From f6a1a44efeba79339bdb114ef9a36a9ba865e64b Mon Sep 17 00:00:00 2001
From: John Preston <johnprestonmail@gmail.com>
Date: Sat, 20 Mar 2021 15:16:50 +0400
Subject: [PATCH] Fix maximize/restore button state in TitleWidget.

---
 ui/platform/ui_platform_window_title.cpp | 43 ++++++++++++++----------
 ui/platform/ui_platform_window_title.h   |  1 +
 2 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/ui/platform/ui_platform_window_title.cpp b/ui/platform/ui_platform_window_title.cpp
index 8a2d5f5..1a5b406 100644
--- a/ui/platform/ui_platform_window_title.cpp
+++ b/ui/platform/ui_platform_window_title.cpp
@@ -122,29 +122,36 @@ void TitleControls::init(Fn<void(bool maximized)> maximize) {
 		updateControlsPosition();
 	}, _close->lifetime());
 
-	const auto winIdEventFilter = std::make_shared<QObject*>(nullptr);
-	*winIdEventFilter = base::install_event_filter(
-		window(),
-		[=](not_null<QEvent*> e) {
-			if (!*winIdEventFilter || e->type() != QEvent::WinIdChange) {
-				return base::EventFilterResult::Continue;
-			}
-
-			QObject::connect(
-				window()->windowHandle(),
-				&QWindow::windowStateChanged,
-				[=](Qt::WindowState state) {
-					handleWindowStateChanged(state);
-				});
-
-			base::take(*winIdEventFilter)->deleteLater();
-			return base::EventFilterResult::Continue;
-		});
+	subscribeToStateChanges();
 
 	_activeState = parent()->isActiveWindow();
 	updateButtonsState();
 }
 
+void TitleControls::subscribeToStateChanges() {
+	const auto subscribe = [=] {
+		QObject::connect(
+			window()->windowHandle(),
+			&QWindow::windowStateChanged,
+			[=](Qt::WindowState state) { handleWindowStateChanged(state); });
+	};
+	if (window()->windowHandle()) {
+		subscribe();
+	} else {
+		const auto winIdEventFilter = std::make_shared<QObject*>(nullptr);
+		*winIdEventFilter = base::install_event_filter(
+			window(),
+			[=](not_null<QEvent*> e) {
+				if (!*winIdEventFilter || e->type() != QEvent::WinIdChange) {
+					return base::EventFilterResult::Continue;
+				}
+				subscribe();
+				base::take(*winIdEventFilter)->deleteLater();
+				return base::EventFilterResult::Continue;
+			});
+	}
+}
+
 void TitleControls::setResizeEnabled(bool enabled) {
 	_resizeEnabled = enabled;
 	updateControlsPosition();
diff --git a/ui/platform/ui_platform_window_title.h b/ui/platform/ui_platform_window_title.h
index af66155..f8373ad 100644
--- a/ui/platform/ui_platform_window_title.h
+++ b/ui/platform/ui_platform_window_title.h
@@ -54,6 +54,7 @@ private:
 	[[nodiscard]] Ui::IconButton *controlWidget(Control control) const;
 
 	void init(Fn<void(bool maximized)> maximize);
+	void subscribeToStateChanges();
 	void updateButtonsState();
 	void updateControlsPosition();
 	void updateControlsPositionBySide(