diff --git a/src/core/text/qmsimplevarexp.cpp b/src/core/text/qmsimplevarexp.cpp
index bae7875..9d9b213 100644
--- a/src/core/text/qmsimplevarexp.cpp
+++ b/src/core/text/qmsimplevarexp.cpp
@@ -110,7 +110,11 @@ static QString parseExpression(QString s, const QHash<QString, QString> &vars,
         int lastIndex = 0;
         while ((index = s.indexOf(reg, index, &match)) != -1) {
             hasMatch = true;
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+            result += QStringView(s).sliced(lastIndex, index - lastIndex);
+#else
             result += s.midRef(lastIndex, index - lastIndex);
+#endif
 
             const auto &name = match.captured(1);
             QString val;
@@ -125,7 +129,11 @@ static QString parseExpression(QString s, const QHash<QString, QString> &vars,
             index += match.captured(0).size();
             lastIndex = index;
         }
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+        result += QStringView(s).sliced(lastIndex);
+#else
         result += s.midRef(lastIndex);
+#endif
         s = result;
     } while (hasMatch);
     s.replace(QStringLiteral("$$"), QStringLiteral("$"));
diff --git a/src/widgets/kernel/qmdecoratorv2.cpp b/src/widgets/kernel/qmdecoratorv2.cpp
index d99a8a6..95cce4a 100644
--- a/src/widgets/kernel/qmdecoratorv2.cpp
+++ b/src/widgets/kernel/qmdecoratorv2.cpp
@@ -557,10 +557,14 @@ QString QMDecoratorV2Private::replaceFontSizes(const QString &stylesheet, double
     QString result;
     result.reserve(stylesheet.size());
     while ((index = stylesheet.indexOf(re, index, &match)) != -1) {
-        result += stylesheet.midRef(lastIndex, index - lastIndex);
-
         QString matchString = match.captured(1);
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+        result += QStringView(stylesheet).sliced(lastIndex, index - lastIndex);
+        double size = QStringView(matchString).sliced(0, matchString.size() - 2).toDouble();
+#else
+        result += stylesheet.midRef(lastIndex, index - lastIndex);
         double size = matchString.midRef(0, matchString.size() - 2).toDouble();
+#endif
         size *= ratio;
         QString valueString = QStringLiteral("font-size: ") +
                               (rounding ? QString::number(int(size)) : QString::number(size)) +
@@ -569,7 +573,11 @@ QString QMDecoratorV2Private::replaceFontSizes(const QString &stylesheet, double
         index += match.captured().size();
         lastIndex = index;
     }
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    result += QStringView(stylesheet).sliced(lastIndex);
+#else
     result += stylesheet.midRef(lastIndex);
+#endif
     return result;
 }
 
@@ -582,10 +590,15 @@ QString QMDecoratorV2Private::replaceSizes(const QString &stylesheet, double rat
     QString result;
     result.reserve(stylesheet.size());
     while ((index = stylesheet.indexOf(re, index, &match)) != -1) {
-        result += stylesheet.midRef(lastIndex, index - lastIndex);
-
         QString matchString = match.captured();
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+        result += QStringView(stylesheet).sliced(lastIndex, index - lastIndex);
+        double size = QStringView(matchString).sliced(0, matchString.size() - 2).toDouble();
+#else
+        result += stylesheet.midRef(lastIndex, index - lastIndex);
         double size = matchString.midRef(0, matchString.size() - 2).toDouble();
+#endif
+
         size *= ratio;
         QString valueString =
             (rounding ? QString::number(int(size)) : QString::number(size)) + QStringLiteral("px");
@@ -594,7 +607,11 @@ QString QMDecoratorV2Private::replaceSizes(const QString &stylesheet, double rat
         index += matchString.size();
         lastIndex = index;
     }
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    result += QStringView(stylesheet).sliced(lastIndex);
+#else
     result += stylesheet.midRef(lastIndex);
+#endif
     return result;
 }
 
@@ -610,7 +627,11 @@ QString QMDecoratorV2Private::replaceCustomKeyWithQProperty(const QString &style
     QString result;
     result.reserve(stylesheet.size());
     while ((index = stylesheet.indexOf(re, index, &match)) != -1) {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+        result += QStringView(stylesheet).sliced(lastIndex, index - lastIndex);
+#else
         result += stylesheet.midRef(lastIndex, index - lastIndex);
+#endif
 
         QString matchString = match.captured();
         int capturedIndex = match.capturedStart(2) - index;
@@ -623,7 +644,11 @@ QString QMDecoratorV2Private::replaceCustomKeyWithQProperty(const QString &style
         index += matchString.size();
         lastIndex = index;
     }
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    result += QStringView(stylesheet).sliced(lastIndex);
+#else
     result += stylesheet.midRef(lastIndex);
+#endif
     return result;
 }
 
