fix(windows): avoid white startup flash after installing Taskly

scripts/e2e/e2e-windows.ps1

@@ -78,6 +78,11 @@ try {
 
     $desktop = [System.Windows.Automation.AutomationElement]::RootElement
     $window = Wait-Until 'Taskly window' {
+        # An early process exit is a startup failure, not slow UI automation.
+        $process.Refresh()
+        if ($process.HasExited) {
+            throw ('Taskly exited before creating a window (PID {0}, exit code {1})' -f $process.Id, $process.ExitCode)
+        }
         $condition = [System.Windows.Automation.PropertyCondition]::new(
             [System.Windows.Automation.AutomationElement]::ProcessIdProperty,
             $process.Id)
@@ -138,6 +143,21 @@ try {
     } | ConvertTo-Json -Depth 5 |
         Set-Content -LiteralPath (Join-Path $output 'interaction-trace.json') -Encoding utf8
 } finally {
+    # Archive process state even on a failed or timed-out launch.
+    if ($process) {
+        try {
+            $process.Refresh()
+            [ordered]@{
+                pid = $process.Id
+                exitedBeforeCleanup = $process.HasExited
+                exitCode = if ($process.HasExited) { $process.ExitCode } else { $null }
+                mainWindowHandle = [int64]$process.MainWindowHandle
+                mainWindowTitle = $process.MainWindowTitle
+                executable = $executable.FullName
+            } | ConvertTo-Json -Depth 3 |
+                Set-Content -LiteralPath (Join-Path $output 'launch-diagnostic.json') -Encoding utf8
+        } catch {}
+    }
     try { Capture-Screen (Join-Path $output 'screen-final.png') } catch {}
     if ($process -and -not $process.HasExited) {
         Stop-Process -Id $process.Id -Force -ErrorAction SilentlyContinue

shared/spec/DATA-FORMAT.md

@@ -110,6 +110,7 @@ sides trimmed; keys case-insensitive. Writer emits two fixed header lines:
 |---|---|---|
 | `last-db-path` | last opened DB — written by `open_database` on success, read at startup by `default_database` (read also accepts legacy `last_db_path`, which rewrites must carry through) | — |
 | `language` | `zh` / `en` | `zh` |
+| `theme` | `system` / `light` / `dark`; Windows applies it before the first window paint | `system` |
 | `last-selected-list-id` | int as string; unparseable → 0 | `0` |
 | `last-update-check` | unix seconds of the last auto-update check (UPDATE.md throttle) | `0` |
 

shared/spec/PRODUCT-SPEC.md

@@ -136,7 +136,9 @@ pickers. Save (blank text silently ignored), Delete (confirm first), Cancel
 - Settings: Language (简体中文 / English, runtime switch, persisted in
   config `language`), Theme submenu — 跟随系统 (follow system) / 浅色
   (light) / 深色 (dark), persisted in config `theme`; follow-system tracks
-  OS personalization live. macOS follows the system appearance at launch
+  OS personalization live. Windows reads the persisted language and theme
+  before first window activation (no temporary English/light frame); the
+  backend settings RPC remains authoritative once connected. macOS follows the system appearance at launch
   and live; its Settings toggle is a per-session override. Plus 检查更新… /
   Check for Updates… (manual online-update check; auto-check runs at
   launch and every 4 h — contract: `UPDATE.md`).

