plezy/windows/runner/flutter_window.cpp

#include "flutter_window.h"

#include <optional>

#include "flutter/generated_plugin_registrant.h"
#include "mpv/display_mode_manager.h"
#include "mpv/mpv_plugin.h"

static constexpr wchar_t kWindowPlacementKey[] = L"Software\\Plezy";
static constexpr wchar_t kWindowPlacementValue[] = L"WindowPlacement";

static UINT_PTR g_saveTimerId = 0;
static HWND g_mainHwnd = nullptr;
// When true, WM_WINDOWPOSCHANGED should not persist placement. Used while a
// native fullscreen toggle is in flux so we don't record the fullscreen rect
// as the user's last "normal" placement.
static bool g_suppressPlacementSave = false;

static void SaveWindowPlacement(HWND hwnd);

static void CALLBACK SaveTimerProc(HWND, UINT, UINT_PTR, DWORD) {
  if (g_mainHwnd) SaveWindowPlacement(g_mainHwnd);
  KillTimer(nullptr, g_saveTimerId);
  g_saveTimerId = 0;
}

static void WriteWindowPlacement(const WINDOWPLACEMENT& wp) {
  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);
  }
}

// GetWindowPlacement with Aero Snap folded in. A snapped window is "arranged":
// Windows keeps the pre-snap rect in rcNormalPosition and still reports
// SW_SHOWNORMAL, so persisting the raw placement restores the window where it
// was *before* the snap. Substitute the on-screen rect instead; there is no
// API to re-enter the snapped state, so relaunch lands a normal window on the
// same rect. IsWindowArranged is exported by user32 since Windows 10 1903 but
// has no header/import-lib declaration; older builds fall through unchanged.
static bool QueryWindowPlacement(HWND hwnd, WINDOWPLACEMENT* wp) {
  wp->length = sizeof(*wp);
  if (!GetWindowPlacement(hwnd, wp)) return false;

  using IsWindowArrangedFn = BOOL(WINAPI*)(HWND);
  static const IsWindowArrangedFn is_window_arranged =
      reinterpret_cast<IsWindowArrangedFn>(GetProcAddress(GetModuleHandleW(L"user32.dll"), "IsWindowArranged"));
  if (!is_window_arranged || IsIconic(hwnd) || IsZoomed(hwnd) || !is_window_arranged(hwnd)) return true;

  // rcNormalPosition uses the window monitor's workspace inset, not the
  // primary work area's screen origin. LoadWindowPlacement reverses this.
  RECT rect{};
  if (!GetWindowRect(hwnd, &rect)) return true;
  MONITORINFO mi{};
  mi.cbSize = sizeof(mi);
  if (!GetMonitorInfoW(MonitorFromWindow(hwnd, MONITOR_DEFAULTTONEAREST), &mi)) return true;
  OffsetRect(&rect, mi.rcMonitor.left - mi.rcWork.left, mi.rcMonitor.top - mi.rcWork.top);
  wp->rcNormalPosition = rect;
  return true;
}

static void SaveWindowPlacement(HWND hwnd) {
  // Never persist a hidden window: the exit path hides the window before its
  // multi-second teardown, and a save landing in that gap would record
  // SW_HIDE over the user's real show state.
  if (!IsWindowVisible(hwnd)) return;
  WINDOWPLACEMENT wp{};
  if (!QueryWindowPlacement(hwnd, &wp)) return;
  WriteWindowPlacement(wp);
}

// Loads the saved WINDOWPLACEMENT and applies it while keeping the window
// hidden; the first-frame callback in OnCreate performs the single show.
// Returns whether the window should be shown maximized.
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 wasMaximized = false;

  if (RegQueryValueExW(hKey, kWindowPlacementValue, nullptr, nullptr, reinterpret_cast<BYTE*>(&wp), &size) ==
          ERROR_SUCCESS &&
      size == sizeof(wp)) {
    // A window minimized away from the maximized state stores SW_SHOWMINIMIZED
    // plus WPF_RESTORETOMAXIMIZED; both spellings mean "maximized" on relaunch.
    wasMaximized = wp.showCmd == SW_SHOWMAXIMIZED || (wp.flags & WPF_RESTORETOMAXIMIZED) != 0;

