If DblClick, do not deliver 'duplicated' MouseButtonPress

QWidgetWIndow: In Qt4, when Qt created a MouseButtonDblClick
event, Qt would consume the causing MouseButtonPress.
It would send only the derived dblclick event to widget
windows and their children.

This change makes Qt5.3 and higher emulate Qt4 delivery
of double click-related events to widget windows and
their children. QML objects (e.g. mousearea) continue to
receive the second MouseButtonPress.

[ChangeLog][QtGui][QWidget] MouseButtonDblClick: Do not send
the 2nd MouseButtonPress event to Widgets. Restore Qt4
behavior in sequence of mouse events delivered to
widget windows and their children.

Task-number: QTBUG-25831

Change-Id: Iff0f9c592bceacb2ca844d30f8180081e136a889
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

src/corelib/global/qnamespace.h

@@ -1609,6 +1609,13 @@ public:
         MouseEventSynthesizedBySystem,
         MouseEventSynthesizedByQt
     };
+
+    enum MouseEventFlag {
+        MouseEventCreatedDoubleClick = 0x01,
+        MouseEventFlagMask = 0xFF
+    };
+    Q_DECLARE_FLAGS(MouseEventFlags, MouseEventFlag)
+
 }
 #ifdef Q_MOC_RUN
  ;
@@ -1632,6 +1639,7 @@ Q_DECLARE_OPERATORS_FOR_FLAGS(Qt::TextInteractionFlags)
 Q_DECLARE_OPERATORS_FOR_FLAGS(Qt::InputMethodQueries)
 Q_DECLARE_OPERATORS_FOR_FLAGS(Qt::InputMethodHints)
 Q_DECLARE_OPERATORS_FOR_FLAGS(Qt::TouchPointStates)
+Q_DECLARE_OPERATORS_FOR_FLAGS(Qt::MouseEventFlags)
 #ifndef QT_NO_GESTURES
 Q_DECLARE_OPERATORS_FOR_FLAGS(Qt::GestureFlags)
 #endif

src/corelib/global/qnamespace.qdoc

@@ -2917,3 +2917,16 @@
 
     \sa Qt::AA_SynthesizeMouseForUnhandledTouchEvents
 */
+
+/*!
+    \enum Qt::MouseEventFlag
+    \since 5.3
+
+    This enum provides additional information concerning a QMouseEvent.
+
+    \value MouseEventCreatedDoubleClick Indicates that Qt has created a
+    MouseButtonDblClick event from this event. The flag is set in the causing
+    MouseButtonPress, and not in the resulting MouseButtonDblCLick.
+
+    \omitvalue MouseEventFlagMask
+*/

src/gui/kernel/qevent.cpp

@@ -293,6 +293,20 @@ Qt::MouseEventSource QMouseEvent::source() const
     return QGuiApplicationPrivate::mouseEventSource(this);
 }
 
+/*!
+     \since 5.3
+
+     Returns the mouse event flags.
+
+     The mouse event flags provide additional information about a mouse event.
+
+     \sa Qt::MouseEventFlag
+ */
+Qt::MouseEventFlags QMouseEvent::flags() const
+{
+    return QGuiApplicationPrivate::mouseEventFlags(this);
+}
+
 /*!
     \fn QPointF QMouseEvent::localPos() const
 

src/gui/kernel/qevent.h

@@ -136,6 +136,7 @@ public:
 #endif
 
     Qt::MouseEventSource source() const;
+    Qt::MouseEventFlags flags() const;
 
 protected:
     QPointF l, w, s;

src/gui/kernel/qguiapplication.cpp

@@ -1600,6 +1600,11 @@ void QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::Mo
         return;
     }
 
+    if (doubleClick && (ev.type() == QEvent::MouseButtonPress)) {
+        // QtBUG-25831, used to suppress delivery in qwidgetwindow.cpp
+        setMouseEventFlags(&ev, ev.flags() | Qt::MouseEventCreatedDoubleClick);
+    }
+
     QGuiApplication::sendSpontaneousEvent(window, &ev);
     if (!e->synthetic && !ev.isAccepted()
         && !frameStrut
@@ -3169,6 +3174,8 @@ enum {
     MouseSourceMaskDst = 0xFF00,
     MouseSourceMaskSrc = MouseCapsMask,
     MouseSourceShift = 8,
+    MouseFlagsCapsMask = 0xFF0000,
+    MouseFlagsShift = 16
 };
 
 int QGuiApplicationPrivate::mouseEventCaps(QMouseEvent *event)
@@ -3204,6 +3211,20 @@ void QGuiApplicationPrivate::setMouseEventSource(QMouseEvent *event, Qt::MouseEv
     event->caps |= (value & MouseSourceMaskSrc) << MouseSourceShift;
 }
 
