Add note about precision of QNativeGestureEvent::delta; fix in Qt 7

We keep QVector2D storage Qt 6 BC (to avoid making QNativeGestureEvent
larger), but in Qt 7 we should return exactly the same value as given
(for what it's worth, in spite of this being overkill for panning a
reasonable distance).

Change-Id: Iecbd4c9b60ad9ae5e0466c7027b038ddb85b8c8b
Pick-to: 6.2
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

2 files changed, 19 insertions, 5 deletions

diff --git a/src/gui/kernel/qevent.cpp b/src/gui/kernel/qevent.cpp
index f7532d4481..73a591f34c 100644
--- a/src/gui/kernel/qevent.cpp
+++ b/src/gui/kernel/qevent.cpp
@@ -2837,18 +2837,22 @@ QNativeGestureEvent::QNativeGestureEvent(Qt::NativeGestureType type, const QPoin
     indicating that the target item should have its scale adjusted like this:
     item.scale = item.scale * (1 + event.value)
 
-    For PanNativeGesture, \a deltas gives the distance in pixels that the
+    For PanNativeGesture, \a delta gives the distance in pixels that the
     viewport, widget or item should be moved or panned.
 
+    \note The \a delta is stored in single precision (QVector2D), so \l delta()
+    may return slightly different values in some cases. This is subject to change
+    in future versions of Qt.
+
     \since 6.2
 */
 QNativeGestureEvent::QNativeGestureEvent(Qt::NativeGestureType type, const QPointingDevice *device, int fingerCount,
                                          const QPointF &localPos, const QPointF &scenePos,
-                                         const QPointF &globalPos, qreal value, const QPointF &deltas,
+                                         const QPointF &globalPos, qreal value, const QPointF &delta,
                                          quint64 sequenceId)
     : QSinglePointEvent(QEvent::NativeGesture, device, localPos, scenePos, globalPos, Qt::NoButton,
                         Qt::NoButton, Qt::NoModifier),
-      m_sequenceId(sequenceId), m_delta(deltas), m_realValue(value), m_gestureType(type), m_fingerCount(fingerCount)
+      m_sequenceId(sequenceId), m_delta(delta), m_realValue(value), m_gestureType(type), m_fingerCount(fingerCount)
 {
     Q_ASSERT(fingerCount < 16); // we store it in 4 bits unsigned
 }
diff --git a/src/gui/kernel/qevent.h b/src/gui/kernel/qevent.h
index 9796886ae1..9c53f7ce92 100644
--- a/src/gui/kernel/qevent.h
+++ b/src/gui/kernel/qevent.h
@@ -416,7 +416,7 @@ public:
 #endif
     QNativeGestureEvent(Qt::NativeGestureType type, const QPointingDevice *dev, int fingerCount,
                         const QPointF &localPos, const QPointF &scenePos, const QPointF &globalPos,
-                        qreal value, const QPointF &deltas, quint64 sequenceId = UINT64_MAX);
+                        qreal value, const QPointF &delta, quint64 sequenceId = UINT64_MAX);
     ~QNativeGestureEvent();
 
     QNativeGestureEvent *clone() const override { return new QNativeGestureEvent(*this); }
@@ -424,7 +424,13 @@ public:
     Qt::NativeGestureType gestureType() const { return m_gestureType; }
     int fingerCount() const { return m_fingerCount; }
     qreal value() const { return m_realValue; }
-    QPointF delta() const { return m_delta.toPointF(); }
+    QPointF delta() const {
+#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
+        return m_delta.toPointF();
+#else
+        return m_delta;
+#endif
+    }
 
 #if QT_DEPRECATED_SINCE(6, 0)
 #ifndef QT_NO_INTEGER_EVENT_COORDINATES
@@ -443,7 +449,11 @@ public:
 
 protected:
     quint64 m_sequenceId;
+#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
     QVector2D m_delta;
+#else
+    QPointF m_delta;
+#endif
     qreal m_realValue;
     Qt::NativeGestureType m_gestureType;
     quint32 m_fingerCount : 4;