKEY_USERS' AND " +
+                $"KeyPath='{currentUser.User.Value}\\\\{ThemeHelpers.HkeyWindowsPersonalizeTheme.Replace("\\", "\\\\")}' AND ValueName='{ThemeHelpers.HValueAppTheme}'");
+            watcher = new ManagementEventWatcher(query);
+            watcher.EventArrived += Watcher_EventArrived;
+            watcher.Start();
+
+            AppTheme = ThemeHelpers.GetAppTheme();
+        }
+
+        private void Watcher_EventArrived(object sender, EventArrivedEventArgs e)
+        {
+            var appTheme = ThemeHelpers.GetAppTheme();
+
+            if (appTheme != AppTheme)
+            {
+                AppTheme = appTheme;
+
+                ThemeChanged?.Invoke(this);
+            }
+        }
+
+        public void Dispose()
+        {
+            watcher.Dispose();
+            GC.SuppressFinalize(this);
+        }
+    }
+}

src/common/Themes/Themes.vcxproj

@@ -31,10 +31,14 @@
   </ItemDefinitionGroup>
   <ItemGroup>
     <ClInclude Include="icon_helpers.h" />
+    <ClInclude Include="theme_listener.h" />
+    <ClInclude Include="theme_helpers.h" />
     <ClInclude Include="windows_colors.h" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="icon_helpers.cpp" />
+    <ClCompile Include="theme_listener.cpp" />
+    <ClCompile Include="theme_helpers.cpp" />
     <ClCompile Include="windows_colors.cpp" />
   </ItemGroup>
   <ItemGroup>

src/common/Themes/theme_helpers.cpp

@@ -0,0 +1,43 @@
+// Port Based on https://stackoverflow.com/a/62811758/5001796
+#include "theme_helpers.h"
+#include "dwmapi.h"
+#include <windows.h>
+#include <vector>
+
+#define DWMWA_USE_IMMERSIVE_DARK_MODE 20
+#define HKEY_WINDOWS_THEME L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize"
+
+// based on https://stackoverflow.com/questions/51334674/how-to-detect-windows-10-light-dark-mode-in-win32-application
+AppTheme ThemeHelpers::GetAppTheme()
+{
+    // The value is expected to be a REG_DWORD, which is a signed 32-bit little-endian
+    auto buffer = std::vector<char>(4);
+    auto cbData = static_cast<DWORD>(buffer.size() * sizeof(char));
+    auto res = RegGetValueW(
+        HKEY_CURRENT_USER,
+        HKEY_WINDOWS_THEME,
+        L"AppsUseLightTheme",
+        RRF_RT_REG_DWORD, // expected value type
+        nullptr,
+        buffer.data(),
+        &cbData);
+
+    if (res != ERROR_SUCCESS)
+    {
+        return AppTheme::Light;
+    }
+
+    // convert bytes written to our buffer to an int, assuming little-endian
+    auto i = int(buffer[3] << 24 |
+                 buffer[2] << 16 |
+                 buffer[1] << 8 |
+                 buffer[0]);
+
+    return AppTheme(i);
+}
+
+void ThemeHelpers::SetImmersiveDarkMode(HWND window, bool enabled)
+{
+    int useImmersiveDarkMode = enabled ? 1 : 0;
+    DwmSetWindowAttribute(window, DWMWA_USE_IMMERSIVE_DARK_MODE, &useImmersiveDarkMode, sizeof(useImmersiveDarkMode));
+}

src/common/Themes/theme_helpers.h

@@ -0,0 +1,14 @@
+#pragma once
+#include <windows.h>
+
+enum class AppTheme
+{
+    Dark = 0,
+    Light = 1
+};
+
+struct ThemeHelpers
+{
+    static AppTheme GetAppTheme();
+    static void ThemeHelpers::SetImmersiveDarkMode(HWND window, bool enabled);
+};

