Code Quality: Introduce flexible pane generation 1

src/Files.App/Actions/Navigation/DuplicateCurrentTabAction.cs

@@ -24,7 +24,7 @@ public async Task ExecuteAsync(object? parameter = null)
 
 			if (arguments is null)
 			{
-				await NavigationHelpers.AddNewTabByPathAsync(typeof(PaneHolderPage), "Home", true);
+				await NavigationHelpers.AddNewTabByPathAsync(typeof(MainPanesPage), "Home", true);
 			}
 			else
 			{

src/Files.App/Actions/Navigation/DuplicateSelectedTabAction.cs

@@ -31,7 +31,7 @@ public async Task ExecuteAsync(object? parameter = null)
 
 			if (arguments is null)
 			{
-				await NavigationHelpers.AddNewTabByPathAsync(typeof(PaneHolderPage), "Home", true);
+				await NavigationHelpers.AddNewTabByPathAsync(typeof(MainPanesPage), "Home", true);
 			}
 			else
 			{

src/Files.App/Actions/Navigation/OpenDirectoryInNewTabAction.cs

@@ -43,7 +43,7 @@ public async Task ExecuteAsync(object? parameter = null)
 				await MainWindow.Instance.DispatcherQueue.EnqueueOrInvokeAsync(async () =>
 				{
 					await NavigationHelpers.AddNewTabByPathAsync(
-						typeof(PaneHolderPage),
+						typeof(MainPanesPage),
 						(listedItem as ShortcutItem)?.TargetPath ?? listedItem.ItemPath,
 						false);
 				},

src/Files.App/App.xaml.cs

@@ -217,7 +217,7 @@ private async void Window_Closed(object sender, WindowEventArgs args)
 				if (instance is null)
 					return;
 
-				var items = (instance.TabItemContent as PaneHolderPage)?.ActivePane?.SlimContentPage?.SelectedItems;
+				var items = (instance.TabItemContent as MainPanesPage)?.ActivePane?.SlimContentPage?.SelectedItems;
 				if (items is null)
 					return;
 

src/Files.App/Constants.cs

@@ -111,6 +111,8 @@ public static class UI
 
 			// For contextmenu hacks
 			public const double ContextMenuItemsMaxWidth = 250;
+
+			public const double MultiplePaneWidthThreshold = 750;
 		}
 
 		public static class Appearance

src/Files.App/Data/Contexts/ContentPage/ContentPageContext.cs

@@ -10,11 +10,11 @@ internal sealed class ContentPageContext : ObservableObject, IContentPageContext
 	{
 		private static readonly IReadOnlyList<ListedItem> emptyItems = Enumerable.Empty<ListedItem>().ToImmutableList();
 
-		private readonly IPageContext context = Ioc.Default.GetRequiredService<IPageContext>();
+		private readonly IMultiPanesContext context = Ioc.Default.GetRequiredService<IMultiPanesContext>();
 
 		private ItemViewModel? filesystemViewModel;
 
-		public IShellPage? ShellPage => context?.PaneOrColumn;
+		public IShellPage? ShellPage => context?.ActivePaneOrColumn;
 
 		public Type PageLayoutType => ShellPage?.CurrentPageType ?? typeof(DetailsLayoutPage);
 
@@ -55,8 +55,8 @@ internal sealed class ContentPageContext : ObservableObject, IContentPageContext
 
 		public ContentPageContext()
 		{
-			context.Changing += Context_Changing;
-			context.Changed += Context_Changed;
+			context.ActivePane_Changing += Context_Changing;
+			context.ActivePane_Changed += Context_Changed;
 			GitHelpers.IsExecutingGitActionChanged += GitHelpers_IsExecutingGitActionChanged;
 
 			Update();
@@ -122,14 +122,14 @@ private void Page_PropertyChanged(object? sender, PropertyChangedEventArgs e)
 			}
 		}
 
