diff --git a/include/FramelessHelper/Quick/private/framelessquickhelper_p.h b/include/FramelessHelper/Quick/private/framelessquickhelper_p.h
index 6f7c855..84bd411 100644
--- a/include/FramelessHelper/Quick/private/framelessquickhelper_p.h
+++ b/include/FramelessHelper/Quick/private/framelessquickhelper_p.h
@@ -97,6 +97,7 @@ private:
     QColor m_savedWindowBackgroundColor = {};
     bool m_blurBehindWindowEnabled = false;
     std::optional<bool> m_extendIntoTitleBar = std::nullopt;
+    bool m_destroying = false;
 };
 
 FRAMELESSHELPER_END_NAMESPACE
diff --git a/include/FramelessHelper/Widgets/private/framelesswidgetshelper_p.h b/include/FramelessHelper/Widgets/private/framelesswidgetshelper_p.h
index 12528d9..f9ed797 100644
--- a/include/FramelessHelper/Widgets/private/framelesswidgetshelper_p.h
+++ b/include/FramelessHelper/Widgets/private/framelesswidgetshelper_p.h
@@ -92,6 +92,7 @@ private:
     QColor m_savedWindowBackgroundColor = {};
     bool m_blurBehindWindowEnabled = false;
     QPointer<QWidget> m_window = nullptr;
+    bool m_destroying = false;
 };
 
 FRAMELESSHELPER_END_NAMESPACE
diff --git a/src/core/framelessmanager.cpp b/src/core/framelessmanager.cpp
index 2ed0190..1542f23 100644
--- a/src/core/framelessmanager.cpp
+++ b/src/core/framelessmanager.cpp
@@ -25,6 +25,7 @@
 #include "framelessmanager_p.h"
 #include <QtCore/qdebug.h>
 #include <QtCore/qmutex.h>
+#include <QtCore/qcoreapplication.h>
 #include <QtGui/qscreen.h>
 #include <QtGui/qwindow.h>
 #include <QtGui/qfontdatabase.h>
@@ -73,14 +74,15 @@ Q_GLOBAL_STATIC(FramelessManagerHelper, g_helper)
 
 Q_GLOBAL_STATIC(FramelessManager, g_manager)
 
+[[maybe_unused]] static constexpr const char kGlobalFlagVarName[] = "__FRAMELESSHELPER__";
 FRAMELESSHELPER_STRING_CONSTANT2(IconFontFilePath, ":/org.wangwenx190.FramelessHelper/resources/fonts/Micon.ttf")
 FRAMELESSHELPER_STRING_CONSTANT2(IconFontFamilyName_win11, "Segoe Fluent Icons")
 FRAMELESSHELPER_STRING_CONSTANT2(IconFontFamilyName_win10, "Segoe MDL2 Assets")
 FRAMELESSHELPER_STRING_CONSTANT2(IconFontFamilyName_common, "micon_nb")
 #ifdef Q_OS_MACOS
-  static constexpr const int kIconFontPointSize = 10;
+  [[maybe_unused]] static constexpr const int kIconFontPointSize = 10;
 #else
-  static constexpr const int kIconFontPointSize = 8;
+  [[maybe_unused]] static constexpr const int kIconFontPointSize = 8;
 #endif
 
 [[nodiscard]] static inline QString iconFontFamilyName()
@@ -352,11 +354,21 @@ void FramelessManagerPrivate::initialize()
     m_wallpaperAspectStyle = Utils::getWallpaperAspectStyle();
 #if (QT_VERSION >= QT_VERSION_CHECK(6, 5, 0))
     QStyleHints * const styleHints = QGuiApplication::styleHints();
-    connect(styleHints, &QStyleHints::appearanceChanged, this, [this](const Qt::Appearance appearance){
-        Q_UNUSED(appearance);
-        notifySystemThemeHasChangedOrNot();
-    });
+    Q_ASSERT(styleHints);
+    if (styleHints) {
+        connect(styleHints, &QStyleHints::appearanceChanged, this, [this](const Qt::Appearance appearance){
+            Q_UNUSED(appearance);
+            notifySystemThemeHasChangedOrNot();
+        });
+    }
 #endif // (QT_VERSION >= QT_VERSION_CHECK(6, 5, 0))
+    static bool flagSet = false;
+    if (!flagSet) {
+        flagSet = true;
+        // Set a global flag so that people can check whether FramelessHelper is being
+        // used without actually accessing the FramelessHelper interface.
+        qApp->setProperty(kGlobalFlagVarName, FramelessHelper::Core::version().version);
+    }
 }
 