+Qt::MouseEventFlags QGuiApplicationPrivate::mouseEventFlags(const QMouseEvent *event)
+{
+    return Qt::MouseEventFlags((event->caps & MouseFlagsCapsMask) >> MouseFlagsShift);
+}
+
+void QGuiApplicationPrivate::setMouseEventFlags(QMouseEvent *event, Qt::MouseEventFlags flags)
+{
+    // use the 0x00FF0000 byte from caps (containing up to 7 mouse event flags)
+    unsigned int value = flags;
+    Q_ASSERT(value <= Qt::MouseEventFlagMask);
+    event->caps &= ~MouseFlagsCapsMask;
+    event->caps |= (value & Qt::MouseEventFlagMask) << MouseFlagsShift;
+}
+
 #include "moc_qguiapplication.cpp"
 
 QT_END_NAMESPACE

src/gui/kernel/qguiapplication_p.h

@@ -272,6 +272,9 @@ public:
     static Qt::MouseEventSource mouseEventSource(const QMouseEvent *event);
     static void setMouseEventSource(QMouseEvent *event, Qt::MouseEventSource source);
 
+    static Qt::MouseEventFlags mouseEventFlags(const QMouseEvent *event);
+    static void setMouseEventFlags(QMouseEvent *event, Qt::MouseEventFlags flags);
+
     const QDrawHelperGammaTables *gammaTables();
 
     // hook reimplemented in QApplication to apply the QStyle function on the QIcon

src/widgets/kernel/qapplication.cpp

@@ -2767,6 +2767,13 @@ bool QApplication::notify(QObject *receiver, QEvent *e)
                 QApplicationPrivate::mouse_buttons |= me->button();
                 break;
             }
+        case QEvent::MouseButtonDblClick:
+            {
+                QMouseEvent *me = static_cast<QMouseEvent*>(e);
+                QApplicationPrivate::modifier_buttons = me->modifiers();
+                QApplicationPrivate::mouse_buttons |= me->button();
+                break;
+            }
         case QEvent::MouseButtonRelease:
             {
                 QMouseEvent *me = static_cast<QMouseEvent*>(e);
@@ -2995,6 +3002,7 @@ bool QApplication::notify(QObject *receiver, QEvent *e)
                                mouse->modifiers());
                 me.spont = mouse->spontaneous();
                 me.setTimestamp(mouse->timestamp());
+                QGuiApplicationPrivate::setMouseEventFlags(&me, mouse->flags());
                 // throw away any mouse-tracking-only mouse events
                 if (!w->hasMouseTracking()
                     && mouse->type() == QEvent::MouseMove && mouse->buttons() == 0) {
@@ -3748,6 +3756,7 @@ void QApplicationPrivate::giveFocusAccordingToFocusPolicy(QWidget *widget, QEven
 
     switch (event->type()) {
         case QEvent::MouseButtonPress:
+        case QEvent::MouseButtonDblClick:
         case QEvent::TouchBegin:
             if (setFocusOnRelease)
                 return;

src/widgets/kernel/qwidgetwindow.cpp

@@ -473,7 +473,7 @@ void QWidgetWindow::handleMouseEvent(QMouseEvent *event)
     if (!widget)
         widget = m_widget;
 
-    if (event->type() == QEvent::MouseButtonPress)
+    if (event->type() == QEvent::MouseButtonPress || event->type() == QEvent::MouseButtonDblClick)
         qt_button_down = widget;
 
     QWidget *receiver = QApplicationPrivate::pickMouseReceiver(m_widget, event->windowPos().toPoint(), &mapped, event->type(), event->buttons(),
@@ -484,12 +484,17 @@ void QWidgetWindow::handleMouseEvent(QMouseEvent *event)
             QApplicationPrivate::mouse_buttons &= ~event->button();
         return;
     }
+    if ((event->type() != QEvent::MouseButtonPress)
+        || !(event->flags().testFlag(Qt::MouseEventCreatedDoubleClick))) {
 
-    QMouseEvent translated(event->type(), mapped, event->windowPos(), event->screenPos(), event->button(), event->buttons(), event->modifiers());
-    translated.setTimestamp(event->timestamp());
-    QApplicationPrivate::sendMouseEvent(receiver, &translated, widget, m_widget, &qt_button_down,
-                                        qt_last_mouse_receiver);
-
+        // The preceding statement excludes MouseButtonPress events which caused
+        // creation of a MouseButtonDblClick event. QTBUG-25831
+        QMouseEvent translated(event->type(), mapped, event->windowPos(), event->screenPos(),
+                               event->button(), event->buttons(), event->modifiers());
+        translated.setTimestamp(event->timestamp());
+        QApplicationPrivate::sendMouseEvent(receiver, &translated, widget, m_widget,
+                                            &qt_button_down, qt_last_mouse_receiver);
+    }
 #ifndef QT_NO_CONTEXTMENU
     if (event->type() == contextMenuTrigger && event->button() == Qt::RightButton) {
         QContextMenuEvent e(QContextMenuEvent::Mouse, mapped, event->globalPos(), event->modifiers());