QVariant::value<T>() fails to convert unless QVariant::fromValue<T>() has been called previously.

src/app/puzzle/vpsettings.cpp

@@ -26,6 +26,7 @@
  **
  *************************************************************************/
 #include "vpsettings.h"
+#include "../vmisc/compatibility.h"
 
 #include <QMarginsF>
 
@@ -66,14 +67,14 @@ VPSettings::VPSettings(Format format, Scope scope, const QString &organization,
                                  QObject *parent)
     : VCommonSettings(format, scope, organization, application, parent)
 {
-    qRegisterMetaTypeStreamOperators<QMarginsF>("QMarginsF");
+    REGISTER_META_TYPE_STREAM_OPERATORS(QMarginsF)
 }
 
 //---------------------------------------------------------------------------------------------------------------------
 VPSettings::VPSettings(const QString &fileName, QSettings::Format format, QObject *parent)
     : VCommonSettings(fileName, format, parent)
 {
-    qRegisterMetaTypeStreamOperators<QMarginsF>("QMarginsF");
+    REGISTER_META_TYPE_STREAM_OPERATORS(QMarginsF)
 }
 
 //---------------------------------------------------------------------------------------------------------------------

src/app/valentina/main.cpp

@@ -69,9 +69,9 @@ auto main(int argc, char *argv[]) -> int
 #endif
 
     // Need to internally move a node inside a piece main path
-    qRegisterMetaTypeStreamOperators<VPieceNode>("VPieceNode");
+    REGISTER_META_TYPE_STREAM_OPERATORS(VPieceNode);
     // Need to internally move a node inside a custom seam allowance path
-    qRegisterMetaTypeStreamOperators<CustomSARecord>("CustomSARecord");
+    REGISTER_META_TYPE_STREAM_OPERATORS(CustomSARecord);
 
 #ifndef Q_OS_MAC // supports natively
     InitHighDpiScaling(argc, argv);

src/libs/vmisc/compatibility.h

@@ -34,6 +34,24 @@
 #include <QVector>
 #include <QFontMetrics>
 
+#include "defglobal.h"
+
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+// WARNING:QVariant::load: unknown user type with name QMarginsF.
+// QVariant::value<T>() fails to convert unless QVariant::fromValue<T>() has been called previously.
+// https://stackoverflow.com/questions/70974383/qvariantvaluet-fails-to-convert-unless-qvariantfromvaluet-has-been-c
+#if QT_VERSION >= QT_VERSION_CHECK(6, 1, 0)
+#define REGISTER_META_TYPE_STREAM_OPERATORS(TYPE)                             \
+QMetaType::fromType<TYPE>().hasRegisteredDataStreamOperators(); // Dummy call
+#else
+#define REGISTER_META_TYPE_STREAM_OPERATORS(TYPE) \
+QVariant::fromValue<TYPE>(TYPE{}); // Dummy call
+#endif // QT_VERSION >= QT_VERSION_CHECK(6, 1, 0)
+#else
+#define REGISTER_META_TYPE_STREAM_OPERATORS(TYPE) \
+qRegisterMetaTypeStreamOperators<TYPE>(#TYPE);
+#endif // QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+
 #if QT_VERSION < QT_VERSION_CHECK(5, 5, 0)
 #include "diagnostic.h"
 #endif // QT_VERSION < QT_VERSION_CHECK(5, 5, 0)

src/libs/vmisc/testvapplication.h

@@ -32,6 +32,7 @@
 #include "vabstractvalapplication.h"
 #include "projectversion.h"
 #include "../vmisc/vcommonsettings.h"
+#include "../vmisc/compatibility.h"
 
 class VTestSettings : public VCommonSettings
 {
@@ -41,7 +42,7 @@ public:
                   QObject *parent = nullptr)
         : VCommonSettings(format, scope, organization, application, parent)
     {
-        qRegisterMetaTypeStreamOperators<QMarginsF>("QMarginsF");
+        REGISTER_META_TYPE_STREAM_OPERATORS(QMarginsF);
     }
 };
 

src/libs/vmisc/vvalentinasettings.cpp

@@ -37,10 +37,11 @@
 #include <QPrinterInfo>
 #include <QtDebug>
 #include <QGlobalStatic>
+#include <QMargins>
+#include <QMetaType>
 
 #include "../vmisc/def.h"
-#include "../vmisc/vmath.h"
-#include "../vlayout/vbank.h"
+#include "../vmisc/compatibility.h"
 #include "qglobal.h"
 
 #ifndef QBS_BUILD
@@ -147,14 +148,14 @@ VValentinaSettings::VValentinaSettings(Format format, Scope scope, const QString
                      QObject *parent)
     :VCommonSettings(format, scope, organization, application, parent)
 {
-    qRegisterMetaTypeStreamOperators<QMarginsF>("QMarginsF");
+    REGISTER_META_TYPE_STREAM_OPERATORS(QMarginsF);
 }
 
 //---------------------------------------------------------------------------------------------------------------------
 VValentinaSettings::VValentinaSettings(const QString &fileName, QSettings::Format format, QObject *parent)
     :VCommonSettings(fileName, format, parent)
 {
-    qRegisterMetaTypeStreamOperators<QMarginsF>("QMarginsF");
+    REGISTER_META_TYPE_STREAM_OPERATORS(QMarginsF);
 }
 
 //---------------------------------------------------------------------------------------------------------------------

src/libs/vmisc/vvalentinasettings.h

@@ -34,10 +34,8 @@
 #include <QSettings>
 #include <QString>
 #include <QtGlobal>
-#include <QMargins>
 
 #include "vcommonsettings.h"
-#include "../vlayout/vbank.h"
 
 class VValentinaSettings : public VCommonSettings
 {