 FramelessManager::FramelessManager(QObject *parent) :
diff --git a/src/core/utils_win.cpp b/src/core/utils_win.cpp
index 272aa1b..7ddb6c1 100644
--- a/src/core/utils_win.cpp
+++ b/src/core/utils_win.cpp
@@ -282,18 +282,20 @@ struct SYSTEM_METRIC
     if (code == ERROR_SUCCESS) {
         return kSuccessMessageText;
     }
-#if 0 // The following code works well, we commented it out just because we want to use as many Qt functionalities as possible.
-    LPWSTR buf = nullptr;
-    if (FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
-                       nullptr, code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), reinterpret_cast<LPWSTR>(&buf), 0, nullptr) == 0) {
-        return kEmptyMessageText;
+    static constexpr const bool flag = false;
+    if (flag) {
+        // The following code works well, we commented it out just because we want to use as many Qt functionalities as possible.
+        LPWSTR buf = nullptr;
+        if (FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                           nullptr, code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), reinterpret_cast<LPWSTR>(&buf), 0, nullptr) == 0) {
+            return kEmptyMessageText;
+        }
+        const QString errorText = QString::fromWCharArray(buf).trimmed();
+        LocalFree(buf);
+        buf = nullptr;
+        return kErrorMessageTemplate.arg(function, QString::number(code), errorText);
     }
-    const QString errorText = QString::fromWCharArray(buf).trimmed();
-    LocalFree(buf);
-    buf = nullptr;
-#else
     const QString errorText = QSystemError::windowsString(code);
-#endif
     return kErrorMessageTemplate.arg(function, QString::number(code), errorText);
 }
 
diff --git a/src/quick/framelessquickhelper.cpp b/src/quick/framelessquickhelper.cpp
index a837941..9b678c5 100644
--- a/src/quick/framelessquickhelper.cpp
+++ b/src/quick/framelessquickhelper.cpp
@@ -103,6 +103,7 @@ FramelessQuickHelperPrivate::FramelessQuickHelperPrivate(FramelessQuickHelper *q
 
 FramelessQuickHelperPrivate::~FramelessQuickHelperPrivate()
 {
+    m_destroying = true;
     extendsContentIntoTitleBar(false);
     m_extendIntoTitleBar = std::nullopt;
 }
@@ -141,7 +142,9 @@ void FramelessQuickHelperPrivate::extendsContentIntoTitleBar(const bool value)
         detach();
     }
     m_extendIntoTitleBar = value;
-    emitSignalForAllInstances(FRAMELESSHELPER_BYTEARRAY_LITERAL("extendsContentIntoTitleBarChanged"));
+    if (!m_destroying) {
+        emitSignalForAllInstances(FRAMELESSHELPER_BYTEARRAY_LITERAL("extendsContentIntoTitleBarChanged"));
+    }
 }
 
 QQuickItem *FramelessQuickHelperPrivate::getTitleBarItem() const
diff --git a/src/widgets/framelesswidgetshelper.cpp b/src/widgets/framelesswidgetshelper.cpp
index 6ac5634..78b8694 100644
--- a/src/widgets/framelesswidgetshelper.cpp
+++ b/src/widgets/framelesswidgetshelper.cpp
@@ -109,6 +109,7 @@ FramelessWidgetsHelperPrivate::FramelessWidgetsHelperPrivate(FramelessWidgetsHel
 
 FramelessWidgetsHelperPrivate::~FramelessWidgetsHelperPrivate()
 {
+    m_destroying = true;
     extendsContentIntoTitleBar(false);
 }
 
@@ -448,7 +449,9 @@ void FramelessWidgetsHelperPrivate::extendsContentIntoTitleBar(const bool value)
     } else {
         detach();
     }
-    emitSignalForAllInstances(FRAMELESSHELPER_BYTEARRAY_LITERAL("extendsContentIntoTitleBarChanged"));
+    if (!m_destroying) {
+        emitSignalForAllInstances(FRAMELESSHELPER_BYTEARRAY_LITERAL("extendsContentIntoTitleBarChanged"));
+    }
 }
 
 QWidget *FramelessWidgetsHelperPrivate::findTopLevelWindow() const