Qt6 port:

* QApplication::setFallbackSessionManagementEnabled has been removed
* QString::medRef() has been removed. Use QString::mid() again.
* QTextStream::setCodec has been removed
* Use operator QVariant of the QFont class to make code Qt5 and Qt6 compatible
* Signature of QTreeWidget::mimeData() has changed in Qt6. Remove TreeWidget::mimeData() because it doesn't change the implementation
* QLayout::setMargin() is deprecated in Qt5 and has been removed in Qt6. Use QLayout::setContentsMargins()
* QDateTime::toTime_t() is deprecated in Qt5 and has been removed in Qt6. Use QDateTime::toSecsSinceEpoch()
* QDesktopWidget is deprecated in Qt5 and has been removed in Qt6. Use QScreen

src/Mod/Part/App/FaceMakerCheese.cpp

@@ -22,6 +22,7 @@
 
 #include "PreCompiled.h"
 #ifndef _PreComp_
+# include <algorithm>
 # include <Bnd_Box.hxx>
 # include <BRep_Builder.hxx>
 # include <BRep_Tool.hxx>

src/Mod/Part/Gui/DlgFilletEdges.cpp

@@ -429,7 +429,7 @@ void DlgFilletEdges::onSelectEdge(const QString& subelement, int type)
 void DlgFilletEdges::onSelectEdgesOfFace(const QString& subelement, int type)
 {
     bool ok;
-    int index = subelement.midRef(4).toInt(&ok);
+    int index = subelement.mid(4).toInt(&ok);
     if (ok) {
         try {
             const TopoDS_Shape& face = d->all_faces.FindKey(index);