Feature: Improved thumbnail placeholder performance (#18179)

Author: workbysaran

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

@@ -0,0 +1,12 @@
+// Copyright (c) Files Community
+// Licensed under the MIT License.
+
+namespace Files.App.Data.Contracts
+{
+	internal interface IIconCacheService
+	{
+		Task<byte[]?> GetIconAsync(string itemPath, string? extension, bool isFolder);
+
+		void Clear();
+	}
+}

src/Files.App/Data/Items/ListedItem.cs

@@ -30,6 +30,8 @@ public partial class ListedItem : ObservableObject, IGroupableItem, IListedItem
 
 		public StorageItemTypes PrimaryItemAttribute { get; set; }
 
+		public byte[]? PreloadedIconData { get; set; }
+
 		private volatile int itemPropertiesInitialized = 0;
 		public bool ItemPropertiesInitialized
 		{

src/Files.App/Helpers/Application/AppLifecycleHelper.cs

@@ -260,6 +260,7 @@ public static IHost ConfigureHost()
 					.AddSingleton<INetworkService, NetworkService>()
 					.AddSingleton<IStartMenuService, StartMenuService>()
 					.AddSingleton<IStorageCacheService, StorageCacheService>()
+					.AddSingleton<IIconCacheService, IconCacheService>()
 					.AddSingleton<IStorageArchiveService, StorageArchiveService>()
 					.AddSingleton<IStorageSecurityService, StorageSecurityService>()
 					.AddSingleton<IWindowsCompatibilityService, WindowsCompatibilityService>()

src/Files.App/Services/Storage/IconCacheService.cs

@@ -0,0 +1,47 @@
+// Copyright (c) Files Community
+// Licensed under the MIT License.
+
+using Files.Shared.Helpers;
+using System.Collections.Concurrent;
+using System.IO;
+
+namespace Files.App.Services
+{
+	internal sealed class IconCacheService : IIconCacheService
+	{
+		// Dummy path to generate generic icons for folders and executables.
+		private static readonly string _dummyPath = Path.Combine(Path.GetPathRoot(Environment.SystemDirectory)!, "x46696c6573");
+
+		private readonly ConcurrentDictionary<string, byte[]?> _cache = new();
+
+		public async Task<byte[]?> GetIconAsync(string itemPath, string? extension, bool isFolder)
+		{
+			var key = isFolder ? ":folder:" : (extension?.ToLowerInvariant() ?? ":noext:");
+
+			if (_cache.TryGetValue(key, out var cached))
+				return cached;
+
+			string iconPath;
+			if (isFolder)
+				iconPath = _dummyPath;
+			else if (FileExtensionHelpers.IsExecutableFile(extension))
+				iconPath = _dummyPath + extension;
+			else
+				iconPath = itemPath;
+
+			var icon = await FileThumbnailHelper.GetIconAsync(
+				iconPath,
+				Constants.ShellIconSizes.Jumbo,
+				isFolder,
+				IconOptions.ReturnIconOnly);
+
+			_cache.TryAdd(key, icon);
+			return icon;
+		}
+
+		public void Clear()
+		{
+			_cache.Clear();
+		}
+	}
+}

src/Files.App/Utils/Storage/Enumerators/Win32StorageEnumerator.cs

@@ -16,6 +16,8 @@ public static class Win32StorageEnumerator
 
 		private static readonly string folderTypeTextLocalized = Strings.Folder.GetLocalizedResource();
 
+		private static readonly IIconCacheService iconCacheService = Ioc.Default.GetRequiredService<IIconCacheService>();
+
 		public static async Task<List<ListedItem>> ListEntries(
 			string path,
 			IntPtr hFile,
@@ -49,6 +51,7 @@ Func<List<ListedItem>, Task> intermediateAction
 						var file = await GetFile(findData, path, isGitRepo, cancellationToken);
 						if (file is not null)
 						{
+							file.PreloadedIconData = await iconCacheService.GetIconAsync(file.ItemPath, file.FileExtension, false);
 							tempList.Add(file);
 							++count;
 
@@ -65,6 +68,7 @@ Func<List<ListedItem>, Task> intermediateAction
 							var folder = await GetFolder(findData, path, isGitRepo, cancellationToken);
 							if (folder is not null)
 							{
+								folder.PreloadedIconData = await iconCacheService.GetIconAsync(folder.ItemPath, null, true);
 								tempList.Add(folder);
 								++count;
 

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

@@ -1241,6 +1241,9 @@ private void RefreshItem(SelectorItem container, object item, bool inRecycleQueu
 			{
 				InitializeDrag(container, listedItem);
 
+				if (listedItem.PreloadedIconData is not null && listedItem.FileImage is null)
+					_ = ApplyPreloadedIconAsync(listedItem);
+
 				if (!listedItem.ItemPropertiesInitialized)
 				{
 					uint callbackPhase = 3;
@@ -1254,6 +1257,13 @@ private void RefreshItem(SelectorItem container, object item, bool inRecycleQueu
 			}
 		}
 
+		private static async Task ApplyPreloadedIconAsync(ListedItem item)
+		{
+			var image = await item.PreloadedIconData.ToBitmapAsync();
+			if (image is not null)
+				item.FileImage = image;
+		}
+
 		protected internal void FileListItem_PointerPressed(object sender, PointerRoutedEventArgs e)
 		{
 			// Set can window to front and bring the window to the front if necessary (#13255)