feat.启动器图片自定义

.trae/specs/launcher-shell-hardening/startup-visuals-addendum.md

@@ -19,6 +19,14 @@
 - `EnableSlideTransition = false && EnableFadeTransition = false` resolves to `StartupVisualMode.StaticSplash`.
 - `EnableSlideTransition = false && EnableFadeTransition = true` resolves to `StartupVisualMode.Fade`.
 
+## Launcher custom splash image
+
+- The hidden Launcher debug menu owns the splash image picker.
+- Saving an image copies it into `.Launcher` as `Launcher Picture.<ext>` and clears the in-memory image cache.
+- Invalid, unsupported, or oversized images must not overwrite the existing managed image.
+- Splash image rendering uses `Uniform` fitting so the full image remains visible.
+- The self-drawn Splash shell uses fixed Fluent corner tokens: `8px` outer radius and `4px` control radius.
+
 ## UX safeguards
 
 - If the host process is still alive at failure time, the failure dialog must prefer:

LanMountainDesktop.Launcher/Resources/Strings.cs

@@ -105,6 +105,17 @@ public static class Strings
     public static string DebugDebug_ButtonCancel => ResourceManager.GetString(nameof(DebugDebug_ButtonCancel), Culture)!;
     public static string DebugDebug_ButtonOk => ResourceManager.GetString(nameof(DebugDebug_ButtonOk), Culture)!;
     public static string DebugDebug_SelectExeDialog => ResourceManager.GetString(nameof(DebugDebug_SelectExeDialog), Culture)!;
+    public static string DebugDebug_BackgroundImage => ResourceManager.GetString(nameof(DebugDebug_BackgroundImage), Culture)!;
+    public static string DebugDebug_BackgroundImageDesc => ResourceManager.GetString(nameof(DebugDebug_BackgroundImageDesc), Culture)!;
+    public static string DebugDebug_BackgroundImageNotSet => ResourceManager.GetString(nameof(DebugDebug_BackgroundImageNotSet), Culture)!;
+    public static string DebugDebug_BackgroundImageSaved => ResourceManager.GetString(nameof(DebugDebug_BackgroundImageSaved), Culture)!;
+    public static string DebugDebug_BackgroundImageCleared => ResourceManager.GetString(nameof(DebugDebug_BackgroundImageCleared), Culture)!;
+    public static string DebugDebug_BackgroundImageSaveFailedFormat => ResourceManager.GetString(nameof(DebugDebug_BackgroundImageSaveFailedFormat), Culture)!;
+    public static string DebugDebug_BackgroundImageReadyFormat => ResourceManager.GetString(nameof(DebugDebug_BackgroundImageReadyFormat), Culture)!;
+    public static string DebugDebug_BackgroundImageInvalidFormat => ResourceManager.GetString(nameof(DebugDebug_BackgroundImageInvalidFormat), Culture)!;
+    public static string DebugDebug_Clear => ResourceManager.GetString(nameof(DebugDebug_Clear), Culture)!;
+    public static string DebugDebug_SelectImageDialog => ResourceManager.GetString(nameof(DebugDebug_SelectImageDialog), Culture)!;
+    public static string DebugDebug_ImageFiles => ResourceManager.GetString(nameof(DebugDebug_ImageFiles), Culture)!;
     public static string Oobe_Title => ResourceManager.GetString(nameof(Oobe_Title), Culture)!;
     public static string Oobe_WelcomeTitle => ResourceManager.GetString(nameof(Oobe_WelcomeTitle), Culture)!;
     public static string Oobe_WelcomeSubtitle => ResourceManager.GetString(nameof(Oobe_WelcomeSubtitle), Culture)!;

LanMountainDesktop.Launcher/Resources/Strings.en-US.resx

@@ -119,6 +119,17 @@
   <data name="DebugDebug_ButtonCancel" xml:space="preserve"><value>Cancel</value></data>
   <data name="DebugDebug_ButtonOk" xml:space="preserve"><value>OK</value></data>
   <data name="DebugDebug_SelectExeDialog" xml:space="preserve"><value>Select LanMountainDesktop host executable</value></data>
+  <data name="DebugDebug_BackgroundImage" xml:space="preserve"><value>Splash image</value></data>
+  <data name="DebugDebug_BackgroundImageDesc" xml:space="preserve"><value>Choose an image to show on the splash screen. It will be copied into the Launcher data directory.</value></data>
+  <data name="DebugDebug_BackgroundImageNotSet" xml:space="preserve"><value>No splash image selected</value></data>
+  <data name="DebugDebug_BackgroundImageSaved" xml:space="preserve"><value>Splash image saved. The current splash screen will refresh immediately.</value></data>
+  <data name="DebugDebug_BackgroundImageCleared" xml:space="preserve"><value>Splash image cleared.</value></data>
+  <data name="DebugDebug_BackgroundImageSaveFailedFormat" xml:space="preserve"><value>Image setting failed: {0}</value></data>
+  <data name="DebugDebug_BackgroundImageReadyFormat" xml:space="preserve"><value>Current splash image is ready ({0} x {1}).</value></data>
+  <data name="DebugDebug_BackgroundImageInvalidFormat" xml:space="preserve"><value>Current splash image is unavailable: {0}</value></data>
+  <data name="DebugDebug_Clear" xml:space="preserve"><value>Clear</value></data>
+  <data name="DebugDebug_SelectImageDialog" xml:space="preserve"><value>Select splash image</value></data>
+  <data name="DebugDebug_ImageFiles" xml:space="preserve"><value>Image files</value></data>
   <data name="Oobe_Title" xml:space="preserve"><value>Welcome to LanMountain Desktop</value></data>
   <data name="Oobe_WelcomeTitle" xml:space="preserve"><value>Welcome to LanMountain Desktop</value></data>
   <data name="Oobe_WelcomeSubtitle" xml:space="preserve"><value>Your desktop, more than one side</value></data>

LanMountainDesktop.Launcher/Resources/Strings.ja-JP.resx

@@ -119,6 +119,17 @@
   <data name="DebugDebug_ButtonCancel" xml:space="preserve"><value>キャンセル</value></data>
   <data name="DebugDebug_ButtonOk" xml:space="preserve"><value>OK</value></data>
   <data name="DebugDebug_SelectExeDialog" xml:space="preserve"><value>蘭山デスクトップホスト実行可能ファイルを選択</value></data>
+  <data name="DebugDebug_BackgroundImage" xml:space="preserve"><value>スプラッシュ画像</value></data>
+  <data name="DebugDebug_BackgroundImageDesc" xml:space="preserve"><value>起動画面に表示する画像を選択します。画像は Launcher のデータディレクトリにコピーされます。</value></data>
+  <data name="DebugDebug_BackgroundImageNotSet" xml:space="preserve"><value>スプラッシュ画像は未設定です</value></data>
+  <data name="DebugDebug_BackgroundImageSaved" xml:space="preserve"><value>スプラッシュ画像を保存しました。現在の起動画面はすぐに更新されます。</value></data>
+  <data name="DebugDebug_BackgroundImageCleared" xml:space="preserve"><value>スプラッシュ画像をクリアしました。</value></data>
+  <data name="DebugDebug_BackgroundImageSaveFailedFormat" xml:space="preserve"><value>画像設定に失敗しました: {0}</value></data>
+  <data name="DebugDebug_BackgroundImageReadyFormat" xml:space="preserve"><value>現在のスプラッシュ画像は使用できます（{0} x {1}）。</value></data>
+  <data name="DebugDebug_BackgroundImageInvalidFormat" xml:space="preserve"><value>現在のスプラッシュ画像は使用できません: {0}</value></data>
+  <data name="DebugDebug_Clear" xml:space="preserve"><value>クリア</value></data>
+  <data name="DebugDebug_SelectImageDialog" xml:space="preserve"><value>スプラッシュ画像を選択</value></data>
+  <data name="DebugDebug_ImageFiles" xml:space="preserve"><value>画像ファイル</value></data>
   <data name="Oobe_Title" xml:space="preserve"><value>蘭山デスクトップへようこそ</value></data>
   <data name="Oobe_WelcomeTitle" xml:space="preserve"><value>蘭山デスクトップへようこそ</value></data>
   <data name="Oobe_WelcomeSubtitle" xml:space="preserve"><value>あなたのデスクトップ、一面だけじゃない</value></data>

