Code Quality: Improved app theme mode handler

src/Files.App/App.xaml.cs

@@ -145,7 +145,6 @@ private IHost ConfigureHost()
 					.AddSingleton<MainPageViewModel>()
 					.AddSingleton<PreviewPaneViewModel>()
 					.AddSingleton<SidebarViewModel>()
-					.AddSingleton<SettingsViewModel>()
 					.AddSingleton<DrivesViewModel>()
 					.AddSingleton<NetworkDrivesViewModel>()
 					.AddSingleton<StatusCenterViewModel>()

src/Files.App/Dialogs/AddBranchDialog.xaml

@@ -14,7 +14,7 @@
 	IsPrimaryButtonEnabled="{x:Bind ViewModel.IsBranchValid, Mode=OneWay}"
 	PrimaryButtonStyle="{StaticResource AccentButtonStyle}"
 	PrimaryButtonText="{helpers:ResourceString Name=Create}"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	SecondaryButtonText="{helpers:ResourceString Name=Cancel}"
 	Style="{StaticResource DefaultContentDialogStyle}"
 	mc:Ignorable="d">

src/Files.App/Dialogs/AddItemDialog.xaml

@@ -14,7 +14,7 @@
 	BorderThickness="0"
 	CornerRadius="{StaticResource OverlayCornerRadius}"
 	Loaded="AddItemDialog_Loaded"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	SecondaryButtonText="{helpers:ResourceString Name=Cancel}"
 	Style="{StaticResource DefaultContentDialogStyle}"
 	mc:Ignorable="d">

src/Files.App/Dialogs/CreateArchiveDialog.xaml

@@ -17,7 +17,7 @@
 	IsPrimaryButtonEnabled="{x:Bind ViewModel.IsNameValid, Mode=OneWay}"
 	Loaded="ContentDialog_Loaded"
 	PrimaryButtonText="{helpers:ResourceString Name=Create}"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	Style="{StaticResource DefaultContentDialogStyle}"
 	mc:Ignorable="d">
 

src/Files.App/Dialogs/CreateShortcutDialog.xaml

@@ -11,7 +11,7 @@
 	IsPrimaryButtonEnabled="{x:Bind ViewModel.IsLocationValid, Mode=OneWay}"
 	PrimaryButtonCommand="{x:Bind ViewModel.PrimaryButtonCommand}"
 	PrimaryButtonText="{helpers:ResourceString Name=Create}"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	SecondaryButtonText="{helpers:ResourceString Name=Cancel}"
 	Style="{StaticResource DefaultContentDialogStyle}"
 	mc:Ignorable="d">

src/Files.App/Dialogs/CredentialDialog.xaml

@@ -12,7 +12,7 @@
 	PrimaryButtonClick="ContentDialog_PrimaryButtonClick"
 	PrimaryButtonStyle="{StaticResource AccentButtonStyle}"
 	PrimaryButtonText="{helpers:ResourceString Name=OK}"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	SecondaryButtonText="{helpers:ResourceString Name=Cancel}"
 	Style="{StaticResource DefaultContentDialogStyle}"
 	mc:Ignorable="d">

src/Files.App/Dialogs/DecompressArchiveDialog.xaml

@@ -11,7 +11,7 @@
 	DefaultButton="Primary"
 	PrimaryButtonClick="ContentDialog_PrimaryButtonClick"
 	PrimaryButtonText="{helpers:ResourceString Name=Extract}"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	SecondaryButtonText="{helpers:ResourceString Name=Cancel}"
 	Style="{StaticResource DefaultContentDialogStyle}"
 	mc:Ignorable="d">

src/Files.App/Dialogs/DynamicDialog.xaml

@@ -18,7 +18,7 @@
 	KeyDown="ContentDialog_KeyDown"
 	PrimaryButtonClick="ContentDialog_PrimaryButtonClick"
 	PrimaryButtonText="{x:Bind ViewModel.PrimaryButtonText, Mode=OneWay}"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	SecondaryButtonClick="ContentDialog_SecondaryButtonClick"
 	SecondaryButtonText="{x:Bind ViewModel.SecondaryButtonText, Mode=OneWay}"
 	Style="{StaticResource DefaultContentDialogStyle}"

