Flickable: ignore trackpad events with px deltas in disallowed direction

If Flickable.flickDirection == HorizontalFlick, then if the accumulated
QWheelEvent::pixelDelta()'s abs(dx) > 2 * abs(dy), clearly the user is
trying to scroll horizontally; otherwise, don't accept the event.
That way the event is allowed to propagate to a parent Flickable that
does allow flicking vertically.  Likewise if the nesting is the other
way around, only allow the inner vertical Flickable to accept if the
flicking is actually vertical.

Fixes: QTBUG-57245
Fixes: QTBUG-80236
Change-Id: Ieb0bf9310a67210ce7e9fe7a80c88baef2cc7ede
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit dccd8f0b5ca8f6faefb49718e33f9090243f3202)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 113 insertions, 0 deletions

diff --git a/tests/auto/quick/qquickflickable/data/nested.qml b/tests/auto/quick/qquickflickable/data/nested.qml
new file mode 100644
index 0000000000..c306bfab23
--- /dev/null
+++ b/tests/auto/quick/qquickflickable/data/nested.qml
@@ -0,0 +1,52 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+import QtQuick 2.12
+
+Flickable {
+    id: root
+    objectName: "root flickable"
+    width: 240; height: 240
+    contentHeight: 1000
+
+    Flickable {
+        flickableDirection: Flickable.HorizontalFlick
+        width: root.width
+        height: 100
+        contentWidth: 1000
+        objectName: "inner flickable"
+        Repeater {
+            model: 10
+            Rectangle {
+                x: 100 * index
+                width: 96
+                height: 96
+                color: Qt.rgba(Math.random(), Math.random(), Math.random(), Math.random())
+            }
+        }
+    }
+}
diff --git a/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp b/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp
index 2bd5d6bd1b..b7a1848949 100644
--- a/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp
+++ b/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp
@@ -170,6 +170,7 @@ private slots:
     void returnToBounds_data();
     void wheel();
     void trackpad();
+    void nestedTrackpad();
     void movingAndFlicking();
     void movingAndFlicking_data();
     void movingAndDragging();
@@ -959,6 +960,66 @@ void tst_qquickflickable::trackpad()
     QCOMPARE(flick->property("movementsAfterEnd").value<int>(), 0); // QTBUG-55886
 }
 
+void tst_qquickflickable::nestedTrackpad()
+{
+    QQuickView window;
+    QVERIFY(QQuickTest::showView(window, testFileUrl("nested.qml")));
+
+    QQuickFlickable *rootFlickable = qmlobject_cast<QQuickFlickable *>(window.rootObject());
+    QVERIFY(rootFlickable);
+    QQuickFlickable *innerFlickable = rootFlickable->findChild<QQuickFlickable*>();
+    QVERIFY(innerFlickable);
+    QSignalSpy outerMoveEndSpy(rootFlickable, SIGNAL(movementEnded()));
+    QSignalSpy innerMoveEndSpy(innerFlickable, SIGNAL(movementEnded()));
+    QPoint pos = innerFlickable->mapToScene(QPoint(50, 50)).toPoint();
+    quint64 timestamp = 10;
+
+    // Scroll horizontally
+    for (int i = 0; i < 10 && qFuzzyIsNull(innerFlickable->contentX()); ++i) {
+        QWheelEvent event(pos, window.mapToGlobal(pos), QPoint(-10,4), QPoint(-20,8),
+                          Qt::NoButton, Qt::NoModifier, i ? Qt::ScrollUpdate : Qt::ScrollBegin, false,
+                          Qt::MouseEventSynthesizedBySystem);
+        event.setAccepted(false);
+        event.setTimestamp(timestamp++);
+        QGuiApplication::sendEvent(&window, &event);
+    }
+    QVERIFY(innerFlickable->contentX() > 0);
+    QCOMPARE(innerFlickable->contentY(), qreal(0));
+    {
+        QWheelEvent event(pos, window.mapToGlobal(pos), QPoint(0,0), QPoint(0,0),
+                          Qt::NoButton, Qt::NoModifier, Qt::ScrollEnd, false,
+                          Qt::MouseEventSynthesizedBySystem);
+        event.setAccepted(false);
+        event.setTimestamp(timestamp++);
+        QGuiApplication::sendEvent(&window, &event);
+    }
+    QTRY_COMPARE(innerMoveEndSpy.count(), 1);
+
+    innerFlickable->setContentX(0);
+    QCOMPARE(innerFlickable->contentX(), qreal(0));
+
+    // Scroll vertically
+    for (int i = 0; i < 10 && qFuzzyIsNull(innerFlickable->contentY()); ++i) {
+        QWheelEvent event(pos, window.mapToGlobal(pos), QPoint(4,-10), QPoint(8,-20),
+                          Qt::NoButton, Qt::NoModifier, i ? Qt::ScrollUpdate : Qt::ScrollBegin, false,
+                          Qt::MouseEventSynthesizedBySystem);
+        event.setAccepted(false);
+        event.setTimestamp(timestamp++);
+        QGuiApplication::sendEvent(&window, &event);
+    }
+    QVERIFY(rootFlickable->contentY() > 0);
+    QCOMPARE(rootFlickable->contentX(), qreal(0));
+    {
+        QWheelEvent event(pos, window.mapToGlobal(pos), QPoint(0,0), QPoint(0,0),
+                          Qt::NoButton, Qt::NoModifier, Qt::ScrollEnd, false,
+                          Qt::MouseEventSynthesizedBySystem);
+        event.setAccepted(false);
+        event.setTimestamp(timestamp++);
+        QGuiApplication::sendEvent(&window, &event);
+    }
+    QTRY_COMPARE(outerMoveEndSpy.count(), 1);
+}
+
 void tst_qquickflickable::movingAndFlicking_data()
 {
     QTest::addColumn<bool>("verticalEnabled");