LanMountainDesktop.Launcher/Resources/Strings.ko-KR.resx

@@ -119,6 +119,17 @@
   <data name="DebugDebug_ButtonCancel" xml:space="preserve"><value>취소</value></data>
   <data name="DebugDebug_ButtonOk" xml:space="preserve"><value>확인</value></data>
   <data name="DebugDebug_SelectExeDialog" xml:space="preserve"><value>란산 데스크톱 호스트 실행 파일 선택</value></data>
+  <data name="DebugDebug_BackgroundImage" xml:space="preserve"><value>스플래시 이미지</value></data>
+  <data name="DebugDebug_BackgroundImageDesc" xml:space="preserve"><value>시작 화면에 표시할 이미지를 선택합니다. 이미지는 Launcher 데이터 디렉터리에 복사됩니다.</value></data>
+  <data name="DebugDebug_BackgroundImageNotSet" xml:space="preserve"><value>스플래시 이미지가 설정되지 않았습니다</value></data>
+  <data name="DebugDebug_BackgroundImageSaved" xml:space="preserve"><value>스플래시 이미지가 저장되었습니다. 현재 시작 화면이 즉시 새로 고쳐집니다.</value></data>
+  <data name="DebugDebug_BackgroundImageCleared" xml:space="preserve"><value>스플래시 이미지가 지워졌습니다.</value></data>
+  <data name="DebugDebug_BackgroundImageSaveFailedFormat" xml:space="preserve"><value>이미지 설정 실패: {0}</value></data>
+  <data name="DebugDebug_BackgroundImageReadyFormat" xml:space="preserve"><value>현재 스플래시 이미지를 사용할 수 있습니다({0} x {1}).</value></data>
+  <data name="DebugDebug_BackgroundImageInvalidFormat" xml:space="preserve"><value>현재 스플래시 이미지를 사용할 수 없습니다: {0}</value></data>
+  <data name="DebugDebug_Clear" xml:space="preserve"><value>지우기</value></data>
+  <data name="DebugDebug_SelectImageDialog" xml:space="preserve"><value>스플래시 이미지 선택</value></data>
+  <data name="DebugDebug_ImageFiles" xml:space="preserve"><value>이미지 파일</value></data>
   <data name="Oobe_Title" xml:space="preserve"><value>란산 데스크톱에 오신 것을 환영합니다</value></data>
   <data name="Oobe_WelcomeTitle" xml:space="preserve"><value>란산 데스크톱에 오신 것을 환영합니다</value></data>
   <data name="Oobe_WelcomeSubtitle" xml:space="preserve"><value>당신의 데스크톱, 한 면이 아닙니다</value></data>

LanMountainDesktop.Launcher/Resources/Strings.resx

@@ -119,6 +119,17 @@
   <data name="DebugDebug_ButtonCancel" xml:space="preserve"><value>取消</value></data>
   <data name="DebugDebug_ButtonOk" xml:space="preserve"><value>确定</value></data>
   <data name="DebugDebug_SelectExeDialog" xml:space="preserve"><value>选择阑山桌面主程序可执行文件</value></data>
+  <data name="DebugDebug_BackgroundImage" xml:space="preserve"><value>启动图</value></data>
+  <data name="DebugDebug_BackgroundImageDesc" xml:space="preserve"><value>选择一张图片显示在启动画面中。图片会复制保存到 Launcher 数据目录。</value></data>
+  <data name="DebugDebug_BackgroundImageNotSet" xml:space="preserve"><value>未设置启动图</value></data>
+  <data name="DebugDebug_BackgroundImageSaved" xml:space="preserve"><value>启动图已保存，当前启动画面会立即刷新。</value></data>
+  <data name="DebugDebug_BackgroundImageCleared" xml:space="preserve"><value>启动图已清除。</value></data>
+  <data name="DebugDebug_BackgroundImageSaveFailedFormat" xml:space="preserve"><value>图片设置失败：{0}</value></data>
+  <data name="DebugDebug_BackgroundImageReadyFormat" xml:space="preserve"><value>当前启动图可用（{0} × {1}）。</value></data>
+  <data name="DebugDebug_BackgroundImageInvalidFormat" xml:space="preserve"><value>当前启动图不可用：{0}</value></data>
+  <data name="DebugDebug_Clear" xml:space="preserve"><value>清除</value></data>
+  <data name="DebugDebug_SelectImageDialog" xml:space="preserve"><value>选择启动图</value></data>
+  <data name="DebugDebug_ImageFiles" xml:space="preserve"><value>图片文件</value></data>
   <data name="Oobe_Title" xml:space="preserve"><value>欢迎使用阑山桌面</value></data>
   <data name="Oobe_WelcomeTitle" xml:space="preserve"><value>欢迎使用阑山桌面</value></data>
   <data name="Oobe_WelcomeSubtitle" xml:space="preserve"><value>你的桌面，不止一面</value></data>

LanMountainDesktop.Launcher/Shell/LauncherBackgroundService.cs

@@ -2,22 +2,28 @@ using Avalonia.Media.Imaging;
 
 namespace LanMountainDesktop.Launcher.Shell;
 
-/// <summary>
-/// 启动器背景图片服务
-/// </summary>
 internal static class LauncherBackgroundService
 {
     private const string PictureFileName = "Launcher Picture";
-    private const long MaxFileSize = 10 * 1024 * 1024; // 10MB
-    private const double WindowAspectRatio = 7.0 / 5.0; // 700:500
-    private const double AspectRatioTolerance = 0.15; // 15% 误差
+    private const long MaxFileSize = 10 * 1024 * 1024;
+
+    private static readonly string[] SupportedExtensions =
+    [
+        ".png",
+        ".jpg",
+        ".jpeg",
+        ".bmp",
+        ".gif",
+        ".webp"
+    ];
 
     private static Bitmap? _cachedBitmap;
     private static string? _cachedPath;
+    private static long _cachedLength;
+    private static DateTime _cachedLastWriteTimeUtc;
+
+    internal static string? LauncherDataDirectoryOverride { get; set; }
 