    // The saved monitor may be gone (undocked laptop, powered-off TV).
    // Resolve the saved rect's monitor before reversing its workspace inset.
    // On a miss, keep the size but fall back to the default creation position
    // so the window never restores invisible.
    RECT screenRect = wp.rcNormalPosition;
    MONITORINFO mi{};
    mi.cbSize = sizeof(mi);
    bool on_screen = false;
    if (GetMonitorInfoW(MonitorFromRect(&screenRect, MONITOR_DEFAULTTONEAREST), &mi)) {
      OffsetRect(&screenRect, mi.rcWork.left - mi.rcMonitor.left, mi.rcWork.top - mi.rcMonitor.top);
      on_screen = MonitorFromRect(&screenRect, MONITOR_DEFAULTTONULL) != nullptr;
    }
    if (!on_screen) {
      // GetWindowPlacement already expresses the creation rect in its own
      // monitor's workspace, including when the default monitor has an inset.
      WINDOWPLACEMENT current{};
      current.length = sizeof(current);
      if (!GetWindowPlacement(hwnd, &current)) {
        RegCloseKey(hKey);
        return false;
      }
      const LONG width = wp.rcNormalPosition.right - wp.rcNormalPosition.left;
      const LONG height = wp.rcNormalPosition.bottom - wp.rcNormalPosition.top;
      wp.rcNormalPosition.left = current.rcNormalPosition.left;
      wp.rcNormalPosition.top = current.rcNormalPosition.top;
      wp.rcNormalPosition.right = wp.rcNormalPosition.left + width;
      wp.rcNormalPosition.bottom = wp.rcNormalPosition.top + height;
    }

    // Apply hidden. A visible showCmd here would display a blank window at
    // the restored spot before Flutter has rendered anything.
    wp.showCmd = SW_HIDE;
    SetWindowPlacement(hwnd, &wp);
  }

  RegCloseKey(hKey);
  return wasMaximized;
}

static void DebounceSaveWindowPlacement(HWND hwnd) {
  g_mainHwnd = hwnd;
  if (g_saveTimerId) KillTimer(nullptr, g_saveTimerId);
  g_saveTimerId = SetTimer(nullptr, 0, 500, SaveTimerProc);
}

FlutterWindow::FlutterWindow(const flutter::DartProject& project) : project_(project) {}

FlutterWindow::~FlutterWindow() {}

bool FlutterWindow::OnCreate() {
  if (!Win32Window::OnCreate()) {
    return false;
  }

  RECT frame = GetClientArea();

  // The size here must match the window dimensions to avoid unnecessary surface
  // creation / destruction in the startup path.
  flutter_controller_ =
      std::make_unique<flutter::FlutterViewController>(frame.right - frame.left, frame.bottom - frame.top, project_);
  if (!flutter_controller_->engine() || !flutter_controller_->view()) {
    return false;
  }
  RegisterPlugins(flutter_controller_->engine());

  OutputDebugStringA("FlutterWindow: About to register MpvPlayerPlugin\n");
  MpvPlayerPluginRegisterWithRegistrar(flutter_controller_->engine()->GetRegistrarForPlugin("MpvPlayerPlugin"));
  MpvAudioPlayerPluginRegisterWithRegistrar(
      flutter_controller_->engine()->GetRegistrarForPlugin("MpvAudioPlayerPlugin"));
  OutputDebugStringA("FlutterWindow: MpvPlayerPlugin registered\n");

  RegisterWindowChannel();

  SetChildContent(flutter_controller_->view()->GetNativeWindow());

  HWND hwnd = GetHandle();
  bool maximized = LoadWindowPlacement(hwnd);

  flutter_controller_->engine()->SetNextFrameCallback(
      [this, maximized]() { ::ShowWindow(this->GetHandle(), maximized ? SW_SHOWMAXIMIZED : SW_SHOWNORMAL); });