src/Files.App/Dialogs/ElevateConfirmDialog.xaml

@@ -13,7 +13,7 @@
 	CornerRadius="{StaticResource OverlayCornerRadius}"
 	DefaultButton="None"
 	PrimaryButtonText="{helpers:ResourceString Name=Yes}"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	Style="{StaticResource DefaultContentDialogStyle}"
 	mc:Ignorable="d">
 

src/Files.App/Dialogs/FileTooLargeDialog.xaml

@@ -10,7 +10,7 @@
 	CornerRadius="{StaticResource OverlayCornerRadius}"
 	DefaultButton="Primary"
 	PrimaryButtonText="{helpers:ResourceString Name=OK}"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	Style="{StaticResource DefaultContentDialogStyle}"
 	mc:Ignorable="d">
 

src/Files.App/Dialogs/FilesystemOperationDialog.xaml

@@ -18,7 +18,7 @@
 	IsPrimaryButtonEnabled="{x:Bind ViewModel.PrimaryButtonEnabled, Mode=OneWay}"
 	Opened="FilesystemOperationDialog_Opened"
 	PrimaryButtonText="{x:Bind ViewModel.PrimaryButtonText, Mode=OneWay}"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	SecondaryButtonCommand="{x:Bind ViewModel.SecondaryButtonClickCommand, Mode=OneWay}"
 	SecondaryButtonText="{x:Bind ViewModel.SecondaryButtonText, Mode=OneWay}"
 	Style="{StaticResource DefaultContentDialogStyle}"

src/Files.App/Dialogs/GitHubLoginDialog.xaml

@@ -14,7 +14,7 @@
 	CornerRadius="{StaticResource OverlayCornerRadius}"
 	PrimaryButtonClick="ContentDialog_PrimaryButtonClick"
 	PrimaryButtonText="{helpers:ResourceString Name=OK}"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	Style="{StaticResource DefaultContentDialogStyle}"
 	mc:Ignorable="d">
 

src/Files.App/Dialogs/PropertiesDialog.xaml

@@ -7,7 +7,7 @@
 	xmlns:local2="using:Files.App.Helpers"
 	xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
 	x:Name="PropertiesDialogMarkup"
-	RequestedTheme="{x:Bind local2:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind local2:AppThemeHelper.RootTheme}"
 	mc:Ignorable="d">
 
 	<ContentDialog.Resources>

src/Files.App/Dialogs/ReleaseNotesDialog.xaml

@@ -9,7 +9,7 @@
 	xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
 	CornerRadius="{StaticResource OverlayCornerRadius}"
 	DefaultButton="None"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	Style="{StaticResource DefaultContentDialogStyle}"
 	mc:Ignorable="d">
 	<ContentDialog.Resources>

src/Files.App/Dialogs/ReorderSidebarItemsDialog.xaml

@@ -12,7 +12,7 @@
 	IsPrimaryButtonEnabled="True"
 	PrimaryButtonCommand="{x:Bind ViewModel.PrimaryButtonCommand}"
 	PrimaryButtonText="{helpers:ResourceString Name=Save}"
-	RequestedTheme="{x:Bind helpers:ThemeHelper.RootTheme}"
+	RequestedTheme="{x:Bind helpers:AppThemeHelper.RootTheme}"
 	SecondaryButtonText="{helpers:ResourceString Name=Cancel}"
 	Style="{StaticResource DefaultContentDialogStyle}"
 	mc:Ignorable="d">

