Feature: Improved behavior when dragging items from an unfocused Files window (#16508)

Author: Jack251970

src/Files.App.CsWin32/Windows.Win32.Extras.cs

@@ -16,5 +16,51 @@ namespace UI.WindowsAndMessaging
 	{
 		[UnmanagedFunctionPointer(CallingConvention.Winapi)]
 		public delegate LRESULT WNDPROC(HWND hWnd, uint msg, WPARAM wParam, LPARAM lParam);
+
+		/// <summary>Contains information about the size and position of a window.</summary>
+		/// <remarks>
+		/// <para><see href="https://learn.microsoft.com/windows/win32/api/winuser/ns-winuser-windowpos">Learn more about this API from docs.microsoft.com</see>.</para>
+		/// </remarks>
+		public partial struct WINDOWPOS
+		{
+			/// <summary>
+			/// <para>Type: <b>HWND</b> A handle to the window.</para>
+			/// <para><see href="https://learn.microsoft.com/windows/win32/api/winuser/ns-winuser-windowpos#members">Read more on docs.microsoft.com</see>.</para>
+			/// </summary>
+			internal HWND hwnd;
+
+			/// <summary>
+			/// <para>Type: <b>HWND</b> The position of the window in Z order (front-to-back position). This member can be a handle to the window behind which this window is placed, or can be one of the special values listed with the <a href="https://docs.microsoft.com/windows/desktop/api/winuser/nf-winuser-setwindowpos">SetWindowPos</a> function.</para>
+			/// <para><see href="https://learn.microsoft.com/windows/win32/api/winuser/ns-winuser-windowpos#members">Read more on docs.microsoft.com</see>.</para>
+			/// </summary>
+			internal HWND hwndInsertAfter;
+
+			/// <summary>
+			/// <para>Type: <b>int</b> The position of the left edge of the window.</para>
+			/// <para><see href="https://learn.microsoft.com/windows/win32/api/winuser/ns-winuser-windowpos#members">Read more on docs.microsoft.com</see>.</para>
+			/// </summary>
+			internal int x;
+
+			/// <summary>
+			/// <para>Type: <b>int</b> The position of the top edge of the window.</para>
+			/// <para><see href="https://learn.microsoft.com/windows/win32/api/winuser/ns-winuser-windowpos#members">Read more on docs.microsoft.com</see>.</para>
+			/// </summary>
+			internal int y;
+
+			/// <summary>
+			/// <para>Type: <b>int</b> The window width, in pixels.</para>
+			/// <para><see href="https://learn.microsoft.com/windows/win32/api/winuser/ns-winuser-windowpos#members">Read more on docs.microsoft.com</see>.</para>
+			/// </summary>
+			internal int cx;
+
+			/// <summary>
+			/// <para>Type: <b>int</b> The window height, in pixels.</para>
+			/// <para><see href="https://learn.microsoft.com/windows/win32/api/winuser/ns-winuser-windowpos#members">Read more on docs.microsoft.com</see>.</para>
+			/// </summary>
+			internal int cy;
+
+			/// <summary>Type: <b>UINT</b></summary>
+			public SET_WINDOW_POS_FLAGS flags;
+		}
 	}
 }

src/Files.App/Helpers/Win32/Win32Helper.WindowManagement.cs

@@ -4,6 +4,7 @@
 using Microsoft.UI.Input;
 using Microsoft.UI.Xaml;
 using System.Reflection;
+using System.Runtime.InteropServices;
 using Windows.Win32;
 using Windows.Win32.UI.WindowsAndMessaging;
 
@@ -58,5 +59,16 @@ public static void ChangeCursor(this UIElement uiElement, InputCursor cursor)
 				[cursor]
 			);
 		}
+
+		/// <summary>
+		/// Force window to stay at bottom of other upper windows.
+		/// </summary>
+		/// <param name="lParam">The lParam of the message.</param>
+		public static void ForceWindowPosition(nint lParam)
+		{
+			var windowPos = Marshal.PtrToStructure<WINDOWPOS>(lParam);
+			windowPos.flags |= SET_WINDOW_POS_FLAGS.SWP_NOZORDER;
+			Marshal.StructureToPtr(windowPos, lParam, false);
+		}
 	}
 }

src/Files.App/MainWindow.xaml.cs

@@ -19,6 +19,8 @@ public sealed partial class MainWindow : WinUIEx.WindowEx
 		public static MainWindow Instance => _Instance ??= new();
 
 		public nint WindowHandle { get; }
+		private bool CanWindowToFront { get; set; } = true;
+		private readonly object _canWindowToFrontLock = new();
 
