Default QQuickItem::acceptTouchEvents to true until Qt 6

This is a partial revert of 1457df74f4
to avoid making a mandatory API change so soon.

Change-Id: I05040579fa36d3dc5ef7616861f6d17adf500d2c
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

src/quick/items/qquickflickable.cpp

@@ -270,6 +270,7 @@ void QQuickFlickablePrivate::init()
     qmlobject_connect(&velocityTimeline, QQuickTimeLine, SIGNAL(completed()),
                       q, QQuickFlickable, SLOT(velocityTimelineCompleted()))
     q->setAcceptedMouseButtons(Qt::LeftButton);
+    q->setAcceptTouchEvents(false); // rely on mouse events synthesized from touch
     q->setFiltersChildMouseEvents(true);
     QQuickItemPrivate *viewportPrivate = QQuickItemPrivate::get(contentItem);
     viewportPrivate->addItemChangeListener(this, QQuickItemPrivate::Geometry);

src/quick/items/qquickitem.cpp

@@ -3171,7 +3171,11 @@ QQuickItemPrivate::QQuickItemPrivate()
     , antialiasingValid(false)
     , isTabFence(false)
     , replayingPressEvent(false)
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+    , touchEnabled(true)
+#else
     , touchEnabled(false)
+#endif
     , dirtyAttributes(0)
     , nextDirtyItem(0)
     , prevDirtyItem(0)

src/quick/items/qquickmousearea.cpp

@@ -85,6 +85,7 @@ void QQuickMouseAreaPrivate::init()
 {
     Q_Q(QQuickMouseArea);
     q->setAcceptedMouseButtons(Qt::LeftButton);
+    q->setAcceptTouchEvents(false); // rely on mouse events synthesized from touch
     q->setFiltersChildMouseEvents(true);
     if (qmlVisualTouchDebugging()) {
         q->setFlag(QQuickItem::ItemHasContents);

src/quick/items/qquickrectangle.cpp

@@ -324,6 +324,9 @@ QQuickRectangle::QQuickRectangle(QQuickItem *parent)
 : QQuickItem(*(new QQuickRectanglePrivate), parent)
 {
     setFlag(ItemHasContents);
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+    setAcceptTouchEvents(false);
+#endif
 }
 
 /*!

src/quick/items/qquickwindow.cpp

@@ -2668,9 +2668,15 @@ void QQuickWindowPrivate::updateFilteringParentItems(const QVector<QQuickItem *>
     }
     filteringParentItems.clear();
     for (QQuickItem *item : targetItems) {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+        bool acceptsTouchEvents = item->acceptTouchEvents();
+#else
+        // In versions prior to Qt 6, we can't trust item->acceptTouchEvents() here, because it defaults to true.
+        bool acceptsTouchEvents = false;
+#endif
         QQuickItemPrivate *itemPriv = QQuickItemPrivate::get(item);
-        // If the item neither handles events nor has handlers which do, then it will never be a receiver, so filtering is irrelevant
-        if (!item->acceptedMouseButtons() && !item->acceptTouchEvents() &&
+        // If the item neither handles events nor has handlers which do, then it will never be a receiver, so filtering is irrelevant.
+        if (!item->acceptedMouseButtons() && !acceptsTouchEvents &&
                 !(itemPriv->extra.isAllocated() && !itemPriv->extra->pointerHandlers.isEmpty()))
             continue;
         QQuickItem *parent = item->parentItem();

tests/auto/quick/qquickflickable/tst_qquickflickable.cpp

@@ -64,7 +64,11 @@ public:
         , ungrabs(0)
         , m_active(false)
     {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
         setAcceptTouchEvents(true);
+#else
+        setAcceptedMouseButtons(Qt::LeftButton); // not really, but we want touch events
+#endif
     }
 
     QPointF pos() const { return m_pos; }

tests/auto/quick/qquickitem/tst_qquickitem.cpp

@@ -46,11 +46,14 @@ class TestItem : public QQuickItem
 Q_OBJECT
 public:
     TestItem(QQuickItem *parent = 0)
-    : QQuickItem(parent), focused(false), pressCount(0), releaseCount(0)
-    , wheelCount(0), acceptIncomingTouchEvents(true)
-    , touchEventReached(false), timestamp(0)
-    , lastWheelEventPos(0, 0), lastWheelEventGlobalPos(0, 0) {
+        : QQuickItem(parent), focused(false), pressCount(0), releaseCount(0)
+        , wheelCount(0), acceptIncomingTouchEvents(true)
+        , touchEventReached(false), timestamp(0)
+        , lastWheelEventPos(0, 0), lastWheelEventGlobalPos(0, 0)
+    {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
         setAcceptTouchEvents(true);
+#endif
     }
 
     bool focused;

tests/auto/quick/touchmouse/tst_touchmouse.cpp

@@ -74,7 +74,9 @@ public:
         : QQuickItem(parent), touchUngrabCount(0), acceptMouse(false), acceptTouch(false), filterTouch(false), point0(-1)
     {
         setAcceptedMouseButtons(Qt::LeftButton);
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
         setAcceptTouchEvents(true);
+#endif
     }
 
     void touchEvent(QTouchEvent *event)