Fix jump and property changes on first move when dragging a Flickable.

Fixes a regression whereby on the first mouse move the contentItem was
moved the total distance from the touch point to where the drag
distance was exceeded. For large drag thresholds this causes a
noticeable jump.

Task-number: QTBUG-30032

Change-Id: I92c119d27dc2e22203484f9ada5978697d171957
Reviewed-by: Martin Jones <martin.jones@jollamobile.com>

3 files changed, 12 insertions, 6 deletions

diff --git a/src/declarative/graphicsitems/qdeclarativeflickable.cpp b/src/declarative/graphicsitems/qdeclarativeflickable.cpp
index c0c7b2a0..64ae2094 100644
--- a/src/declarative/graphicsitems/qdeclarativeflickable.cpp
+++ b/src/declarative/graphicsitems/qdeclarativeflickable.cpp
@@ -789,9 +789,9 @@ void QDeclarativeFlickablePrivate::handleMouseMoveEvent(QGraphicsSceneMouseEvent
 
     if (q->yflick()) {
         int dy = int(event->pos().y() - pressPos.y());
-        if (vData.dragStartOffset == 0)
-            vData.dragStartOffset = dy;
         if (qAbs(dy) > QApplication::startDragDistance() || QDeclarativeItemPrivate::elapsed(pressTime) > 200) {
+            if (!vMoved)
+                vData.dragStartOffset = dy;
             qreal newY = dy + vData.pressPos - vData.dragStartOffset;
             const qreal minY = vData.dragMinBound;
             const qreal maxY = vData.dragMaxBound;
@@ -818,9 +818,9 @@ void QDeclarativeFlickablePrivate::handleMouseMoveEvent(QGraphicsSceneMouseEvent
 
     if (q->xflick()) {
         int dx = int(event->pos().x() - pressPos.x());
-        if (hData.dragStartOffset == 0)
-            hData.dragStartOffset = dx;
         if (qAbs(dx) > QApplication::startDragDistance() || QDeclarativeItemPrivate::elapsed(pressTime) > 200) {
+            if (!hMoved)
+                hData.dragStartOffset = dx;
             qreal newX = dx + hData.pressPos - hData.dragStartOffset;
             const qreal minX = hData.dragMinBound;
             const qreal maxX = hData.dragMaxBound;
diff --git a/tests/auto/declarative/qdeclarativeflickable/tst_qdeclarativeflickable.cpp b/tests/auto/declarative/qdeclarativeflickable/tst_qdeclarativeflickable.cpp
index b0fa7bd6..c8a98d33 100644
--- a/tests/auto/declarative/qdeclarativeflickable/tst_qdeclarativeflickable.cpp
+++ b/tests/auto/declarative/qdeclarativeflickable/tst_qdeclarativeflickable.cpp
@@ -576,6 +576,9 @@ void tst_qdeclarativeflickable::nestedStopAtBounds()
     axis += invert ? threshold : -threshold;
     moveEvent.setScenePos(position);
     QApplication::sendEvent(view.scene(), &moveEvent);
+    axis += invert ? threshold : -threshold;
+    moveEvent.setScenePos(position);
+    QApplication::sendEvent(view.scene(), &moveEvent);
     QVERIFY(outer->contentX() != 50 || outer->contentY() != 50);
     QVERIFY((inner->contentX() == 0 || inner->contentX() == 100)
             && (inner->contentY() == 0 || inner->contentY() == 100));
@@ -594,6 +597,9 @@ void tst_qdeclarativeflickable::nestedStopAtBounds()
     axis += invert ? -threshold : threshold;
     moveEvent.setScenePos(position);
     QApplication::sendEvent(view.scene(), &moveEvent);
+    axis += invert ? -threshold : threshold;
+    moveEvent.setScenePos(position);
+    QApplication::sendEvent(view.scene(), &moveEvent);
     QVERIFY(outer->contentX() == 50 && outer->contentY() == 50);
     QVERIFY((inner->contentX() != 0 && inner->contentX() != 100)
             || (inner->contentY() != 0 && inner->contentY() != 100));
diff --git a/tests/auto/declarative/qdeclarativemousearea/tst_qdeclarativemousearea.cpp b/tests/auto/declarative/qdeclarativemousearea/tst_qdeclarativemousearea.cpp
index 37e64d4d..855ad602 100644
--- a/tests/auto/declarative/qdeclarativemousearea/tst_qdeclarativemousearea.cpp
+++ b/tests/auto/declarative/qdeclarativemousearea/tst_qdeclarativemousearea.cpp
@@ -597,8 +597,8 @@ void tst_QDeclarativeMouseArea::preventStealing()
     QVERIFY(!mouseArea->pressed());
 
     // Flickable content should have moved.
-    QCOMPARE(flickable->contentX(), 30.);
-    QCOMPARE(flickable->contentY(), 30.);
+    QCOMPARE(flickable->contentX(), 15.);
+    QCOMPARE(flickable->contentY(), 15.);
 
     QTest::mouseRelease(canvas->viewport(), Qt::LeftButton, 0, canvas->mapFromScene(QPoint(50, 50)));