src/common/Themes/theme_listener.cpp

@@ -0,0 +1,57 @@
+#include "theme_listener.h"
+
+#define HKEY_WINDOWS_THEME L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize"
+
+DWORD WINAPI _checkTheme(LPVOID lpParam)
+{
+    auto listener = (ThemeListener*)lpParam;
+    listener->CheckTheme();
+    return 0;
+}
+
+void ThemeListener::AddChangedHandler(THEME_HANDLE handle)
+{
+    handles.push_back(handle);
+}
+
+void ThemeListener::DelChangedHandler(THEME_HANDLE handle)
+{
+    auto it = std::find(handles.begin(), handles.end(), handle);
+    handles.erase(it);
+}
+
+void ThemeListener::CheckTheme()
+{
+    HANDLE hEvent;
+    HKEY hKey;
+
+    // Open the Key to listen
+    RegOpenKeyEx(HKEY_CURRENT_USER, HKEY_WINDOWS_THEME, 0, KEY_NOTIFY, &hKey);
+
+    while (true)
+    {
+        // Create an event.
+        hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
+        if (hEvent != 0)
+        {
+            // Watch the registry key for a change of value.
+            RegNotifyChangeKeyValue(hKey,
+                                    TRUE,
+                                    REG_NOTIFY_CHANGE_LAST_SET,
+                                    hEvent,
+                                    TRUE);
+
+            WaitForSingleObject(hEvent, INFINITE);
+
+            auto _theme = ThemeHelpers::GetAppTheme();
+            if (AppTheme != _theme)
+            {
+                AppTheme = _theme;
+                for (int i = 0; i < handles.size(); i++)
+                {
+                    handles[i]();
+                }
+            }
+        }
+    }
+}

src/common/Themes/theme_listener.h

@@ -0,0 +1,34 @@
+#include "theme_helpers.h"
+#include "dwmapi.h"
+#include <windows.h>
+#include <iostream>
+#include <vector>
+
+typedef void (*THEME_HANDLE)();
+DWORD WINAPI _checkTheme(LPVOID lpParam);
+
+#pragma once
+class ThemeListener
+{
+public:
+    ThemeListener()
+    {
+        AppTheme = ThemeHelpers::GetAppTheme();
+        dwThreadHandle = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)_checkTheme, this, 0, &dwThreadId);
+    }
+    ~ThemeListener()
+    {
+        CloseHandle(dwThreadHandle);
+        dwThreadId = 0;
+    }
+
+    AppTheme AppTheme;
+    void ThemeListener::AddChangedHandler(THEME_HANDLE handle);
+    void ThemeListener::DelChangedHandler(THEME_HANDLE handle);
+    void CheckTheme();
+
+private:
+    HANDLE dwThreadHandle;
+    DWORD dwThreadId;
+    std::vector<THEME_HANDLE> handles;
+};

src/common/Themes/windows_colors.cpp

@@ -1,4 +1,5 @@
 #include "windows_colors.h"
+#include "theme_helpers.h"
 
 DWORD WindowsColors::rgb_color(DWORD abgr_color)
 {
@@ -65,7 +66,7 @@ WindowsColors::Color WindowsColors::get_background_color()
 
 bool WindowsColors::is_dark_mode()
 {
-    return rgb_color(get_background_color()) == 0;
+    return ThemeHelpers::GetAppTheme() == AppTheme::Dark;
 }
 
 bool WindowsColors::update()

