fix: better handle Windows shutting down in newer Qt versions (#6368)

src/Application.cpp

@@ -607,6 +607,8 @@ void Application::aboutToQuit()
 
     this->hotkeys->save();
     this->windows->save();
+
+    this->windows->closeAll();
 }
 
 void Application::stop()

src/singletons/WindowManager.cpp

@@ -350,7 +350,7 @@ Window &WindowManager::createWindow(WindowType type, bool show, QWidget *parent)
     {
         window->setAttribute(Qt::WA_DeleteOnClose);
 
-        QObject::connect(window, &QWidget::destroyed, [this, window] {
+        QObject::connect(window, &QWidget::destroyed, this, [this, window] {
             for (auto it = this->windows_.begin(); it != this->windows_.end();
                  it++)
             {

src/singletons/WindowManager.hpp

@@ -5,6 +5,7 @@
 #include "widgets/splits/SplitContainer.hpp"
 
 #include <pajlada/settings/settinglistener.hpp>
+#include <QObject>
 #include <QPoint>
 #include <QTimer>
 
@@ -36,8 +37,10 @@ enum class WindowType;
 enum class SettingsDialogPreference;
 class FramelessEmbedWindow;
 
-class WindowManager final
+class WindowManager final : public QObject
 {
+    Q_OBJECT
+
     Theme &themes;
     const Args &appArgs;
 

src/widgets/Window.cpp

@@ -153,10 +153,19 @@ bool Window::event(QEvent *event)
 
 void Window::closeEvent(QCloseEvent *)
 {
+    if (isAppAboutToQuit())
+    {
+        qCWarning(chatterinoWidget)
+            << "Window closeEvent ran when Application is already dead";
+        return;
+    }
+
+    auto *app = getApp();
+
     if (this->type_ == WindowType::Main)
     {
-        getApp()->getWindows()->save();
-        getApp()->getWindows()->closeAll();
+        app->getWindows()->save();
+        app->getWindows()->closeAll();
     }
     else
     {
@@ -167,7 +176,7 @@ void Window::closeEvent(QCloseEvent *)
     // Ensure selectedWindow_ is never an invalid pointer.
     // WindowManager will return the main window if no window is pointed to by
     // `selectedWindow_`.
-    getApp()->getWindows()->selectedWindow_ = nullptr;
+    app->getWindows()->selectedWindow_ = nullptr;
 
     this->closed.invoke();