-    /// <summary>
-    /// 背景图片信息
-    /// </summary>
     public record BackgroundImageInfo
     {
         public required bool Exists { get; init; }
@@ -30,29 +36,29 @@ internal static class LauncherBackgroundService
         public string? ErrorMessage { get; init; }
     }
 
-    /// <summary>
-    /// 加载背景图片
-    /// </summary>
+    public record BackgroundImageMutationResult
+    {
+        public required bool IsSuccess { get; init; }
+        public string? FilePath { get; init; }
+        public string? ErrorMessage { get; init; }
+    }
+
     public static BackgroundImageInfo LoadBackgroundImage()
     {
         try
         {
-            var resolver = new DataLocationResolver(AppContext.BaseDirectory);
-            var launcherPath = resolver.ResolveLauncherDataPath();
-
-            // 查找图片文件
+            var launcherPath = ResolveLauncherDataPath();
             var imagePath = FindImageFile(launcherPath);
-            if (imagePath == null)
+            if (imagePath is null)
             {
                 return new BackgroundImageInfo
                 {
                     Exists = false,
                     IsValid = false,
-                    ErrorMessage = "未找到背景图片文件"
+                    ErrorMessage = "No launcher background image was found."
                 };
             }
 
-            // 检查文件大小
             var fileInfo = new FileInfo(imagePath);
             if (fileInfo.Length > MaxFileSize)
             {
@@ -61,12 +67,11 @@ internal static class LauncherBackgroundService
                     Exists = true,
                     IsValid = false,
                     FilePath = imagePath,
-                    ErrorMessage = $"图片文件过大 ({fileInfo.Length / 1024 / 1024}MB > 10MB)"
+                    ErrorMessage = $"Image file is too large ({fileInfo.Length / 1024 / 1024}MB > 10MB)."
                 };
             }
 
-            // 使用缓存
-            if (_cachedBitmap != null && _cachedPath == imagePath)
+            if (IsCacheCurrent(imagePath, fileInfo))
             {
                 return new BackgroundImageInfo
                 {
@@ -74,40 +79,40 @@ internal static class LauncherBackgroundService
                     IsValid = true,
                     FilePath = imagePath,
                     Bitmap = _cachedBitmap,
-                    Width = _cachedBitmap.PixelSize.Width,
+                    Width = _cachedBitmap!.PixelSize.Width,
                     Height = _cachedBitmap.PixelSize.Height,
                     AspectRatio = (double)_cachedBitmap.PixelSize.Width / _cachedBitmap.PixelSize.Height
                 };
             }
 
-            // 加载图片
-            var bitmap = new Bitmap(imagePath);
-            var width = bitmap.PixelSize.Width;
-            var height = bitmap.PixelSize.Height;
-            var aspectRatio = (double)width / height;
+            DisposeCache();
 
-            // 校验比例
-            var ratioDiff = Math.Abs(aspectRatio - WindowAspectRatio) / WindowAspectRatio;
-            if (ratioDiff > AspectRatioTolerance)
+            Bitmap bitmap;
+            try
+            {
+                bitmap = new Bitmap(imagePath);
+            }
+            catch (Exception ex)
             {
-                bitmap.Dispose();
                 return new BackgroundImageInfo
                 {
                     Exists = true,
                     IsValid = false,
                     FilePath = imagePath,
-                    Width = width,
-                    Height = height,
-                    AspectRatio = aspectRatio,
-                    ErrorMessage = $"图片比例不符合要求 ({aspectRatio:F2}，需要接近 {WindowAspectRatio:F2})"
+                    ErrorMessage = $"Image could not be decoded: {ex.Message}"
                 };
             }
 
-            // 缓存图片
+            var width = bitmap.PixelSize.Width;
+            var height = bitmap.PixelSize.Height;
+            var aspectRatio = height == 0 ? 0d : (double)width / height;
+
             _cachedBitmap = bitmap;
             _cachedPath = imagePath;
+            _cachedLength = fileInfo.Length;
+            _cachedLastWriteTimeUtc = fileInfo.LastWriteTimeUtc;
 
-            Logger.Info($"[LauncherBackground] 背景图片加载成功: {imagePath} ({width}x{height}, 比例: {aspectRatio:F2})");
+            Logger.Info($"[LauncherBackground] Background image loaded: {imagePath} ({width}x{height}).");
 
             return new BackgroundImageInfo
             {
@@ -122,38 +127,159 @@ internal static class LauncherBackgroundService
         }
         catch (Exception ex)
         {
-            Logger.Warn($"[LauncherBackground] 加载背景图片失败: {ex.Message}");
+            Logger.Warn($"[LauncherBackground] Failed to load background image: {ex.Message}");
             return new BackgroundImageInfo
             {
                 Exists = false,
                 IsValid = false,
-                ErrorMessage = $"加载失败: {ex.Message}"
+                ErrorMessage = $"Load failed: {ex.Message}"
             };
         }
     }
 
-    /// <summary>
-    /// 查找图片文件
-    /// </summary>
+    public static BackgroundImageMutationResult SaveBackgroundImage(string sourcePath)
+    {
+        try
+        {
+            if (string.IsNullOrWhiteSpace(sourcePath))
+            {
+                return FailMutation("No image file was selected.");
+            }
+
+            var fullSourcePath = Path.GetFullPath(sourcePath);
+            if (!File.Exists(fullSourcePath))
+            {
+                return FailMutation("The selected image file does not exist.");
+            }
+
+            var extension = NormalizeExtension(Path.GetExtension(fullSourcePath));
+            if (!IsSupportedExtension(extension))
+            {
+                return FailMutation("The selected image format is not supported.");
+            }
+
+            var sourceInfo = new FileInfo(fullSourcePath);
+            if (sourceInfo.Length > MaxFileSize)
+            {
+                return FailMutation($"Image file is too large ({sourceInfo.Length / 1024 / 1024}MB > 10MB).");
+            }
+
+            try
+            {
+                using var bitmap = new Bitmap(fullSourcePath);
+                _ = bitmap.PixelSize;
+            }
+            catch (Exception ex)
+            {
+                return FailMutation($"The selected image could not be decoded: {ex.Message}");
+            }
+
+            var launcherPath = ResolveLauncherDataPath();
+            Directory.CreateDirectory(launcherPath);
+
+            var destinationPath = Path.Combine(launcherPath, PictureFileName + extension);
+            var tempPath = Path.Combine(launcherPath, $".{PictureFileName}.{Guid.NewGuid():N}.tmp");
+
+            try
+            {
+                File.Copy(fullSourcePath, tempPath, overwrite: true);
+                ClearCache();
+                File.Move(tempPath, destinationPath, overwrite: true);
+                DeleteManagedImageFiles(launcherPath, destinationPath);
+            }
+            finally
+            {
+                TryDeleteFile(tempPath);
+            }
+
+            ClearCache();
+
+            Logger.Info($"[LauncherBackground] Background image saved: {destinationPath}.");
+            return new BackgroundImageMutationResult
+            {
+                IsSuccess = true,
+                FilePath = destinationPath
+            };
+        }
+        catch (Exception ex)
+        {
+            Logger.Warn($"[LauncherBackground] Failed to save background image: {ex.Message}");
+            return FailMutation($"Save failed: {ex.Message}");
+        }
+    }
+
+    public static BackgroundImageMutationResult ClearBackgroundImage()
+    {
+        try
+        {
+            var launcherPath = ResolveLauncherDataPath();
+            ClearCache();
+            DeleteManagedImageFiles(launcherPath, exceptPath: null);
+
+            Logger.Info("[LauncherBackground] Background image cleared.");
+            return new BackgroundImageMutationResult
+            {
+                IsSuccess = true
+            };
+        }
+        catch (Exception ex)
+        {
+            Logger.Warn($"[LauncherBackground] Failed to clear background image: {ex.Message}");
+            return FailMutation($"Clear failed: {ex.Message}");
+        }
+    }
+
+    public static void ClearCache()
+    {
+        DisposeCache();
+        _cachedPath = null;
+        _cachedLength = 0;
+        _cachedLastWriteTimeUtc = DateTime.MinValue;
+    }
+
+    internal static string? FindManagedImageFile()
+    {
+        return FindImageFile(ResolveLauncherDataPath());
+    }
+
+    internal static IReadOnlyList<string> GetSupportedExtensions() => SupportedExtensions;
+
+    private static BackgroundImageMutationResult FailMutation(string message)
+    {
+        return new BackgroundImageMutationResult
+        {
+            IsSuccess = false,
+            ErrorMessage = message
+        };
+    }
+
+    private static bool IsCacheCurrent(string imagePath, FileInfo fileInfo)
+    {
+        return _cachedBitmap is not null &&
+               string.Equals(_cachedPath, imagePath, StringComparison.OrdinalIgnoreCase) &&
+               _cachedLength == fileInfo.Length &&
+               _cachedLastWriteTimeUtc == fileInfo.LastWriteTimeUtc;
+    }
+
     private static string? FindImageFile(string directory)
     {
-        var extensions = new[] { ".png", ".jpg", ".jpeg", ".bmp", ".gif", ".webp" };
-
-        foreach (var ext in extensions)
+        if (!Directory.Exists(directory))
         {
-            var path = Path.Combine(directory, PictureFileName + ext);
+            return null;
+        }
+
+        foreach (var extension in SupportedExtensions)
+        {
+            var path = Path.Combine(directory, PictureFileName + extension);
             if (File.Exists(path))
             {
                 return path;
             }
         }
 