 		public MainWindow()
 		{
@@ -35,6 +37,8 @@ public MainWindow()
 			AppWindow.TitleBar.ButtonPressedBackgroundColor = Colors.Transparent;
 			AppWindow.TitleBar.ButtonHoverBackgroundColor = Colors.Transparent;
 			AppWindow.SetIcon(AppLifecycleHelper.AppIconPath);
+
+			WinUIEx.WindowManager.Get(this).WindowMessageReceived += WindowManager_WindowMessageReceived;
 		}
 
 		public void ShowSplashScreen()
@@ -339,5 +343,28 @@ x.tabItem.NavigationParameter.NavigationParameter is PaneNavigationArguments pan
 				}
 			}
 		}
+
+		public bool SetCanWindowToFront(bool canWindowToFront)
+		{
+			lock (_canWindowToFrontLock)
+			{
+				if (CanWindowToFront != canWindowToFront)
+				{
+					CanWindowToFront = canWindowToFront;
+					return true;
+				}
+				return false;
+			}
+		}
+
+		private const int WM_WINDOWPOSCHANGING = 0x0046;
+		private void WindowManager_WindowMessageReceived(object? sender, WinUIEx.Messaging.WindowMessageEventArgs e)
+		{
+			if ((!CanWindowToFront) && e.Message.MessageId == WM_WINDOWPOSCHANGING)
+			{
+				Win32Helper.ForceWindowPosition(e.Message.LParam);
+				e.Handled = true;
+			}
+		}
 	}
 }

src/Files.App/Views/Layouts/BaseLayoutPage.cs

@@ -66,6 +66,7 @@ public abstract class BaseLayoutPage : Page, IBaseLayoutPage, INotifyPropertyCha
 		private CancellationTokenSource? groupingCancellationToken;
 
 		private bool shiftPressed;
+		private bool itemDragging;
 
 		private ListedItem? dragOverItem = null;
 		private ListedItem? hoveredItem = null;
@@ -1012,13 +1013,23 @@ protected virtual void FileList_DragItemsStarting(object sender, DragItemsStarti
 					var storageItemList = orderedItems.Where(x => !(x.IsHiddenItem && x.IsLinkItem && x.IsRecycleBinItem && x.IsShortcut)).Select(x => VirtualStorageItem.FromListedItem(x));
 					e.Data.SetStorageItems(storageItemList, false);
 				}
+
+				MainWindow.Instance.SetCanWindowToFront(false);
+				itemDragging = true;
 			}
 			catch (Exception)
 			{
 				e.Cancel = true;
 			}
 		}
 
+		protected virtual void FileList_DragItemsCompleted(ListViewBase sender, DragItemsCompletedEventArgs args)
+		{
+			itemDragging = false;
+			MainWindow.Instance.SetCanWindowToFront(true);
+			// No need to bring the window to the front
+		}
+
 		private void Item_DragLeave(object sender, DragEventArgs e)
 		{
 			var item = GetItemFromElement(sender);
@@ -1147,13 +1158,19 @@ protected void FileList_ContainerContentChanging(ListViewBase sender, ContainerC
 		{
 			RefreshContainer(args.ItemContainer, args.InRecycleQueue);
 			RefreshItem(args.ItemContainer, args.Item, args.InRecycleQueue, args);
+
+			itemDragging = false;
+			MainWindow.Instance.SetCanWindowToFront(true);
+			// No need to bring the window to the front
 		}
 
 		private void RefreshContainer(SelectorItem container, bool inRecycleQueue)
 		{
 			container.PointerPressed -= FileListItem_PointerPressed;
 			container.PointerEntered -= FileListItem_PointerEntered;
 			container.PointerExited -= FileListItem_PointerExited;
+			container.Tapped -= FileListItem_Tapped;
+			container.DoubleTapped -= FileListItem_DoubleTapped;
 			container.RightTapped -= FileListItem_RightTapped;
 
 			if (inRecycleQueue)
@@ -1163,12 +1180,11 @@ private void RefreshContainer(SelectorItem container, bool inRecycleQueue)
 			else
 			{
 				container.PointerPressed += FileListItem_PointerPressed;
+				container.PointerEntered += FileListItem_PointerEntered;
+				container.PointerExited += FileListItem_PointerExited;
+				container.Tapped += FileListItem_Tapped;
+				container.DoubleTapped += FileListItem_DoubleTapped;
 				container.RightTapped += FileListItem_RightTapped;
-				if (UserSettingsService.FoldersSettingsService.SelectFilesOnHover)
-				{
-					container.PointerEntered += FileListItem_PointerEntered;
-					container.PointerExited += FileListItem_PointerExited;
-				}
 			}
 		}
 
