QEvent: start to de-inline copy ctor and clone() of all subclasses

There's no advantage to them being inline: Absent de-virtualisation,
clone() is only supposed to be called through the vtable, and the copy
ctor is only supposed to be used in the implementation of clone().

And when the compiler de-virtualises, we don't want the code
duplication associated with inlining.

Enforce this by introducing new macros to hide the boilerplate.

This fixes missing out-of-line dtors in:
- QSinglePointEvent
- QApplicationStateChangeEvent
- QFutureCallOutEvent

Wrong covariant return in:
- QFutureCallOutEvent

And missing clone() reimplementations in:
- QCloseEvent
- QIconDragEvent
- QShowEvent
- QHideEvent
- QDragEnterEvent
- QDragLeaveEvent

While these don't carry extra data or members, a dynamic_cast of the
result of clone() as well as using the expected covariant return value
would fail:

   QShowEvent *e = ~~~;
   QShowEvent *e2 = e->clone(); // ERROR: converting QEvent* to QShowEvent*

Check that reimplementing clone() is binary compatible (covariant
returns may change the numerical pointer value returned, cf.
https://community.kde.org/Policies/Binary_Compatibility_Issues_With_C%2B%2B).

The copy-assignment operator stays inline for the time being, as the
goal is to = delete it in the future.

This patch covers, roughly, QtCore and QtGui.

[ChangeLog][QtGui][QEvent subclasses] Fixed missing clone()
reimplementations on QCloseEvent, QIconDragEvent, QShowEvent,
QHideEvent, QDragEnterEvent, and QDragLeaveEvent.

Task-number: QTBUG-45582
Task-number: QTBUG-97601
Change-Id: Ib8a0519dbe85a7a8da61050d48be338004dfa69a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

4 files changed, 36 insertions, 46 deletions

diff --git a/src/corelib/kernel/qcoreevent.cpp b/src/corelib/kernel/qcoreevent.cpp
index 34b57bb4f8..2289938d4b 100644
--- a/src/corelib/kernel/qcoreevent.cpp
+++ b/src/corelib/kernel/qcoreevent.cpp
@@ -559,12 +559,7 @@ QTimerEvent::QTimerEvent(int timerId)
     : QEvent(Timer), id(timerId)
 {}
 
-/*!
-    \internal
-*/
-QTimerEvent::~QTimerEvent()
-{
-}
+Q_IMPL_EVENT_COMMON(QTimerEvent)
 
 /*!
     \fn int QTimerEvent::timerId() const
@@ -606,12 +601,7 @@ QChildEvent::QChildEvent(Type type, QObject *child)
     : QEvent(type), c(child)
 {}
 
-/*!
-    \internal
-*/
-QChildEvent::~QChildEvent()
-{
-}
+Q_IMPL_EVENT_COMMON(QChildEvent)
 
 /*!
     \fn QObject *QChildEvent::child() const
@@ -663,12 +653,7 @@ QDynamicPropertyChangeEvent::QDynamicPropertyChangeEvent(const QByteArray &name)
 {
 }
 
-/*!
-    \internal
-*/
-QDynamicPropertyChangeEvent::~QDynamicPropertyChangeEvent()
-{
-}
+Q_IMPL_EVENT_COMMON(QDynamicPropertyChangeEvent)
 
 /*!
     \fn QByteArray QDynamicPropertyChangeEvent::propertyName() const
@@ -687,11 +672,7 @@ QDeferredDeleteEvent::QDeferredDeleteEvent()
     , level(0)
 { }
 
-/*!
-    \internal
-*/
-QDeferredDeleteEvent::~QDeferredDeleteEvent()
-{ }
+Q_IMPL_EVENT_COMMON(QDeferredDeleteEvent)
 
 /*! \fn int QDeferredDeleteEvent::loopLevel() const
 
diff --git a/src/corelib/kernel/qcoreevent.h b/src/corelib/kernel/qcoreevent.h
index 4a4910e893..f737a55514 100644
--- a/src/corelib/kernel/qcoreevent.h
+++ b/src/corelib/kernel/qcoreevent.h
@@ -53,6 +53,29 @@ protected: \
     Class &operator=(const Class &other) = default; \
     Class &operator=(Class &&) = delete
 