-        // 也尝试不带扩展名的匹配（如果文件本身就有扩展名）
-        var files = Directory.GetFiles(directory, PictureFileName + ".*");
-        foreach (var file in files)
+        foreach (var file in Directory.GetFiles(directory, PictureFileName + ".*"))
         {
-            var ext = Path.GetExtension(file).ToLowerInvariant();
-            if (extensions.Contains(ext))
+            if (IsSupportedExtension(Path.GetExtension(file)))
             {
                 return file;
             }
@@ -162,13 +288,72 @@ internal static class LauncherBackgroundService
         return null;
     }
 
-    /// <summary>
-    /// 清除缓存
-    /// </summary>
-    public static void ClearCache()
+    private static void DeleteManagedImageFiles(string directory, string? exceptPath)
+    {
+        if (!Directory.Exists(directory))
+        {
+            return;
+        }
+
+        foreach (var file in Directory.GetFiles(directory, PictureFileName + ".*"))
+        {
+            if (!IsSupportedExtension(Path.GetExtension(file)))
+            {
+                continue;
+            }
+
+            if (!string.IsNullOrWhiteSpace(exceptPath) &&
+                string.Equals(Path.GetFullPath(file), Path.GetFullPath(exceptPath), StringComparison.OrdinalIgnoreCase))
+            {
+                continue;
+            }
+
+            TryDeleteFile(file);
+        }
+    }
+
+    private static void TryDeleteFile(string path)
+    {
+        try
+        {
+            if (File.Exists(path))
+            {
+                File.Delete(path);
+            }
+        }
+        catch (Exception ex)
+        {
+            Logger.Warn($"[LauncherBackground] Failed to delete '{path}': {ex.Message}");
+        }
+    }
+
+    private static string NormalizeExtension(string? extension)
+    {
+        return string.IsNullOrWhiteSpace(extension)
+            ? string.Empty
+            : extension.Trim().ToLowerInvariant();
+    }
+
+    private static bool IsSupportedExtension(string? extension)
+    {
+        var normalized = NormalizeExtension(extension);
+        return SupportedExtensions.Contains(normalized, StringComparer.OrdinalIgnoreCase);
+    }
+
+    private static string ResolveLauncherDataPath()
+    {
+        if (!string.IsNullOrWhiteSpace(LauncherDataDirectoryOverride))
+        {
+            return Path.GetFullPath(LauncherDataDirectoryOverride);
+        }
+
+        var resolver = new DataLocationResolver(AppContext.BaseDirectory);
+        return resolver.ResolveLauncherDataPath();
+    }
+
+    private static void DisposeCache()
     {
         _cachedBitmap?.Dispose();
         _cachedBitmap = null;
-        _cachedPath = null;
     }
 }

LanMountainDesktop.Launcher/Views/ErrorDebugWindow.axaml

@@ -5,25 +5,37 @@
         xmlns:views="clr-namespace:LanMountainDesktop.Launcher.Views"
         xmlns:res="clr-namespace:LanMountainDesktop.Launcher.Resources"
         mc:Ignorable="d"
-        d:DesignWidth="420"
-        d:DesignHeight="320"
+        d:DesignWidth="460"
+        d:DesignHeight="500"
         x:Class="LanMountainDesktop.Launcher.Views.ErrorDebugWindow"
         x:DataType="views:ErrorDebugWindow"
         x:CompileBindings="False"
         Title="{x:Static res:Strings.DebugDebug_Title}"
-        Width="420"
-        Height="320"
+        Width="460"
+        Height="500"
         CanResize="False"
         WindowStartupLocation="CenterOwner"
         Background="{DynamicResource SolidBackgroundFillColorBaseBrush}"
         TransparencyLevelHint="None"
         Icon="/Assets/logo.ico">
+  <Window.Resources>
+    <CornerRadius x:Key="DesignCornerRadiusMicro">2</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusXs">4</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusSm">4</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusMd">8</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusLg">8</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusXl">12</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusIsland">16</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusComponent">8</CornerRadius>
+    <CornerRadius x:Key="OverlayCornerRadius">8</CornerRadius>
+    <CornerRadius x:Key="ControlCornerRadius">4</CornerRadius>
+  </Window.Resources>
+
   <Design.DataContext>
     <views:ErrorDebugWindow />
   </Design.DataContext>
 
   <Grid Margin="24" RowDefinitions="Auto,*,Auto">
-    <!-- 标题 -->
     <TextBlock Grid.Row="0"
                Text="{x:Static res:Strings.DebugDebug_SettingsTitle}"
                FontSize="20"
@@ -31,65 +43,108 @@
                Foreground="{DynamicResource TextFillColorPrimaryBrush}"
                Margin="0,0,0,16" />
 