-		private void Page_ContentChanged(object? sender, CustomTabViewItemParameter e) => Update();
+		private void Page_ContentChanged(object? sender, TabBarItemParameter e) => Update();
 
 		private void PaneHolder_PropertyChanged(object? sender, PropertyChangedEventArgs e)
 		{
 			switch (e.PropertyName)
 			{
-				case nameof(IPaneHolder.IsMultiPaneEnabled):
-				case nameof(IPaneHolder.IsMultiPaneActive):
+				case nameof(IPanesPage.IsMultiPaneEnabled):
+				case nameof(IPanesPage.IsMultiPaneActive):
 					OnPropertyChanged(e.PropertyName);
 					break;
 			}

src/Files.App/Data/Contexts/DisplayPage/DisplayPageContext.cs

@@ -8,7 +8,7 @@ namespace Files.App.Data.Contexts
 {
 	internal sealed class DisplayPageContext : ObservableObject, IDisplayPageContext
 	{
-		private readonly IPageContext context = Ioc.Default.GetRequiredService<IPageContext>();
+		private readonly IMultiPanesContext context = Ioc.Default.GetRequiredService<IMultiPanesContext>();
 		private readonly IFoldersSettingsService settings = Ioc.Default.GetRequiredService<IFoldersSettingsService>();
 		private readonly ILayoutSettingsService layoutSettingsService = Ioc.Default.GetRequiredService<ILayoutSettingsService>();
 
@@ -125,12 +125,12 @@ public bool SortFilesFirst
 			}
 		}
 
-		private LayoutPreferencesManager? FolderSettings => context.PaneOrColumn?.InstanceViewModel?.FolderSettings;
+		private LayoutPreferencesManager? FolderSettings => context.ActivePaneOrColumn?.InstanceViewModel?.FolderSettings;
 
 		public DisplayPageContext()
 		{
-			context.Changing += Context_Changing;
-			context.Changed += Context_Changed;
+			context.ActivePane_Changing += Context_Changing;
+			context.ActivePane_Changed += Context_Changed;
 			layoutSettingsService.PropertyChanged += Settings_PropertyChanged;
 		}
 

src/Files.App/Data/Contexts/MultiPanes/IMultiPanesContext.cs

@@ -0,0 +1,31 @@
+// Copyright (c) 2024 Files Community
+// Licensed under the MIT License. See the LICENSE.
+
+namespace Files.App.Data.Contexts
+{
+	/// <summary>
+	/// Represents context for <see cref="MainPanesPage"/>, which manages multiple panes.
+	/// </summary>
+	public interface IMultiPanesContext
+	{
+		/// <summary>
+		/// Gets invoked when active pane is changing.
+		/// </summary>
+		event EventHandler? ActivePane_Changing;
+
+		/// <summary>
+		/// Gets invoked when active pane is changed.
+		/// </summary>
+		event EventHandler? ActivePane_Changed;
+
+		/// <summary>
+		/// Gets active pane.
+		/// </summary>
+		IShellPage? ActivePane { get; }
+
+		/// <summary>
+		/// Gets active pane or column.
+		/// </summary>
+		IShellPage? ActivePaneOrColumn { get; }
+	}
+}

