PointHandler: distribute simultaneous touch presses properly

If multiple touchpoints are pressed simultaneously, each point can
be grabbed by one PointHandler instance. Each PointHandler instance
cannot grab more than one point, nor grab a point that is already
chosen by another PointHandler.  This was always the intention, but
got broken (perhaps by 3523b676382db4aa39adeb9126d8bb2185e84403),
and there was no test coverage of this case until now.

Fixes: QTBUG-71431
Change-Id: I6d7614eb4767c677d929291f917cf62d9c03bd93
Reviewed-by: Andre de la Rocha <andre.rocha@qt.io>

3 files changed, 166 insertions, 1 deletions

diff --git a/src/quick/handlers/qquicksinglepointhandler.cpp b/src/quick/handlers/qquicksinglepointhandler.cpp
index 82e5b1b05d..ae162bed87 100644
--- a/src/quick/handlers/qquicksinglepointhandler.cpp
+++ b/src/quick/handlers/qquicksinglepointhandler.cpp
@@ -108,7 +108,7 @@ bool QQuickSinglePointHandler::wantsPointerEvent(QQuickPointerEvent *event)
         int candidatePointCount = 0;
         int c = event->pointCount();
         QQuickEventPoint *chosen = nullptr;
-        for (int i = 0; i < c; ++i) {
+        for (int i = 0; i < c && !chosen; ++i) {
             QQuickEventPoint *p = event->point(i);
             if (!p->exclusiveGrabber() && wantsEventPoint(p)) {
                 if (!chosen)
diff --git a/tests/auto/quick/pointerhandlers/qquickpointhandler/data/multiPointTracker.qml b/tests/auto/quick/pointerhandlers/qquickpointhandler/data/multiPointTracker.qml
new file mode 100644
index 0000000000..3f50d7c761
--- /dev/null
+++ b/tests/auto/quick/pointerhandlers/qquickpointhandler/data/multiPointTracker.qml
@@ -0,0 +1,86 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 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
+
+Item {
+    id: root
+    width: 400; height: 400
+
+    PointHandler {
+        id: ph1
+        objectName: "ph1"
+
+        target: Rectangle {
+            parent: root
+            visible: ph1.active
+            x: ph1.point.position.x - width / 2
+            y: ph1.point.position.y - height / 2
+            width: 140
+            height: width
+            radius: width / 2
+            color: "orange"
+            opacity: 0.3
+        }
+    }
+
+    PointHandler {
+        id: ph2
+        objectName: "ph2"
+
+        target: Rectangle {
+            parent: root
+            visible: ph2.active
+            x: ph2.point.position.x - width / 2
+            y: ph2.point.position.y - height / 2
+            width: 140
+            height: width
+            radius: width / 2
+            color: "orange"
+            opacity: 0.3
+        }
+    }
+
+    PointHandler {
+        id: ph3
+        objectName: "ph3"
+
+        target: Rectangle {
+            parent: root
+            visible: ph3.active
+            x: ph3.point.position.x - width / 2
+            y: ph3.point.position.y - height / 2
+            width: 140
+            height: width
+            radius: width / 2
+            color: "orange"
+            opacity: 0.3
+        }
+    }
+}
+
diff --git a/tests/auto/quick/pointerhandlers/qquickpointhandler/tst_qquickpointhandler.cpp b/tests/auto/quick/pointerhandlers/qquickpointhandler/tst_qquickpointhandler.cpp
index d91c89d833..d0b3bc3d36 100644
--- a/tests/auto/quick/pointerhandlers/qquickpointhandler/tst_qquickpointhandler.cpp
+++ b/tests/auto/quick/pointerhandlers/qquickpointhandler/tst_qquickpointhandler.cpp
@@ -55,6 +55,7 @@ private slots:
     void initTestCase();
 
     void singleTouch();
+    void simultaneousMultiTouch();
     void pressedMultipleButtons_data();
     void pressedMultipleButtons();
 
@@ -135,6 +136,84 @@ void tst_PointHandler::singleTouch()
     QCOMPARE(translationSpy.count(), 3);
 }
 