src/Files.App/Helpers/UI/AppThemeHelper.cs

@@ -0,0 +1,130 @@
+// Copyright (c) 2023 Files Community
+// Licensed under the MIT License. See the LICENSE.
+
+using Microsoft.UI;
+using Microsoft.UI.Xaml;
+using Windows.UI;
+using Windows.UI.ViewManagement;
+
+namespace Files.App.Helpers
+{
+	/// <summary>
+	/// Provides static helper for switching and restoring app theme settings.
+	/// </summary>
+	public static class AppThemeHelper
+	{
+		private static readonly IUserSettingsService _userSettingsService = Ioc.Default.GetRequiredService<IUserSettingsService>();
+
+		private static bool _isInitialized = false;
+
+		private static UISettings? uiSettings;
+
+		/// <summary>
+		/// Gets the UI theme mode that is used by the root window content for resource determination.
+		/// </summary>
+		/// <remarks>
+		/// The UI theme mode specified with RequestedTheme can override the app-level RequestedTheme.
+		/// </remarks>
+		public static ElementTheme RootTheme =>
+			!string.IsNullOrEmpty(_userSettingsService.AppearanceSettingsService.AppThemeMode)
+				? EnumExtensions.GetEnum<ElementTheme>(_userSettingsService.AppearanceSettingsService.AppThemeMode)
+				: ElementTheme.Default;
+
+		public static event EventHandler? ThemeModeChanged;
+
+		/// <summary>
+		/// Initializes a new <see cref="AppThemeHelper"/> instance.
+		/// </summary>
+		/// <remarks>
+		/// Once this class was initialized, this class doesn't need to be initialized again in somewhere else.
+		/// </remarks>
+		/// <returns>Returns true if initialization succeed; otherwise false.</returns>
+		public static bool Initialize()
+		{
+			if (_isInitialized)
+				return false;
+			else
+				_isInitialized = true;
+
+			// Apply the desired theme based on what is set in the application settings
+			ApplyTheme();
+
+			// Registering to color changes, thus we notice when user changes theme system wide
+			uiSettings = new UISettings();
+			uiSettings.ColorValuesChanged += UISettings_ColorValuesChanged;
+
+			return true;
+		}
+
+		/// <summary>
+		/// Refreshes theme mode.
+		/// </summary>
+		/// <remarks>
+		/// To reload the app resources, the theme will be toggled between dark and light, and the correct theme will be applied.
+		/// </remarks>
+		public static void RefreshThemeMode()
+		{
+			// Toggle between the themes to force reload the resource styles
+			ApplyTheme(MainWindow.Instance, ElementTheme.Dark);
+			ApplyTheme(MainWindow.Instance, ElementTheme.Light);
+
+			// Restore the theme to the correct theme
+			ApplyTheme();
+		}
+
+		/// <summary>
+		/// Applies theme mode to the requested theme of a specific window.
+		/// </summary>
+		/// <param name="window">A window whose requested theme will be changed.</param>
+		/// <param name="rootTheme">Requested theme mode</param>
+		/// <param name="executeChangedEvent">Determines if the event should be triggered. if the main window's requested theme will be changed, the event should be called</param>
+		public static void ApplyTheme(Window? window = null, ElementTheme? rootTheme = null, bool executeChangedEvent = true)
+		{
+			// Validate variables
+			window ??= MainWindow.Instance;
+			rootTheme ??= RootTheme;
+
+			// Set theme mode on the window
+			if (window.Content is FrameworkElement rootElement)
+				rootElement.RequestedTheme = (ElementTheme)rootTheme;
+
+			// Store theme mode setting
+			_userSettingsService.AppearanceSettingsService.AppThemeMode = rootTheme.ToString()!;
+
+			// Update title bar buttons color
+			var titleBar = window.AppWindow.TitleBar;
+			if (titleBar is not null)
+			{
+				// Remove normal state background
+				titleBar.ButtonBackgroundColor = Colors.Transparent;
+				titleBar.ButtonInactiveBackgroundColor = Colors.Transparent;
+
+				// Pointer over state background
+				titleBar.ButtonHoverBackgroundColor = rootTheme switch
+				{
+					ElementTheme.Light => titleBar.ButtonHoverBackgroundColor = Color.FromArgb(0x33, 0x00, 0x00, 0x00),
+					ElementTheme.Dark => titleBar.ButtonHoverBackgroundColor = Color.FromArgb(0x33, 0xFF, 0xFF, 0xFF),
+					_ => titleBar.ButtonHoverBackgroundColor = (Color)Application.Current.Resources["SystemBaseLowColor"],
+				};
+
+				// Pointer over state foreground
+				titleBar.ButtonForegroundColor = rootTheme switch
+				{
+					ElementTheme.Light => titleBar.ButtonHoverBackgroundColor = Colors.Black,
+					ElementTheme.Dark => titleBar.ButtonHoverBackgroundColor = Colors.White,
+					_ => titleBar.ButtonHoverBackgroundColor = (Color)Application.Current.Resources["SystemBaseHighColor"],
+				};
+			}
+
+			// Trigger theme mode changed event
+			if (executeChangedEvent)
+				ThemeModeChanged?.Invoke(null, EventArgs.Empty);
+		}
+
+		private static async void UISettings_ColorValuesChanged(UISettings sender, object args)
+		{
+			// Dispatch on UI thread so that we have a current app bar to access and change
+			await MainWindow.Instance.DispatcherQueue.EnqueueOrInvokeAsync(() => ApplyTheme());
+		}
+	}
+}