MultiPointTouchArea: capture the mouse position on press

QTouchEvent::TouchPoint already remembers the start position from
where the touch point was pressed.  But when MPTA handles mouse
events, it populates a synthetic touchpoint (the _mouseQpaTouchPoint
variable).  So to be fully consistent, it needs to store the mouse
press position there too.

Since this was not done, gestureStarted was emitted for almost any
mouse movement (while pressed) because the stored startPos was 0,0,
so MPTA would nearly always think the drag threshold had already been
exceeded.  In a QML onGestureStarted callback
gesture.touchPoints[0].startX and startY were always zero too.

Amends fe2de633f9b9454ec8a9c2a5874ad85f49d8d54d

Fixes: QTBUG-70258

Change-Id: I5bc0abbe0cb52c1aa02d60a76c52ec26bb0683e6
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

2 files changed, 62 insertions, 0 deletions

diff --git a/tests/auto/quick/qquickmultipointtoucharea/data/mouse.qml b/tests/auto/quick/qquickmultipointtoucharea/data/mouse.qml
index 0abcc76f7c..b0410dac4a 100644
--- a/tests/auto/quick/qquickmultipointtoucharea/data/mouse.qml
+++ b/tests/auto/quick/qquickmultipointtoucharea/data/mouse.qml
@@ -6,6 +6,9 @@ MultiPointTouchArea {
 
     property int touchCount: 0
     property int cancelCount: 0
+    property int gestureStartedX: 0
+    property int gestureStartedY: 0
+    property bool grabGesture: false
 
     minimumTouchPoints: 1
     maximumTouchPoints: 4
@@ -17,6 +20,12 @@ MultiPointTouchArea {
     onPressed: { touchCount = touchPoints.length }
     onTouchUpdated: { touchCount = touchPoints.length }
     onCanceled: { cancelCount = touchPoints.length }
+    onGestureStarted: {
+        gestureStartedX = gesture.touchPoints[0].startX
+        gestureStartedY = gesture.touchPoints[0].startY
+        if (grabGesture)
+            gesture.grab()
+    }
 
     Rectangle {
         color: "red"
diff --git a/tests/auto/quick/qquickmultipointtoucharea/tst_qquickmultipointtoucharea.cpp b/tests/auto/quick/qquickmultipointtoucharea/tst_qquickmultipointtoucharea.cpp
index 73f3cab318..d4ad282701 100644
--- a/tests/auto/quick/qquickmultipointtoucharea/tst_qquickmultipointtoucharea.cpp
+++ b/tests/auto/quick/qquickmultipointtoucharea/tst_qquickmultipointtoucharea.cpp
@@ -69,6 +69,8 @@ private slots:
     void transformedTouchArea();
     void mouseInteraction();
     void mouseInteraction_data();
+    void mouseGestureStarted_data();
+    void mouseGestureStarted();
     void cancel();
 
 private:
@@ -1196,6 +1198,57 @@ void tst_QQuickMultiPointTouchArea::mouseInteraction()
     QCOMPARE(area->property("touchCount").toInt(), 0);
 }
 
+void tst_QQuickMultiPointTouchArea::mouseGestureStarted_data()
+{
+    QTest::addColumn<bool>("grabGesture");
+    QTest::addColumn<int>("distanceFromOrigin");
+
+    QTest::newRow("near origin, don't grab") << false << 4;
+    QTest::newRow("near origin, grab") << true << 4;
+    QTest::newRow("away from origin, don't grab") << false << 100;
+    QTest::newRow("away from origin, grab") << true << 100;
+}
+
+void tst_QQuickMultiPointTouchArea::mouseGestureStarted() // QTBUG-70258
+{
+    const int dragThreshold = QGuiApplication::styleHints()->startDragDistance();
+    QFETCH(bool, grabGesture);
+    QFETCH(int, distanceFromOrigin);
+
+    QScopedPointer<QQuickView> view(createAndShowView("mouse.qml"));
+    QVERIFY(view->rootObject() != nullptr);
+
+    QQuickMultiPointTouchArea *area = qobject_cast<QQuickMultiPointTouchArea *>(view->rootObject());
+    QVERIFY(area);
+    area->setProperty("grabGesture", grabGesture);
+    QQuickTouchPoint *point1 = view->rootObject()->findChild<QQuickTouchPoint*>("point1");
+    QCOMPARE(point1->pressed(), false);
+    QSignalSpy gestureStartedSpy(area, SIGNAL(gestureStarted(QQuickGrabGestureEvent *)));
+
+    QPoint p1 = QPoint(distanceFromOrigin, distanceFromOrigin);
+    QTest::mousePress(view.data(), Qt::LeftButton, Qt::NoModifier, p1);
+    QCOMPARE(gestureStartedSpy.count(), 0);
+
+    p1 += QPoint(dragThreshold, dragThreshold);
+    QTest::mouseMove(view.data(), p1);
+    QCOMPARE(gestureStartedSpy.count(), 0);
+
+    p1 += QPoint(1, 1);
+    QTest::mouseMove(view.data(), p1);
+    QTRY_COMPARE(gestureStartedSpy.count(), 1);
+    QTRY_COMPARE(area->property("gestureStartedX").toInt(), distanceFromOrigin);
+    QCOMPARE(area->property("gestureStartedY").toInt(), distanceFromOrigin);
+
+    p1 += QPoint(10, 10);
+    QTest::mouseMove(view.data(), p1);
+    // if nobody called gesteure->grab(), gestureStarted will keep happening
+    QTRY_COMPARE(gestureStartedSpy.count(), grabGesture ? 1 : 2);
+    QCOMPARE(area->property("gestureStartedX").toInt(), distanceFromOrigin);
+    QCOMPARE(area->property("gestureStartedY").toInt(), distanceFromOrigin);
+
+    QTest::mouseRelease(view.data(), Qt::LeftButton);
+}
+
 void tst_QQuickMultiPointTouchArea::cancel()
 {
     QScopedPointer<QQuickView> window(createAndShowView("cancel.qml"));