+void tst_PointHandler::simultaneousMultiTouch()
+{
+    QScopedPointer<QQuickView> windowPtr;
+    createView(windowPtr, "multiPointTracker.qml");
+    QQuickView * window = windowPtr.data();
+    QList<QQuickPointHandler *> handlers = window->rootObject()->findChildren<QQuickPointHandler *>();
+    QCOMPARE(handlers.count(), 3);
+
+    QVector<QSignalSpy*> activeSpies;
+    QVector<QSignalSpy*> pointSpies;
+    QVector<QSignalSpy*> translationSpies;
+    QVector<QPoint> points{{100,100}, {200, 200}, {100, 300}};
+    QVector<QPoint> pressPoints = points;
+    for (auto h : handlers) {
+        activeSpies << new QSignalSpy(h, SIGNAL(activeChanged()));
+        pointSpies << new QSignalSpy(h, SIGNAL(pointChanged()));
+        translationSpies << new QSignalSpy(h, SIGNAL(translationChanged()));
+    }
+
+    QTest::touchEvent(window, touchDevice).press(1, points[0], window).press(2, points[1], window).press(3, points[2], window);
+    QQuickTouchUtils::flush(window);
+    QVector<int> pointIndexPerHandler;
+    int i = 0;
+    for (auto h : handlers) {
+        QTRY_COMPARE(h->active(), true);
+        QCOMPARE(activeSpies[i]->count(), 1);
+        QCOMPARE(pointSpies[i]->count(), 1);
+        int chosenPointIndex = points.indexOf(h->point().position().toPoint());
+        QVERIFY(chosenPointIndex != -1);
+        // Verify that each handler chose a unique point
+        QVERIFY(!pointIndexPerHandler.contains(chosenPointIndex));
+        pointIndexPerHandler.append(chosenPointIndex);
+        QPoint point = points[chosenPointIndex];
+        QCOMPARE(h->point().scenePosition().toPoint(), point);
+        QCOMPARE(h->point().pressedButtons(), Qt::NoButton);
+        QCOMPARE(h->translation(), QVector2D());
+        QCOMPARE(translationSpies[i]->count(), 1);
+        ++i;
+    }
+
+    for (int i = 0; i < 3; ++i)
+        points[i] += QPoint(10 + 10 * i, 10 + 10 * i % 2);
+    QTest::touchEvent(window, touchDevice).move(1, points[0], window).move(2, points[1], window).move(3, points[2], window);
+    QQuickTouchUtils::flush(window);
+    i = 0;
+    for (auto h : handlers) {
+        QCOMPARE(h->active(), true);
+        QCOMPARE(activeSpies[i]->count(), 1);
+        QCOMPARE(pointSpies[i]->count(), 2);
+        QCOMPARE(h->point().position().toPoint(), points[pointIndexPerHandler[i]]);
+        QCOMPARE(h->point().scenePosition().toPoint(), points[pointIndexPerHandler[i]]);
+        QCOMPARE(h->point().pressPosition().toPoint(), pressPoints[pointIndexPerHandler[i]]);
+        QCOMPARE(h->point().scenePressPosition().toPoint(), pressPoints[pointIndexPerHandler[i]]);
+        QCOMPARE(h->point().pressedButtons(), Qt::NoButton);
+        QVERIFY(h->point().velocity().x() > 0);
+        QVERIFY(h->point().velocity().y() > 0);
+        QCOMPARE(h->translation(), QVector2D(10 + 10 * pointIndexPerHandler[i], 10 + 10 * pointIndexPerHandler[i] % 2));
+        QCOMPARE(translationSpies[i]->count(), 2);
+        ++i;
+    }
+
+    QTest::touchEvent(window, touchDevice).release(1, points[0], window).release(2, points[1], window).release(3, points[2], window);
+    QQuickTouchUtils::flush(window);
+    i = 0;
+    for (auto h : handlers) {
+        QTRY_COMPARE(h->active(), false);
+        QCOMPARE(activeSpies[i]->count(), 2);
+        QCOMPARE(pointSpies[i]->count(), 3);
+        QCOMPARE(h->translation(), QVector2D());
+        QCOMPARE(translationSpies[i]->count(), 3);
+        ++i;
+    }
+
+    qDeleteAll(activeSpies);
+    qDeleteAll(pointSpies);
+    qDeleteAll(translationSpies);
+}
+
 void tst_PointHandler::pressedMultipleButtons_data()
 {
     QTest::addColumn<Qt::MouseButtons>("accepted");