Feature: Added an option to keep Files running in the background for quicker startup time

src/Files.App/App.xaml.cs

@@ -21,6 +21,7 @@
 using Microsoft.Extensions.Logging;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Media.Animation;
 using Microsoft.Windows.AppLifecycle;
 using System.IO;
 using System.Text;
@@ -40,7 +41,7 @@ public partial class App : Application
 		private static bool ShowErrorNotification = false;
 		public static string OutputPath { get; set; }
 		public static CommandBarFlyout? LastOpenedFlyout { get; set; }
-		public static TaskCompletionSource? SplashScreenLoadingTCS { get; set; }
+		public static TaskCompletionSource? SplashScreenLoadingTCS { get; private set; }
 
 		public static StorageHistoryWrapper HistoryWrapper { get; } = new();
 		public static AppModel AppModel { get; private set; }
@@ -300,6 +301,34 @@ private async void Window_Closed(object sender, WindowEventArgs args)
 				return;
 			}
 
+			if (Ioc.Default.GetRequiredService<IUserSettingsService>().GeneralSettingsService.LeaveAppRunning)
+			{
+				// Cache the window istead of closing it
+				MainWindow.Instance.AppWindow.Hide();
+				args.Handled = true;
+
+				// Save and close all tabs
+				SaveSessionTabs();
+				MainPageViewModel.AppInstances.ForEach(tabItem => tabItem.Unload());
+				MainPageViewModel.AppInstances.Clear();
+				await Task.Delay(100);
+
+				// Wait for all properties windows to close
+				await FilePropertiesHelpers.WaitClosingAll();
+
+				Program.Pool = new(0, 1, "Files-Instance");
+				Thread.Yield();
+				if (Program.Pool.WaitOne())
+				{
+					Program.Pool.Dispose();
+					MainWindow.Instance.AppWindow.Show();
+					MainWindow.Instance.Activate();
+					MainWindow.Instance.EnsureWindowIsInitialized().Navigate(typeof(MainPage), null, new SuppressNavigationTransitionInfo());
+				}
+
+				return;
+			}
+
 			// Method can take a long time, make sure the window is hidden
 			await Task.Yield();
 

src/Files.App/Data/Contexts/Multitasking/MultitaskingContext.cs

@@ -1,13 +1,10 @@
 // Copyright (c) 2023 Files Community
 // Licensed under the MIT License. See the LICENSE.
 
-using CommunityToolkit.Mvvm.ComponentModel;
 using Files.App.UserControls.MultitaskingControl;
-using Files.App.ViewModels;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Input;
 using System.Collections.Specialized;
-using System.ComponentModel;
 
 namespace Files.App.Data.Contexts
 {
@@ -46,7 +43,8 @@ private void AppInstances_CollectionChanged(object? sender, NotifyCollectionChan
 		}
 		private void AppModel_PropertyChanged(object? sender, PropertyChangedEventArgs e)
 		{
-			UpdateCurrentTabIndex();
+			if (e.PropertyName is nameof(AppModel.TabStripSelectedIndex))
+				UpdateCurrentTabIndex();
 		}
 		private void BaseMultitaskingControl_OnLoaded(object? sender, IMultitaskingControl control)
 		{

src/Files.App/Data/Models/AppModel.cs

@@ -33,19 +33,13 @@ public int TabStripSelectedIndex
 			get => tabStripSelectedIndex;
 			set
 			{
-				if (value >= 0)
-				{
-					if (tabStripSelectedIndex != value)
-					{
-						SetProperty(ref tabStripSelectedIndex, value);
-					}
+				SetProperty(ref tabStripSelectedIndex, value);
 
-					if (value < MainPageViewModel.AppInstances.Count)
-					{
-						Frame rootFrame = (Frame)MainWindow.Instance.Content;
-						var mainView = (MainPage)rootFrame.Content;
-						mainView.ViewModel.SelectedTabItem = MainPageViewModel.AppInstances[value];
-					}
+				if (value >= 0 && value < MainPageViewModel.AppInstances.Count)
+				{
+					Frame rootFrame = (Frame)MainWindow.Instance.Content;
+					var mainView = (MainPage)rootFrame.Content;
+					mainView.ViewModel.SelectedTabItem = MainPageViewModel.AppInstances[value];
 				}
 			}
 		}

src/Files.App/MainWindow.xaml.cs

@@ -4,11 +4,11 @@
 using Files.App.UserControls.MultitaskingControl;
 using Microsoft.UI;
 using Microsoft.UI.Windowing;
+using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
 using Microsoft.UI.Xaml.Media.Animation;
 using Microsoft.UI.Xaml.Navigation;
 using System.IO;
-using System.Runtime.InteropServices;
 using Windows.ApplicationModel;
 using Windows.ApplicationModel.Activation;
 using Windows.Storage;
@@ -176,7 +176,7 @@ public async Task InitializeApplication(object activatedEventArgs)
 				rootFrame.Navigate(typeof(MainPage), null, new SuppressNavigationTransitionInfo());
 		}
 