src/modules/keyboardmanager/KeyboardManagerEditor/KeyboardManagerEditor.vcxproj

@@ -102,7 +102,7 @@
       <AdditionalIncludeDirectories>./;$(SolutionDir)src\modules\;$(SolutionDir)src\modules\KeyboardManager\KeyboardManagerEditorLibrary\;$(SolutionDir)src\common\Display;$(SolutionDir)src\common\inc;$(SolutionDir)src\common\Telemetry;$(SolutionDir)src;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
-      <AdditionalDependencies>Display.lib;shcore.lib;Dbghelp.lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>Display.lib;shcore.lib;Dbghelp.lib;dwmapi.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <AdditionalLibraryDirectories>$(SolutionDir)$(Platform)\$(ConfigurationName);%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
     </Link>
   </ItemDefinitionGroup>
@@ -113,7 +113,7 @@
     <Link>
       <EnableCOMDATFolding>true</EnableCOMDATFolding>
       <OptimizeReferences>true</OptimizeReferences>
-      <AdditionalDependencies>Display.lib;shcore.lib;Dbghelp.lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>Display.lib;shcore.lib;Dbghelp.lib;dwmapi.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <AdditionalLibraryDirectories>$(SolutionDir)$(Platform)\$(ConfigurationName);%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
     </Link>
   </ItemDefinitionGroup>

src/modules/keyboardmanager/KeyboardManagerEditorLibrary/EditKeyboardWindow.cpp

@@ -22,6 +22,7 @@
 #include "UIHelpers.h"
 #include "ShortcutErrorType.h"
 #include "EditorConstants.h"
+#include <common/Themes/theme_listener.h>
 
 using namespace winrt::Windows::Foundation;
 
@@ -42,6 +43,20 @@ std::mutex editKeyboardWindowMutex;
 // Stores a pointer to the Xaml Bridge object so that it can be accessed from the window procedure
 static XamlBridge* xamlBridgePtr = nullptr;
 
+// Theming
+ThemeListener theme_listener{};
+
+void handleTheme()
+{
+    auto theme = theme_listener.AppTheme;
+    auto isDark = theme == AppTheme::Dark;
+    Logger::info(L"Theme is now {}", isDark ? L"Dark" : L"Light");
+    if (hwndEditKeyboardNativeWindow != nullptr)
+    {
+        ThemeHelpers::SetImmersiveDarkMode(hwndEditKeyboardNativeWindow, isDark);
+    }
+}
+
 static IAsyncOperation<bool> OrphanKeysConfirmationDialog(
     KBMEditor::KeyboardManagerState& state,
     const std::vector<DWORD>& keys,
@@ -130,7 +145,7 @@ inline void CreateEditKeyboardWindowImpl(HINSTANCE hInst, KBMEditor::KeyboardMan
             48,
             48,
             LR_DEFAULTCOLOR);
-        
+
         if (RegisterClassEx(&windowClass) == NULL)
         {
             MessageBox(NULL, GET_RESOURCE_STRING(IDS_REGISTERCLASSFAILED_ERRORMESSAGE).c_str(), GET_RESOURCE_STRING(IDS_REGISTERCLASSFAILED_ERRORTITLE).c_str(), NULL);
@@ -149,7 +164,7 @@ inline void CreateEditKeyboardWindowImpl(HINSTANCE hInst, KBMEditor::KeyboardMan
 
     DPIAware::ConvertByCursorPosition(windowWidth, windowHeight);
     DPIAware::GetScreenDPIForCursor(g_currentDPI);
-    
+
     // Window Creation
     HWND _hWndEditKeyboardWindow = CreateWindow(
         szWindowClass,
@@ -163,7 +178,7 @@ inline void CreateEditKeyboardWindowImpl(HINSTANCE hInst, KBMEditor::KeyboardMan
         NULL,
         hInst,
         NULL);
-    
+
     if (_hWndEditKeyboardWindow == NULL)
     {
         MessageBox(NULL, GET_RESOURCE_STRING(IDS_CREATEWINDOWFAILED_ERRORMESSAGE).c_str(), GET_RESOURCE_STRING(IDS_CREATEWINDOWFAILED_ERRORTITLE).c_str(), NULL);
@@ -181,12 +196,15 @@ inline void CreateEditKeyboardWindowImpl(HINSTANCE hInst, KBMEditor::KeyboardMan
     hwndEditKeyboardNativeWindow = _hWndEditKeyboardWindow;
     hwndLock.unlock();
 
+    handleTheme();
+    theme_listener.AddChangedHandler(handleTheme);
+
     // Create the xaml bridge object
     XamlBridge xamlBridge(_hWndEditKeyboardWindow);
 
