add QQuickPointerHandler::handleGrabCancel; call in setGrab

Only one handler can be the grabber at one time, so we need to ensure
that we notify the others when they lose the grab. Also handle this
in QQuickPointerSingleHandler: forget m_currentPointId, so that
wantsPointerEvent will not continue to "want" the same ID.
Also add the canceled(QQuickEventPoint *point) signal, which
is one of the four possible "state signals" (press, update, release,
cancel) but which we didn't commit to adding yet.

Change-Id: I46256acb75ece863d84e812af2d30cb0b12e3c1f
Reviewed-by: Jan Arve Sæther <jan-arve.saether@theqtcompany.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/src/quick/handlers/qquickpointerhandler.cpp b/src/quick/handlers/qquickpointerhandler.cpp
index 4c60180f46..731de295e9 100644
--- a/src/quick/handlers/qquickpointerhandler.cpp
+++ b/src/quick/handlers/qquickpointerhandler.cpp
@@ -65,10 +65,14 @@ QQuickPointerHandler::QQuickPointerHandler(QObject *parent)
 
 void QQuickPointerHandler::setGrab(QQuickEventPoint *point, bool grab)
 {
-    if (grab)
+    if (grab) {
+        QQuickPointerHandler *oldGrabber = point->grabberPointerHandler();
+        if (oldGrabber && oldGrabber != this)
+            oldGrabber->handleGrabCancel(point);
         point->setGrabberPointerHandler(this);
-    else if (point->grabberPointerHandler() == this)
+    } else if (point->grabberPointerHandler() == this) {
         point->setGrabberPointerHandler(nullptr);
+    }
 }
 
 QPointF QQuickPointerHandler::eventPos(const QQuickEventPoint *point) const
@@ -130,6 +134,15 @@ void QQuickPointerHandler::handlePointerEvent(QQuickPointerEvent *event)
         handlePointerEventImpl(event);
 }
 
+void QQuickPointerHandler::handleGrabCancel(QQuickEventPoint *point)
+{
+    qCDebug(lcPointerHandlerDispatch) << point;
+    Q_ASSERT(point);
+    setActive(false);
+    point->setAccepted(false);
+    emit canceled(point);
+}
+
 bool QQuickPointerHandler::wantsPointerEvent(QQuickPointerEvent *event)
 {
     Q_UNUSED(event)