Add handlers declared as Flickable children to its contentItem

QQuickItemPrivate::data_append() was not invoked when any kind of
Pointer Handler was directly declared in a Flickable (or subclass)
because QQuickFlickable redefines the default property to be its own
flickableData property. So we need to repeat the special handling
in QQuickFlickablePrivate::data_append() too.  The handler must
be added to the private->extra->pointerHandlers vector, so that
QQuickItemPrivate::handlePointerEvent() will attempt to deliver
events to those handlers.

TapHandler seems OK (especially with its default gesturePolicy
so that it does not do an exclusive grab).

PointHandler seems OK.

DragHandler competes with Flickable for the exclusive grab.
pressDelay can help; or set acceptedDevices: PointerDevice.Mouse
to allow the mouse to drag but not flick, and the touchscreen
to flick but not drag.

Fixes: QTBUG-71918
Fixes: QTBUG-73035
Change-Id: Icb97ed5230abe0cb6ec0230b5b5759a0528df7e8
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

5 files changed, 21 insertions, 5 deletions

diff --git a/src/quick/handlers/qquicktaphandler.cpp b/src/quick/handlers/qquicktaphandler.cpp
index f24b2bfd7e..c1658ec5d2 100644
--- a/src/quick/handlers/qquicktaphandler.cpp
+++ b/src/quick/handlers/qquicktaphandler.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtQuick module of the Qt Toolkit.
@@ -315,6 +315,8 @@ void QQuickTapHandler::setPressed(bool press, bool cancel, QQuickEventPoint *poi
         if (cancel) {
             emit canceled(point);
             setExclusiveGrab(point, false);
+            // In case there is a filtering parent (Flickable), we should not give up the passive grab,
+            // so that it can continue to filter future events.
             reset();
             emit pointChanged();
         }
diff --git a/src/quick/items/qquickflickable.cpp b/src/quick/items/qquickflickable.cpp
index 85045be411..cf882e8c9e 100644
--- a/src/quick/items/qquickflickable.cpp
+++ b/src/quick/items/qquickflickable.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtQuick module of the Qt Toolkit.
@@ -61,6 +61,8 @@
 
 QT_BEGIN_NAMESPACE
 
+Q_DECLARE_LOGGING_CATEGORY(lcHandlerParent)
+
 // FlickThreshold determines how far the "mouse" must have moved
 // before we perform a flick.
 static const int FlickThreshold = 15;
@@ -1897,6 +1899,8 @@ void QQuickFlickablePrivate::data_append(QQmlListProperty<QObject> *prop, QObjec
 {
     if (QQuickItem *i = qmlobject_cast<QQuickItem *>(o)) {
         i->setParentItem(static_cast<QQuickFlickablePrivate*>(prop->data)->contentItem);
+    } else if (QQuickPointerHandler *pointerHandler = qmlobject_cast<QQuickPointerHandler *>(o)) {
+        static_cast<QQuickFlickablePrivate*>(prop->data)->addPointerHandler(pointerHandler);
     } else {
         o->setParent(prop->object); // XXX todo - do we want this?
     }
@@ -2356,6 +2360,14 @@ void QQuickFlickablePrivate::cancelInteraction()
     }
 }
 
+void QQuickFlickablePrivate::addPointerHandler(QQuickPointerHandler *h)
+{
+    Q_Q(const QQuickFlickable);
+    qCDebug(lcHandlerParent) << "reparenting handler" << h << "to contentItem of" << q;
+    h->setParent(contentItem);
+    QQuickItemPrivate::get(contentItem)->addPointerHandler(h);
+}
+
 /*!
     QQuickFlickable::filterMouseEvent checks filtered mouse events and potentially steals them.
 
diff --git a/src/quick/items/qquickflickable_p.h b/src/quick/items/qquickflickable_p.h
index b7c4fa5b67..f21fe94177 100644
--- a/src/quick/items/qquickflickable_p.h
+++ b/src/quick/items/qquickflickable_p.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtQuick module of the Qt Toolkit.
diff --git a/src/quick/items/qquickflickable_p_p.h b/src/quick/items/qquickflickable_p_p.h
index c538cf7878..835c54170f 100644
--- a/src/quick/items/qquickflickable_p_p.h
+++ b/src/quick/items/qquickflickable_p_p.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtQuick module of the Qt Toolkit.
@@ -206,6 +206,8 @@ public:
 
     void cancelInteraction();
 
+    void addPointerHandler(QQuickPointerHandler *h) override;
+
 public:
     QQuickItem *contentItem;
 
diff --git a/src/quick/items/qquickitem_p.h b/src/quick/items/qquickitem_p.h
index 4ca3a01d02..771228914b 100644
--- a/src/quick/items/qquickitem_p.h
+++ b/src/quick/items/qquickitem_p.h
@@ -281,7 +281,7 @@ public:
 
     bool hasPointerHandlers() const;
     bool hasHoverHandlers() const;
-    void addPointerHandler(QQuickPointerHandler *h);
+    virtual void addPointerHandler(QQuickPointerHandler *h);
 
     // data property
     static void data_append(QQmlListProperty<QObject> *, QObject *);