Allow MouseArea to prevent mouse grab begin stolen by Flickable.

Placing a MouseArea in a Flickable (or PinchArea, or PathView) allows
the Flickable to steal mouse events when it detects a flick/drag event.
In some cases this is not desireable and MouseArea should be able to
retain its grab.  Added a 'preventStealing' property to prevent
an ancestor item from stealing the MouseArea's grab.

Change-Id: I6277fbb76919b2b35d4e32a247b38a90e305dbdf
Task-number: QTBUG-17285
Reviewed-by: Joona Petrell

4 files changed, 44 insertions, 3 deletions

diff --git a/src/declarative/graphicsitems/qdeclarativeitemsmodule.cpp b/src/declarative/graphicsitems/qdeclarativeitemsmodule.cpp
index bc4a2d0..3c8f64e 100644
--- a/src/declarative/graphicsitems/qdeclarativeitemsmodule.cpp
+++ b/src/declarative/graphicsitems/qdeclarativeitemsmodule.cpp
@@ -180,6 +180,7 @@ void QDeclarativeItemModule::defineModule()
     qmlRegisterType<QDeclarativePinch>("QtQuick",1,1,"Pinch");
     qmlRegisterType<QDeclarativePinchEvent>();
     qmlRegisterType<QDeclarativeItem,1>("QtQuick",1,1,"Item");
+    qmlRegisterType<QDeclarativeMouseArea,1>("QtQuick",1,1,"MouseArea");
     qmlRegisterType<QDeclarativeFlickable,1>("QtQuick",1,1,"Flickable");
     qmlRegisterType<QDeclarativeListView,1>("QtQuick",1,1,"ListView");
     qmlRegisterType<QDeclarativeGridView,1>("QtQuick",1,1,"GridView");
diff --git a/src/declarative/graphicsitems/qdeclarativemousearea.cpp b/src/declarative/graphicsitems/qdeclarativemousearea.cpp
index 0aa0c1b..1308e73 100644
--- a/src/declarative/graphicsitems/qdeclarativemousearea.cpp
+++ b/src/declarative/graphicsitems/qdeclarativemousearea.cpp
@@ -416,6 +416,40 @@ void QDeclarativeMouseArea::setEnabled(bool a)
         emit enabledChanged();
     }
 }
+
+/*!
+    \qmlproperty bool MouseArea::preventStealing
+    \since Quick 1.1
+    This property holds whether the mouse events may be stolen from this
+    MouseArea.
+
+    If a MouseArea is placed within an item that filters child mouse
+    events, such as Flickable, the mouse
+    events may be stolen from the MouseArea if a gesture is recognized
+    by the parent element, e.g. a flick gesture.  If preventStealing is
+    set to true, no element will steal the mouse events.
+
+    Note that setting preventStealing to true once an element has started
+    stealing events will have no effect until the next press event.
+
+    By default this property is false.
+*/
+bool QDeclarativeMouseArea::preventStealing() const
+{
+    Q_D(const QDeclarativeMouseArea);
+    return d->preventStealing;
+}
+
+void QDeclarativeMouseArea::setPreventStealing(bool prevent)
+{
+    Q_D(QDeclarativeMouseArea);
+    if (prevent != d->preventStealing) {
+        d->preventStealing = prevent;
+        setKeepMouseGrab(d->preventStealing && d->absorb);
+        emit preventStealingChanged();
+    }
+}
+
 /*!
     \qmlproperty MouseButtons MouseArea::pressedButtons
     This property holds the mouse buttons currently pressed.
@@ -443,7 +477,7 @@ void QDeclarativeMouseArea::mousePressEvent(QGraphicsSceneMouseEvent *event)
 {
     Q_D(QDeclarativeMouseArea);
     d->moved = false;
-    d->stealMouse = false;
+    d->stealMouse = d->preventStealing;
     if (!d->absorb)
         QDeclarativeItem::mousePressEvent(event);
     else {
@@ -460,7 +494,7 @@ void QDeclarativeMouseArea::mousePressEvent(QGraphicsSceneMouseEvent *event)
         // we should only start timer if pressAndHold is connected to.
         if (d->isPressAndHoldConnected())
             d->pressAndHoldTimer.start(PressAndHoldDelay, this);
-        setKeepMouseGrab(false);
+        setKeepMouseGrab(d->stealMouse);
         event->setAccepted(setPressed(true));
     }
 }
diff --git a/src/declarative/graphicsitems/qdeclarativemousearea_p.h b/src/declarative/graphicsitems/qdeclarativemousearea_p.h
index 937ac78..985f27e 100644
--- a/src/declarative/graphicsitems/qdeclarativemousearea_p.h
+++ b/src/declarative/graphicsitems/qdeclarativemousearea_p.h
@@ -129,6 +129,7 @@ class Q_AUTOTEST_EXPORT QDeclarativeMouseArea : public QDeclarativeItem
     Q_PROPERTY(Qt::MouseButtons acceptedButtons READ acceptedButtons WRITE setAcceptedButtons NOTIFY acceptedButtonsChanged)
     Q_PROPERTY(bool hoverEnabled READ hoverEnabled WRITE setHoverEnabled NOTIFY hoverEnabledChanged)
     Q_PROPERTY(QDeclarativeDrag *drag READ drag CONSTANT) //### add flicking to QDeclarativeDrag or add a QDeclarativeFlick ???
+    Q_PROPERTY(bool preventStealing READ preventStealing WRITE setPreventStealing NOTIFY preventStealingChanged REVISION 1)
 
 public:
     QDeclarativeMouseArea(QDeclarativeItem *parent=0);
@@ -153,6 +154,9 @@ public:
 
     QDeclarativeDrag *drag();
 
+    bool preventStealing() const;
+    void setPreventStealing(bool prevent);
+
 Q_SIGNALS:
     void hoveredChanged();
     void pressedChanged();
@@ -161,6 +165,7 @@ Q_SIGNALS:
     void hoverEnabledChanged();
     void positionChanged(QDeclarativeMouseEvent *mouse);
     void mousePositionChanged(QDeclarativeMouseEvent *mouse);
+    Q_REVISION(1) void preventStealingChanged();
 
     void pressed(QDeclarativeMouseEvent *mouse);
     void pressAndHold(QDeclarativeMouseEvent *mouse);
diff --git a/src/declarative/graphicsitems/qdeclarativemousearea_p_p.h b/src/declarative/graphicsitems/qdeclarativemousearea_p_p.h
index 2a327af..67694fb 100644
--- a/src/declarative/graphicsitems/qdeclarativemousearea_p_p.h
+++ b/src/declarative/graphicsitems/qdeclarativemousearea_p_p.h
@@ -68,7 +68,7 @@ class QDeclarativeMouseAreaPrivate : public QDeclarativeItemPrivate
 public:
     QDeclarativeMouseAreaPrivate()
       : absorb(true), hovered(false), pressed(false), longPress(false),
-      moved(false), stealMouse(false), doubleClick(false), drag(0)
+      moved(false), stealMouse(false), doubleClick(false), preventStealing(false), drag(0)
     {
     }
 
@@ -110,6 +110,7 @@ public:
     bool dragY : 1;
     bool stealMouse : 1;
     bool doubleClick : 1;
+    bool preventStealing : 1;
     QDeclarativeDrag *drag;
     QPointF startScene;
     qreal startX;