feat(windows): persist window position

windows/runner/flutter_window.cpp

@@ -5,6 +5,71 @@
 #include "flutter/generated_plugin_registrant.h"
 #include "mpv/mpv_plugin.h"
 
+// Registry key for window placement persistence
+static constexpr wchar_t kWindowPlacementKey[] = L"Software\\Plezy";
+static constexpr wchar_t kWindowPlacementValue[] = L"WindowPlacement";
+
+// Debounce timer for saving window placement
+static UINT_PTR g_saveTimerId = 0;
+static HWND g_mainHwnd = nullptr;
+
+// Forward declaration
+static void SaveWindowPlacement(HWND hwnd);
+
+// Timer callback for debounced save
+static void CALLBACK SaveTimerProc(HWND, UINT, UINT_PTR, DWORD) {
+  if (g_mainHwnd) SaveWindowPlacement(g_mainHwnd);
+  KillTimer(nullptr, g_saveTimerId);
+  g_saveTimerId = 0;
+}
+
+// Save WINDOWPLACEMENT to registry
+static void SaveWindowPlacement(HWND hwnd) {
+  WINDOWPLACEMENT wp{};
+  wp.length = sizeof(wp);
+  if (!GetWindowPlacement(hwnd, &wp)) return;
+
+  HKEY hKey;
+  if (RegCreateKeyExW(HKEY_CURRENT_USER, kWindowPlacementKey, 0, nullptr,
+                      REG_OPTION_NON_VOLATILE, KEY_WRITE, nullptr, &hKey,
+                      nullptr) == ERROR_SUCCESS) {
+    RegSetValueExW(hKey, kWindowPlacementValue, 0, REG_BINARY,
+                   reinterpret_cast<const BYTE*>(&wp), sizeof(wp));
+    RegCloseKey(hKey);
+  }
+}
+
+// Load and apply WINDOWPLACEMENT from registry
+static bool LoadWindowPlacement(HWND hwnd) {
+  HKEY hKey;
+  if (RegOpenKeyExW(HKEY_CURRENT_USER, kWindowPlacementKey, 0, KEY_READ,
+                    &hKey) != ERROR_SUCCESS)
+    return false;
+
+  WINDOWPLACEMENT wp{};
+  wp.length = sizeof(wp);
+  DWORD size = sizeof(wp);
+  bool success = false;
+
+  if (RegQueryValueExW(hKey, kWindowPlacementValue, nullptr, nullptr,
+                       reinterpret_cast<BYTE*>(&wp), &size) == ERROR_SUCCESS &&
+      size == sizeof(wp)) {
+    // Prevent restoring as minimized
+    if (wp.showCmd == SW_SHOWMINIMIZED) wp.showCmd = SW_SHOWNORMAL;
+    success = SetWindowPlacement(hwnd, &wp) != 0;
+  }
+
+  RegCloseKey(hKey);
+  return success;
+}
+
+// Debounce save to avoid excessive registry writes during resize/move
+static void DebounceSaveWindowPlacement(HWND hwnd) {
+  g_mainHwnd = hwnd;
+  if (g_saveTimerId) KillTimer(nullptr, g_saveTimerId);
+  g_saveTimerId = SetTimer(nullptr, 0, 500, SaveTimerProc);  // 500ms debounce
+}
+
 FlutterWindow::FlutterWindow(const flutter::DartProject& project)
     : project_(project) {}
 
@@ -35,7 +100,11 @@ bool FlutterWindow::OnCreate() {
 
   SetChildContent(flutter_controller_->view()->GetNativeWindow());
 
-  flutter_controller_->engine()->SetNextFrameCallback([&]() {
+  // Load saved window placement before showing
+  HWND hwnd = GetHandle();
+  bool hasPlacement = LoadWindowPlacement(hwnd);
+
+  flutter_controller_->engine()->SetNextFrameCallback([this, hasPlacement]() {
     this->Show();
   });
 
@@ -48,6 +117,13 @@ bool FlutterWindow::OnCreate() {
 }
 
 void FlutterWindow::OnDestroy() {
+  // Cancel any pending save timer and save immediately
+  if (g_saveTimerId) {
+    KillTimer(nullptr, g_saveTimerId);
+    g_saveTimerId = 0;
+  }
+  SaveWindowPlacement(GetHandle());
+
   if (flutter_controller_) {
     flutter_controller_ = nullptr;
   }
@@ -73,6 +149,9 @@ FlutterWindow::MessageHandler(HWND hwnd, UINT const message,
     case WM_FONTCHANGE:
       flutter_controller_->engine()->ReloadSystemFonts();
       break;
+    case WM_WINDOWPOSCHANGED:
+      DebounceSaveWindowPlacement(hwnd);
+      break;
   }
 
   return Win32Window::MessageHandler(hwnd, message, wparam, lparam);