windows/MainWindow.xaml.cpp

@@ -72,6 +72,72 @@ std::wstring wide(std::string const& text) {
 
 namespace {
 
+// Bootstrap only the visual preferences before Window.Activate(), rather
+// than painting the default light theme while the Racket backend starts.
+// The backend remains the source of truth and refreshes these settings once
+// get_settings completes. Keep this parser consistent with DATA-FORMAT §7.
+struct StartupPreferences {
+  std::string language{"zh"};
+  std::string theme{"system"};
+};
+
+std::string ascii_trim(std::string value) {
+  auto const first = value.find_first_not_of(" \t\r\n");
+  if (first == std::string::npos) return {};
+  auto const last = value.find_last_not_of(" \t\r\n");
+  return value.substr(first, last - first + 1);
+}
+
+std::string ascii_lower(std::string value) {
+  for (auto& c : value) {
+    if (c >= 'A' && c <= 'Z') c = static_cast<char>(c - 'A' + 'a');
+  }
+  return value;
+}
+
+StartupPreferences read_startup_preferences() {
+  StartupPreferences result;
+  std::wstring home;
+  // Same Windows home precedence as racket/taskly/paths.rkt.
+  for (auto const* variable : {L"USERPROFILE", L"HOME"}) {
+    auto const required = ::GetEnvironmentVariableW(variable, nullptr, 0);
+    if (required <= 1) continue;
+    std::wstring value(required, L'\0');
+    auto const length =
+        ::GetEnvironmentVariableW(variable, value.data(), required);
+    if (length == 0 || length >= required) continue;
+    value.resize(length);
+    home = std::move(value);
+    break;
+  }
+  if (home.empty()) return result;
+
+  try {
+    std::ifstream config(std::filesystem::path(home) / L".taskly" /
+                         L"config.ini", std::ios::binary);
+    std::string line;
+    while (std::getline(config, line)) {
+      line = ascii_trim(std::move(line));
+      if (line.empty() || line.front() == '#' || line.front() == ';') continue;
+      auto const separator = line.find('=');
+      if (separator == std::string::npos) continue;
+      auto const key = ascii_lower(ascii_trim(line.substr(0, separator)));
+      auto const value = ascii_lower(ascii_trim(line.substr(separator + 1)));
+      // Match config-language/config-theme: last occurrence wins, and an
+      // invalid value falls back to that setting's documented default.
+      if (key == "language") {
+        result.language = (value == "zh" || value == "en") ? value : "zh";
+      } else if (key == "theme") {
+        result.theme = (value == "system" || value == "light" ||
+                        value == "dark") ? value : "system";
+      }
+    }
+  } catch (std::exception const&) {
+    // Missing/unreadable config should never delay or prevent a GUI launch.
+  }
+  return result;
+}
+
 rivet::windows::RacketRuntimeConfig runtime_config() {
   auto const exe = executable_path();
   auto const root = exe.parent_path();
@@ -514,22 +580,34 @@ MainWindow::MainWindow() {
   } catch (...) {
     // The fallback tables stay usable even if the exe path fails.
   }
-  set_i18n_language("en");  // corrected once get_settings reports
+  // Read only language/theme synchronously: the window is not activated
+  // yet, so dark-mode users never see a white/English startup frame.
+  // Full settings still load via the backend's get_settings_async RPC.
+  auto const initial = read_startup_preferences();
+  settings_.language = initial.language;
+  settings_.theme = initial.theme;
+  set_i18n_language(settings_.language);
   SetStatus(t("statusDatabaseNotConnected"));
-  // ApplyLanguage is the single source for every built-in string: the first
-  // paint is uniformly English (no XAML-default or blank elements), and the
-  // get_settings landing (OnLangZh/OnLangEn too) re-runs it wholesale so the
-  // final state always matches the user's language — never a mix.
   ApplyLanguage();
   // Hand-built rows take their brushes from code at build time, so a theme
   // flip must re-render them; the title bar colors ride the same event.
+  // Apply the persisted theme before subscribing to theme-change events.
+  // RequestedTheme may synchronously trigger ActualThemeChanged; if the
+  // handler runs during construction, it re-renders rows before activation.
+  // The initial UI already has its XAML controls and language applied.
+  ApplyTheme(settings_.theme);
+  // Do not reference a resource defined in the same Grid's
+  // ThemeDictionaries from the Grid's own XAML attribute: on a cold
+  // WinUI launch the forward ThemeResource lookup can surface as an
+  // unhandled XAML load exception before the window is created.
+  // Resolve the brush only after InitializeComponent + RequestedTheme.
+  RootGrid().Background(ThemeBrush(L"TasklySurfaceBrush"));
   RootGrid().ActualThemeChanged(
       [weak = get_weak()](auto&&, auto&&) {
         if (auto window = weak.get()) {
           window->OnEffectiveThemeChanged();
         }
       });
-  ApplyTitleBarTheme();
   InitializeBackendAsync();
 }
 
@@ -726,6 +804,7 @@ void MainWindow::ApplyTitleBarTheme() {
 // time — XAML ThemeResource bindings update themselves, hand-built rows do
 // not.
 void MainWindow::OnEffectiveThemeChanged() {
+  RootGrid().Background(ThemeBrush(L"TasklySurfaceBrush"));
   ApplyTitleBarTheme();
   RenderSidebar();
   RenderTasks();