  // Flutter can complete the first frame before the "show window" callback is
  // registered. The following call ensures a frame is pending to ensure the
  // window is shown. It is a no-op if the first frame hasn't completed yet.
  flutter_controller_->ForceRedraw();

  return true;
}

void FlutterWindow::OnDestroy() {
  // Cancel any pending save timer and save immediately
  if (g_saveTimerId) {
    KillTimer(nullptr, g_saveTimerId);
    g_saveTimerId = 0;
  }
  // If still fullscreen at shutdown, persist the pre-fullscreen placement
  // rather than the fullscreen rect so the next launch restores correctly.
  if (is_fullscreen_ && placement_before_fullscreen_.length != 0) {
    WriteWindowPlacement(placement_before_fullscreen_);
  } else {
    SaveWindowPlacement(GetHandle());
  }

  window_channel_ = nullptr;

  if (flutter_controller_) {
    flutter_controller_ = nullptr;
  }

  Win32Window::OnDestroy();
}

LRESULT
FlutterWindow::MessageHandler(HWND hwnd, UINT const message, WPARAM const wparam, LPARAM const lparam) noexcept {
  // Give Flutter, including plugins, an opportunity to handle window messages.
  if (flutter_controller_) {
    std::optional<LRESULT> result = flutter_controller_->HandleTopLevelWindowProc(hwnd, message, wparam, lparam);
    if (result) {
      return *result;
    }
  }

  switch (message) {
    case WM_DISPLAYCHANGE:
      // One bounded, serialized retry for a display that may have reconnected.
      mpv::DisplayModeManager::RecoverIfNeeded();
      break;
    case WM_FONTCHANGE:
      flutter_controller_->engine()->ReloadSystemFonts();
      break;
    case WM_WINDOWPOSCHANGED:
      // Don't persist placement while fullscreen, mid-toggle, or hidden — the
      // rect would overwrite the user's real window position or show state.
      if (!is_fullscreen_ && !g_suppressPlacementSave && IsWindowVisible(hwnd)) {
        DebounceSaveWindowPlacement(hwnd);
      }
      break;
  }

  return Win32Window::MessageHandler(hwnd, message, wparam, lparam);
}

// ---------------------------------------------------------------------------
// Native fullscreen (plezy/window method channel)
//
// Works around window_manager 0.5.1's multi-monitor fullscreen bug where the
// window ends up on the wrong monitor and renders only a fragment of the
// Flutter surface. We:
//   1) Resolve the target monitor by the current window's center point
//      (robust across DPI and restore transitions).
//   2) Save WINDOWPLACEMENT + styles once.
//   3) Strip WS_OVERLAPPEDWINDOW and move+size in a single SetWindowPos so
//      Flutter only relayouts once, at the final DPI/size.
//   4) On exit, restore styles and WINDOWPLACEMENT, re-maximizing if needed.
// ---------------------------------------------------------------------------
void FlutterWindow::RegisterWindowChannel() {
  auto messenger = flutter_controller_->engine()->messenger();
  window_channel_ = std::make_unique<flutter::MethodChannel<flutter::EncodableValue>>(
      messenger, "plezy/window", &flutter::StandardMethodCodec::GetInstance());

  window_channel_->SetMethodCallHandler([this](
                                            const flutter::MethodCall<flutter::EncodableValue>& call,
                                            std::unique_ptr<flutter::MethodResult<flutter::EncodableValue>> result) {
    const std::string& name = call.method_name();
    if (name == "setFullScreen") {
      bool value = false;
      if (const auto* args = std::get_if<flutter::EncodableMap>(call.arguments())) {
        auto it = args->find(flutter::EncodableValue("isFullScreen"));
        if (it != args->end()) {
          if (const bool* b = std::get_if<bool>(&it->second)) value = *b;
        }
      }
      SetNativeFullScreen(value);
      result->Success();
    } else if (name == "isFullScreen") {
      result->Success(flutter::EncodableValue(is_fullscreen_));
    } else {
      result->NotImplemented();
    }
  });
}