-    <!-- 设置内容 -->
-    <StackPanel Grid.Row="1" Spacing="16">
-      <!-- 开发模式开关 -->
-      <Border Background="{DynamicResource CardBackgroundFillColorDefaultBrush}"
-              CornerRadius="{DynamicResource ControlCornerRadius}"
-              Padding="16,12">
-        <Grid ColumnDefinitions="*,Auto">
-          <StackPanel Grid.Column="0" VerticalAlignment="Center">
-            <TextBlock Text="{x:Static res:Strings.DebugDebug_DevMode}"
+    <ScrollViewer Grid.Row="1"
+                  VerticalScrollBarVisibility="Auto">
+      <StackPanel Spacing="16">
+        <Border Background="{DynamicResource CardBackgroundFillColorDefaultBrush}"
+                CornerRadius="{DynamicResource DesignCornerRadiusMd}"
+                Padding="16,12">
+          <Grid ColumnDefinitions="*,Auto">
+            <StackPanel Grid.Column="0" VerticalAlignment="Center">
+              <TextBlock Text="{x:Static res:Strings.DebugDebug_DevMode}"
+                         FontSize="14"
+                         Foreground="{DynamicResource TextFillColorPrimaryBrush}" />
+              <TextBlock Text="{x:Static res:Strings.DebugDebug_DevModeDesc}"
+                         FontSize="12"
+                         Foreground="{DynamicResource TextFillColorSecondaryBrush}"
+                         Margin="0,2,0,0" />
+            </StackPanel>
+            <ToggleSwitch x:Name="DevModeToggle"
+                          Grid.Column="1"
+                          OnContent="{x:Static res:Strings.DebugDebug_On}"
+                          OffContent="{x:Static res:Strings.DebugDebug_Off}" />
+          </Grid>
+        </Border>
+
+        <Border Background="{DynamicResource CardBackgroundFillColorDefaultBrush}"
+                CornerRadius="{DynamicResource DesignCornerRadiusMd}"
+                Padding="16,12">
+          <Grid RowDefinitions="Auto,Auto" ColumnDefinitions="*,Auto">
+            <TextBlock Grid.Row="0" Grid.Column="0"
+                       Text="{x:Static res:Strings.DebugDebug_AppPath}"
                        FontSize="14"
                        Foreground="{DynamicResource TextFillColorPrimaryBrush}" />
-            <TextBlock Text="{x:Static res:Strings.DebugDebug_DevModeDesc}"
+            <TextBlock x:Name="PathTextBlock"
+                       Grid.Row="1" Grid.Column="0"
+                       Text="{x:Static res:Strings.DebugDebug_NotSelected}"
                        FontSize="12"
                        Foreground="{DynamicResource TextFillColorSecondaryBrush}"
-                       Margin="0,2,0,0" />
-          </StackPanel>
-          <ToggleSwitch x:Name="DevModeToggle"
+                       TextTrimming="CharacterEllipsis"
+                       Margin="0,4,12,0" />
+            <Button x:Name="BrowseButton"
+                    Grid.Row="0" Grid.RowSpan="2" Grid.Column="1"
+                    Content="{x:Static res:Strings.DebugDebug_Browse}"
+                    VerticalAlignment="Center" />
+          </Grid>
+        </Border>
+
+        <Border Background="{DynamicResource CardBackgroundFillColorDefaultBrush}"
+                CornerRadius="{DynamicResource DesignCornerRadiusMd}"
+                Padding="16,12">
+          <Grid RowDefinitions="Auto,Auto,Auto" ColumnDefinitions="*,Auto">
+            <StackPanel Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="2" Spacing="2">
+              <TextBlock Text="{x:Static res:Strings.DebugDebug_BackgroundImage}"
+                         FontSize="14"
+                         Foreground="{DynamicResource TextFillColorPrimaryBrush}" />
+              <TextBlock Text="{x:Static res:Strings.DebugDebug_BackgroundImageDesc}"
+                         FontSize="12"
+                         Foreground="{DynamicResource TextFillColorSecondaryBrush}"
+                         TextWrapping="Wrap" />
+            </StackPanel>
+
+            <TextBlock x:Name="BackgroundImagePathTextBlock"
+                       Grid.Row="1" Grid.Column="0"
+                       Text="{x:Static res:Strings.DebugDebug_BackgroundImageNotSet}"
+                       FontSize="12"
+                       Foreground="{DynamicResource TextFillColorSecondaryBrush}"
+                       TextTrimming="CharacterEllipsis"
+                       Margin="0,10,12,0" />
+
+            <StackPanel Grid.Row="1"
                         Grid.Column="1"
-                        OnContent="{x:Static res:Strings.DebugDebug_On}"
-                        OffContent="{x:Static res:Strings.DebugDebug_Off}" />
-        </Grid>
-      </Border>
+                        Orientation="Horizontal"
+                        Spacing="8"
+                        Margin="0,6,0,0">
+              <Button x:Name="BrowseImageButton"
+                      Content="{x:Static res:Strings.DebugDebug_Browse}"
+                      VerticalAlignment="Center" />
+              <Button x:Name="ClearImageButton"
+                      Content="{x:Static res:Strings.DebugDebug_Clear}"
+                      VerticalAlignment="Center" />
+            </StackPanel>
 
-      <!-- 应用路径选择 -->
-      <Border Background="{DynamicResource CardBackgroundFillColorDefaultBrush}"
-              CornerRadius="{DynamicResource ControlCornerRadius}"
-              Padding="16,12">
-        <Grid RowDefinitions="Auto,Auto" ColumnDefinitions="*,Auto">
-          <TextBlock Grid.Row="0" Grid.Column="0"
-                     Text="{x:Static res:Strings.DebugDebug_AppPath}"
-                     FontSize="14"
-                     Foreground="{DynamicResource TextFillColorPrimaryBrush}" />
-          <TextBlock x:Name="PathTextBlock"
-                     Grid.Row="1" Grid.Column="0"
-                     Text="{x:Static res:Strings.DebugDebug_NotSelected}"
+            <TextBlock x:Name="BackgroundImageStatusTextBlock"
+                       Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="2"
+                       Text="{x:Static res:Strings.DebugDebug_BackgroundImageNotSet}"
+                       FontSize="12"
+                       Foreground="{DynamicResource TextFillColorSecondaryBrush}"
+                       TextWrapping="Wrap"
+                       Margin="0,8,0,0" />
+          </Grid>
+        </Border>
+
+        <Border Background="{DynamicResource SystemFillColorCautionBackgroundBrush}"
+                CornerRadius="{DynamicResource DesignCornerRadiusMd}"
+                Padding="12,10"
+                IsVisible="True">
+          <TextBlock Text="{x:Static res:Strings.DebugDebug_Warning}"
                      FontSize="12"
-                     Foreground="{DynamicResource TextFillColorSecondaryBrush}"
-                     TextTrimming="CharacterEllipsis"
-                     Margin="0,4,12,0" />
-          <Button x:Name="BrowseButton"
-                  Grid.Row="0" Grid.RowSpan="2" Grid.Column="1"
-                  Content="{x:Static res:Strings.DebugDebug_Browse}"
-                  VerticalAlignment="Center" />
-        </Grid>
-      </Border>
+                     Foreground="{DynamicResource SystemFillColorCautionBrush}"
+                     TextWrapping="Wrap" />
+        </Border>
+      </StackPanel>
+    </ScrollViewer>
 