-		private Frame EnsureWindowIsInitialized()
+		public Frame EnsureWindowIsInitialized()
 		{
 			// NOTE:
 			//  Do not repeat app initialization when the Window already has content,

src/Files.App/Program.cs

@@ -14,6 +14,19 @@ namespace Files.App
 {
 	internal class Program
 	{
+		public static Semaphore Pool;
+
+		static Program()
+		{
+			Pool = new(0, 1, "Files-Instance", out var isNew);
+			if (!isNew)
+			{
+				Pool.Release();
+				Environment.Exit(0);
+			}
+			Pool.Dispose();
+		}
+
 		// Note:
 		//  We can't declare Main to be async because in a WinUI app
 		//  This prevents Narrator from reading XAML elements

src/Files.App/Services/Settings/GeneralSettingsService.cs

@@ -208,6 +208,12 @@ public bool ShowOpenInNewPane
 			set => Set(value);
 		}
 
+		public bool LeaveAppRunning
+		{
+			get => Get(false);
+			set => Set(value);
+		}
+
 		public FileNameConflictResolveOptionType ConflictsResolveOption
 		{
 			get => (FileNameConflictResolveOptionType)Get((long)FileNameConflictResolveOptionType.GenerateNewName);

src/Files.App/Strings/en-US/Resources.resw

@@ -3447,4 +3447,7 @@
   <data name="FilesRunningAsAdminContent" xml:space="preserve">
     <value>Due to platform limitations, drag and drop isn't available when running Files as administrator.</value>
   </data>
+  <data name="SettingsLeaveAppRunning" xml:space="preserve">
+    <value>Leave app running in the background when the window is closed</value>
+  </data>
 </root>

src/Files.App/Utils/Storage/Helpers/FilePropertiesHelpers.cs

@@ -31,6 +31,8 @@ public static class FilePropertiesHelpers
 		public static nint GetWindowHandle(Window w)
 			=> WinRT.Interop.WindowNative.GetWindowHandle(w);
 
+		private static int WindowCount = 0;
+		private static TaskCompletionSource? PropertiesWindowsClosingTCS;
 		private static BlockingCollection<WinUIEx.WindowEx> WindowCache = new();
 
 		/// <summary>
@@ -140,8 +142,10 @@ public static void OpenPropertiesWindow(object item, IShellPage associatedInstan
 					+ Math.Max(0, Math.Min(displayArea.WorkArea.Height - appWindow.Size.Height, pointerPosition.Y - displayArea.WorkArea.Y)),
 			};
 
-			appWindow.Move(appWindowPos);
+			if (Interlocked.Increment(ref WindowCount) == 1)
+				PropertiesWindowsClosingTCS = new();
 
+			appWindow.Move(appWindowPos);
 			appWindow.Show();
 		}
 
@@ -156,9 +160,19 @@ private static void PropertiesWindow_Closed(object sender, WindowEventArgs args)
 				window.AppWindow.Hide();
 				window.Content = null;
 				WindowCache.Add(window);
+
+				if (Interlocked.Decrement(ref WindowCount) == 0)
+				{
+					PropertiesWindowsClosingTCS!.TrySetResult();
+					PropertiesWindowsClosingTCS = null;
+				}
 			}
 		}
 
+		/// <summary>
+		/// Destroy all cached properties windows
+		/// </summary>
+		/// <returns></returns>
 		public static void DestroyCachedWindows()
 		{
 			while (WindowCache.TryTake(out var window))
@@ -167,5 +181,11 @@ public static void DestroyCachedWindows()
 				window.Close();
 			}
 		}
+
+		/// <summary>
+		/// Returns task to wait for all properties windows to close
+		/// </summary>
+		/// <returns>Task to wait</returns>
+		public static Task WaitClosingAll() => PropertiesWindowsClosingTCS?.Task ?? Task.CompletedTask;
 	}
 }

src/Files.App/ViewModels/Settings/AdvancedViewModel.cs

@@ -297,6 +297,20 @@ public bool CanOpenOnWindowsStartup
 			set => SetProperty(ref canOpenOnWindowsStartup, value);
 		}
 