src/Files.App/Data/Contexts/MultiPanes/MultiPanesContext.cs

@@ -0,0 +1,98 @@
+// Copyright (c) 2024 Files Community
+// Licensed under the MIT License. See the LICENSE.
+
+namespace Files.App.Data.Contexts
+{
+	/// <inheritdoc cref="IMultiPanesContext"/>
+	internal sealed class MultiPanesContext : IMultiPanesContext
+	{
+		private MainPanesPage? _mainPanesPage;
+
+		private IShellPage? _ActivePane;
+		/// <inheritdoc/>
+		public IShellPage? ActivePane
+			=> _ActivePane;
+
+		private IShellPage? _ActivePaneOrColumn;
+		/// <inheritdoc/>
+		public IShellPage? ActivePaneOrColumn
+			=> _ActivePaneOrColumn;
+
+		/// <inheritdoc/>
+		public event EventHandler? ActivePane_Changing;
+
+		/// <inheritdoc/>
+		public event EventHandler? ActivePane_Changed;
+
+		/// <summary>
+		/// Initializes an instance of <see cref="MultiPanesContext"/>.
+		/// </summary>
+		public MultiPanesContext()
+		{
+			MainPanesPage.CurrentInstanceChanged += Page_CurrentInstanceChanged;
+		}
+
+		private void Page_CurrentInstanceChanged(object? sender, MainPanesPage? modifiedPage)
+		{
+			if (_mainPanesPage is not null && !_mainPanesPage.IsCurrentInstance)
+			{
+				UpdatePage(null);
+			}
+			else if (modifiedPage is not null && modifiedPage.IsCurrentInstance)
+			{
+				UpdatePage(modifiedPage);
+			}
+		}
+
+		private void Page_ContentChanged(object? sender, TabBarItemParameter e)
+		{
+			UpdateContent();
+		}
+
+		private void Page_PropertyChanged(object? sender, PropertyChangedEventArgs e)
+		{
+			switch (e.PropertyName)
+			{
+				case nameof(IPanesPage.ActivePaneOrColumn):
+					UpdateContent();
+					break;
+			}
+		}
+
+		private void UpdatePage(MainPanesPage? newPage)
+		{
+			if (Equals(_mainPanesPage, newPage))
+				return;
+
+			if (_mainPanesPage is not null)
+			{
+				_mainPanesPage.ContentChanged -= Page_ContentChanged;
+				_mainPanesPage.PropertyChanged -= Page_PropertyChanged;
+			}
+
+			_mainPanesPage = newPage;
+
+			if (_mainPanesPage is not null)
+			{
+				_mainPanesPage.ContentChanged += Page_ContentChanged;
+				_mainPanesPage.PropertyChanged += Page_PropertyChanged;
+			}
+
+			UpdateContent();
+		}
+
+		private void UpdateContent()
+		{
+			if (_ActivePane == _mainPanesPage?.ActivePane &&
+				_ActivePaneOrColumn == _mainPanesPage?.ActivePaneOrColumn)
+				return;
+
+			ActivePane_Changing?.Invoke(this, EventArgs.Empty);
+
+			_ActivePane = _mainPanesPage?.ActivePane;
+			_ActivePaneOrColumn = _mainPanesPage?.ActivePaneOrColumn;
+
+			ActivePane_Changed?.Invoke(this, EventArgs.Empty);
+		}
+	}
+}

src/Files.App/Data/Contracts/IMultiPaneInfo.cs

@@ -0,0 +1,10 @@
+// Copyright (c) 2024 Files Community
+// Licensed under the MIT License. See the LICENSE.
+
+namespace Files.App.Data.Contracts
+{
+	public interface IMultiPaneInfo
+	{
+		public IPanesPage PaneHolder { get; }
+	}
+}

src/Files.App/Data/Contracts/IPanesPage.cs

@@ -0,0 +1,31 @@
+// Copyright (c) 2024 Files Community
+// Licensed under the MIT License. See the LICENSE.
+
+namespace Files.App.Data.Contracts
+{
+	public interface IPanesPage : IDisposable, INotifyPropertyChanged
+	{
+		public IShellPage? ActivePane { get; set; }
+
+		// If column view, returns the last column shell page, otherwise returns the active pane normally
+		public IShellPage? ActivePaneOrColumn { get; }
+
+		public IFilesystemHelpers? FilesystemHelpers { get; }
+
+		public TabBarItemParameter? TabBarItemParameter { get; set; }
+
+		public void OpenPathInNewPane(string path);
+
+		public void CloseActivePane();
+
+		public bool IsLeftPaneActive { get; }
+
+		public bool IsRightPaneActive { get; }
+
+		// Another pane is shown
+		public bool IsMultiPaneActive { get; }
+
+		// Multi pane is enabled
+		public bool IsMultiPaneEnabled { get; }
+	}
+}