-      <!-- 提示信息 -->
-      <Border Background="{DynamicResource SystemFillColorCautionBackgroundBrush}"
-              CornerRadius="{DynamicResource ControlCornerRadius}"
-              Padding="12,10"
-              IsVisible="True">
-        <TextBlock Text="{x:Static res:Strings.DebugDebug_Warning}"
-                   FontSize="12"
-                   Foreground="{DynamicResource SystemFillColorCautionBrush}"
-                   TextWrapping="Wrap" />
-      </Border>
-    </StackPanel>
-
-    <!-- 按钮区域 -->
     <StackPanel Grid.Row="2"
                 Orientation="Horizontal"
                 HorizontalAlignment="Right"

LanMountainDesktop.Launcher/Views/ErrorDebugWindow.axaml.cs

@@ -3,6 +3,7 @@ using Avalonia.Interactivity;
 using Avalonia.Markup.Xaml;
 using Avalonia.Platform.Storage;
 using LanMountainDesktop.Launcher.Resources;
+using LanMountainDesktop.Launcher.Shell;
 
 namespace LanMountainDesktop.Launcher.Views;
 
@@ -46,6 +47,7 @@ public partial class ErrorDebugWindow : Window
         }
 
         UpdatePathDisplay(_selectedHostPath);
+        RefreshBackgroundImageDisplay();
     }
 
     private void InitializeComponents()
@@ -63,6 +65,16 @@ public partial class ErrorDebugWindow : Window
             browseButton.Click += OnBrowseClick;
         }
 
+        if (this.FindControl<Button>("BrowseImageButton") is { } browseImageButton)
+        {
+            browseImageButton.Click += OnBrowseImageClick;
+        }
+
+        if (this.FindControl<Button>("ClearImageButton") is { } clearImageButton)
+        {
+            clearImageButton.Click += OnClearImageClick;
+        }
+
         if (this.FindControl<Button>("OkButton") is { } okButton)
         {
             okButton.Click += (_, _) =>
@@ -111,6 +123,56 @@ public partial class ErrorDebugWindow : Window
         UpdatePathDisplay(_selectedHostPath);
     }
 
+    private async void OnBrowseImageClick(object? sender, RoutedEventArgs e)
+    {
+        var storageProvider = StorageProvider;
+        if (storageProvider is null)
+        {
+            return;
+        }
+
+        var patterns = LauncherBackgroundService
+            .GetSupportedExtensions()
+            .Select(extension => "*" + extension)
+            .ToArray();
+
+        var options = new FilePickerOpenOptions
+        {
+            Title = Strings.DebugDebug_SelectImageDialog,
+            AllowMultiple = false,
+            FileTypeFilter =
+            [
+                new FilePickerFileType(Strings.DebugDebug_ImageFiles)
+                {
+                    Patterns = patterns
+                }
+            ]
+        };
+
+        var result = await storageProvider.OpenFilePickerAsync(options);
+        if (result.Count <= 0)
+        {
+            return;
+        }
+
+        var saveResult = LauncherBackgroundService.SaveBackgroundImage(result[0].Path.LocalPath);
+        var status = saveResult.IsSuccess
+            ? Strings.DebugDebug_BackgroundImageSaved
+            : string.Format(Strings.DebugDebug_BackgroundImageSaveFailedFormat, saveResult.ErrorMessage ?? string.Empty);
+
+        RefreshBackgroundImageDisplay(status);
+    }
+
+    private void OnClearImageClick(object? sender, RoutedEventArgs e)
+    {
+        var clearResult = LauncherBackgroundService.ClearBackgroundImage();
+        var status = clearResult.IsSuccess
+            ? Strings.DebugDebug_BackgroundImageCleared
+            : string.Format(Strings.DebugDebug_BackgroundImageSaveFailedFormat, clearResult.ErrorMessage ?? string.Empty);
+
+        RefreshBackgroundImageDisplay(status);
+    }
+
     private void UpdatePathDisplay(string? path)
     {
         if (this.FindControl<TextBlock>("PathTextBlock") is { } pathTextBlock)
@@ -118,4 +180,46 @@ public partial class ErrorDebugWindow : Window
             pathTextBlock.Text = string.IsNullOrEmpty(path) ? Strings.DebugDebug_NotSelected : path;
         }
     }
+
+    private void RefreshBackgroundImageDisplay(string? statusOverride = null)
+    {
+        var imageInfo = LauncherBackgroundService.LoadBackgroundImage();
+
+        if (this.FindControl<TextBlock>("BackgroundImagePathTextBlock") is { } pathTextBlock)
+        {
+            pathTextBlock.Text = imageInfo.Exists && !string.IsNullOrWhiteSpace(imageInfo.FilePath)
+                ? imageInfo.FilePath
+                : Strings.DebugDebug_BackgroundImageNotSet;
+        }
+
+        if (this.FindControl<TextBlock>("BackgroundImageStatusTextBlock") is { } statusTextBlock)
+        {
+            statusTextBlock.Text = statusOverride ?? ResolveBackgroundImageStatus(imageInfo);
+        }
+
+        if (this.FindControl<Button>("ClearImageButton") is { } clearButton)
+        {
+            clearButton.IsEnabled = imageInfo.Exists;
+        }
+    }
+
+    private static string ResolveBackgroundImageStatus(LauncherBackgroundService.BackgroundImageInfo imageInfo)
+    {
+        if (imageInfo.IsValid)
+        {
+            return string.Format(
+                Strings.DebugDebug_BackgroundImageReadyFormat,
+                imageInfo.Width,
+                imageInfo.Height);
+        }
+
+        if (imageInfo.Exists)
+        {
+            return string.Format(
+                Strings.DebugDebug_BackgroundImageInvalidFormat,
+                imageInfo.ErrorMessage ?? string.Empty);
+        }
+
+        return Strings.DebugDebug_BackgroundImageNotSet;
+    }
 }

LanMountainDesktop.Launcher/Views/SplashWindow.axaml

@@ -15,72 +15,91 @@
         ShowInTaskbar="False"
         WindowStartupLocation="CenterScreen"
         WindowDecorations="None"
-        Background="#0B0B0B"
-        TransparencyLevelHint="None"
+        Background="Transparent"
+        TransparencyLevelHint="Transparent"
         Icon="/Assets/logo.ico">
+  <Window.Resources>
+    <CornerRadius x:Key="DesignCornerRadiusMicro">2</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusXs">4</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusSm">4</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusMd">8</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusLg">8</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusXl">12</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusIsland">16</CornerRadius>
+    <CornerRadius x:Key="DesignCornerRadiusComponent">8</CornerRadius>
+    <CornerRadius x:Key="OverlayCornerRadius">8</CornerRadius>
+    <CornerRadius x:Key="ControlCornerRadius">4</CornerRadius>
+  </Window.Resources>
+
   <Design.DataContext>
     <views:SplashWindow />
   </Design.DataContext>
 
-  <Grid RowDefinitions="*,Auto">
-    <!-- 背景图片 -->
-    <Image x:Name="BackgroundImage"
-           Grid.RowSpan="2"
-           Stretch="UniformToFill"
-           IsVisible="False"
-           Opacity="0"/>
+  <Border x:Name="RootShell"
+          Background="#0B0B0B"
+          CornerRadius="{DynamicResource DesignCornerRadiusComponent}"
+          ClipToBounds="True">
+    <Grid RowDefinitions="*,Auto">
+      <Image x:Name="BackgroundImage"
+             Grid.RowSpan="2"
+             Stretch="Uniform"
+             HorizontalAlignment="Center"
+             VerticalAlignment="Center"
+             IsVisible="False"
+             Opacity="0"/>
 
