Widgets: Use pmf-style connects

Replace some more string-based connects with pmf-style to trigger a
compiler error instead a runtime error if a signal or slot does no
longer exists.

Change-Id: Ibc047cc935885a30ea58367fa97e9f962b87ca2c
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
(cherry picked from commit 9e78256579e8dc704066a98cb4816a1aab0e7e3b)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/widgets/kernel/qtooltip.cpp

@@ -179,8 +179,8 @@ void QTipLabel::reuseTip(const QString &text, int msecDisplayTime, const QPoint
 {
 #ifndef QT_NO_STYLE_STYLESHEET
     if (styleSheetParent){
-        disconnect(styleSheetParent, SIGNAL(destroyed()),
+        disconnect(styleSheetParent, &QWidget::destroyed,
-                   QTipLabel::instance, SLOT(styleSheetParentDestroyed()));
+                   this, &QTipLabel::styleSheetParentDestroyed);
         styleSheetParent = nullptr;
     }
 #endif
@@ -354,8 +354,8 @@ void QTipLabel::placeTip(const QPoint &pos, QWidget *w)
         // Set up for cleaning up this later...
         QTipLabel::instance->styleSheetParent = w;
         if (w) {
-            connect(w, SIGNAL(destroyed()),
+            connect(w, &QWidget::destroyed,
-                QTipLabel::instance, SLOT(styleSheetParentDestroyed()));
+                    QTipLabel::instance, &QTipLabel::styleSheetParentDestroyed);
         }
         // QTBUG-64550: A font inherited by the style sheet might change the size,
         // particular on Windows, where the tip is not parented on a window.

src/widgets/kernel/qwhatsthis.cpp

@@ -464,7 +464,7 @@ QWhatsThisAction::QWhatsThisAction(QObject *parent) : QAction(tr("What's This?")
     setIcon(p);
 #endif
     setCheckable(true);
-    connect(this, SIGNAL(triggered()), this, SLOT(actionTriggered()));
+    connect(this, &QWhatsThisAction::triggered, this, &QWhatsThisAction::actionTriggered);
 #ifndef QT_NO_SHORTCUT
     setShortcut(Qt::ShiftModifier | Qt::Key_F1);
 #endif

src/widgets/kernel/qwidgetaction.cpp

@@ -82,9 +82,9 @@ QWidgetAction::QWidgetAction(QObject *parent)
 QWidgetAction::~QWidgetAction()
 {
     Q_D(QWidgetAction);
-    for (int i = 0; i < d->createdWidgets.size(); ++i)
+    for (QWidget *w : std::as_const(d->createdWidgets))
-        disconnect(d->createdWidgets.at(i), SIGNAL(destroyed(QObject*)),
+        QObjectPrivate::disconnect(w, &QWidget::destroyed,
-                   this, SLOT(_q_widgetDestroyed(QObject*)));
+                                   d, &QWidgetActionPrivate::widgetDestroyed);
     QList<QWidget *> widgetsToDelete = d->createdWidgets;
     d->createdWidgets.clear();
     qDeleteAll(widgetsToDelete);
@@ -147,8 +147,8 @@ QWidget *QWidgetAction::requestWidget(QWidget *parent)
         return d->defaultWidget;
     }
 
-    connect(w, SIGNAL(destroyed(QObject*)),
+    QObjectPrivate::connect(w, &QWidget::destroyed,
-            this, SLOT(_q_widgetDestroyed(QObject*)));
+                            d, &QWidgetActionPrivate::widgetDestroyed);
     d->createdWidgets.append(w);
     return w;
 }
@@ -175,8 +175,8 @@ void QWidgetAction::releaseWidget(QWidget *widget)
     if (!d->createdWidgets.contains(widget))
         return;
 
-    disconnect(widget, SIGNAL(destroyed(QObject*)),
+    QObjectPrivate::disconnect(widget, &QWidget::destroyed,
-               this, SLOT(_q_widgetDestroyed(QObject*)));
+                               d, &QWidgetActionPrivate::widgetDestroyed);
     d->createdWidgets.removeAll(widget);
     deleteWidget(widget);
 }

src/widgets/kernel/qwidgetaction.h

@@ -37,7 +37,6 @@ protected:
 
 private:
     Q_DISABLE_COPY(QWidgetAction)
-    Q_PRIVATE_SLOT(d_func(), void _q_widgetDestroyed(QObject *))
     friend class QToolBar;
 };
 

src/widgets/kernel/qwidgetaction_p.h

@@ -34,7 +34,7 @@ public:
     uint defaultWidgetInUse : 1;
     uint autoCreated : 1; // created by QToolBar::addWidget and the like
 
-    inline void _q_widgetDestroyed(QObject *o) {
+    inline void widgetDestroyed(QObject *o) {
         createdWidgets.removeAll(static_cast<QWidget *>(o));
     }
 };

src/widgets/kernel/qwindowcontainer.cpp

@@ -219,7 +219,8 @@ QWindowContainer::QWindowContainer(QWindow *embeddedWindow, QWidget *parent, Qt:
 
     setAcceptDrops(true);
 
-    connect(QGuiApplication::instance(), SIGNAL(focusWindowChanged(QWindow*)), this, SLOT(focusWindowChanged(QWindow*)));
+    connect(qGuiApp, &QGuiApplication::focusWindowChanged,
+            this, &QWindowContainer::focusWindowChanged);
 }
 
 QWindow *QWindowContainer::containedWindow() const