void FlutterWindow::NotifyFullScreenChanged() {
  if (!window_channel_) return;
  window_channel_->InvokeMethod("onFullScreenChanged", std::make_unique<flutter::EncodableValue>(is_fullscreen_));
}

void FlutterWindow::SetNativeFullScreen(bool fullscreen) {
  HWND hwnd = GetHandle();
  if (!hwnd) return;
  if (fullscreen == is_fullscreen_) return;

  g_suppressPlacementSave = true;
  // Also cancel any pending save so a WM_WINDOWPOSCHANGED just before the
  // toggle doesn't fire SaveTimerProc mid-transition.
  if (g_saveTimerId) {
    KillTimer(nullptr, g_saveTimerId);
    g_saveTimerId = 0;
  }

  if (fullscreen) {
    // Resolve target monitor first — if this fails we bail before mutating
    // any saved state, so a subsequent exit call has nothing stale to act on.
    RECT wr{};
    ::GetWindowRect(hwnd, &wr);
    // Center point is stable across maximize/straddle cases where
    // MonitorFromWindow would resolve to the neighbor monitor.
    POINT center{(wr.left + wr.right) / 2, (wr.top + wr.bottom) / 2};
    MONITORINFO mi{};
    mi.cbSize = sizeof(mi);
    if (!::GetMonitorInfoW(::MonitorFromPoint(center, MONITOR_DEFAULTTONEAREST), &mi)) {
      g_suppressPlacementSave = false;
      return;
    }

    // Save pre-fullscreen state (showCmd inside the placement carries the
    // maximize bit, so no separate flag is needed).
    QueryWindowPlacement(hwnd, &placement_before_fullscreen_);
    style_before_fullscreen_ = ::GetWindowLongPtr(hwnd, GWL_STYLE);
    ex_style_before_fullscreen_ = ::GetWindowLongPtr(hwnd, GWL_EXSTYLE);

    // Strip frame/caption. Stripping WS_OVERLAPPEDWINDOW alone is enough to
    // make the following SetWindowPos use the given rect exactly — no need
    // to ShowWindow(SW_SHOWNORMAL) first (would cause a second relayout).
    ::SetWindowLongPtr(hwnd, GWL_STYLE, style_before_fullscreen_ & ~WS_OVERLAPPEDWINDOW);
    ::SetWindowLongPtr(
        hwnd, GWL_EXSTYLE,
        ex_style_before_fullscreen_ & ~(WS_EX_DLGMODALFRAME | WS_EX_WINDOWEDGE | WS_EX_CLIENTEDGE | WS_EX_STATICEDGE));

    const RECT& r = mi.rcMonitor;
    ::SetWindowPos(
        hwnd, HWND_TOP, r.left, r.top, r.right - r.left, r.bottom - r.top,
        SWP_FRAMECHANGED | SWP_NOZORDER | SWP_NOACTIVATE);

    is_fullscreen_ = true;
  } else {
    if (style_before_fullscreen_ != 0) {
      ::SetWindowLongPtr(hwnd, GWL_STYLE, style_before_fullscreen_);
      ::SetWindowLongPtr(hwnd, GWL_EXSTYLE, ex_style_before_fullscreen_);
    }

    if (placement_before_fullscreen_.length == sizeof(WINDOWPLACEMENT)) {
      WINDOWPLACEMENT wp = placement_before_fullscreen_;
      if (wp.showCmd == SW_SHOWMINIMIZED) wp.showCmd = SW_SHOWNORMAL;
      ::SetWindowPlacement(hwnd, &wp);
    }

    // Force a frame refresh so restored chrome paints.
    ::SetWindowPos(
        hwnd, nullptr, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_NOACTIVATE | SWP_FRAMECHANGED);

    is_fullscreen_ = false;
    placement_before_fullscreen_ = {};
    style_before_fullscreen_ = 0;
    ex_style_before_fullscreen_ = 0;
  }

  g_suppressPlacementSave = false;
  NotifyFullScreenChanged();
}