     // DesktopSource needs to be declared before the RelativePanel xamlContainer object to avoid errors
     winrt::Windows::UI::Xaml::Hosting::DesktopWindowXamlSource desktopSource;
-    
+
     // Create the desktop window xaml source object and set its content
     hWndXamlIslandEditKeyboardWindow = xamlBridge.InitDesktopWindowsXamlSource(desktopSource);
 
@@ -253,10 +271,10 @@ inline void CreateEditKeyboardWindowImpl(HINSTANCE hInst, KBMEditor::KeyboardMan
     SingleKeyRemapControl::keyboardManagerState = &keyboardManagerState;
     KeyDropDownControl::keyboardManagerState = &keyboardManagerState;
     KeyDropDownControl::mappingConfiguration = &mappingConfiguration;
-    
+
     // Clear the single key remap buffer
     SingleKeyRemapControl::singleKeyRemapBuffer.clear();
-    
+
     // Vector to store dynamically allocated control objects to avoid early destruction
     std::vector<std::vector<std::unique_ptr<SingleKeyRemapControl>>> keyboardRemapControlObjects;
 
@@ -378,6 +396,7 @@ inline void CreateEditKeyboardWindowImpl(HINSTANCE hInst, KBMEditor::KeyboardMan
     xamlBridgePtr = nullptr;
     hWndXamlIslandEditKeyboardWindow = nullptr;
     hwndLock.lock();
+    theme_listener.DelChangedHandler(handleTheme);
     hwndEditKeyboardNativeWindow = nullptr;
     keyboardManagerState.ResetUIState();
     keyboardManagerState.ClearRegisteredKeyDelays();
@@ -450,8 +469,7 @@ LRESULT CALLBACK EditKeyboardWindowProc(HWND hWnd, UINT messageCode, WPARAM wPar
             rect->top,
             rect->right - rect->left,
             rect->bottom - rect->top,
-            SWP_NOZORDER | SWP_NOACTIVATE
-        );
+            SWP_NOZORDER | SWP_NOACTIVATE);
 
         Logger::trace(L"WM_DPICHANGED: new dpi {} rect {} {} ", newDPI, rect->right - rect->left, rect->bottom - rect->top);
     }
@@ -487,7 +505,7 @@ bool CheckEditKeyboardWindowActive()
         {
             ShowWindow(hwndEditKeyboardNativeWindow, SW_RESTORE);
         }
-        
+
         // If there is an already existing window no need to create a new open bring it on foreground.
         SetForegroundWindow(hwndEditKeyboardNativeWindow);
         result = true;

src/modules/powerrename/PowerRenameUILib/MainWindow.xaml.cpp

@@ -21,6 +21,8 @@
 #include "microsoft.ui.xaml.window.h"
 #include <winrt/Microsoft.UI.Interop.h>
 #include <winrt/Microsoft.UI.Windowing.h>
+#include <common/Themes/theme_helpers.h>
+#include <common/Themes/theme_listener.h>
 
 using namespace winrt;
 using namespace Windows::UI::Xaml;
@@ -35,15 +37,31 @@ HINSTANCE g_hostHInst;
 
 extern std::vector<std::wstring> g_files;
 
+// Theming
+ThemeListener theme_listener{};
+HWND CurrentWindow;
+
+void handleTheme() {
+    auto theme = theme_listener.AppTheme;
+    auto isDark = theme == AppTheme::Dark;
+    Logger::info(L"Theme is now {}", isDark ? L"Dark" : L"Light");
+    ThemeHelpers::SetImmersiveDarkMode(CurrentWindow, isDark);
+}
+
 namespace winrt::PowerRenameUI::implementation
 {
     MainWindow::MainWindow() :
         m_instance{ nullptr }, m_allSelected{ true }, m_managerEvents{ this }
     {
-
         auto windowNative{ this->try_as<::IWindowNative>() };
         winrt::check_bool(windowNative);
         windowNative->get_WindowHandle(&m_window);
+        CurrentWindow = m_window;
+
+        // Attach theme handling
+        theme_listener.AddChangedHandler(handleTheme);
+        handleTheme();
+
         Microsoft::UI::WindowId windowId =
             Microsoft::UI::GetWindowIdFromWindow(m_window);
 
