QQMultiPointerHandler: don't steal grab if keepMouseGrab/keepTouchGrab

An Item (such as MPTA with onGestureStarted: gesture.grab()) may set
these flags, traditionally to prevent Flickable from stealing the grab.
QQuickMultiPointerHandler (and thus PinchHandler) now respects these
flags too.

Change-Id: Iac3ab796c5aa410be45639d679ecf82b7c44a442
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

3 files changed, 15 insertions, 6 deletions

diff --git a/src/quick/handlers/qquickmultipointerhandler.cpp b/src/quick/handlers/qquickmultipointerhandler.cpp
index 1a5684d80e..016210beff 100644
--- a/src/quick/handlers/qquickmultipointerhandler.cpp
+++ b/src/quick/handlers/qquickmultipointerhandler.cpp
@@ -238,10 +238,19 @@ void QQuickMultiPointerHandler::acceptPoints(const QVector<QQuickEventPoint *> &
         point->setAccepted();
 }
 
-void QQuickMultiPointerHandler::grabPoints(QVector<QQuickEventPoint *> points)
+bool QQuickMultiPointerHandler::grabPoints(QVector<QQuickEventPoint *> points)
 {
-    for (QQuickEventPoint* point : points)
-        setExclusiveGrab(point);
+    bool canGrab = true;
+    for (QQuickEventPoint* point : points) {
+        auto grabber = point->grabberItem();
+        if (grabber && (grabber->keepMouseGrab() || grabber->keepTouchGrab()))
+            canGrab = false;
+    }
+    if (canGrab) {
+        for (QQuickEventPoint* point : points)
+            setExclusiveGrab(point);
+    }
+    return canGrab;
 }
 
 QT_END_NAMESPACE
diff --git a/src/quick/handlers/qquickmultipointerhandler_p.h b/src/quick/handlers/qquickmultipointerhandler_p.h
index be92a39631..ce014d658c 100644
--- a/src/quick/handlers/qquickmultipointerhandler_p.h
+++ b/src/quick/handlers/qquickmultipointerhandler_p.h
@@ -98,7 +98,7 @@ protected:
     QVector<PointData> angles(const QPointF &ref) const;
     static qreal averageAngleDelta(const QVector<PointData> &old, const QVector<PointData> &newAngles);
     void acceptPoints(const QVector<QQuickEventPoint *> &points);
-    void grabPoints(QVector<QQuickEventPoint *> points);
+    bool grabPoints(QVector<QQuickEventPoint *> points);
 
 protected:
     QVector<QQuickEventPoint *> m_currentPoints;
diff --git a/src/quick/handlers/qquickpinchhandler.cpp b/src/quick/handlers/qquickpinchhandler.cpp
index 67d32cdb18..3af77593e2 100644
--- a/src/quick/handlers/qquickpinchhandler.cpp
+++ b/src/quick/handlers/qquickpinchhandler.cpp
@@ -232,8 +232,8 @@ void QQuickPinchHandler::handlePointerEventImpl(QQuickPointerEvent *event)
         // Verify that least one of the points have moved beyond threshold needed to activate the handler
         for (QQuickEventPoint *point : qAsConst(m_currentPoints)) {
             if (QQuickWindowPrivate::dragOverThreshold(point)) {
-                grabPoints(m_currentPoints);
-                setActive(true);
+                if (grabPoints(m_currentPoints))
+                    setActive(true);
                 break;
             }
         }