QtWidgets: restore Qt 5 compatibility for save/restore state

Several classes in QWidget use QDataStream internally in order
to save and restore state. These QDataStream usages were not
versioned, meaning that if Qt changes the serialization for some
datatype, then the data saved between different Qt versions becomes
incompatible. Note that the save/restore API in question just produce
opaque blobs as QByteArrays -- the user has no control over the
QDataStream objects and thus versions.

Fix by version the usages.

In QHeaderView this has caused a regression because QBitArray *did*
change version between Qt 5 and 6. In general, using QDataStream without
explicit versioning is a mistake, so deploy the same fix elsewhere as
well.

Fixes: QTBUG-99487
Pick-to: 5.15 6.2 6.3
Change-Id: I82bb5c266f4e5dedc0887cbef855dccab1015e29
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: <doctor.whom@gmail.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/widgets/itemviews/qheaderview.cpp b/src/widgets/itemviews/qheaderview.cpp
index a081a7d0f9..413857bf6c 100644
--- a/src/widgets/itemviews/qheaderview.cpp
+++ b/src/widgets/itemviews/qheaderview.cpp
@@ -1742,6 +1742,7 @@ QByteArray QHeaderView::saveState() const
     Q_D(const QHeaderView);
     QByteArray data;
     QDataStream stream(&data, QIODevice::WriteOnly);
+    stream.setVersion(QDataStream::Qt_5_0);
     stream << QHeaderViewPrivate::VersionMarker;
     stream << 0; // current version is 0
     d->write(stream);
@@ -1763,6 +1764,7 @@ bool QHeaderView::restoreState(const QByteArray &state)
         return false;
     QByteArray data = state;
     QDataStream stream(&data, QIODevice::ReadOnly);
+    stream.setVersion(QDataStream::Qt_5_0);
     int marker;
     int ver;
     stream >> marker;