@@ -69,7 +87,6 @@ namespace winrt::PowerRenameUI::implementation
             }
         }
 
-
         Microsoft::UI::Windowing::AppWindow appWindow =
             Microsoft::UI::Windowing::AppWindow::GetFromWindowId(windowId);
         appWindow.SetIcon(PowerRenameUIIco);

src/modules/powerrename/PowerRenameUILib/PowerRenameUI.vcxproj

@@ -69,6 +69,9 @@
     <ClCompile>
       <PreprocessorDefinitions>_DEBUG;%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>
+    <Link>
+      <AdditionalDependencies>kernel32.lib;user32.lib;dwmapi.lib;%(AdditionalDependencies)</AdditionalDependencies>
+    </Link>
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)'=='Release'">
     <ClCompile>
@@ -77,6 +80,7 @@
     <Link>
       <EnableCOMDATFolding>true</EnableCOMDATFolding>
       <OptimizeReferences>true</OptimizeReferences>
+      <AdditionalDependencies>kernel32.lib;user32.lib;dwmapi.lib;%(AdditionalDependencies)</AdditionalDependencies>
     </Link>
   </ItemDefinitionGroup>
   <ItemGroup>
@@ -161,6 +165,9 @@
     <ProjectReference Include="..\..\..\common\logger\logger.vcxproj">
       <Project>{d9b8fc84-322a-4f9f-bbb9-20915c47ddfd}</Project>
     </ProjectReference>
+    <ProjectReference Include="..\..\..\common\Themes\Themes.vcxproj">
+      <Project>{98537082-0fdb-40de-abd8-0dc5a4269bab}</Project>
+    </ProjectReference>
     <ProjectReference Include="..\..\..\common\version\version.vcxproj">
       <Project>{cc6e41ac-8174-4e8a-8d22-85dd7f4851df}</Project>
     </ProjectReference>

src/runner/runner.vcxproj

@@ -39,7 +39,7 @@
     <Link>
       <UACExecutionLevel>AsInvoker</UACExecutionLevel>
       <OutputFile>$(OutDir)$(TargetName)$(TargetExt)</OutputFile>
-      <AdditionalDependencies>Shcore.lib;gdiplus.lib;Msi.lib;WindowsApp.lib;taskschd.lib;Rstrtmgr.lib;Shlwapi.lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>Shcore.lib;gdiplus.lib;Msi.lib;WindowsApp.lib;taskschd.lib;Rstrtmgr.lib;Shlwapi.lib;dwmapi.lib;%(AdditionalDependencies)</AdditionalDependencies>
     </Link>
     <Manifest>
       <EnableDpiAwareness>false</EnableDpiAwareness>

src/settings-ui/Settings.UI/App.xaml.cs

@@ -15,7 +15,6 @@ using Microsoft.PowerToys.Settings.UI.Library.Telemetry.Events;
 using Microsoft.PowerToys.Telemetry;
 using Microsoft.UI.Xaml;
 using Windows.UI.Popups;
-using Windows.UI.ViewManagement;
 using WinRT.Interop;
 
 namespace Microsoft.PowerToys.Settings.UI
@@ -73,7 +72,7 @@ namespace Microsoft.PowerToys.Settings.UI
         {
             if (settingsWindow == null)
             {
-                settingsWindow = new MainWindow();
+                settingsWindow = new MainWindow(IsDarkTheme());
             }
 
             settingsWindow.Activate();
@@ -88,6 +87,7 @@ namespace Microsoft.PowerToys.Settings.UI
         protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
         {
             var cmdArgs = Environment.GetCommandLineArgs();
+            var isDark = IsDarkTheme();
 