+#define Q_DECL_EVENT_COMMON(Class) \
+    protected: \
+        Class(const Class &); \
+        Class(Class &&) = delete; \
+        Class &operator=(const Class &other) = default; \
+        Class &operator=(Class &&) = delete; \
+    public: \
+        Class* clone() const override; \
+        ~Class() override; \
+    private:
+
+#define Q_IMPL_EVENT_COMMON(Class) \
+    Class::Class(const Class &) = default; \
+    Class::~Class() = default; \
+    Class* Class::clone() const \
+    { \
+        auto c = new Class(*this); \
+        QEvent *e = c; \
+        /* check that covariant return is safe to add */ \
+        Q_ASSERT(reinterpret_cast<quintptr>(c) == reinterpret_cast<quintptr>(e)); \
+        return c; \
+    }
+
 class QEventPrivate;
 class Q_CORE_EXPORT QEvent           // event base class
 {
@@ -367,14 +390,11 @@ private:
 
 class Q_CORE_EXPORT QTimerEvent : public QEvent
 {
-    Q_EVENT_DISABLE_COPY(QTimerEvent);
+    Q_DECL_EVENT_COMMON(QTimerEvent)
 public:
     explicit QTimerEvent(int timerId);
-    ~QTimerEvent();
     int timerId() const { return id; }
 
-    QTimerEvent *clone() const override { return new QTimerEvent(*this); }
-
 protected:
     int id;
 };
@@ -383,46 +403,38 @@ class QObject;
 
 class Q_CORE_EXPORT QChildEvent : public QEvent
 {
-    Q_EVENT_DISABLE_COPY(QChildEvent);
+    Q_DECL_EVENT_COMMON(QChildEvent)
 public:
     QChildEvent(Type type, QObject *child);
-    ~QChildEvent();
+
     QObject *child() const { return c; }
     bool added() const { return type() == ChildAdded; }
     bool polished() const { return type() == ChildPolished; }
     bool removed() const { return type() == ChildRemoved; }
 
-    QChildEvent *clone() const override { return new QChildEvent(*this); }
-
 protected:
     QObject *c;
 };
 
 class Q_CORE_EXPORT QDynamicPropertyChangeEvent : public QEvent
 {
-    Q_EVENT_DISABLE_COPY(QDynamicPropertyChangeEvent);
+    Q_DECL_EVENT_COMMON(QDynamicPropertyChangeEvent)
 public:
     explicit QDynamicPropertyChangeEvent(const QByteArray &name);
-    ~QDynamicPropertyChangeEvent();
 
     inline QByteArray propertyName() const { return n; }
 
-    QDynamicPropertyChangeEvent *clone() const override { return new QDynamicPropertyChangeEvent(*this); }
-
 private:
     QByteArray n;
 };
 
 class Q_CORE_EXPORT QDeferredDeleteEvent : public QEvent
 {
-    Q_EVENT_DISABLE_COPY(QDeferredDeleteEvent);
+    Q_DECL_EVENT_COMMON(QDeferredDeleteEvent)
 public:
     explicit QDeferredDeleteEvent();
-    ~QDeferredDeleteEvent();
     int loopLevel() const { return level; }
 
-    QDeferredDeleteEvent *clone() const override { return new QDeferredDeleteEvent(*this); }
-
 private:
     int level;
     friend class QCoreApplication;
diff --git a/src/corelib/thread/qfutureinterface.cpp b/src/corelib/thread/qfutureinterface.cpp
index 0fde190bc0..71d6670538 100644
--- a/src/corelib/thread/qfutureinterface.cpp
+++ b/src/corelib/thread/qfutureinterface.cpp
@@ -74,6 +74,8 @@ const auto suspendingOrSuspended =
 QFutureCallOutInterface::~QFutureCallOutInterface()
     = default;
 
+Q_IMPL_EVENT_COMMON(QFutureCallOutEvent)
+
 QFutureInterfaceBase::QFutureInterfaceBase(State initialState)
     : d(new QFutureInterfaceBasePrivate(initialState))
 { }
diff --git a/src/corelib/thread/qfutureinterface_p.h b/src/corelib/thread/qfutureinterface_p.h
index 24902cbc9a..c6ea30b07f 100644
--- a/src/corelib/thread/qfutureinterface_p.h
+++ b/src/corelib/thread/qfutureinterface_p.h
@@ -65,9 +65,9 @@ QT_REQUIRE_CONFIG(future);
 
 QT_BEGIN_NAMESPACE
 
-class QFutureCallOutEvent : public QEvent
+class Q_CORE_EXPORT QFutureCallOutEvent : public QEvent
 {
-    Q_EVENT_DISABLE_COPY(QFutureCallOutEvent);
+    Q_DECL_EVENT_COMMON(QFutureCallOutEvent)
 public:
     enum CallOutType {
         Started,
@@ -104,11 +104,6 @@ public:
     int index2;
     QString text;
 
-    QEvent *clone() const override
-    {
-        return new QFutureCallOutEvent(callOutType, index1, index2, text);
-    }
-
 private:
     QFutureCallOutEvent(CallOutType callOutType,
                         int index1,