Remove WindowingOwner.hasTopLevelWindows (flutter#178033)

This function doesn't seem to serve any purpose.
Top level is not a term we are currently using in the multi window code.
If we want to track if we have open windows, this can be done in the
Flutter framework - it doesn't need to be done at the platform level.

Author: robert-ancell

engine/src/flutter/shell/platform/windows/window_manager.cc

@@ -27,10 +27,6 @@ void WindowManager::Initialize(const WindowingInitRequest* request) {
   isolate_ = Isolate::Current();
 }
 
-bool WindowManager::HasTopLevelWindows() const {
-  return !active_windows_.empty();
-}
-
 FlutterViewId WindowManager::CreateRegularWindow(
     const RegularWindowCreationRequest* request) {
   auto window = HostWindow::CreateRegularWindow(
@@ -121,13 +117,6 @@ void InternalFlutterWindows_WindowManager_Initialize(
   engine->window_manager()->Initialize(request);
 }
 
-bool InternalFlutterWindows_WindowManager_HasTopLevelWindows(
-    int64_t engine_id) {
-  flutter::FlutterWindowsEngine* engine =
-      flutter::FlutterWindowsEngine::GetEngineForId(engine_id);
-  return engine->window_manager()->HasTopLevelWindows();
-}
-
 FlutterViewId InternalFlutterWindows_WindowManager_CreateRegularWindow(
     int64_t engine_id,
     const flutter::RegularWindowCreationRequest* request) {

engine/src/flutter/shell/platform/windows/window_manager.h

@@ -88,8 +88,6 @@ class WindowManager {
 
   void Initialize(const WindowingInitRequest* request);
 
-  bool HasTopLevelWindows() const;
-
   FlutterViewId CreateRegularWindow(
       const RegularWindowCreationRequest* request);
 
@@ -132,9 +130,6 @@ void InternalFlutterWindows_WindowManager_Initialize(
     int64_t engine_id,
     const flutter::WindowingInitRequest* request);
 
-FLUTTER_EXPORT
-bool InternalFlutterWindows_WindowManager_HasTopLevelWindows(int64_t engine_id);
-
 FLUTTER_EXPORT
 FlutterViewId InternalFlutterWindows_WindowManager_CreateRegularWindow(
     int64_t engine_id,

engine/src/flutter/shell/platform/windows/window_manager_unittests.cc

@@ -82,20 +82,6 @@ TEST_F(WindowManagerTest, WindowingInitialize) {
   EXPECT_TRUE(received_message);
 }
 
-TEST_F(WindowManagerTest, HasTopLevelWindows) {
-  IsolateScope isolate_scope(isolate());
-
-  bool has_top_level_windows =
-      InternalFlutterWindows_WindowManager_HasTopLevelWindows(engine_id());
-  EXPECT_FALSE(has_top_level_windows);
-
-  InternalFlutterWindows_WindowManager_CreateRegularWindow(
-      engine_id(), regular_creation_request());
-  has_top_level_windows =
-      InternalFlutterWindows_WindowManager_HasTopLevelWindows(engine_id());
-  EXPECT_TRUE(has_top_level_windows);
-}
-
 TEST_F(WindowManagerTest, CreateRegularWindow) {
   IsolateScope isolate_scope(isolate());
 

packages/flutter/lib/src/widgets/_window.dart

@@ -657,13 +657,6 @@ abstract class WindowingOwner {
     BaseWindowController? parent,
     String? title,
   });
-
-  /// Returns whether the application has any top level windows created by this
-  /// windowing owner.
-  ///
-  /// {@macro flutter.widgets.windowing.experimental}
-  @internal
-  bool hasTopLevelWindows();
 }
 
 /// Creates default windowing owner for standard desktop embedders.
@@ -709,11 +702,6 @@ class _WindowingOwnerUnsupported extends WindowingOwner {
   }) {
     throw UnsupportedError(errorMessage);
   }
-
-  @override
-  bool hasTopLevelWindows() {
-    throw UnsupportedError(errorMessage);
-  }
 }
 
 /// The [RegularWindow] widget provides a way to render a regular window in the

packages/flutter/lib/src/widgets/_window_linux.dart

@@ -512,9 +512,6 @@ class WindowingOwnerLinux extends WindowingOwner {
     );
   }
 
