Fix stay-on-top Ui::Window-s on macOS.

ui/platform/mac/ui_window_mac.h

@@ -23,6 +23,7 @@ public:
 	void setTitleStyle(const style::WindowTitle &st) override;
 	void setMinimumSize(QSize size) override;
 	void setFixedSize(QSize size) override;
+	void setStaysOnTop(bool enabled) override;
 	void setGeometry(QRect rect) override;
 	void close() override;
 

ui/platform/mac/ui_window_mac.mm

@@ -117,6 +117,7 @@ public:
 	[[nodiscard]] QRect controlsRect() const;
 	[[nodiscard]] bool checkNativeMove(void *nswindow) const;
 	void activateBeforeNativeMove();
+	void setStaysOnTop(bool enabled);
 	void close();
 
 private:
@@ -127,6 +128,7 @@ private:
 
 	[[nodiscard]] Fn<void(bool)> toggleCustomTitleCallback();
 	[[nodiscard]] Fn<void()> enforceStyleCallback();
+	void enforceStyle();
 
 	const not_null<WindowHelper*> _owner;
 	const WindowObserver *_observer = nullptr;
@@ -141,13 +143,14 @@ private:
 };
 
 WindowHelper::Private::Private(not_null<WindowHelper*> owner)
-: _owner(owner)
+: _owner(owner) {
-, _observer([[WindowObserver alloc] initWithToggle:toggleCustomTitleCallback() enforce:enforceStyleCallback()]) {
 	init();
 }
 
 WindowHelper::Private::~Private() {
-	[_observer release];
+	if (_observer) {
+		[_observer release];
+	}
 }
 
 int WindowHelper::Private::customTitleHeight() const {
@@ -201,6 +204,12 @@ void WindowHelper::Private::activateBeforeNativeMove() {
 	[_nativeWindow makeKeyAndOrderFront:_nativeWindow];
 }
 
+void WindowHelper::Private::setStaysOnTop(bool enabled) {
+	_owner->BasicWindowHelper::setStaysOnTop(enabled);
+	resolveWeakPointers();
+	initCustomTitle();
+}
+
 void WindowHelper::Private::close() {
 	const auto weak = Ui::MakeWeak(_owner->window());
 	QCloseEvent e;
@@ -218,11 +227,13 @@ Fn<void(bool)> WindowHelper::Private::toggleCustomTitleCallback() {
 }
 
 Fn<void()> WindowHelper::Private::enforceStyleCallback() {
-	return crl::guard(_owner->window(), [=] {
+	return crl::guard(_owner->window(), [=] { enforceStyle(); });
-		if (_nativeWindow && _customTitleHeight > 0) {
+}
-			[_nativeWindow setStyleMask:[_nativeWindow styleMask] | NSFullSizeContentViewWindowMask];
+
-		}
+void WindowHelper::Private::enforceStyle() {
-	});
+	if (_nativeWindow && _customTitleHeight > 0) {
+		[_nativeWindow setStyleMask:[_nativeWindow styleMask] | NSFullSizeContentViewWindowMask];
+	}
 }
 
 void WindowHelper::Private::initOpenGL() {
@@ -246,6 +257,10 @@ void WindowHelper::Private::initCustomTitle() {
 
 	[_nativeWindow setTitlebarAppearsTransparent:YES];
 
+	if (_observer) {
+		[_observer release];
+	}
+	_observer = [[WindowObserver alloc] initWithToggle:toggleCustomTitleCallback() enforce:enforceStyleCallback()];
 	[[NSNotificationCenter defaultCenter] addObserver:_observer selector:@selector(windowWillEnterFullScreen:) name:NSWindowWillEnterFullScreenNotification object:_nativeWindow];
 	[[NSNotificationCenter defaultCenter] addObserver:_observer selector:@selector(windowWillExitFullScreen:) name:NSWindowWillExitFullScreenNotification object:_nativeWindow];
 	[[NSNotificationCenter defaultCenter] addObserver:_observer selector:@selector(windowDidExitFullScreen:) name:NSWindowDidExitFullScreenNotification object:_nativeWindow];
@@ -342,6 +357,10 @@ void WindowHelper::setFixedSize(QSize size) {
 		(_title ? _title->height() : 0) + size.height());
 }
 
+void WindowHelper::setStaysOnTop(bool enabled) {
+	_private->setStaysOnTop(enabled);
+}
+
 void WindowHelper::setGeometry(QRect rect) {
 	window()->setGeometry(
 		rect.marginsAdded({ 0, (_title ? _title->height() : 0), 0, 0 }));

ui/platform/ui_platform_window.cpp

@@ -52,6 +52,10 @@ void BasicWindowHelper::setFixedSize(QSize size) {
 	_window->setFixedSize(size);
 }
 
+void BasicWindowHelper::setStaysOnTop(bool enabled) {
+	_window->setWindowFlag(Qt::WindowStaysOnTopHint, enabled);
+}
+
 void BasicWindowHelper::setGeometry(QRect rect) {
 	_window->setGeometry(rect);
 }

ui/platform/ui_platform_window.h

@@ -32,6 +32,7 @@ public:
 	virtual void setTitleStyle(const style::WindowTitle &st);
 	virtual void setMinimumSize(QSize size);
 	virtual void setFixedSize(QSize size);
+	virtual void setStaysOnTop(bool enabled);
 	virtual void setGeometry(QRect rect);
 	virtual void showFullScreen();
 	virtual void showNormal();

ui/widgets/window.cpp

@@ -44,6 +44,10 @@ void Window::setFixedSize(QSize size) {
 	_helper->setFixedSize(size);
 }
 
+void Window::setStaysOnTop(bool enabled) {
+	_helper->setStaysOnTop(enabled);
+}
+
 void Window::setGeometry(QRect rect) {
 	_helper->setGeometry(rect);
 }

ui/widgets/window.h

@@ -41,6 +41,7 @@ public:
 	void setTitleStyle(const style::WindowTitle &st);
 	void setMinimumSize(QSize size);
 	void setFixedSize(QSize size);
+	void setStaysOnTop(bool enabled);
 	void setGeometry(QRect rect);
 	void showFullScreen();
 	void showNormal();