@@ -1200,6 +1216,10 @@ private void RefreshItem(SelectorItem container, object item, bool inRecycleQueu
 
 		protected internal void FileListItem_PointerPressed(object sender, PointerRoutedEventArgs e)
 		{
+			// Set can window to front and bring the window to the front if necessary
+			if ((!itemDragging) && MainWindow.Instance.SetCanWindowToFront(true))
+				Win32Helper.BringToForegroundEx(new(MainWindow.Instance.WindowHandle));
+
 			if (sender is not SelectorItem selectorItem)
 				return;
 
@@ -1225,6 +1245,10 @@ protected internal void FileListItem_PointerPressed(object sender, PointerRouted
 
 		protected internal void FileListItem_PointerEntered(object sender, PointerRoutedEventArgs e)
 		{
+			// Set can window to front before the item is dragged
+			if (sender is SelectorItem selectorItem && selectorItem.IsSelected)
+				MainWindow.Instance.SetCanWindowToFront(false);
+
 			if (!UserSettingsService.FoldersSettingsService.SelectFilesOnHover)
 				return;
 
@@ -1271,15 +1295,37 @@ selectedItems is not null &&
 
 		protected internal void FileListItem_PointerExited(object sender, PointerRoutedEventArgs e)
 		{
+			// Set can window to front
+			if (!itemDragging)
+				MainWindow.Instance.SetCanWindowToFront(true);
+
 			if (!UserSettingsService.FoldersSettingsService.SelectFilesOnHover)
 				return;
 
 			hoverTimer.Stop();
 			hoveredItem = null;
 		}
 
+		protected void FileListItem_Tapped(object sender, TappedRoutedEventArgs e)
+		{
+			// Set can window to front and bring the window to the front if necessary
+			if ((!itemDragging) && MainWindow.Instance.SetCanWindowToFront(true))
+				Win32Helper.BringToForegroundEx(new(MainWindow.Instance.WindowHandle));
+		}
+
+		protected void FileListItem_DoubleTapped(object sender, DoubleTappedRoutedEventArgs e)
+		{
+			// Set can window to front and bring the window to the front if necessary
+			if ((!itemDragging) && MainWindow.Instance.SetCanWindowToFront(true))
+				Win32Helper.BringToForegroundEx(new(MainWindow.Instance.WindowHandle));
+		}
+
 		protected void FileListItem_RightTapped(object sender, RightTappedRoutedEventArgs e)
 		{
+			// Set can window to front and bring the window to the front if necessary
+			if ((!itemDragging) && MainWindow.Instance.SetCanWindowToFront(true))
+				Win32Helper.BringToForegroundEx(new(MainWindow.Instance.WindowHandle));
+
 			var rightClickedItem = GetItemFromElement(sender);
 
 			if (rightClickedItem is not null && !((SelectorItem)sender).IsSelected)

src/Files.App/Views/Layouts/ColumnLayoutPage.xaml

@@ -183,6 +183,7 @@
 					CanDragItems="{x:Bind AllowItemDrag, Mode=OneWay}"
 					ContainerContentChanging="FileList_ContainerContentChanging"
 					DoubleTapped="FileList_DoubleTapped"
+					DragItemsCompleted="FileList_DragItemsCompleted"
 					DragItemsStarting="FileList_DragItemsStarting"
 					DragOver="ItemsLayout_DragOver"
 					Drop="ItemsLayout_Drop"

src/Files.App/Views/Layouts/DetailsLayoutPage.xaml

@@ -229,6 +229,7 @@
 					CanDragItems="{x:Bind AllowItemDrag, Mode=OneWay}"
 					ContainerContentChanging="FileList_ContainerContentChanging"
 					DoubleTapped="FileList_DoubleTapped"
+					DragItemsCompleted="FileList_DragItemsCompleted"
 					DragItemsStarting="FileList_DragItemsStarting"
 					DragOver="ItemsLayout_DragOver"
 					Drop="ItemsLayout_Drop"

src/Files.App/Views/Layouts/GridLayoutPage.xaml

@@ -787,6 +787,7 @@
 					ContainerContentChanging="FileList_ContainerContentChanging"
 					DoubleTapped="FileList_DoubleTapped"
 					DragEnter="ItemsLayout_DragEnter"
+					DragItemsCompleted="FileList_DragItemsCompleted"
 					DragItemsStarting="FileList_DragItemsStarting"
 					DragLeave="ItemsLayout_DragLeave"
 					DragOver="ItemsLayout_DragOver"