-  /// Number of windows being managed by Flutter.
-  int _windowCount = 0;
-
   @internal
   @override
   RegularWindowController createRegularWindowController({
@@ -523,9 +520,7 @@ class WindowingOwnerLinux extends WindowingOwner {
     String? title,
     required RegularWindowControllerDelegate delegate,
   }) {
-    _windowCount++;
     return RegularWindowControllerLinux(
-      owner: this,
       delegate: delegate,
       preferredSize: preferredSize,
       preferredConstraints: preferredConstraints,
@@ -544,12 +539,6 @@ class WindowingOwnerLinux extends WindowingOwner {
   }) {
     throw UnimplementedError('Dialog windows are not yet implemented on Linux.');
   }
-
-  @internal
-  @override
-  bool hasTopLevelWindows() {
-    return _windowCount > 0;
-  }
 }
 
 /// Implementation of [RegularWindowController] for the Linux platform.
@@ -572,13 +561,11 @@ class RegularWindowControllerLinux extends RegularWindowController {
   ///  * [RegularWindowController], the base class for regular windows.
   @internal
   RegularWindowControllerLinux({
-    required WindowingOwnerLinux owner,
     required RegularWindowControllerDelegate delegate,
     Size? preferredSize,
     BoxConstraints? preferredConstraints,
     String? title,
-  }) : _owner = owner,
-       _delegate = delegate,
+  }) : _delegate = delegate,
        _window = _GtkWindow(),
        super.empty() {
     if (!isWindowingEnabled) {
@@ -621,7 +608,6 @@ class RegularWindowControllerLinux extends RegularWindowController {
     _window.present();
   }
 
-  final WindowingOwnerLinux _owner;
   final RegularWindowControllerDelegate _delegate;
   final _GtkWindow _window;
   late final _FlWindowMonitor _windowMonitor;
@@ -640,7 +626,6 @@ class RegularWindowControllerLinux extends RegularWindowController {
     _windowMonitor.close();
     _windowMonitor.unref();
     _destroyed = true;
-    _owner._windowCount--;
   }
 
   @override

packages/flutter/lib/src/widgets/_window_macos.dart

@@ -90,11 +90,6 @@ class WindowingOwnerMacOS extends WindowingOwner {
     return res;
   }
 
-  @override
-  bool hasTopLevelWindows() {
-    return _activeControllers.isNotEmpty;
-  }
-
   final List<BaseWindowController> _activeControllers = <BaseWindowController>[];
 
   /// Returns the window handle for the given [view], or null is the window

packages/flutter/lib/src/widgets/_window_win32.dart

@@ -219,12 +219,6 @@ class WindowingOwnerWin32 extends WindowingOwner {
       }
     }
   }
-
-  @internal
-  @override
-  bool hasTopLevelWindows() {
-    return _Win32PlatformInterface.hasTopLevelWindows(PlatformDispatcher.instance.engineId!);
-  }
 }
 
 class _RegularWindowMesageHandler implements _WindowsMessageHandler {
@@ -673,11 +667,6 @@ class DialogWindowControllerWin32 extends DialogWindowController {
 }
 
 class _Win32PlatformInterface {
-  @ffi.Native<ffi.Bool Function(ffi.Int64)>(
-    symbol: 'InternalFlutterWindows_WindowManager_HasTopLevelWindows',
-  )
-  external static bool hasTopLevelWindows(int engineId);
-
   static void initializeWindowing(
     ffi.Allocator allocator,
     int engineId,

packages/flutter/test/widgets/windowing_test.dart

@@ -136,21 +136,6 @@ void main() {
         );
       });
 
-      test('default WindowingOwner throws when accessing hasTopLevelWindows', () {
-        final WindowingOwner owner = createDefaultWindowingOwner();
-        expect(() => owner.hasTopLevelWindows(), throwsUnsupportedError);
-      });
-
-      testWidgets('RegularWindow throws UnsupportedError', (WidgetTester tester) async {
-        expect(
-          () => RegularWindow(
-            controller: _StubRegularWindowController(tester),
-            child: const Text('Test'),
-          ),
-          throwsUnsupportedError,
-        );
-      });
-
       testWidgets('DialogWindow throws UnsupportedError', (WidgetTester tester) async {
         expect(
           () => DialogWindow(