DragHandler: onGrabChanged, enforceConstraints

If the grab is stolen by a parent such as a Flickable, ensure that
the DragHandler doesn't keep dragging.  This helps to prevent dragging
sliders out of their "groove" constraints.

Change-Id: Id24f53e137ed186b1c02ab9c73a69a59022e80b0
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

2 files changed, 7 insertions, 0 deletions

diff --git a/src/quick/handlers/qquickdraghandler.cpp b/src/quick/handlers/qquickdraghandler.cpp
index 3b1ec1c344..73ad97712e 100644
--- a/src/quick/handlers/qquickdraghandler.cpp
+++ b/src/quick/handlers/qquickdraghandler.cpp
@@ -73,6 +73,12 @@ bool QQuickDragHandler::wantsEventPoint(QQuickEventPoint *point)
             || QQuickPointerSingleHandler::wantsEventPoint(point));
 }
 
+void QQuickDragHandler::onGrabChanged(QQuickPointerHandler *grabber, QQuickEventPoint::GrabState stateChange, QQuickEventPoint *point)
+{
+    enforceConstraints();
+    QQuickPointerSingleHandler::onGrabChanged(grabber, stateChange, point);
+}
+
 void QQuickDragHandler::handleEventPoint(QQuickEventPoint *point)
 {
     point->setAccepted();
diff --git a/src/quick/handlers/qquickdraghandler_p.h b/src/quick/handlers/qquickdraghandler_p.h
index cfccc19115..a75ea6f2c7 100644
--- a/src/quick/handlers/qquickdraghandler_p.h
+++ b/src/quick/handlers/qquickdraghandler_p.h
@@ -112,6 +112,7 @@ Q_SIGNALS:
 
 protected:
     bool wantsEventPoint(QQuickEventPoint *point) override;
+    void onGrabChanged(QQuickPointerHandler *grabber, QQuickEventPoint::GrabState stateChange, QQuickEventPoint *point) override;
 
 private:
     void ungrab();