Introduce QEvent::isSinglePointEvent()

This makes high-level event dispatching easier: for example we often
need to cast an event to access getters like button() and buttons().
We can so far assume that any QPointerEvent that is not a QTouchEvent
is a QSinglePointEvent; but more explicit type-checking looks safer.

Implemented in a similar way as c7f727996909338c3689396160f3060480521846.

Change-Id: I980d759e2a7538b6b30fd3bdc3be0c351ec6c246
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

2 files changed, 25 insertions, 3 deletions

diff --git a/src/corelib/kernel/qcoreevent.cpp b/src/corelib/kernel/qcoreevent.cpp
index 6fdc2a94af..af89524dc4 100644
--- a/src/corelib/kernel/qcoreevent.cpp
+++ b/src/corelib/kernel/qcoreevent.cpp
@@ -294,7 +294,8 @@ QT_BEGIN_NAMESPACE
     Contructs an event object of type \a type.
 */
 QEvent::QEvent(Type type)
-    : d(nullptr), t(type), posted(false), spont(false), m_accept(true), m_inputEvent(false), m_pointerEvent(false)
+    : d(nullptr), t(type), posted(false), spont(false), m_accept(true),
+      m_inputEvent(false), m_pointerEvent(false), m_singlePointEvent(false)
 {
     Q_TRACE(QEvent_ctor, this, t);
 }
@@ -305,7 +306,8 @@ QEvent::QEvent(Type type)
 */
 QEvent::QEvent(const QEvent &other)
     : d(other.d), t(other.t), posted(other.posted), spont(other.spont),
-      m_accept(other.m_accept), m_inputEvent(other.m_inputEvent), m_pointerEvent(other.m_pointerEvent)
+      m_accept(other.m_accept), m_inputEvent(other.m_inputEvent),
+      m_pointerEvent(other.m_pointerEvent), m_singlePointEvent(other.m_singlePointEvent)
 {
     Q_TRACE(QEvent_ctor, this, t);
     // if QEventPrivate becomes available, make sure to implement a
@@ -332,6 +334,15 @@ QEvent::QEvent(const QEvent &other)
 
 /*!
     \internal
+    \since 6.0
+    \fn QEvent::QEvent(Type type, QEvent::SinglePointEventTag)
+
+    Constructs an event object of type \a type, setting the singlePointEvent,
+    pointerEvent and inputEvent flags to \c true.
+*/
+
+/*!
+    \internal
     Attempts to copy the \a other event.
 
     Copying events is a bad idea, yet some Qt 4 code does it (notably,
@@ -438,6 +449,13 @@ QEvent::~QEvent()
     subclasses.
 */
 
+/*!
+    \fn bool QEvent::isSinglePointEvent() const
+    \since 6.0
+
+    Returns \c true if the event object is a subclass of QSinglePointEvent.
+*/
+
 namespace {
 template <size_t N>
 struct QBasicAtomicBitField {
diff --git a/src/corelib/kernel/qcoreevent.h b/src/corelib/kernel/qcoreevent.h
index b56d5ab401..32f2ba75c7 100644
--- a/src/corelib/kernel/qcoreevent.h
+++ b/src/corelib/kernel/qcoreevent.h
@@ -308,6 +308,7 @@ public:
 
     inline bool isInputEvent() const noexcept { return m_inputEvent; }
     inline bool isPointerEvent() const noexcept { return m_pointerEvent; }
+    inline bool isSinglePointEvent() const noexcept { return m_singlePointEvent; }
 
     static int registerEventType(int hint = -1) noexcept;
 
@@ -316,6 +317,8 @@ protected:
     QEvent(Type type, InputEventTag) : QEvent(type) { m_inputEvent = true; }
     struct PointerEventTag { explicit PointerEventTag() = default; };
     QEvent(Type type, PointerEventTag) : QEvent(type, InputEventTag{}) { m_pointerEvent = true; }
+    struct SinglePointEventTag { explicit SinglePointEventTag() = default; };
+    QEvent(Type type, SinglePointEventTag) : QEvent(type, PointerEventTag{}) { m_singlePointEvent = true; }
     QEventPrivate *d;
     ushort t;
 
@@ -325,7 +328,8 @@ private:
     ushort m_accept : 1;
     ushort m_inputEvent : 1;
     ushort m_pointerEvent : 1;
-    ushort reserved : 11;
+    ushort m_singlePointEvent : 1;
+    ushort reserved : 10;
 
     friend class QCoreApplication;
     friend class QCoreApplicationPrivate;