             if (cmdArgs != null && cmdArgs.Length >= RequiredArgumentsQty)
             {
@@ -143,7 +143,7 @@ namespace Microsoft.PowerToys.Settings.UI
 
                 if (!ShowOobe && !ShowScoobe)
                 {
-                    settingsWindow = new MainWindow();
+                    settingsWindow = new MainWindow(isDark);
                     settingsWindow.Activate();
                     settingsWindow.NavigateToSection(StartupPage);
                 }
@@ -152,19 +152,19 @@ namespace Microsoft.PowerToys.Settings.UI
                     // Create the Settings window hidden so that it's fully initialized and
                     // it will be ready to receive the notification if the user opens
                     // the Settings from the tray icon.
-                    settingsWindow = new MainWindow(true);
+                    settingsWindow = new MainWindow(isDark, true);
 
                     if (ShowOobe)
                     {
                         PowerToysTelemetry.Log.WriteEvent(new OobeStartedEvent());
-                        OobeWindow oobeWindow = new OobeWindow(OOBE.Enums.PowerToysModules.Overview);
+                        OobeWindow oobeWindow = new OobeWindow(OOBE.Enums.PowerToysModules.Overview, isDark);
                         oobeWindow.Activate();
                         SetOobeWindow(oobeWindow);
                     }
                     else if (ShowScoobe)
                     {
                         PowerToysTelemetry.Log.WriteEvent(new ScoobeStartedEvent());
-                        OobeWindow scoobeWindow = new OobeWindow(OOBE.Enums.PowerToysModules.WhatsNew);
+                        OobeWindow scoobeWindow = new OobeWindow(OOBE.Enums.PowerToysModules.WhatsNew, isDark);
                         scoobeWindow.Activate();
                         SetOobeWindow(scoobeWindow);
                     }
@@ -174,7 +174,7 @@ namespace Microsoft.PowerToys.Settings.UI
             {
                 // For debugging purposes
                 // Window is also needed to show MessageDialog
-                settingsWindow = new MainWindow();
+                settingsWindow = new MainWindow(isDark);
                 settingsWindow.Activate();
                 ShowMessageDialog("The application cannot be run as a standalone process. Please start the application through the runner.", "Forbidden");
             }
@@ -203,18 +203,50 @@ namespace Microsoft.PowerToys.Settings.UI
             return ipcmanager;
         }
 
+        public static string SelectedTheme()
+        {
+            return SettingsRepository<GeneralSettings>.GetInstance(settingsUtils).SettingsConfig.Theme.ToUpper(CultureInfo.InvariantCulture);
+        }
+
         public static bool IsDarkTheme()
         {
-            var selectedTheme = SettingsRepository<GeneralSettings>.GetInstance(settingsUtils).SettingsConfig.Theme.ToUpper(CultureInfo.InvariantCulture);
-            var defaultTheme = new UISettings();
-            var uiTheme = defaultTheme.GetColorValue(UIColorType.Background).ToString(System.Globalization.CultureInfo.InvariantCulture);
-            return selectedTheme == "DARK" || (selectedTheme == "SYSTEM" && uiTheme == "#FF000000");
+            var selectedTheme = SelectedTheme();
+            return selectedTheme == "DARK" || (selectedTheme == "SYSTEM" && ThemeHelpers.GetAppTheme() == AppTheme.Dark);
+        }
+
+        public static void HandleThemeChange()
+        {
+            var isDark = IsDarkTheme();
+            if (settingsWindow != null)
+            {
+                var hWnd = WinRT.Interop.WindowNative.GetWindowHandle(settingsWindow);
+                ThemeHelpers.SetImmersiveDarkMode(hWnd, isDark);
+            }
+
+            if (oobeWindow != null)
+            {
+                var hWnd = WinRT.Interop.WindowNative.GetWindowHandle(oobeWindow);
+                ThemeHelpers.SetImmersiveDarkMode(hWnd, isDark);
+            }
+
+            var selectedTheme = SelectedTheme();
+            if (selectedTheme == "SYSTEM")
+            {
+                themeListener = new ThemeListener();
+                themeListener.ThemeChanged += (_) => HandleThemeChange();
+            }
+            else if (themeListener != null)
+            {
+                themeListener.Dispose();
+                themeListener = null;
+            }
         }
 