-    <!-- 半透明遮罩层 -->
-    <Border x:Name="BackgroundOverlay"
-            Grid.RowSpan="2"
-            Background="#0B0B0B"
-            Opacity="0.85"/>
+      <Border x:Name="BackgroundOverlay"
+              Grid.RowSpan="2"
+              Background="#0B0B0B"
+              Opacity="0.42"/>
 
-    <Grid Grid.Row="0"
-          Margin="24">
-      <TextBlock x:Name="AppNameText"
-                 Text="LanMountain Desktop"
-                 FontSize="24"
-                 FontWeight="SemiBold"
-                 VerticalAlignment="Top"
-                 HorizontalAlignment="Left"
-                 Foreground="#F6F7FB" />
-    </Grid>
-
-    <Border Grid.Row="1"
-            Padding="24,18,24,24"
-            Background="Transparent">
-      <Grid RowDefinitions="Auto,Auto"
-            RowSpacing="10">
-        <Grid ColumnDefinitions="*,Auto">
-          <Border x:Name="VersionTextBorder"
-                  Background="Transparent"
-                  Cursor="Hand"
-                  HorizontalAlignment="Left">
-            <TextBlock x:Name="VersionText"
-                       FontSize="11"
-                       Foreground="#B9C0CC"
-                       Text="0.0.0-dev (Administrate)" />
-          </Border>
-
-          <TextBlock x:Name="StatusText"
-                     Grid.Column="1"
-                     FontSize="11"
-                     Foreground="#B9C0CC"
-                     HorizontalAlignment="Right"
-                     Text="{x:Static res:Strings.Splash_StatusInitializing}" />
-        </Grid>
-
-        <ProgressBar x:Name="ProgressIndicator"
-                     Grid.Row="1"
-                     Minimum="0"
-                     Maximum="100"
-                     Value="0"
-                     Height="4"
-                     IsIndeterminate="False"
-                     Foreground="#F6F7FB"
-                     Background="#2C313D" />
+      <Grid Grid.Row="0"
+            Margin="24">
+        <TextBlock x:Name="AppNameText"
+                   Text="{x:Static res:Strings.Splash_AppName}"
+                   FontSize="24"
+                   FontWeight="SemiBold"
+                   VerticalAlignment="Top"
+                   HorizontalAlignment="Left"
+                   Foreground="#F6F7FB" />
       </Grid>
-    </Border>
-  </Grid>
+
+      <Border Grid.Row="1"
+              Padding="24,18,24,24"
+              Background="Transparent">
+        <Grid RowDefinitions="Auto,Auto"
+              RowSpacing="10">
+          <Grid ColumnDefinitions="*,Auto">
+            <Border x:Name="VersionTextBorder"
+                    Background="Transparent"
+                    Cursor="Hand"
+                    CornerRadius="{DynamicResource DesignCornerRadiusSm}"
+                    HorizontalAlignment="Left">
+              <TextBlock x:Name="VersionText"
+                         FontSize="11"
+                         Foreground="#D8DEE9"
+                         Text="0.0.0-dev (Administrate)" />
+            </Border>
+
+            <TextBlock x:Name="StatusText"
+                       Grid.Column="1"
+                       FontSize="11"
+                       Foreground="#D8DEE9"
+                       HorizontalAlignment="Right"
+                       Text="{x:Static res:Strings.Splash_StatusInitializing}" />
+          </Grid>
+
+          <ProgressBar x:Name="ProgressIndicator"
+                       Grid.Row="1"
+                       Minimum="0"
+                       Maximum="100"
+                       Value="0"
+                       Height="4"
+                       IsIndeterminate="False"
+                       Foreground="#F6F7FB"
+                       Background="#592C313D" />
+        </Grid>
+      </Border>
+    </Grid>
+  </Border>
 </Window>

LanMountainDesktop.Launcher/Views/SplashWindow.axaml.cs

@@ -42,6 +42,8 @@ public partial class SplashWindow : Window, ISplashStageReporter
     {
         try
         {
+            ResetBackgroundImage();
+
             var imageInfo = LauncherBackgroundService.LoadBackgroundImage();
             if (imageInfo is { IsValid: true, Bitmap: not null })
             {
@@ -51,16 +53,27 @@ public partial class SplashWindow : Window, ISplashStageReporter
                     backgroundImage.IsVisible = true;
                     backgroundImage.Opacity = 1;
                 }
-                Logger.Info("[SplashWindow] 背景图片加载成功");
+
+                Logger.Info("[SplashWindow] Background image loaded.");
             }
             else if (imageInfo is { Exists: true, IsValid: false })
             {
-                Logger.Warn($"[SplashWindow] 背景图片校验失败: {imageInfo.ErrorMessage}");
+                Logger.Warn($"[SplashWindow] Background image validation failed: {imageInfo.ErrorMessage}");
             }
         }
         catch (Exception ex)
         {
-            Logger.Warn($"[SplashWindow] 加载背景图片失败: {ex.Message}");
+            Logger.Warn($"[SplashWindow] Failed to load background image: {ex.Message}");
+        }
+    }
+
+    private void ResetBackgroundImage()
+    {
+        if (this.FindControl<Image>("BackgroundImage") is { } backgroundImage)
+        {
+            backgroundImage.Source = null;
+            backgroundImage.IsVisible = false;
+            backgroundImage.Opacity = 0;
         }
     }
 
@@ -224,6 +237,7 @@ public partial class SplashWindow : Window, ISplashStageReporter
                         debugWindow.SelectedHostPath));
                 }
 
+                InitializeBackgroundImage();
                 _isDebugModeOpened = false;
                 _versionTextClickCount = 0;
             };

