QQuickFlickable: fix flicking when item is rotated

QEventPoint::velocity() is in screen coordinates, as documented; it needs
to be transformed to local coordinates in case the Flickable is rotated
and/or scaled. windowToItemTransform() gives us a composite transform
matrix; we remove the translation components to get only the rotation
and scaling.

Also fix the press position calculation in handleReleaseEvent().

With the manual test one can pinch to scale and rotate a Flickable, then
verify that with a single finger, the Flickable gets scrolled by an
appropriate distance in spite of that.

Done-with: Ivan Solovev
Fixes: QTBUG-99639
Change-Id: I60af1dd932835d358baa1422523cc24b2ab046a0
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>
(cherry picked from commit 8068bde891eefe99a43deb83e58166b476f65225)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

3 files changed, 169 insertions, 0 deletions

diff --git a/tests/auto/quick/qquickflickable/data/rotatedFlickable.qml b/tests/auto/quick/qquickflickable/data/rotatedFlickable.qml
new file mode 100644
index 0000000000..04816c178b
--- /dev/null
+++ b/tests/auto/quick/qquickflickable/data/rotatedFlickable.qml
@@ -0,0 +1,32 @@
+import QtQuick 2.0
+
+Item {
+    width: 300
+    height: 300
+
+    Flickable {
+        id: flickable
+        anchors.fill: parent
+        contentHeight: column.height
+        flickDeceleration: 5000 // speed up the test run
+
+        Column {
+            id: column
+            width: parent.width
+
+            Repeater {
+                model: 255
+
+                delegate: Rectangle {
+                    width: column.width
+                    height: 50
+                    color: "gray"
+                    Text {
+                        anchors.centerIn: parent
+                        text: index
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp b/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp
index ad785f069f..9682079e84 100644
--- a/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp
+++ b/tests/auto/quick/qquickflickable/tst_qquickflickable.cpp
@@ -236,6 +236,8 @@ private slots:
     void ignoreNonLeftMouseButtons();
     void ignoreNonLeftMouseButtons_data();
     void receiveTapOutsideContentItem();
+    void flickWhenRotated_data();
+    void flickWhenRotated();
 
 private:
     void flickWithTouch(QQuickWindow *window, const QPoint &from, const QPoint &to);
@@ -2800,6 +2802,57 @@ void tst_qquickflickable::receiveTapOutsideContentItem()
     QCOMPARE(clickedSpy.count(), 2);
 }
 
+void tst_qquickflickable::flickWhenRotated_data()
+{
+    QTest::addColumn<qreal>("rootRotation");
+    QTest::addColumn<qreal>("flickableRotation");
+    QTest::addColumn<qreal>("scale");
+
+    static constexpr qreal rotations[] = { 0, 30, 90, 180, 270 };
+    static constexpr qreal scales[] = { 0.3, 1, 1.5 };
+
+    for (const auto pr : rotations) {
+        for (const auto fr : rotations) {
+            if (pr <= 90) {
+                for (const auto s : scales)
+                    QTest::addRow("parent: %g, flickable: %g, scale: %g", pr, fr) << pr << fr << s;
+            } else {
+                // don't bother trying every scale with every set of rotations, to save time
+                QTest::addRow("parent: %g, flickable: %g, scale: 1", pr, fr) << pr << fr << qreal(1);
+            }
+        }
+    }
+}
+
+void tst_qquickflickable::flickWhenRotated() // QTBUG-99639
+{
+    QFETCH(qreal, rootRotation);
+    QFETCH(qreal, flickableRotation);
+    QFETCH(qreal, scale);
+
+    QQuickView window;
+    QVERIFY(QQuickTest::showView(window, testFileUrl("rotatedFlickable.qml")));
+    QQuickItem *rootItem = window.rootObject();
+    QVERIFY(rootItem);
+    QQuickFlickable *flickable = rootItem->findChild<QQuickFlickable*>();
+    QVERIFY(flickable);
+
+    rootItem->setRotation(rootRotation);
+    flickable->setRotation(flickableRotation);
+    rootItem->setScale(scale);
+    QVERIFY(flickable->isAtYBeginning());
+
+    // Flick in Y direction in Flickable's coordinate system and check how much it moved
+    const QPointF startPoint = flickable->mapToGlobal(QPoint(20, 180));
+    const QPointF endPoint = flickable->mapToGlobal(QPoint(20, 40));
+    flick(&window, window.mapFromGlobal(startPoint).toPoint(), window.mapFromGlobal(endPoint).toPoint(), 100);
+    QTRY_VERIFY(flickable->isMoving());
+    QTRY_VERIFY(!flickable->isMoving());
+    qCDebug(lcTests) << "flicking from" << startPoint << "to" << endPoint << ": ended at contentY" << flickable->contentY();
+    // usually flickable->contentY() is at 275 or very close
+    QVERIFY(!flickable->isAtYBeginning());
+}
+
 QTEST_MAIN(tst_qquickflickable)
 
 #include "tst_qquickflickable.moc"
diff --git a/tests/manual/pointer/pinchFlickable.qml b/tests/manual/pointer/pinchFlickable.qml
new file mode 100644
index 0000000000..48a00b4b1b
--- /dev/null
+++ b/tests/manual/pointer/pinchFlickable.qml
@@ -0,0 +1,84 @@
+/****************************************************************************
+**
+** Copyright (C) 2022 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the manual tests of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick
+
+Item {
+    width: 300
+    height: 300
+
+    Flickable {
+        id: flickable
+        anchors.fill: parent
+        contentHeight: column.height
+
+        Column {
+            id: column
+            width: parent.width
+
+            Repeater {
+                model: 255
+
+                delegate: Rectangle {
+                    width: column.width
+                    height: 50
+                    color: flickable.dragging ? "steelblue" : "gray"
+                    Text {
+                        anchors.centerIn: parent
+                        text: index
+                    }
+                }
+            }
+        }
+    }
+    PinchHandler {
+        target: flickable
+    }
+}