         private static ISettingsUtils settingsUtils = new SettingsUtils();
 
         private static MainWindow settingsWindow;
         private static OobeWindow oobeWindow;
+        private static ThemeListener themeListener;
 
         public static void ClearSettingsWindow()
         {

src/settings-ui/Settings.UI/MainWindow.xaml.cs

@@ -3,7 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Drawing;
+using ManagedCommon;
 using Microsoft.PowerLauncher.Telemetry;
 using Microsoft.PowerToys.Settings.UI.Helpers;
 using Microsoft.PowerToys.Settings.UI.Library.Utilities;
@@ -22,7 +22,7 @@ namespace Microsoft.PowerToys.Settings.UI
     /// </summary>
     public sealed partial class MainWindow : Window
     {
-        public MainWindow(bool createHidden = false)
+        public MainWindow(bool isDark, bool createHidden = false)
         {
             var bootTime = new System.Diagnostics.Stopwatch();
             bootTime.Start();
@@ -36,6 +36,12 @@ namespace Microsoft.PowerToys.Settings.UI
             AppWindow appWindow = AppWindow.GetFromWindowId(windowId);
             appWindow.SetIcon("icon.ico");
 
+            // Passed by parameter, as it needs to be evaluated ASAP, otherwise there is a white flash
+            if (isDark)
+            {
+                ThemeHelpers.SetImmersiveDarkMode(hWnd, isDark);
+            }
+
             var placement = Utils.DeserializePlacementOrDefault(hWnd);
             if (createHidden)
             {
@@ -72,7 +78,7 @@ namespace Microsoft.PowerToys.Settings.UI
             {
                 if (App.GetOobeWindow() == null)
                 {
-                    App.SetOobeWindow(new OobeWindow(Microsoft.PowerToys.Settings.UI.OOBE.Enums.PowerToysModules.Overview));
+                    App.SetOobeWindow(new OobeWindow(Microsoft.PowerToys.Settings.UI.OOBE.Enums.PowerToysModules.Overview, App.IsDarkTheme()));
                 }
 
                 App.GetOobeWindow().Activate();

src/settings-ui/Settings.UI/OobeWindow.xaml.cs

@@ -4,6 +4,7 @@
 
 using System;
 using interop;
+using ManagedCommon;
 using Microsoft.PowerToys.Settings.UI.Helpers;
 using Microsoft.PowerToys.Settings.UI.OOBE.Enums;
 using Microsoft.PowerToys.Settings.UI.OOBE.Views;
@@ -30,7 +31,7 @@ namespace Microsoft.PowerToys.Settings.UI
         private IntPtr _hWnd;
         private AppWindow _appWindow;
 
-        public OobeWindow(PowerToysModules initialModule)
+        public OobeWindow(PowerToysModules initialModule, bool isDark)
         {
             this.InitializeComponent();
 
@@ -40,6 +41,12 @@ namespace Microsoft.PowerToys.Settings.UI
             _appWindow = AppWindow.GetFromWindowId(_windowId);
             _appWindow.SetIcon("icon.ico");
 
+            // Passed by parameter, as it needs to be evaluated ASAP, otherwise there is a white flash
+            if (isDark)
+            {
+                ThemeHelpers.SetImmersiveDarkMode(_hWnd, isDark);
+            }
+
             OverlappedPresenter presenter = _appWindow.Presenter as OverlappedPresenter;
             presenter.IsMinimizable = false;
             presenter.IsMaximizable = false;

src/settings-ui/Settings.UI/Views/GeneralPage.xaml.cs

@@ -78,6 +78,7 @@ namespace Microsoft.PowerToys.Settings.UI.Views
                     break;
             }
 
+            App.HandleThemeChange();
             return 0;
         }