LanMountainDesktop.Tests/LauncherBackgroundServiceTests.cs

@@ -0,0 +1,182 @@
+using Avalonia;
+using LanMountainDesktop.Launcher.Shell;
+using Xunit;
+
+namespace LanMountainDesktop.Tests;
+
+public sealed class LauncherBackgroundServiceTests : IDisposable
+{
+    private const string RedPng1x1 =
+        "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAANSURBVBhXY/jPwPAfAAUAAf+mXJtdAAAAAElFTkSuQmCC";
+
+    private const string BluePng2x2 =
+        "iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAYAAABytg0kAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAASSURBVBhXY2Bg+P8fgsHE//8AP9IH+WMJIRIAAAAASUVORK5CYII=";
+
+    private const string GreenJpeg1x1 =
+        "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";
+
+    private readonly string _tempDirectory;
+    private readonly string _launcherDataDirectory;
+    private static readonly object AvaloniaGate = new();
+    private static bool _avaloniaInitialized;
+
+    public LauncherBackgroundServiceTests()
+    {
+        EnsureAvaloniaInitialized();
+
+        _tempDirectory = Path.Combine(
+            Path.GetTempPath(),
+            "LanMountainDesktop.BackgroundImageTests",
+            Guid.NewGuid().ToString("N"));
+        _launcherDataDirectory = Path.Combine(_tempDirectory, ".Launcher");
+        Directory.CreateDirectory(_launcherDataDirectory);
+        LauncherBackgroundService.LauncherDataDirectoryOverride = _launcherDataDirectory;
+        LauncherBackgroundService.ClearCache();
+    }
+
+    private static void EnsureAvaloniaInitialized()
+    {
+        lock (AvaloniaGate)
+        {
+            if (_avaloniaInitialized)
+            {
+                return;
+            }
+
+            if (Application.Current is null)
+            {
+                AppBuilder
+                    .Configure<Application>()
+                    .UsePlatformDetect()
+                    .SetupWithoutStarting();
+            }
+
+            _avaloniaInitialized = true;
+        }
+    }
+
+    [Fact]
+    public void SaveBackgroundImage_CopiesSelectedImageToLauncherDataDirectory()
+    {
+        var sourcePath = WriteImage("selected.png", RedPng1x1);
+
+        var result = LauncherBackgroundService.SaveBackgroundImage(sourcePath);
+
+        Assert.True(result.IsSuccess, result.ErrorMessage);
+        Assert.Equal(Path.Combine(_launcherDataDirectory, "Launcher Picture.png"), result.FilePath);
+        Assert.True(File.Exists(result.FilePath));
+        Assert.Equal(File.ReadAllBytes(sourcePath), File.ReadAllBytes(result.FilePath));
+    }
+
+    [Fact]
+    public void SaveBackgroundImage_ReplacesPreviousManagedExtension()
+    {
+        var pngSourcePath = WriteImage("first.png", RedPng1x1);
+        var jpegSourcePath = WriteImage("second.jpg", GreenJpeg1x1);
+
+        var firstResult = LauncherBackgroundService.SaveBackgroundImage(pngSourcePath);
+        var secondResult = LauncherBackgroundService.SaveBackgroundImage(jpegSourcePath);
+
+        Assert.True(firstResult.IsSuccess, firstResult.ErrorMessage);
+        Assert.True(secondResult.IsSuccess, secondResult.ErrorMessage);
+        Assert.False(File.Exists(Path.Combine(_launcherDataDirectory, "Launcher Picture.png")));
+        Assert.True(File.Exists(Path.Combine(_launcherDataDirectory, "Launcher Picture.jpg")));
+    }
+
+    [Fact]
+    public void LoadBackgroundImage_AcceptsNonSevenByFiveImage()
+    {
+        var sourcePath = WriteImage("square.png", RedPng1x1);
+
+        var saveResult = LauncherBackgroundService.SaveBackgroundImage(sourcePath);
+        var imageInfo = LauncherBackgroundService.LoadBackgroundImage();
+
+        Assert.True(saveResult.IsSuccess, saveResult.ErrorMessage);
+        Assert.True(imageInfo.IsValid, imageInfo.ErrorMessage);
+        Assert.Equal(1, imageInfo.Width);
+        Assert.Equal(1, imageInfo.Height);
+    }
+
+    [Theory]
+    [InlineData("oversized.png", InvalidImageKind.Oversized)]
+    [InlineData("unknown.txt", InvalidImageKind.UnknownExtension)]
+    [InlineData("broken.png", InvalidImageKind.BrokenImage)]
+    public void SaveBackgroundImage_WhenInvalid_DoesNotOverwriteExistingImage(
+        string invalidFileName,
+        InvalidImageKind invalidImageKind)
+    {
+        var existingPath = WriteImage("existing.png", RedPng1x1);
+        var existingResult = LauncherBackgroundService.SaveBackgroundImage(existingPath);
+        var managedPath = existingResult.FilePath!;
+        var originalBytes = File.ReadAllBytes(managedPath);
+        var invalidPath = WriteInvalidFile(invalidFileName, invalidImageKind);
+
+        var invalidResult = LauncherBackgroundService.SaveBackgroundImage(invalidPath);
+
+        Assert.False(invalidResult.IsSuccess);
+        Assert.True(File.Exists(managedPath));
+        Assert.Equal(originalBytes, File.ReadAllBytes(managedPath));
+    }
+
+    [Fact]
+    public void LoadBackgroundImage_WhenFileChangesAtSamePath_RefreshesCachedBitmap()
+    {
+        var sourcePath = WriteImage("source.png", RedPng1x1);
+        var saveResult = LauncherBackgroundService.SaveBackgroundImage(sourcePath);
+        Assert.True(saveResult.IsSuccess, saveResult.ErrorMessage);
+
+        var firstLoad = LauncherBackgroundService.LoadBackgroundImage();
+        Assert.True(firstLoad.IsValid, firstLoad.ErrorMessage);
+        Assert.Equal(1, firstLoad.Width);
+
+        var managedPath = saveResult.FilePath!;
+        File.WriteAllBytes(managedPath, Convert.FromBase64String(BluePng2x2));
+        File.SetLastWriteTimeUtc(managedPath, DateTime.UtcNow.AddSeconds(2));
+
+        var secondLoad = LauncherBackgroundService.LoadBackgroundImage();
+
+        Assert.True(secondLoad.IsValid, secondLoad.ErrorMessage);
+        Assert.Equal(2, secondLoad.Width);
+        Assert.Equal(2, secondLoad.Height);
+    }
+
+    public void Dispose()
+    {
+        LauncherBackgroundService.ClearCache();
+        LauncherBackgroundService.LauncherDataDirectoryOverride = null;
+
+        if (Directory.Exists(_tempDirectory))
+        {
+            Directory.Delete(_tempDirectory, recursive: true);
+        }
+    }
+
+    private string WriteImage(string fileName, string base64)
+    {
+        var path = Path.Combine(_tempDirectory, fileName);
+        File.WriteAllBytes(path, Convert.FromBase64String(base64));
+        return path;
+    }
+
+    private string WriteInvalidFile(string fileName, InvalidImageKind kind)
+    {
+        var path = Path.Combine(_tempDirectory, fileName);
+        var bytes = kind switch
+        {
+            InvalidImageKind.Oversized => new byte[(10 * 1024 * 1024) + 1],
+            InvalidImageKind.UnknownExtension => Convert.FromBase64String(RedPng1x1),
+            InvalidImageKind.BrokenImage => "not an image"u8.ToArray(),
+            _ => []
+        };
+
+        File.WriteAllBytes(path, bytes);
+        return path;
+    }
+
+    public enum InvalidImageKind
+    {
+        Oversized,
+        UnknownExtension,
+        BrokenImage
+    }
+}

docs/LAUNCHER_STARTUP_VISUALS.md

@@ -21,6 +21,14 @@ This supplement records the startup rules that are shared by the launcher and th
 - Slide splash enters from the right edge of the target screen and exits back to the right edge.
 - Static splash uses the same fullscreen black surface without motion.
 
+## Launcher splash image rules
+
+- The hidden launcher debug menu can save a custom splash image.
+- The selected image is copied into the Launcher data directory as `Launcher Picture.<ext>`.
+- Supported formats are `.png`, `.jpg`, `.jpeg`, `.bmp`, `.gif`, and `.webp`; files larger than `10MB` are rejected.
+- Splash displays the image with `Uniform` fitting, preserving the full image and allowing black letterboxing.
+- The splash window uses a transparent self-drawn shell with a fixed Fluent `8px` outer corner radius.
+
 ## Recovery rules
 
 - Closing Launcher during startup does not cancel the startup attempt.