@@ -640,7 +665,11 @@ QString QMDecoratorV2Private::replaceCssGrammars(const QString &stylesheet) {
         int index = 0;
         int lastIndex = 0;
         while ((index = stylesheet.indexOf(re, index, &match)) != -1) {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+            result += QStringView(stylesheet).sliced(lastIndex, index - lastIndex);
+#else
             result += stylesheet.midRef(lastIndex, index - lastIndex);
+#endif
 
             QString matchString = match.captured();
             QString valueString = QStringLiteral(":!") + match.captured(1).trimmed();
@@ -648,7 +677,11 @@ QString QMDecoratorV2Private::replaceCssGrammars(const QString &stylesheet) {
             index += matchString.size();
             lastIndex = index;
         }
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+        result += QStringView(stylesheet).sliced(lastIndex);
+#else
         result += stylesheet.midRef(lastIndex);
+#endif
     }
 
     // Replace "svg(...);" to "url(\"[[...]].svgx\");"
@@ -671,12 +704,20 @@ QString QMDecoratorV2Private::removeAllComments(const QString &stylesheet) {
     QString result;
     result.reserve(stylesheet.size());
     while ((index = stylesheet.indexOf(re, index, &match)) != -1) {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+        result += QStringView(stylesheet).sliced(lastIndex, index - lastIndex);
+#else
         result += stylesheet.midRef(lastIndex, index - lastIndex);
+#endif
 
         index += match.captured(0).size();
         lastIndex = index;
     }
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    result += QStringView(stylesheet).sliced(lastIndex);
+#else
     result += stylesheet.midRef(lastIndex);
+#endif
     return result;
 }
 
diff --git a/src/widgets/widgets/cmenu.cpp b/src/widgets/widgets/cmenu.cpp
index 25aa03d..e7b3660 100644
--- a/src/widgets/widgets/cmenu.cpp
+++ b/src/widgets/widgets/cmenu.cpp
@@ -553,7 +553,7 @@ class CMenuPrivate : public QObject {
         DwmSetWindowAttribute(reinterpret_cast<HWND>(this->q->winId()),
                               DWMWA_WINDOW_CORNER_PREFERENCE_, &dwcp, sizeof(dwcp));
         // Disconnect this connection, don't run again
-        disconnect(q, &CMenu::aboutToShow, this, &CMenuPrivate::_q_menuFirstAboutToShow);
+        //        disconnect(q, &CMenu::aboutToShow, this, &CMenuPrivate::_q_menuFirstAboutToShow);
     }
 #endif
 };
diff --git a/src/widgets/widgettools/cnavframe.cpp b/src/widgets/widgettools/cnavframe.cpp
index d92ffe7..15dd397 100644
--- a/src/widgets/widgettools/cnavframe.cpp
+++ b/src/widgets/widgettools/cnavframe.cpp
@@ -51,11 +51,9 @@ CNavFrame::CNavFrame(QWidget *parent) : QFrame(parent), d_ptr(new CNavFramePriva
 
     // Left
     d->buttonLayout = new QVBoxLayout();
-    d->buttonLayout->setMargin(0);
     d->buttonLayout->setSpacing(0);
 
     d->leftLayout = new QVBoxLayout();
-    d->leftLayout->setMargin(0);
     d->leftLayout->setSpacing(0);
 
     d->leftLayout->addLayout(d->buttonLayout);
@@ -67,7 +65,6 @@ CNavFrame::CNavFrame(QWidget *parent) : QFrame(parent), d_ptr(new CNavFramePriva
 
     // Right
     d->stack = new QStackedLayout();
-    d->stack->setMargin(0);
 
     d->rightFrame = new QFrame();
     d->rightFrame->setObjectName("right-frame");
@@ -84,9 +81,20 @@ CNavFrame::CNavFrame(QWidget *parent) : QFrame(parent), d_ptr(new CNavFramePriva
     d->splitter->setStretchFactor(1, 1);
 
     d->layout = new QHBoxLayout();
-    d->layout->setMargin(0);
     d->layout->setSpacing(0);
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    d->buttonLayout->setContentsMargins({});
+    d->leftLayout->setContentsMargins({});
+    d->stack->setContentsMargins({});
+    d->layout->setContentsMargins({});
+#else
+    d->buttonLayout->setMargin(0);
+    d->leftLayout->setMargin(0);
+    d->stack->setMargin(0);
+    d->layout->setMargin(0);
+#endif
+
     d->layout->addWidget(d->splitter);
     setLayout(d->layout);