+		public bool LeaveAppRunning
+		{
+			get => UserSettingsService.GeneralSettingsService.LeaveAppRunning;
+			set
+			{
+				if (value != UserSettingsService.GeneralSettingsService.LeaveAppRunning)
+				{
+					UserSettingsService.GeneralSettingsService.LeaveAppRunning = value;
+
+					OnPropertyChanged();
+				}
+			}
+		}
+
 		public async Task OpenFilesOnWindowsStartup()
 		{
 			var stateMode = await ReadState();

src/Files.App/Views/Properties/MainPropertiesPage.xaml.cs

@@ -1,20 +1,13 @@
 // Copyright (c) 2023 Files Community
 // Licensed under the MIT License. See the LICENSE.
 
-using CommunityToolkit.Mvvm.DependencyInjection;
-using CommunityToolkit.WinUI;
-using Files.App.Data.Parameters;
-using Files.App.Helpers;
-using Files.App.ViewModels;
 using Files.App.ViewModels.Properties;
 using Microsoft.UI;
 using Microsoft.UI.Windowing;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
 using Microsoft.UI.Xaml.Input;
 using Microsoft.UI.Xaml.Navigation;
-using System;
-using System.Threading.Tasks;
 using Windows.System;
 using Windows.UI;
 
@@ -45,16 +38,15 @@ protected override void OnNavigatedTo(NavigationEventArgs e)
 			AppWindow = parameter.AppWindow;
 			Window = parameter.Window;
 
-			AppSettings = Ioc.Default.GetRequiredService<SettingsViewModel>();
-			AppSettings.ThemeModeChanged += AppSettings_ThemeModeChanged;
-
 			base.OnNavigatedTo(e);
 
 			MainPropertiesViewModel = new(Window, AppWindow, MainContentFrame, BaseProperties, parameter);
 		}
 
 		private void Page_Loaded(object sender, RoutedEventArgs e)
 		{
+			AppSettings = Ioc.Default.GetRequiredService<SettingsViewModel>();
+			AppSettings.ThemeModeChanged += AppSettings_ThemeModeChanged;
 			Window.Closed += Window_Closed;
 
 			UpdatePageLayout();
@@ -89,6 +81,9 @@ private void UpdatePageLayout()
 
 		private async void AppSettings_ThemeModeChanged(object? sender, EventArgs e)
 		{
+			if (Parent is null)
+				return;
+
 			await DispatcherQueue.EnqueueOrInvokeAsync(() =>
 			{
 				((Frame)Parent).RequestedTheme = ThemeHelper.RootTheme;

src/Files.App/Views/Settings/AdvancedPage.xaml

@@ -98,6 +98,17 @@
 				</ToggleSwitch>
 			</local:SettingsBlockControl>
 
+			<!--  Leave App Running  -->
+			<local:SettingsBlockControl Title="{helpers:ResourceString Name=SettingsLeaveAppRunning}" HorizontalAlignment="Stretch">
+				<local:SettingsBlockControl.Icon>
+					<FontIcon Glyph="&#xE708;" />
+				</local:SettingsBlockControl.Icon>
+				<ToggleSwitch
+					AutomationProperties.Name="{helpers:ResourceString Name=SettingsLeaveAppRunning}"
+					IsOn="{x:Bind ViewModel.LeaveAppRunning, Mode=TwoWay}"
+					Style="{StaticResource RightAlignedToggleSwitchStyle}" />
+			</local:SettingsBlockControl>
+
 			<!--  Experimental Settings  -->
 			<TextBlock
 				Padding="0,16,0,4"

src/Files.Core/Services/Settings/IGeneralSettingsService.cs

@@ -169,6 +169,11 @@ public interface IGeneralSettingsService : IBaseSettingsService, INotifyProperty
 		/// </summary>
 		bool ShowSendToMenu { get; set; }
 
+		/// <summary>
+		/// Gets or sets a value indicating whether or not to leave app running in the background.
+		/// </summary>
+		bool LeaveAppRunning { get; set; }
+
 		/// <summary>
 		/// Gets or sets a value indicating the default option to resolve conflicts.
 		/// </summary>